Control device for internal combustion engine

Abstract

To suppress occurrence of knocking in an internal combustion engine during increase in engine rotation speed.SOLUTION: A control device can execute ignition timing correction processing for correcting ignition timing of an ignition plug on the basis of a feedback correction value AKCS and a knocking learning value AGKNK. In the ignition timing correction processing, the feedback correction value AKCS is updated so as to delay the ignition timing by a specific angle when knocking occurs in the internal combustion engine, and the knocking learning value AGKNK is updated when the feedback correction value AKCS reaches a value on the timing delay side of a specified value. During increase in engine rotation speed NE (Yes in step S10), the control device increases a change amount to the timing delay side per update of the feedback correction value AKCS compared to when the engine rotation speed NE is in a steady state (step S30), and prohibits updating of the knocking learning value AGKNK (step S40).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] The internal combustion engine disclosed in Patent Document 1 has a cylinder, an ignition plug that ignites the cylinder, and a knock sensor that detects vibrations of the internal combustion engine. A control device that controls the internal combustion engine detects the occurrence of knocking based on the output of the knock sensor. Furthermore, when knocking occurs in the internal combustion engine, the control device corrects the ignition timing to be retarded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-148185 A Summary of the Invention [Problem to be solved by the invention]

[0004] Some internal combustion engines are equipped with both a turbocharger and an EGR passage. The turbocharger has a compressor wheel located in the intake passage and a turbine wheel located in the exhaust passage. The turbine wheel rotates according to the flow of exhaust air. The compressor wheel rotates integrally with the turbine wheel to supercharge the intake air. The EGR passage connects a portion of the exhaust passage upstream from the turbine wheel to a portion of the intake passage downstream from the compressor wheel. In this configuration, the EGR passage recirculates exhaust gas from the portion of the exhaust passage upstream from the turbine wheel to the intake passage.

[0005] In the above-mentioned internal combustion engine, when the accelerator pedal is depressed, the engine speed of the internal combustion engine increases relatively quickly, but there is a time lag before the rotation speed of the turbine wheel increases. In a transient state in which the rotation speed of the turbine wheel has not yet increased completely, the amount of supercharging by the compressor wheel is small, and the amount of exhaust gas is also small accordingly. In such a situation, the amount of exhaust gas recirculated to the intake passage through the EGR passage, i.e., the amount of inert gas introduced into the cylinder, may not reach the originally targeted amount. In this case, even if the ignition timing is retarded as in the technology of Patent Document 1, the amount of retardation may be insufficient, and knocking may occur. [Means for solving the problem]

[0006] A control device for an internal combustion engine for solving the above problems is applied to an internal combustion engine having a cylinder in which a mixture of intake air and fuel is burned, an ignition plug for igniting the mixture in the cylinder, an intake passage and an exhaust passage connected to the cylinder, a turbine wheel located midway through the exhaust passage, and a supercharger including a compressor wheel located midway through the intake passage and rotating integrally with the turbine wheel, and an EGR passage connecting an upstream portion of the exhaust passage as viewed from the turbine wheel and a downstream portion of the intake passage as viewed from the compressor wheel, and the control device includes a feedback correction value calculated in accordance with the presence or absence of knocking in the internal combustion engine, and a feedback control value for the feedback correction value. An ignition timing correction process can be executed to correct the ignition timing of the spark plug based on a knocking learning value calculated as a value that suppresses an increase in the absolute value of a feedback correction value, and in the ignition timing correction process, when knocking occurs in the internal combustion engine, the feedback correction value is updated so that the ignition timing is retarded by a certain angle, and when the feedback correction value becomes a value that is more retarded than a predetermined specified value, the knocking learning value is updated to the side to retard the ignition timing, and while the engine speed is increasing, the amount of change to the retard side per update of the feedback correction value is made larger than when the engine speed is in a steady state, and updating of the knocking learning value is prohibited.

[0007] In the above configuration, the amount of change to the retard side per update of the feedback correction value is increased while the engine speed is increasing. In this case, the ignition timing of the spark plug can be quickly retarded. Therefore, even if the amount of exhaust gas recirculated to the intake passage via the EGR passage is small, the occurrence of knocking can be suppressed. In addition, in the above configuration, the update of the knocking learning value is prohibited in accordance with the increase in the amount of change per update of the feedback correction value. Therefore, the knocking learning value is not updated to a value corresponding to a situation in which knocking is likely to occur. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine. [Diagram 2] FIG. 2 is a diagram for explaining a situation in which condition (ii) is met. [Diagram 3] FIG. 3 is a flowchart showing the procedure of the information designation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings. 1, a vehicle 300 has an internal combustion engine 100. The internal combustion engine 100 is a drive source of the vehicle 300.

[0010] The internal combustion engine 100 has an engine body 100A and a knock sensor 19. The engine body 100A has a plurality of cylinders 11. Note that FIG. 1 shows only one of the plurality of cylinders 11. The cylinder 11 is a space partitioned in the engine body 100A. In the cylinder 11, a mixture of intake air and fuel is burned. The knock sensor 19 is attached to the engine body 100A. The knock sensor 19 detects a vibration amount KN of the engine body 100A.

[0011] The internal combustion engine 100 has a plurality of pistons 12, a plurality of connecting rods 18, a crankshaft 15, and a crank angle sensor 13. As with the cylinders 11, FIG. 1 shows only one of the plurality of pistons 12. The same is true for the connecting rod 18. A piston 12 is provided for each cylinder 11. A connecting rod 18 is also provided for each cylinder 11. The piston 12 is located in the cylinder 11. The piston 12 can reciprocate within the cylinder 11. The connecting rod 18 connects the piston 12 to the crankshaft 15. The crankshaft 15 rotates in response to the reciprocating motion of the piston 12. The crank angle sensor 13 is located near the crankshaft 15. The crank angle sensor 13 detects a rotational position Scr of the crankshaft 15.

[0012] The internal combustion engine 100 has a plurality of spark plugs 14. Note that Fig. 1 shows only one of the plurality of spark plugs 14. The spark plug 14 is provided for each cylinder 11. The tip of the spark plug 14 is located inside the cylinder 11. The spark plug 14 ignites the air-fuel mixture inside the cylinder 11.

[0013] The internal combustion engine 100 has an intake passage 20 and an exhaust passage 30. The intake passage 20 is a passage for introducing intake air into each cylinder 11. The intake passage 20 is connected to each cylinder 11. The exhaust passage 30 is a passage for discharging exhaust gas from each cylinder 11. The exhaust passage 30 is connected to each cylinder 11.

[0014] The internal combustion engine 100 has a turbocharger 40. The turbocharger 40 has a compressor wheel 41 and a turbine wheel 42. The turbine wheel 42 is located in the exhaust passage 30. The turbine wheel 42 rotates in accordance with the flow of the exhaust gas. The compressor wheel 41 is located in the intake passage 20. The compressor wheel 41 rotates integrally with the turbine wheel 42. In response to the rotation of the compressor wheel 41, the compressor wheel 41 supercharges the intake air.

[0015] The internal combustion engine 100 has an airflow meter 22, an intake pressure sensor 27, an intercooler 23, a throttle valve 24, and a plurality of fuel injection valves 26. The airflow meter 22 is located upstream of the intake passage 20 as viewed from the compressor wheel 41. The airflow meter 22 detects the flow rate GA of intake air flowing through the intake passage 20. The intake pressure sensor 27 is located downstream of the intake passage 20 as viewed from the compressor wheel 41. The intake pressure sensor 27 detects the pressure of the intake air (hereinafter referred to as supercharging pressure) PR at the portion of the intake passage 20 where the intake pressure sensor 27 is located. The intercooler 23 is located downstream of the intake pressure sensor 27 in the intake passage 20. The intercooler 23 cools the intake air. The throttle valve 24 is located downstream of the intercooler 23 in the intake passage 20. The throttle valve 24 opens and closes the intake passage 20. A fuel injection valve 26 is provided for each cylinder 11. The fuel injection valve 26 injects fuel into the cylinder 11 through the intake passage 20. Note that only one of the multiple fuel injection valves 26 is shown in FIG.

[0016] The internal combustion engine 100 has a bypass passage 44 and a wastegate valve (hereinafter, referred to as WGV) 46. The bypass passage 44 connects the upstream side and downstream side of the exhaust passage 30 when viewed from the turbine wheel 42. In other words, the bypass passage 44 is a passage that bypasses the turbine wheel 42. The WGV 46 is located in the bypass passage 44. The WGV 46 opens and closes the bypass passage 44.

[0017] The internal combustion engine 100 has an EGR passage 50 and an EGR valve 53. The EGR passage 50 connects an upstream portion of the exhaust passage 30 as viewed from the turbine wheel 42 to a downstream portion of the intake passage 20 as viewed from the throttle valve 24. The EGR passage 50 is a passage for recirculating exhaust gas to the intake passage 20. The EGR valve 53 is located midway through the EGR passage 50. The EGR valve 53 opens and closes the EGR passage 50.

[0018] The vehicle 300 includes an accelerator sensor 301 and a vehicle speed sensor 302. The accelerator sensor 301 detects the amount of operation of an accelerator pedal of the vehicle 300 as an accelerator operation amount ACCP. The vehicle speed sensor 302 detects the traveling speed of the vehicle 300 as a vehicle speed SP.

[0019] <Overview of the control device> The vehicle 300 has a control device 110. The control device 110 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 110 may be configured as one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a circuit including a combination thereof. The processor includes a CPU and memories such as a RAM and a ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute the processes. The memory, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 110 has a storage device that is an electrically rewritable non-volatile memory.

[0020] The control device 110 receives detection signals from various sensors mounted on the vehicle 300. Specifically, the control device 110 receives detection signals for the following parameters: The intake air flow rate GA detected by the air flow meter 22 - Boost pressure PR detected by intake pressure sensor 27 The rotational position Scr of the crankshaft 15 detected by the crank angle sensor 13 Vibration amount KN of the engine body 100A detected by the knock sensor 19 Accelerator operation amount ACCP detected by the accelerator sensor 301 Vehicle speed SP detected by the vehicle speed sensor 302 The control device 110 calculates parameters indicating the engine operating state at any time based on detection signals received from various sensors. Specifically, the control device 110 calculates the engine speed NE based on the rotational position Scr of the crankshaft 15. The control device 110 also calculates the engine load factor KL based on the engine speed NE and the intake air flow rate GA.

[0021] The control device 110 also constantly determines whether or not knocking has occurred in the internal combustion engine 100 based on the vibration amount KN of the engine body 100A detected by the knock sensor 19. When the vibration amount KN of the engine body 100A is within the allowable range, the control device 110 determines that knocking has not occurred. On the other hand, when the vibration amount KN of the engine body 100A exceeds the allowable range, the control device 110 determines that knocking has occurred.

[0022] The control device 110 controls various parts of the internal combustion engine 100. For example, the control device 110 controls the WGV 46. When the required output value for the internal combustion engine 100 is high, for example, during acceleration of the vehicle 300, the control device 110 closes the WGV 46. The control device 110 calculates the required output value for the internal combustion engine 100 based on the accelerator operation amount ACCP. The control device 110 also controls the EGR valve 53. The control device 110 basically opens the EGR valve 53 except when the engine speed NE or the engine load factor KL is considerably small. For example, the control device 110 increases the opening degree of the EGR valve 53 as the engine speed NE increases or the engine load factor KL increases.

[0023] <Ignition timing correction processing> The control device 110 has an ignition control unit 112 as one of a plurality of functional units that control the internal combustion engine 100. The ignition control unit 112 controls the ignition plug 14. As a process for this purpose, the ignition control unit 112 is capable of executing an ignition timing correction process.

[0024] The ignition timing correction process includes a main process and a sub process. The main process is a process for calculating the final ignition timing AFIN, which is a target value of the ignition timing of the spark plug 14. The final ignition timing AFIN is an ignition timing that is set as far forward as possible while suppressing the occurrence of knocking.

[0025] A method for calculating the final ignition timing AFIN will now be described. The ignition control unit 112 calculates the final ignition timing AFIN based on the following equations (1) to (3). In this embodiment, the ignition timing is expressed as an advance amount of the rotational position Scr of the crankshaft 15 with respect to the compression top dead center of the cylinder 11 to be ignited.

[0026] As shown in equation (1), the final ignition timing AFIN is a value obtained by subtracting the retard amount AKNK from the base ignition timing ABASE. AFIN=ABASE-AKNK…(1) In formula (1), the base ignition timing ABASE is the more retarded value of the MBT ignition timing AMBT and the knock limit ignition timing AKNOK. The MBT ignition timing AMBT is the ignition timing that can obtain maximum torque in the current engine operating state. The knock limit ignition timing AKNOK is the advance limit timing of the ignition timing that can keep the vibration amount KN of the engine body 100A within the allowable range under the best assumed conditions when using high octane fuel with a high knock limit.

[0027] The retard amount AKNK in formula (1) is a value obtained by subtracting the knocking learning value AGKNK from the maximum retard amount AKMAX and adding the feedback correction value AKCS to the result, as shown in formula (2). As the retard amount AKNK increases, the final ignition timing AFIN becomes more retarded, making knocking less likely to occur.

[0028] AKNK = AKMAX - AGKNK + AKCS ... (2) In equation (2), the feedback correction value AKCS is a term for quickly correcting the final ignition timing AFIN depending on whether knocking has occurred. When the value of the feedback correction value AKCS is negative, the value of the retard amount AKNK becomes smaller. As a result, the final ignition timing AFIN calculated from equation (1) above is corrected to a timing that is more advanced. On the other hand, when the value of the feedback correction value AKCS is positive, the value of the retard amount AKNK becomes larger. As a result, the final ignition timing AFIN calculated from equation (1) above is corrected to a timing that is more retarded. The knocking learning value AGKNK is a term for suppressing an increase in the absolute value of the feedback correction value AKCS.

[0029] The maximum retard amount AKMAX in equation (2) is a value obtained by subtracting the most retarded ignition timing AKMF from the base ignition timing ABASE, as shown in the following equation (3). AKMAX=ABASE-AKMF…(3) In equation (3), the most retarded ignition timing AKMF is the maximum advancement timing of the ignition timing that can keep the vibration amount KN of the engine body 100A within the allowable range even under the worst-case conditions when using a low-octane fuel with a low knock limit.

[0030] The ignition control unit 112 calculates the final ignition timing AFIN using the above formulas (1) to (3) once per execution of the main process. The ignition control unit 112 repeats such main process at a predetermined control period while the internal combustion engine 100 is operating. After calculating the final ignition timing AFIN, the ignition control unit 112 controls the spark plug 14 so that ignition is performed at the final ignition timing AFIN.

[0031] In calculating the final ignition timing AFIN, the ignition control unit 112 calculates the base ignition timing ABASE used in equations (1) and (3) based on the latest engine speed NE and the latest engine load factor KL. Similarly, the ignition control unit 112 calculates the knock limit ignition timing AKNOK used in equation (1) and the most retarded ignition timing AKMF used in equation (3) based on the latest engine speed NE and the latest engine load factor KL. For the knocking learning value AGKNK used in equation (2), the ignition control unit 112 uses a value calculated in a sub-processing described later.

[0032] Furthermore, the ignition control unit 112 updates the value of the feedback correction value AKCS used in equation (2) every time the main process is executed. That is, the ignition control unit 112 holds the latest value of the feedback correction value AKCS previously calculated. The ignition control unit 112 updates the value of the feedback correction value AKCS by performing arithmetic processing on the feedback correction value AKCS currently held. Then, the ignition control unit 112 uses the updated value to calculate the final ignition timing AFIN.

[0033] The ignition control unit 112 updates the feedback correction value AKCS depending on whether knocking occurs or not. When knocking does not occur in the internal combustion engine 100, the ignition control unit 112 sets the latest feedback correction value AKCS to a value obtained by subtracting a positive advance update value Z1 from the currently held feedback correction value AKCS. That is, the control device 110 updates the feedback correction value AKCS so that the final ignition timing AFIN is advanced by a certain angle. The above-mentioned advance update value Z1 is determined in advance, for example, by experiment or simulation, as a value suitable for gradually advancing the final ignition timing AFIN while suppressing the occurrence of knocking.

[0034] On the other hand, when knocking occurs in the internal combustion engine 100, the ignition control unit 112 sets the current feedback correction value AKCS to a positive retardation update value Z2. That is, the ignition control unit 112 updates the feedback correction value AKCS so that the final ignition timing AFIN is retarded by a certain angle. There are two types of retardation update value Z2: a normal update value Z2N and an acceleration update value Z2T. The ignition control unit 112 selects one of the normal update value Z2N and the acceleration update value Z2T as the retardation update value Z2 based on a use prohibition flag F1 described later.

[0035] <Details of retardation update value> When the accelerator pedal is depressed to accelerate the vehicle 300, the engine speed NE increases relatively quickly. On the other hand, the turbine wheel 42, which rotates according to the flow of exhaust gas, takes time to start rotating. Therefore, in a situation where the engine speed NE starts to increase at the beginning of acceleration, the actual rotation speed TWR of the turbine wheel 42 is lower than the steady rotation speed TWK, which is a rotation speed according to the current engine operating state. Here, it is assumed that the current engine speed NE is a first value, and the current engine load factor KL is a second value. The steady rotation speed TWK is the rotation speed of the turbine wheel 42 when it is assumed that the engine speed NE is constant at a first value in the time change of the engine speed NE, and the engine load factor KL is constant at a second value in the time change of the engine load factor KL. Now, in a situation where the actual rotation speed TWR of the turbine wheel 42 is lower than the steady rotation speed TWK, the amount of supercharging by the compressor wheel 41 is small, and the amount of exhaust gas is also small accordingly. As a result, the amount of exhaust gas recirculated to the intake passage 20 through the EGR passage 50, i.e., the amount of inert gas introduced into the cylinder 11, may not reach the amount originally targeted, which may result in knocking. The acceleration update value Z2T is a value required to quickly retard the final ignition timing AFIN to suppress the occurrence of knocking when the actual rotation speed TWR of the turbine wheel 42 is lower than the steady rotation speed TWK by a judgment value Q or more. The acceleration update value Z2T is determined in advance, for example, by an experiment or a simulation. The definition of the judgment value Q will be described later.

[0036] The normal update value Z2N is a value suitable for suppressing the occurrence of knocking under a condition where the actual rotation speed TWR of the turbine wheel 42 is approximately equal to the steady rotation speed TWK. The normal update value Z2N is smaller than the acceleration update value Z2T. The normal update value Z2N is determined in advance, for example, by experiment or simulation. The normal update value Z2N is effective under a condition where the engine operating state is approximately steady, such as a period when the vehicle 300 transitions from acceleration to constant speed running, and a period when the vehicle 300 runs at a constant speed thereafter. Here, a value obtained by subtracting the actual rotation speed TWR of the turbine wheel 42 from the steady rotation speed TWK corresponding to the current engine operating state is referred to as the rotation speed difference ΔTW. The above-mentioned judgment value Q is determined, for example, by experiment or simulation, as a minimum value of the rotation speed difference ΔTW at which the occurrence of knocking cannot be dealt with by using the normal update value Z2N in suppressing the occurrence of knocking.

[0037] Of the three running states of the vehicle 300, namely, accelerating, running at a constant speed, and decelerating, ignition is not necessarily required during deceleration because, for example, fuel cut is performed. Of the remaining two running states, accelerating and running at a constant speed, the above-mentioned acceleration update value Z2T and normal update value Z2N are determined based on the correspondence between the actual rotation speed TWR and the steady rotation speed TWK of the turbine wheel 42 for the initial acceleration period and the remaining periods. In the following description, the actual rotation speed TWR of the turbine wheel 42 may also be referred to as the current rotation speed TWR of the turbine wheel 42 depending on the context.

[0038] <Sub-process> The sub-processing of the ignition timing correction process is a process for updating the knocking learning value AGKNK. The ignition control unit 112 continues to execute the sub-processing during the operation of the internal combustion engine 100, on the condition that an execution prohibition flag F2 described later is off. In the sub-processing, the ignition control unit 112 updates the knocking learning value AGKNK when the absolute value of the feedback correction value AKCS becomes large to a certain extent. That is, the ignition control unit 112 holds the latest value of the previously calculated knocking learning value AGKNK, similar to the feedback correction value AKCS. Then, when the state in which the absolute value of the feedback correction value AKCS is larger than a specified value A continues for a determination period or more, the ignition control unit 112 performs an arithmetic process on the currently held knocking learning value AGKNK so as to reduce the absolute value of the feedback correction value AKCS.

[0039] More specifically, when the feedback correction value AKCS continues to have a positive value and its absolute value is greater than the specified value A, that is, when the engine is in a state in which knocking is likely to occur, the ignition control unit 112 updates the knocking learning value AGKNK as follows. That is, as shown in equation (4), the ignition control unit 112 subtracts a change value B, which is a positive value, from the currently held value of the knocking learning value AGKNKp. At the same time, the ignition control unit 112 also subtracts the change value B from the currently held value of the feedback correction value AKCSp. As a result, the absolute value of the feedback correction value AKCS after the subtraction becomes equal to or less than the specified value A.

[0040] AKNK=AKMAX-(AGKNKp-B)+(AKCSp-B)…(4) By subtracting the same value B from both the knocking learning value AGKNKp and the feedback correction value AKCSp as described above, the value of the retardation amount AKNK does not change from the value before the subtraction, as shown in equation (4). In other words, even if the knocking learning value AGKNK is updated, the value of the final ignition timing AFIN does not change.

[0041] Here, as shown in the above formulas (1) and (2), when the feedback correction value AKCS becomes larger, the final ignition timing AFIN becomes more retarded through the retard amount AKNK. In other words, the feedback correction value AKCS indicates a more retarded ignition timing as its value becomes larger. Therefore, updating the knocking learning value AGKNK when the feedback correction value AKCS is larger than the positive specified value A as described above means updating the knocking learning value AGKNK when the feedback correction value AKCS is more retarded than the specified value A. When updating the knocking learning value AGKNK, the change value B is subtracted from the currently held knocking learning value AGKNKp as shown in formula (4). This contributes to increasing the retard amount AKNK in consideration of the sign in formula (4). In other words, the ignition control unit 112 updates the knocking learning value AGKNK to the side where the final ignition timing AFIN is retarded. In this manner, in the sub-processing, when the feedback correction value AKCS is more retarded than the specified value A, the ignition control unit 112 updates the knocking learning value AGKNK so that the final ignition timing AFIN is retarded.

[0042] On the other hand, when the feedback correction value AKCS remains negative and its absolute value is greater than the specified value A, that is, when knocking is unlikely to occur, the ignition control unit 112 updates the knocking learning value AGKNK as follows. That is, the ignition control unit 112 adds the above-mentioned change value B to the currently held values ​​of the knocking learning value AGKNK and the feedback correction value AKCS, respectively. As a result, the absolute value of the feedback correction value AKCS after the addition becomes equal to or less than the specified value A. By adding the same value B to both the knocking learning value AGKNK and the feedback correction value AKCS as described above, the value of the retard amount AKNK and therefore the value of the final ignition timing AFIN do not change from the values ​​before the addition.

[0043] The specified value A is determined in advance as the maximum allowable absolute value of the feedback correction value AKCS. The change value B is determined in advance as a value that can make the absolute value of the feedback correction value AKCS sufficiently smaller than the specified value A. The determination period is determined in advance as the length of time during which the state in which the feedback correction value AKCS is larger than the specified value A is considered to be continuous rather than instantaneous. The values ​​of these parameters are set, for example, through experiments or simulations.

[0044] <Information specification processing> The control device 110 has an information designation unit 114 as one of a plurality of functional units that control the internal combustion engine 100. The information designation unit 114 can execute information designation processing for designating information required in the ignition timing correction processing. More specifically, the information designation processing is processing for designating the retardation update value Z2 to be used in the main processing, and designating whether or not to execute the sub-processing.

[0045] In the information designation process, the information designation unit 114 switches the information to be designated depending on whether or not both of the following two conditions (a) and (b) are satisfied. (a) In terms of the change over time of the engine speed NE, the engine speed NE is increasing.

[0046] (b) The rotational speed difference ΔTW relating to the turbine wheel 42 is equal to or greater than the judgment value Q. As described above, in the early stage of acceleration, the actual rotation speed TWR of the turbine wheel 42 becomes lower than the steady rotation speed TWK, and the rotation speed difference ΔTW becomes large. Therefore, the situation in which both of the two conditions (A) and (B) are satisfied substantially corresponds to the situation in the early stage of acceleration of the vehicle 300. Here, as shown in FIG. 2, consider an orthogonal coordinate system in which the actual rotation speed TWR of the turbine wheel 42 is on the horizontal axis and the steady rotation speed TWK is on the vertical axis. In this orthogonal coordinate system, a straight line with a slope of "1" and passing through the origin is called a first straight line D1. This first straight line D1 indicates that the actual rotation speed TWR of the turbine wheel 42 and the steady rotation speed TWK are the same value. For example, as shown by a black circle V1 in FIG. 2, when a combination of the actual rotation speed TWR of the turbine wheel 42 and the steady rotation speed TWK according to the current engine operating state is located in an area near the first straight line D1, the condition (B) is not satisfied. Now, the line with a slope of "1" and an intercept of "-Q" is referred to as the second line D2. For example, as shown by the black circle V2 in Fig. 2, when the combination of the actual rotation speed TWR of the turbine wheel 42 and the steady rotation speed TWK according to the current engine operating state is located in the area DA between the second line D2 and the horizontal axis, the condition (ii) is satisfied.

[0047] The information designation unit 114 prestores a first map as information for calculating the steady rotation speed TWK corresponding to the current engine operating state. Specifically, the first map represents the correspondence relationship between the engine rotation speed NE, the engine load factor KL, and the steady rotation speed TWK. That is, the first map represents the steady rotation speed TWK for each of various combinations of the engine rotation speed NE and the engine load factor KL. The first map is created, for example, by an experiment or a simulation.

[0048] Further, the information designation unit 114 prestores a second map as information for calculating the actual rotation speed TWR of the turbine wheel 42. Specifically, the second map represents the correspondence relationship between the intake air flow rate GA, the supercharging pressure PR, and the actual rotation speed TWR of the turbine wheel 42. That is, the second map represents the actual rotation speed TWR of the turbine wheel 42 for each of various combinations of the intake air flow rate GA and the supercharging pressure PR. The second map is created, for example, by an experiment or a simulation.

[0049] Now, when both of the above two conditions (A) and (B) are satisfied, the information designation unit 114 designates the use of the acceleration update value Z2T as the retardation update value Z2. That is, the amount of change to the retardation side per update of the feedback correction value AKCS is increased compared to when the engine operating state is in a steady state. Furthermore, when both of the above two conditions (A) and (B) are satisfied, the information designation unit 114 prohibits the execution of the sub-processing. That is, the information designation unit 114 prohibits the update of the knocking learning value AGKNK.

[0050] On the other hand, when at least one of the above two conditions (A) and (B) is not satisfied, the information designation unit 114 designates the use of the normal update value Z2N as the retardation update value Z2. Also, when at least one of the above two conditions (A) and (B) is not satisfied, the information designation unit 114 permits the execution of the sub-processing.

[0051] <Specific processing steps for information designation processing> The information designation unit 114 repeats the information designation process at a predetermined control period while the internal combustion engine 100 is operating. As shown in FIG. 3, when the information designation unit 114 starts the information designation process, it first executes the process of step S10. In step S10, the information designation unit 114 judges whether the engine rotation speed NE is increasing. In making this judgment, the information designation unit 114 refers to the history of the engine rotation speed NE. Regarding the engine rotation speed NE at two consecutive timings, a state in which a newer value is higher than an older value is called an increasing state. If the increasing state continues for a specified period or more in the history of the engine rotation speed NE, the information designation unit 114 judges that the engine rotation speed NE is increasing, and if not, judges that the engine rotation speed NE is not increasing. The specified period is predetermined as a length of time during which the increasing state can be considered to be continuous and not instantaneous. If the engine rotation speed NE is not increasing (step S10: NO), the information designation unit 114 advances the process to step S130.

[0052] In step S130, the information designation unit 114 designates the normal update value Z2N as the retardation update value Z2 used to update the feedback correction value AKCS in the main process. As a specific process of this step S130, the information designation unit 114 sets the use prohibition flag F1, which is a flag indicating prohibition of use of the normal update value Z2N, to OFF. Here, the ignition control unit 112 is set to prioritize use of the normal update value Z2N among the normal update value Z2N and the acceleration update value Z2T. Therefore, when the use prohibition flag F1 is OFF, the ignition control unit 112 selects the normal update value Z2N as the retardation update value Z2 in the main process. After setting the use prohibition flag F1 to OFF, the information designation unit 114 advances the process to step S140.

[0053] In step S140, the information designation unit 114 permits the execution of the sub-processing, i.e., the update of the knocking learning value AGKNK. As a specific process of step S140, the information designation unit 114 sets the execution prohibition flag F2, which is a flag indicating that the execution of the sub-processing is prohibited, to OFF. After this, the information designation unit 114 temporarily ends the series of processes of the information designation process.

[0054] On the other hand, in step S10, if the engine rotation speed NE is increasing (step S10: YES), the information designation unit 114 advances the process to step S20. In step S20, the information designation unit 114 determines whether the rotation speed difference ΔTW of the turbine wheel 42 is equal to or greater than the determination value Q. As a specific process of step S20, the information designation unit 114 first calculates a steady rotation speed TWK corresponding to the current engine operating state. That is, the information designation unit 114 refers to the latest engine rotation speed NE, the latest engine load factor KL, and the first map. Then, the information designation unit 114 calculates the steady rotation speed TWK corresponding to the latest engine rotation speed NE and the latest engine load factor KL based on the first map. After that, the information designation unit 114 calculates the current rotation speed TWR of the turbine wheel 42. That is, the information designation unit 114 refers to the latest intake air flow rate GA, the latest supercharging pressure PR, and the second map. Then, the information designation unit 114 calculates the rotation speed TWR of the turbine wheel 42 corresponding to the latest intake air flow rate GA and the latest supercharging pressure PR based on the second map. Thereafter, the information designation unit 114 calculates the rotation speed difference ΔTW by taking the difference between the two parameters calculated as described above. Then, the information designation unit 114 compares the rotation speed difference ΔTW with the judgment value Q. If the rotation speed difference ΔTW is less than the judgment value Q (step S20: NO), the information designation unit 114 advances the process to step S130.

[0055] On the other hand, if the rotation speed difference ΔTW is equal to or greater than the determination value Q (step S20: YES), the information designation unit 114 advances the process to step S30. In step S30, the information designation unit 114 designates the acceleration update value Z2T as the retardation update value Z2 used to update the feedback correction value AKCS in the main processing. As a specific process of this step S30, the information designation unit 114 sets the above-mentioned use prohibition flag F1, which is a flag indicating prohibition of use of the normal update value Z2N, to ON. In this case, the ignition control unit 112 selects the acceleration update value Z2T as the retardation update value Z2 in the main processing. After setting the use prohibition flag F1 to ON, the information designation unit 114 proceeds to the process of step S40.

[0056] In step S40, the information designation unit 114 prohibits the execution of the sub-processing, i.e., prohibits the update of the knocking learning value AGKNK. As a specific process of step S40, the information designation unit 114 sets an execution prohibition flag F2, which is a flag indicating that the execution of the sub-processing is prohibited, to ON. After this, the information designation unit 114 temporarily ends the series of processes of the information designation process.

[0057] <Operation of the embodiment> Assume that the accelerator pedal is depressed. Then, the engine speed NE starts to increase in order to accelerate the vehicle 300 (step S10: YES). At this time, the rotation speed difference ΔTW becomes large due to the fact that the turbine wheel 42 takes time to start rotating (step S20: YES). Then, the information designation unit 114 turns on the use prohibition flag F1 of the normal update value Z2N in order to instruct the use of the acceleration update value Z2T as the retardation update value Z2 (step S30). In response to this, the ignition control unit 112 updates the feedback correction value AKCS using the acceleration update value Z2T. In this case, the amount of change to the retardation side per update of the feedback correction value AKCS becomes larger than when the feedback correction value AKCS is updated using the normal update value Z2N under the condition that the engine speed NE is in a steady state. In addition, in response to the instruction to use the acceleration update value Z2T as the retardation update value Z2, the information designation unit 114 turns on the execution prohibition flag F2 to prohibit the update of the knocking learning value AGKNK (step S40). In response to this, the ignition control unit 112 stops the execution of the sub-processing of the ignition timing correction process, i.e., the update of the knocking learning value AGKNK.

[0058] <Effects of the embodiment> In the early stage of acceleration of the vehicle 300, when the rotational speed difference ΔTW of the turbine wheel 42 is large, the amount of supercharging by the compressor wheel 41 is small, and the amount of exhaust gas is accordingly small. In such a situation, the amount of exhaust gas recirculated to the intake passage 20 through the EGR passage 50, i.e., the amount of inert gas introduced into the cylinder 11, may not reach the originally targeted amount.

[0059] Therefore, in this embodiment, when the vehicle 300 is in the early stage of acceleration and the rotation speed difference ΔTW is large, the amount of change to the retard side per update of the feedback correction value AKCS is increased. In this case, the final ignition timing AFIN can be quickly corrected to retard. Therefore, even if the amount of exhaust gas recirculated to the intake passage 20 via the EGR passage 50 is small, the occurrence of knocking can be suppressed. In addition, in this embodiment, in accordance with the increase in the amount of change per update of the feedback correction value AKCS, the update of the knocking learning value AGKNK is prohibited. Therefore, the knocking learning value AGKNK is not updated to a value corresponding to a situation in which knocking is likely to occur.

[0060] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0061] The contents of the sub-processing, that is, the method of updating the knocking learning value AGKNK, are not limited to the example of the above embodiment. For example, the condition for updating the knocking learning value AGKNK may be changed from the example of the above embodiment. For example, a moving average is applied to the time series of the feedback correction value AKCS. Then, when the absolute value of the time series value after the moving average is applied becomes larger than the specified value A, the knocking learning value AGKNK may be updated. If the knocking learning value AGKNK can be updated to the side where the final ignition timing AFIN is retarded when the feedback correction value AKCS becomes a value on the retard side of the predetermined specified value A, the method of updating the knocking learning value AGKNK does not matter. The specified value A may be set to an appropriate value according to the method of updating the knocking learning value AGKNK. When the change value B is used as in the above embodiment, the change value B may also be set to an appropriate value according to the method of updating the knocking learning value AGKNK.

[0062] The method of updating the feedback correction value AKCS is not limited to the example of the above embodiment. For example, the change amount to the retard side per update of the feedback correction value AKCS, i.e., the retard update value Z2, may be changed each time depending on the magnitude of the vibration amount KN of the engine body 100A. Even in this case, it is sufficient that different retard update values ​​Z2 are pre-determined depending on the magnitude of the vibration amount KN. In other words, the retard update value Z2 does not always have to be a constant fixed value, and if the feedback correction value AKCS is updated with the same change amount under the same circumstances, it can be said that the feedback correction value AKCS is updated so as to retard the final ignition timing AFIN by a certain angle. The method of updating the feedback correction value AKCS may be any method that can update the feedback correction value AKCS so that the final ignition timing AFIN is retarded by a certain angle when knocking occurs in the internal combustion engine 100.

[0063] When the retardation update value Z2 is set to be variable as in the above modified example, both the acceleration update value Z2T and the normal update value Z2N may be set to be variable, or only one of them may be set to be variable. For example, when both the acceleration update value Z2T and the normal update value Z2N are set to be variable, it is sufficient that the acceleration update value Z2T and the normal update value Z2N are determined so that the minimum value that the acceleration update value Z2T can take is greater than the maximum value that the normal update value Z2N can take. From the same perspective, when only one of the acceleration update value Z2T and the normal update value Z2N is set to be variable, it is sufficient that these values ​​are determined so that the acceleration update value Z2T is greater than the normal update value Z2N.

[0064] In the information designation process, the process of step S20 relating to condition (ii) may be omitted. Regardless of the magnitude of the rotational speed difference ΔTW, while the engine rotational speed NE is increasing, the amount of exhaust gas recirculated to the intake passage 20 via the EGR passage 50 may decrease. Therefore, in order to suppress the occurrence of knocking, it is also effective to use the acceleration update value Z2T for updating the feedback correction value AKCS and to prohibit the knocking learning value AGKNK only under condition (i) that the engine rotational speed NE is increasing.

[0065] The method of determining that the engine speed NE is increasing is not limited to the example of the above embodiment. Any method of determination may be used as long as it can be determined that the engine speed NE is continuously increasing. The engine speed NE being increased corresponds to the vehicle 300 accelerating. Therefore, it may be determined that the engine speed NE is increasing when the acceleration of the vehicle 300 is greater than zero. In this case, an acceleration sensor may be attached to the vehicle 300. Furthermore, when determining that the engine speed NE is increasing, it may be determined based on the accelerator operation amount ACCP and the vehicle speed SP instead of or in addition to the engine speed NE.

[0066] In the above embodiment, the steady-state rotation speed TWK is defined as the rotation speed of the turbine wheel 42 when both the engine speed NE and the engine load factor KL are steady. Alternatively, the steady-state rotation speed TWK may be defined by considering only the engine speed NE without considering the engine load factor KL. In other words, the steady-state rotation speed TWK may be defined as the rotation speed of the turbine wheel 42 when only the engine speed NE is steady.

[0067] The method of calculating the final ignition timing AFIN is not limited to the above embodiment, but may be any method as long as the final ignition timing AFIN is corrected based on the feedback correction value AKCS and the knocking learning value AGKNK.

[0068] The configuration of the internal combustion engine 100 is not limited to the example of the above embodiment. The internal combustion engine 100 only needs to have the cylinders 11, the spark plugs 14, the intake passage 20, the exhaust passage 30, the turbocharger 40, and the EGR passage 50. For example, a rotation sensor that detects the rotation position of the turbine wheel 42 may be attached near the turbine wheel 42. Then, the actual rotation speed TWR of the turbine wheel 42 may be calculated based on the detection result of the rotation sensor.

[0069] The configuration of the vehicle 300 is not limited to the example of the above embodiment. For example, the vehicle 300 may have a motor generator in addition to the internal combustion engine 100 as a drive source of the vehicle 300. [Explanation of symbols]

[0070] 11…Cylinder 14…Spark plug 20…Intake passage 30…Exhaust passage 40…Turbocharger 41…Compressor wheel 42…Turbine wheel 50...EGR passage 100…Internal combustion engine 110...Control device 112…Ignition control unit 114...Information specification section

Claims

[Claim 1] A cylinder in which an intake air / fuel mixture is burned; A spark plug for igniting an ignition in the cylinder; an intake passage and an exhaust passage connected to the cylinder; a turbocharger including a turbine wheel located in the exhaust passage and a compressor wheel located in the intake passage and rotating integrally with the turbine wheel; an EGR passage connecting a portion of the exhaust passage upstream of the turbine wheel and a portion of the intake passage downstream of the compressor wheel; The present invention is applied to an internal combustion engine having an ignition timing correction process can be executed to correct the ignition timing of the spark plug based on a feedback correction value calculated in accordance with the occurrence or absence of knocking in the internal combustion engine and a knocking learning value calculated as a value for suppressing an increase in the absolute value of the feedback correction value, In the ignition timing correction process, updating the feedback correction value so that the ignition timing is retarded by a certain angle when knocking occurs in the internal combustion engine; When the feedback correction value becomes a value on the retard side relative to a predetermined specified value, the knocking learning value is updated to a side on which the ignition timing is retarded, During an increase in the engine rotation speed, the amount of change to the retard side per update of the feedback correction value is made larger than when the engine rotation speed is in a steady state, and updating of the knocking learning value is prohibited. A control device for an internal combustion engine.

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