Control device for internal combustion engine

Abstract

To suppress misfire during increase correction of a fuel injection amount.SOLUTION: A control device 100 for an internal combustion engine includes a correction coefficient calculation unit 28 that calculates a correction coefficient for increasing a reference injection amount of fuel injected into a combustion chamber of the internal combustion engine, which is calculated according to an operation state of the internal combustion engine, over a predetermined period from a startup start time point of the internal combustion engine, a limit value calculation unit 29 that calculates a limit value of an intake amount of the internal combustion engine over the predetermined period, and an intake control unit 25 that calculates a target value of the intake amount so as not to exceed the limit value and controls the intake amount based on the calculated target value. The electronic control unit is configured to calculate the correction coefficient such that the correction coefficient gradually decreases as a combustion cycle of the internal combustion engine elapses. The limit value calculation unit calculates the limit value such that the limit value gradually increases as the correction coefficient decreases.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, research and development has been conducted into the control of internal combustion engines that contributes to improving emissions in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A known example of this type of technology is a device that controls fuel injection immediately after starting an internal combustion engine (see, for example, Patent Document 1). In the device described in Patent Document 1, if a load fluctuation occurs during a prohibited period for acceleration increase in the engine's idle state immediately after starting the engine, the prohibited period is changed and acceleration increase is performed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-206782 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the fuel injection amount is increased in response to demands such as load fluctuations, as in the device described in Patent Document 1, the end of fuel injection (EOI (End Of Injection)) may be delayed, and some of the injected fuel may not be sufficiently vaporized by the time of ignition, which could lead to misfire. [Means for solving the problem]

[0005] An internal combustion engine control device according to one aspect of the present invention includes a correction coefficient calculation unit that calculates a correction coefficient for increasing a base injection amount of fuel injected into a combustion chamber of the internal combustion engine, the correction coefficient being calculated according to the operating state of the internal combustion engine over a predetermined period from the start of startup of the internal combustion engine, a limit value calculation unit that calculates a limit value for an intake air amount of the internal combustion engine over the predetermined period, and an intake control unit that calculates a target value for the intake air amount so that it does not exceed the limit value and controls the intake air amount based on the calculated target value. The correction coefficient calculation unit calculates the correction coefficient so that it gradually decreases as the combustion cycle of the internal combustion engine progresses. The limit value calculation unit calculates the limit value so that it gradually increases as the correction coefficient decreases. [Effects of the Invention]

[0006] According to the present invention, misfires can be suppressed during the increase correction of the fuel injection amount. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing an example of a configuration of a main part of an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied; [Figure 2] 1 is a block diagram that schematically shows an example of the overall configuration of a control device for an internal combustion engine according to an embodiment of the present invention; [Figure 3] 3 is a diagram for explaining an example of a limit value calculated by the limit value calculation unit in FIG. 2 when the accelerator opening degree is increasing. [Figure 4] 3 at a constant throttle opening. [Figure 5] A diagram similar to Figure 3 when the accelerator is depressed from a constant accelerator opening state. [Figure 6] A diagram similar to Figure 3 when the accelerator is released from a constant throttle opening state. [Figure 7] 3 is a flowchart showing an example of processing executed by the ECU of FIG. 2; DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 7. A control device for an internal combustion engine according to an embodiment of the present invention can be applied to a direct injection spark ignition internal combustion engine. In particular, an example in which the control device is applied to a direct injection spark ignition internal combustion engine mounted on a vehicle supplied with an alcohol-containing fuel containing alcohol such as bioethanol will be described below.

[0009] FIG. 1 is a diagram that schematically shows an example of the configuration of the main parts of an engine 1 to which an internal combustion engine control device according to an embodiment of the present invention is applied. The engine 1 is a direct-injection, spark-ignition internal combustion engine mounted on a vehicle (not shown), and is a four-stroke engine that undergoes four strokes during one combustion cycle: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The engine 1 has multiple cylinders, such as four cylinders, but FIG. 1 shows the configuration of a single cylinder. Note that the configuration of each cylinder is identical to one another.

[0010] As shown in Fig. 1, the engine 1 has a cylinder 2a formed in a cylinder block 2, a piston 3 slidably disposed inside the cylinder 2a, and a combustion chamber 5 formed between the crown surface of the piston 3 (piston crown surface) and a cylinder head 4. The piston 3 is connected to a crankshaft 7 via a connecting rod 6, and the crankshaft 7 rotates as the piston 3 reciprocates along the inner wall of the cylinder 2a.

[0011] The cylinder head 4 is provided with an intake port 8 and an exhaust port 9. An intake passage 10 communicates with the combustion chamber 5 via the intake port 8, and an exhaust passage 11 communicates with the combustion chamber 5 via the exhaust port 9. The intake port 8 is opened and closed by an intake valve 12, and the exhaust port 9 is opened and closed by an exhaust valve 13. A throttle valve 14 is provided in the intake passage 10 upstream of the intake valve 12. The throttle valve 14 is formed, for example, by a butterfly valve, and adjusts the amount of air intake into the combustion chamber 5. The intake valve 12 and the exhaust valve 13 are driven to open and close by a valve mechanism 15.

[0012] An ignition plug 16 and a direct injection injector 17 are attached to the cylinder head 4 so that they each face the combustion chamber 5. The ignition plug 16 is positioned between the intake port 8 and the exhaust port 9, and generates a spark using electrical energy to ignite the fuel-air mixture in the combustion chamber 5.

[0013] The injector 17 is disposed near the intake valve 12 and is driven by electrical energy to inject fuel. More specifically, the injector 17 receives high-pressure fuel from a fuel tank via a fuel pump. The injector 17 atomizes the fuel and injects the fuel diagonally downward into the combustion chamber 5 at a predetermined timing. The location of the injector 17 is not limited to this, and it may also be disposed near the spark plug 16, for example.

[0014] The valve train 15 has an intake camshaft 18 and an exhaust camshaft 19. The intake camshaft 18 has integrally therewith intake cams 18a corresponding to each cylinder (cylinder 2a), and the exhaust camshaft 19 has integrally therewith exhaust cams 19a corresponding to each cylinder. The intake camshaft 18 and the exhaust camshaft 19 are connected to the crankshaft 7 via a timing belt (not shown), and each rotates once for every two rotations of the crankshaft 7.

[0015] The intake valve 12 opens and closes at a predetermined timing according to the profile of an intake cam 18a via an intake rocker arm (not shown) as a result of the rotation of the intake camshaft 18. The exhaust valve 13 opens and closes at a predetermined timing according to the profile of an exhaust cam 19a via an exhaust rocker arm (not shown) as a result of the rotation of the exhaust camshaft 19.

[0016] Fig. 2 is a block diagram showing an example of the overall configuration of an internal combustion engine control device (hereinafter referred to as device) 100 according to an embodiment of the present invention. As shown in Fig. 2, the device 100 mainly includes an electronic control unit (ECU (Electronic Control Unit)) 20 that controls the engine 1 shown in Fig. 1. Connected to the ECU 20 are a crank angle sensor 21, an accelerator opening sensor 22, a water temperature sensor 23, an intake amount sensor 24, the throttle valve 14 shown in Fig. 1, the spark plug 16, and the injector 17.

[0017] The ECU 20 includes a computer having a processor such as a CPU, memories such as RAM and ROM, and other peripheral circuits. The ECU 20 has an intake control unit 25, an ignition control unit 26, an injection control unit 27, a correction coefficient calculation unit 28, and a limit value calculation unit 29 as functional components, and functions as the intake control unit 25, the ignition control unit 26, the injection control unit 27, the correction coefficient calculation unit 28, and the limit value calculation unit 29.

[0018] 1, and is configured to output a pulse signal in accordance with the rotation of the crankshaft 7. Based on the pulse signal from the crank angle sensor 21, the ECU 20 determines the rotation angle (crank angle) of the crankshaft 7 relative to the position of top dead center (TDC) when the piston 3 starts the intake stroke, and calculates the engine speed.

[0019] Accelerator opening sensor 22 is provided on an accelerator pedal (not shown) of the vehicle and detects accelerator opening A, which is the amount of accelerator pedal operation. The accelerator opening A when the accelerator is fully closed is set to 0%, and the accelerator opening A when the accelerator is fully open is set to 100%. ECU 20 calculates a target torque for engine 1 based on accelerator opening A detected by accelerator opening sensor 22, and calculates a target value Ga of the intake amount and a target opening of throttle valve 14 (target throttle opening) for generating the target torque.

[0020] The water temperature sensor 23 is provided in a path through which coolant for cooling the engine 1 flows, and detects the temperature of the coolant (engine water temperature).

[0021] The intake air amount sensor 24 is a sensor that detects the amount of intake air of the engine 1, and is configured, for example, by an air flow meter that is arranged in the intake passage 10 (more specifically, upstream of the throttle valve 14). The ECU 20 calculates a target injection amount (reference injection amount Q0) based on the intake air amount detected by the intake air amount sensor 24 so that the actual air-fuel ratio becomes the target air-fuel ratio.

[0022] The intake control unit 25 calculates the target value Ga of the intake amount of the engine 1 and the target throttle opening based on the accelerator opening A detected by the accelerator opening sensor 22, and outputs a control signal to the throttle valve 14 so that the actual throttle opening becomes the target throttle opening.

[0023] The ignition control unit 26 outputs a control signal to the spark plug 16 so that the ignition timing becomes a target ignition timing according to a characteristic that is predetermined depending on the operating state of the engine 1.

[0024] The injection control unit 27 calculates a target injection amount (reference injection amount Q0) based on the intake amount detected by the intake amount sensor 24 and outputs a control signal to the injector 17 to inject the target injection amount at a predetermined timing. The fuel is injected in a region other than a predetermined injection prohibition region near the intake top dead center (TDC) at the start of the intake stroke (a crank angle range of 0° to 180°) and the compression top dead center (TDC) at the end of the compression stroke (a crank angle range of 180° to 360°), i.e., a region where the piston crown is away from the injector 17 (injection possible region). The injection prohibition region is set, for example, to a part or almost the entire first half of the intake stroke and a part or almost the entire second half of the compression stroke. More specifically, the injection prohibition region is set according to the engine speed. The higher the engine speed, the faster the piston crown retracts from the injector 17 during the intake stroke and the faster the piston crown approaches the injector 17 during the compression stroke. Therefore, the higher the engine speed, the narrower the injection prohibition region in the intake stroke (the end of the injection prohibition region moves toward the advance side), and the wider the injection prohibition region in the compression stroke (the start of the injection prohibition region moves toward the advance side).

[0025] The correction coefficient calculation unit 28 calculates a correction coefficient K for increasing the reference injection amount Q0 of fuel calculated in accordance with the operating state of the engine 1 over a predetermined period (increase correction period) from the start of starting the engine 1. That is, when the engine 1 is started, the temperatures (in-cylinder temperatures) of the piston crown surface and the cylinder head wall surface facing the combustion chamber 5 in FIG. 1 are low, so some of the fuel injected from the injector 17 adheres to the piston crown surface and the cylinder wall surface without vaporizing. The fuel that adheres to the piston crown surface and the cylinder wall surface without vaporizing does not contribute to combustion.

[0026] The correction coefficient K is a value equal to or greater than "1" that is multiplied by the reference injection amount Q0 to perform an increase correction to compensate for the fuel that does not contribute to combustion, and is determined in advance according to the operating conditions (e.g., engine water temperature) at the time of starting the engine 1. More specifically, the lower the engine water temperature, the higher the proportion of fuel that does not contribute to combustion, so the correction coefficient K is calculated to increase, and the higher the engine water temperature, the lower the proportion of fuel that does not contribute to combustion, so the correction coefficient K is calculated to decrease. The correction coefficient K may be calculated to decrease as the in-cylinder temperature estimated based on the operating conditions of the engine 1 becomes higher or as the total work load from the start of starting becomes larger.

[0027] Since the engine water temperature gradually increases as the combustion cycle of the engine 1 progresses, the correction coefficient K is calculated to gradually decrease as the combustion cycle of the engine 1 progresses. When the increase correction period has elapsed, the in-cylinder temperature rises to a warm-up state, the engine water temperature reaches a predetermined water temperature during in-cylinder warm-up, the correction coefficient K becomes "1", and the increase correction ends. The increase correction period is the period from the start of engine 1 startup to the time the in-cylinder warm-up state is reached, and the length of the increase correction period varies depending on the engine water temperature (in-cylinder temperature) at the start of startup and the operating state of the engine 1 after startup (load and total workload since startup).

[0028] However, when such an increase correction of the fuel injection amount is made, the end of fuel injection (EOI (End of Injection)) may be delayed and fall into the injection prohibition region. In this case, a portion of the injected fuel may not be sufficiently vaporized by the ignition timing, and an appropriate air-fuel mixture may not be formed, which may lead to misfire. In particular, when using an alcohol-containing fuel containing alcohol, which has a lower calorific value than gasoline, the reference injection amount Q0 becomes even larger, further increasing the possibility that the injection end EOI will fall into the injection prohibition region during the increase correction. Therefore, in this embodiment, the device 100 is configured as follows so that misfires can be suppressed by limiting the intake amount of the engine 1 (i.e., limiting the output) during the increase correction.

[0029] The limit value calculation unit 29 calculates a limit value GaL of the intake air amount of the engine 1, and the intake control unit 25 calculates a target value Ga of the intake air amount so that it does not exceed the limit value GaL, and controls the intake air amount based on the calculated target value Ga. The limit value GaL can be calculated, for example, according to the maximum value of the correction coefficient K calculated corresponding to the operating state of the engine 1 (engine water temperature) at the start of starting. In this case, the intake air amount of the engine 1 is limited to a certain limit value GaL or less over the increase correction period, and the output of the engine 1 is limited, so that misfires during the increase correction period can be reliably suppressed.

[0030] However, if the intake amount during the increase correction period is limited to a certain limit value GaL or less, excessive output restriction will be performed when the engine water temperature rises and the fuel injection amount correction coefficient K becomes small. If such excessive output restriction is performed, there is a risk that the vehicle user's request, such as running at high speed immediately after starting the engine 1, will not be satisfied, and there is a risk that the marketability of the vehicle will be impaired. Therefore, the limit value calculation unit 29 calculates the limit value GaL in accordance with the actual correction coefficient K calculated corresponding to the operating state of the engine 1 (engine water temperature), so that the limit value GaL gradually increases as the correction coefficient K decreases.

[0031] 3 to 6 are diagrams illustrating an example of the limit value GaL calculated by the limit value calculation unit 29. As shown in FIGS. 3 to 6, when the engine 1 starts at time t0, a correction coefficient K for the fuel injection amount is calculated according to the operating state of the engine 1 (engine water temperature) based on predetermined characteristics. The limit value calculation unit 29 calculates the limit value GaL for the intake air amount according to the correction coefficient K calculated according to the engine water temperature. Thereafter, as the number of times top dead center TDC has been passed (the number of elapsed TDCs) increases and the combustion cycle of the engine 1 progresses, the engine water temperature gradually rises, the correction coefficient K gradually decreases, and the limit value GaL gradually increases. The intake control unit 25 calculates a target value Ga for the intake air amount so that it does not exceed the limit value GaL calculated according to the correction coefficient K, and controls the intake air amount based on the calculated target value Ga.

[0032] In this way, by calculating the limit value GaL according to the actual correction coefficient K calculated in accordance with the operating conditions of the engine 1, such as the engine water temperature, misfires can be reliably suppressed during the increase correction period without excessive output restriction. That is, as the engine 1 combustion cycle progresses and the engine water temperature increases and the correction coefficient K decreases, a margin of time is created between the end of fuel injection (EOI) and the start of the injection prohibition region, so the limit value GaL is increased by that amount. This makes it possible to relax the output restriction while reliably suppressing misfires during the increase correction period.

[0033] In the example of FIG. 3, the accelerator is depressed at time t1, and the accelerator opening A increases. When the target value Ga of the intake air amount reaches the limit value GaL at time t2, the intake control unit 25 determines whether the change amount |ΔA| in the accelerator opening A is equal to or less than a threshold value α (e.g., approximately 3 to 5%). That is, it determines whether the accelerator opening A is maintained substantially constant. When the intake control unit 25 determines that the change amount |ΔA| in the accelerator opening A is not equal to or less than the threshold value α at time t2, it calculates the target value Ga of the intake air amount so as not to exceed the limit value GaL, that is, so as to increase in accordance with the limit value GaL. When the accelerator opening A is increasing, the driver intends to accelerate. Since the target value Ga of the intake air amount increases in accordance with the relaxation of the output limit (increase in the limit value GaL) accompanying an increase in engine water temperature, the torque request corresponding to the driver's accelerator depression amount (accelerator opening A) can be satisfied even when the engine water temperature is low, such as immediately after starting the engine.

[0034] In the example of FIG. 4, the accelerator is depressed at time t3, and the accelerator opening A is maintained constant. When the target value Ga of the intake air amount reaches the limit value GaL at time t4, the intake control unit 25 determines whether the change amount |ΔA| of the accelerator opening A is equal to or less than the threshold value α, and determines whether the accelerator opening A is maintained approximately constant. If the intake control unit 25 determines that the change amount |ΔA| of the accelerator opening A is equal to or less than the threshold value α at time t4, it starts maintenance control to maintain the target value Ga of the intake air amount at the target value Ga(t4) at time t4 when the limit value GaL is reached. When the accelerator opening A is maintained constant, the driver intends to drive at a constant speed. Even if the engine water temperature rises, the output limit is relaxed, and the limit value GaL of the intake air amount increases, by maintaining the target value Ga of the intake air amount constant while the accelerator opening A is maintained constant, it is possible to prevent acceleration against the driver's intention.

[0035] In the example of FIG. 5 , the accelerator is depressed at time t5, and accelerator opening A is maintained constant. Then, at time t7, the accelerator is depressed from a constant state, and accelerator opening A increases. Thereafter, at time t9, accelerator opening A is maintained constant again. In this case, at time t6, the target value Ga of the intake air amount reaches the limit value GaL, and when it is determined that the accelerator opening A is being maintained constant, maintenance control is initiated, and the target value Ga of the intake air amount is maintained at the target value Ga(t6) at time t6 when the limit value GaL was reached. Thereafter, when the accelerator is depressed at time t7, and it is determined that the accelerator opening A is not being maintained constant, maintenance control is stopped, and the target value Ga of the intake air amount is calculated so as not to exceed the limit value GaL. More specifically, when the target value Ga of the intake air amount reaches the limit value GaL at time t8, the target value Ga is calculated so as to increase to coincide with the limit value GaL. Thereafter, when it is determined at time t9 that the accelerator opening A is being maintained constant, maintenance control is initiated and the target value Ga of the intake air amount is maintained at the target value Ga(t9) at time t9 when it has reached the limit value GaL.

[0036] In this way, while the intake control unit 25 is performing the maintenance control (time points t6 to t7), it determines whether the change amount |ΔA| in the accelerator pedal position A is equal to or less than the threshold value α. If it determines that the accelerator pedal position A has increased and the change amount |ΔA| has exceeded the threshold value α (time point t7), it discontinues the maintenance control. While performing the maintenance control, the intake control unit 25 further determines whether the accelerator pedal position A has decreased to approximately 0 (for example, approximately 0 to 3%), and discontinues the maintenance control if it determines that the accelerator pedal position A has become approximately 0. That is, the maintenance control is also discontinued when the driver simply places his or her foot on the accelerator pedal but does not depress the accelerator. In this case, while the maintenance control is discontinued (time points t7 to t9), the target value Ga of the intake air amount can be increased up to the limit value GaL corresponding to the most recent increase in engine water temperature. Furthermore, when the maintenance control is subsequently resumed (time point t9), it can perform the maintenance control at the target value Ga (t9) of the intake air amount corresponding to the most recent increase in engine water temperature. This makes it possible to satisfy, to the maximum extent possible, the torque demand corresponding to the driver's accelerator depression amount (accelerator opening degree A) according to the latest increased engine water temperature.

[0037] In the example of Figure 6, the accelerator is depressed at time t10 and accelerator opening A is maintained constant. Then, at time t12, the accelerator is released from the constant accelerator opening A state, causing the accelerator opening A to decrease. Thereafter, at time t13, the accelerator opening A is maintained constant again. In this case, at time t11, the target value Ga of the intake air amount reaches the limit value GaL, and if it is determined that the accelerator opening A is being maintained constant, maintenance control is initiated, and the target value Ga of the intake air amount is maintained at the target value Ga(t11) at time t11 when it reached the limit value GaL. Thereafter, the accelerator is released at time t12, and if it is determined that the accelerator opening A is not being maintained constant, maintenance control is stopped, and the target value Ga of the intake air amount is calculated so that it does not exceed the limit value GaL. Thereafter, the accelerator is depressed at time t13, and at time t14 the target value Ga of the intake air volume reaches the limit value GaL. When it is determined that the accelerator opening A is maintained constant, maintenance control is initiated and the target value Ga(t14) at time t14 when the limit value GaL is reached is maintained.

[0038] In this way, while the intake control unit 25 is performing the maintenance control (time points t11 to t12), it determines whether the change amount |ΔA| in the accelerator pedal position A is equal to or less than the threshold value α. If it determines that the accelerator pedal position A has decreased and the change amount |ΔA| has exceeded the threshold value α (time point t12), it stops the maintenance control. It also determines whether the accelerator pedal position A has decreased to approximately 0, and if it determines that the accelerator pedal position A has become approximately 0, it stops the maintenance control. In this case, while the maintenance control is stopped (time points t12 to t14), the target value Ga of the intake air amount can be increased up to the limit value GaL corresponding to the most recent increase in engine water temperature. Furthermore, when the maintenance control is subsequently resumed (time point t14), it can perform the maintenance control at the target value Ga (t14) of the intake air amount corresponding to the most recent increase in engine water temperature. This allows the torque request corresponding to the driver's accelerator depression amount (accelerator pedal position A) to be satisfied to the maximum extent possible according to the most recent increase in engine water temperature.

[0039] As the threshold value α of the change amount |ΔA| of the accelerator pedal position A, a start threshold value α for starting the maintenance control when the accelerator pedal position A is maintained substantially constant, and a stop threshold value α for stopping the maintenance control when the accelerator pedal position A increases or decreases, may be separately set. The start threshold value α and the stop threshold value α may be different values ​​or the same value. Also, an increase stop threshold value α for stopping the maintenance control when the accelerator pedal position A increases as the accelerator pedal is depressed, and a decrease stop threshold value α for stopping the maintenance control when the accelerator pedal position A decreases as the accelerator pedal is released, may be separately set. The increase stop threshold value α and the decrease stop threshold value α may be different values ​​or the same value.

[0040] 7 is a flowchart showing an example of processing executed by the ECU 20. The processing shown in this flowchart starts when the vehicle is started and the ECU 20 is started, and is repeated at predetermined time intervals. As shown in FIG. 7, first, in step S1, it is determined whether or not maintenance control is being performed. If maintenance control is not being performed, the result in step S1 is affirmative, and the process proceeds to step S2. If maintenance control is being performed, the result in step S1 is negative, and the process proceeds to step S7.

[0041] In step S2, it is determined whether the target value Ga of the intake air amount is equal to or greater than the limit value GaL. If the target value Ga has reached the limit value GaL, the result in step S2 is affirmative, and the process proceeds to step S3. If the target value Ga has not reached the limit value GaL, the result in step S2 is negative, and the process ends without limiting the target value Ga.

[0042] In step S3, it is determined whether the amount of change |ΔA| in accelerator opening A is equal to or less than threshold value α. If accelerator opening A is not maintained substantially constant, the result in step S3 is negative, the process proceeds to step S4, where the target value Ga of the intake air amount is limited to the limit value GaL corresponding to the most recent increase in engine water temperature, and the process ends. If accelerator opening A is maintained substantially constant, the result in step S3 is positive, the process proceeds to steps S5 and S6, where maintenance control is started and the target value Ga of the intake air amount is maintained (limited) to the target value Ga(t) at the time t when the limit value GaL is reached, and the process ends.

[0043] In step S7, it is determined whether the amount of change |ΔA| in accelerator opening A is greater than threshold value α or whether accelerator opening A is approximately 0. If accelerator opening A is maintained approximately constant and is not approximately 0, the result in step S7 is negative, the process proceeds to step S6, where the target value Ga of the intake amount is maintained (limited) to the target value Ga(t) at the time t when the limit value GaL is reached, and the process ends. If accelerator opening A is not maintained approximately constant or if accelerator opening A has become approximately 0, the result in step S7 is positive, the process proceeds to step S8, where the maintenance control is stopped, and the process returns to step S1.

[0044] As a result, even when the engine water temperature is relatively low, such as immediately after engine start, the intake air amount is not limited until the target value Ga reaches the limit value GaL, and the torque requirement corresponding to the driver's accelerator depression amount (accelerator opening degree A) is satisfied (NO in S2). Furthermore, even when the target value Ga reaches the limit value GaL and the intake air amount is limited, the limit value GaL increases as the engine water temperature rises, so the torque requirement can be satisfied to the maximum extent possible according to the latest increased engine water temperature (S4). Furthermore, when the accelerator opening degree A is maintained constant, the intake air amount is maintained constant, so acceleration against the driver's intention can be prevented (S5, S6).

[0045] According to the embodiment of the present invention, the following advantageous effects can be achieved. (1) The device 100 includes a correction coefficient calculation unit 28 that calculates a correction coefficient K for increasing a reference injection amount Q0 of fuel injected into a combustion chamber 5 of the engine 1, the correction coefficient K being calculated according to the operating state of the engine 1 over an increase correction period from the start of engine startup of the engine 1; a limit value calculation unit 29 that calculates a limit value GaL of the intake air amount of the engine 1 over the increase correction period; and an intake control unit 25 that calculates a target value Ga of the intake air amount so that the target value Ga does not exceed the limit value GaL and controls the intake air amount based on the calculated target value Ga (FIGS. 1 and 2). The correction coefficient calculation unit 28 calculates the correction coefficient K so that it gradually decreases as the combustion cycle of the engine 1 progresses (FIGS. 3 to 6). The limit value calculation unit 29 calculates the limit value GaL so that it gradually increases as the correction coefficient K decreases (FIGS. 3 to 6). This makes it possible to suppress misfires during the increase correction period without excessively restricting output.

[0046] (2) The engine 1 is mounted on a vehicle. The intake control unit 25 calculates a target value Ga according to an accelerator opening A of the vehicle. When the target value Ga reaches a limit value GaL, the intake control unit 25 determines whether the amount of change |ΔA| in the accelerator opening A is equal to or less than a threshold value α (start threshold value α), and if it determines that the amount of change |ΔA| is equal to or less than the threshold value α (start threshold value α), it starts maintenance control to maintain the target value Ga at the target value Ga(t) at the time t when the limit value GaL is reached (FIGS. 4 to 6). As a result, even if the output limitation is relaxed and the intake amount limit value GaL increases, the intake amount is maintained constant as long as the accelerator opening A is maintained approximately constant, making it possible to prevent acceleration against the driver's intention.

[0047] (3) After starting the maintenance control, the intake control unit 25 determines whether the accelerator pedal position A increases and the change |ΔA| exceeds the threshold α (the stop threshold for increasing the throttle position α). If it determines that the change |ΔA| exceeds the threshold α (the stop threshold for increasing the throttle position α), it stops the maintenance control and calculates the target value Ga according to the accelerator pedal position A (FIG. 5). Furthermore, after starting the maintenance control, the intake control unit 25 determines whether the accelerator pedal position A decreases and the change |ΔA| exceeds the threshold α (the stop threshold for decreasing the throttle position α) or the accelerator pedal position A becomes substantially zero. If it determines that the change |ΔA| exceeds the threshold α (the stop threshold for decreasing the throttle position α) or the accelerator pedal position A becomes substantially zero, it stops the maintenance control and calculates the target value Ga according to the accelerator pedal position A (FIG. 6). In this case, when the maintenance control is stopped and then resumed, the torque request corresponding to the accelerator pedal position A can be satisfied to the maximum extent possible according to the latest relaxed output limit.

[0048] In the above embodiment, an example was described in which the device 100 is applied to an engine 1 mounted on a vehicle supplied with alcohol-containing fuel, but the internal combustion engine is not limited to this and may be an internal combustion engine mounted on a vehicle (FFV (Flexible-Fuel Vehicle)) supplied with either gasoline fuel or alcohol-containing fuel, or an internal combustion engine mounted on a vehicle (gasoline vehicle) supplied with only gasoline fuel.

[0049] The above description is merely an example, and the present invention is not limited to the above-described embodiment and modifications as long as the features of the present invention are not impaired. One or more of the above-described embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other. [Explanation of symbols]

[0050] 1 engine, 2a cylinder, 3 piston, 5 combustion chamber, 14 throttle valve, 16 spark plug, 17 injector, 20 electronic control unit (ECU), 21 crank angle sensor, 22 accelerator opening sensor, 23 water temperature sensor, 24 intake amount sensor, 25 intake control unit, 26 ignition control unit, 27 injection control unit, 28 correction coefficient calculation unit, 29 limit value calculation unit, 100 control device (device) of internal combustion engine

Claims

1. a correction coefficient calculation unit that calculates a correction coefficient for increasing a reference injection amount of fuel injected into a combustion chamber of the internal combustion engine, the correction coefficient being calculated in accordance with an operating state of the internal combustion engine over a predetermined period from the start of startup of the internal combustion engine; a limit value calculation unit that calculates a limit value of an intake air amount of the internal combustion engine over the predetermined period; an intake control unit that calculates a target value of the intake air amount so that the intake air amount does not exceed the limit value and controls the intake air amount based on the calculated target value, the correction coefficient calculation unit calculates the correction coefficient so that it gradually decreases as the combustion cycle of the internal combustion engine progresses; The control device for an internal combustion engine, wherein the limit value calculation unit calculates the limit value so that the limit value gradually increases as the correction coefficient decreases.

2. 2. The control device for an internal combustion engine according to claim 1, The internal combustion engine is mounted on a vehicle, The control device for an internal combustion engine, wherein the intake control unit calculates the target value in accordance with an accelerator opening of the vehicle.

3. 3. The control device for an internal combustion engine according to claim 2, A control device for an internal combustion engine, characterized in that when the target value reaches the limit value, the intake control unit determines whether the change in the accelerator opening is less than or equal to a start threshold, and when it determines that the change is less than or equal to the start threshold, starts maintenance control to maintain the target value at the value at which the target value reached the limit value.

4. 4. The control device for an internal combustion engine according to claim 3, A control device for an internal combustion engine, characterized in that, after starting the maintenance control, the intake control unit determines whether the accelerator opening increases and the amount of change exceeds the increase-time stop threshold, and if it determines that the amount of change has exceeded the increase-time stop threshold, it stops the maintenance control and calculates the target value according to the accelerator opening.

5. 5. The control device for an internal combustion engine according to claim 3 or 4, A control device for an internal combustion engine, characterized in that, after starting the maintenance control, the intake control unit determines whether the accelerator opening has decreased and the amount of change has exceeded a stop threshold when decreasing, or whether the accelerator opening has become approximately 0, and if it determines that the amount of change has exceeded the stop threshold when decreasing, or the accelerator opening has become approximately 0, it stops the maintenance control and calculates the target value according to the accelerator opening.

6. 2. The control device for an internal combustion engine according to claim 1, 10. A control device for an internal combustion engine, wherein the fuel is an alcohol-containing fuel that contains alcohol.

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