Control device for internal combustion engines

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 Art

[0002] In recent years, research and development on the control of internal combustion engines that contribute to emission improvement have been conducted in order to enable more people to access affordable, reliable, sustainable, and advanced energy. As this type of technology, a device that conventionally controls fuel injection immediately after starting an internal combustion engine has been known (see, for example, Patent Document 1). In the device described in Patent Document 1, when there is a load fluctuation immediately after starting the internal combustion engine and within the prohibited period of acceleration increase in the idle state, the prohibited period is changed to perform acceleration increase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when performing an increment correction of the fuel injection amount in response to requirements such as load fluctuations as in the device described in Patent Document 1 above, the end of fuel injection (EOI (End Of Injection)) shifts to the retard side, and a part of the injected fuel may not be sufficiently vaporized by the ignition timing, leading to the risk of misfire.

Means for Solving the Problems

[0005] [[ID=A1]] [[ID=X2]]A control device for an internal combustion engine according to one aspect of the present invention is spark ignitionA correction coefficient calculation unit calculates a correction coefficient to increase the standard fuel injection amount injected into the combustion chamber of the internal combustion engine, calculated according to the operating state of the internal combustion engine, over a predetermined period from the start of the internal combustion engine; a limit value calculation unit calculates a limit value for the intake volume of the internal combustion engine over a predetermined period; and a target value for the intake volume is calculated so as not to exceed the limit value, and based on the calculated target value... Do not exceed the limit The system includes an intake control unit that controls the intake air volume. The correction coefficient calculation unit calculates a correction coefficient that gradually decreases as the combustion cycle of the internal combustion engine progresses. The limit value calculation unit calculates a limit value that gradually increases as the correction coefficient decreases. [Effects of the Invention]

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

[0007] [Figure 1] A schematic diagram showing an example of the main components 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] A schematic block diagram showing 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] This figure illustrates an example of a limit value calculated by the limit value calculation unit in Figure 2 when the accelerator opening is increasing. [Figure 4] A diagram similar to Figure 3, showing the case when the accelerator opening is constant. [Figure 5] A diagram similar to Figure 3, showing the situation when the accelerator is pressed down from a state where the accelerator opening is constant. [Figure 6] A diagram similar to Figure 3, showing the situation when the accelerator is released from a state where the accelerator opening is constant. [Figure 7] A flowchart showing an example of the process performed by the ECU in Figure 2. [Modes for carrying out the invention]

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

[0009] Figure 1 is a schematic diagram showing an example of the main components of an engine 1 to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. 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 in one combustion cycle: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Engine 1 has multiple cylinders, such as four cylinders, but Figure 1 shows the configuration of a single cylinder. Note that the configuration of each cylinder is identical to that of the others.

[0010] As shown in Figure 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 the cylinder head 4. The piston 3 is connected to the 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. The combustion chamber 5 is connected to an intake passage 10 via the intake port 8, and to an exhaust passage 11 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 configured, for example, as a butterfly valve, and the amount of intake air into the combustion chamber 5 is adjusted by the throttle valve 14. The intake valve 12 and the exhaust valve 13 are opened and closed by a valve train 15.

[0012] The cylinder head 4 is fitted with a spark plug 16 and a direct-injection injector 17, each facing the combustion chamber 5. The spark 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 positioned near the intake valve 12 and is driven by electrical energy to inject fuel. More specifically, the injector 17 is supplied with high-pressure fuel from the fuel tank via a fuel pump. The injector 17 atomizes the fuel into fine particles and injects the fuel into the combustion chamber 5 at a predetermined timing, diagonally downward. Note that the position of the injector 17 is not limited to this, and it can also be positioned, for example, near the spark plug 16.

[0014] The valve train 15 includes an intake camshaft 18 and an exhaust camshaft 19. The intake camshaft 18 has an intake cam 18a that corresponds to each cylinder (cylinder 2a), and the exhaust camshaft 19 has an exhaust cam 19a that corresponds 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 the intake cam 18a via an intake rocker arm (not shown) due to the rotation of the intake camshaft 18. The exhaust valve 13 opens and closes at a predetermined timing according to the profile of the exhaust cam 19a via an exhaust rocker arm (not shown) due to the rotation of the exhaust camshaft 19.

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

[0017] The ECU 20 is configured to include a computer having a processor such as a CPU, a memory 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 configurations, 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] The crank angle sensor 21 is provided on the crankshaft 7 of Figure 1 and is configured to output a pulse signal as the crankshaft 7 rotates. The ECU 20 specifies the rotation angle (crank angle) of the crankshaft 7 based on the piston 3's top dead center TDC position at the start of the intake stroke based on the pulse signal from the crank angle sensor 21, and calculates the engine speed.

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

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

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

[0022] The intake control unit 25 calculates a target intake air volume Ga and a target throttle opening for the engine 1 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 predetermined characteristic based 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 air volume detected by the intake air volume sensor 24, and outputs a control signal to the injector 17 to inject the target injection amount at a predetermined timing. Fuel is injected in areas other than predetermined injection prohibition areas near the intake top dead center (TDC) at the start of the intake stroke (crank angle range of 0° to 180°) and the compression top dead center (TDC) at the end of the compression stroke (crank angle range of 180° to 360°), i.e., in areas where the piston crown is away from the injector 17 (injectionable area). The injection prohibition area is set, for example, to be part or almost the entire first half of the intake stroke and part or almost the entire second half of the compression stroke. More specifically, the injection prohibition area 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 no-injection region becomes during the intake stroke (the end of the injection no-injection region shifts towards the advance ignition timing side), and the wider the injection no-injection region becomes during the compression stroke (the start of the injection no-injection region shifts towards the advance ignition timing side).

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

[0026] The correction coefficient K is a value of "1" or greater that is multiplied by the standard injection amount Q0 to perform an increase correction to compensate for the fuel that does not contribute to combustion, and is predetermined according to the operating conditions of engine 1 at startup (e.g., engine water temperature). More specifically, the lower the engine water temperature, the greater 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 greater the proportion of fuel that does not contribute to combustion, so the correction coefficient K is calculated to decrease. The correction coefficient K may also be calculated to decrease as the in-cylinder temperature estimated based on the operating conditions of engine 1 increases, or as the total amount of work done from the start of startup increases.

[0027] As the engine water temperature gradually rises with the progress of the combustion cycle of engine 1, the correction coefficient K is calculated to gradually decrease with the progress of the combustion cycle of engine 1. After the enrichment correction period has elapsed, the in-cylinder temperature rises to a warm-up state, the engine water temperature reaches a predetermined temperature for in-cylinder warm-up, the correction coefficient K becomes "1", and the enrichment correction ends. The enrichment correction period is the period from the start of engine 1 to the point when the in-cylinder warm-up state is reached, and the length of the enrichment correction period varies depending on the engine water temperature (in-cylinder temperature) at the start of startup and the operating state of engine 1 after startup (load and total work done from the start of startup).

[0028] However, performing such a fuel injection amount increase correction may cause the fuel injection end time (EOI) to be delayed, potentially entering the injection no-go region. In this case, some of the injected fuel may not vaporize sufficiently by the ignition timing, preventing the formation of a mixture with the appropriate air-fuel ratio and potentially leading to misfire. In particular, when using alcohol-containing fuels, which have a lower calorific value than gasoline, the standard injection amount Q0 becomes even larger, further increasing the likelihood that the injection end EOI will enter the injection no-go region during the increase correction. Therefore, in this embodiment, the device 100 is configured as follows to suppress misfires by limiting the intake amount of engine 1 (i.e., limiting the output) during the increase correction.

[0029] The limit value calculation unit 29 calculates a limit value GaL for the intake volume of engine 1, and the intake control unit 25 calculates a target value Ga for the intake volume so as not to exceed the limit value GaL, and controls the intake volume 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, which is calculated in accordance with the operating state (engine water temperature) of engine 1 at the start of startup. In this case, the intake volume of engine 1 is limited to a certain limit value GaL or less throughout the enrichment correction period, and the output of engine 1 is limited, so misfires during the enrichment correction period can be reliably suppressed.

[0030] However, if the intake air volume during the enrichment correction period is limited to a certain limit value GaL or less, excessive power limiting will occur if the engine water temperature rises and the fuel injection amount correction coefficient K decreases. Such excessive power limiting may not satisfy the demands of vehicle users, such as driving at high speed immediately after starting the engine 1, and may impair the marketability of the vehicle. Therefore, the limit value calculation unit 29 calculates the limit value GaL in accordance with the actual correction coefficient K calculated in relation to the operating state of the engine 1 (engine water temperature), so as the correction coefficient K decreases, the limit value GaL gradually increases.

[0031] Figures 3 to 6 illustrate an example of a limit value GaL calculated by the limit value calculation unit 29. As shown in Figures 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 (engine water temperature) of the engine 1 based on predetermined characteristics. The limit value calculation unit 29 calculates the intake air limit value GaL according to the correction coefficient K calculated according to the engine water temperature. Subsequently, as the number of times top dead center (TDC) has passed (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 intake air amount Ga so as not to 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 response to the operating conditions of engine 1, such as engine water temperature, misfires during the enrichment correction period can be reliably suppressed without excessive power limiting. Specifically, as the combustion cycle of engine 1 progresses and the engine water temperature rises, the correction coefficient K decreases, creating a margin between the end of fuel injection (EOI) and the start of the injection prohibition region, the limit value GaL is increased by that amount. This makes it possible to relax power limiting while reliably suppressing misfires during the enrichment correction period.

[0033] In the example in Figure 3, at time t1 the accelerator is pressed and the accelerator opening A increases. When the target intake air volume Ga reaches the limit value GaL at time t2, the intake control unit 25 determines whether the change in accelerator opening A |ΔA| is less than or equal to the threshold α (for example, about 3-5%). That is, it determines whether the accelerator opening A is maintained at approximately a constant level. If the intake control unit 25 determines at time t2 that the change in accelerator opening A |ΔA| is not less than or equal to the threshold α, it calculates the target intake air volume Ga so as not to exceed the limit value GaL, i.e., to increase in line with the limit value GaL. When the accelerator opening A is increasing, the driver intends to accelerate. As the target intake air volume Ga increases in accordance with the relaxation of the output limit (increase in the limit value GaL) due to the rise in engine water temperature, the torque requirement corresponding to the driver's accelerator pedal depression (accelerator opening A) can be met even when the engine water temperature is low, such as immediately after engine start-up.

[0034] In the example shown in Figure 4, the accelerator is pressed at time t3, and the accelerator opening A is kept constant. When the target intake air volume Ga reaches the limit value GaL at time t4, the intake control unit 25 determines whether the change in accelerator opening A |ΔA| is less than or equal to the threshold α, and determines whether the accelerator opening A is kept approximately constant. If the intake control unit 25 determines that the change in accelerator opening A |ΔA| is less than or equal to the threshold α at time t4, it starts maintenance control to maintain the target intake air volume Ga at the target value Ga(t4) at time t4 when the limit value GaL was reached. When the accelerator opening A is kept constant, the driver intends to drive at a constant speed. Even if the engine water temperature rises, the output limit is relaxed, and the intake air volume limit value GaL increases, when the accelerator opening A is kept constant, maintaining the target intake air volume Ga constant prevents acceleration contrary to the driver's intention.

[0035] In the example in Figure 5, at time t5 the accelerator is pressed and the accelerator opening A is maintained at a constant level. Then, at time t7 the accelerator is pressed again from a state where the accelerator opening A is constant, causing the accelerator opening A to increase. Subsequently, at time t9 the accelerator opening A is maintained at a constant level again. In this case, at time t6, if it is determined that the target intake air volume Ga has reached the limit value GaL and the accelerator opening A is maintained at a constant level, maintenance control is initiated, and the target intake air volume Ga is maintained at the target value Ga(t6) at time t6, where it reached the limit value GaL. Subsequently, at time t7 the accelerator is pressed and it is determined that the accelerator opening A is not maintained at a constant level, maintenance control is terminated, and the target intake air volume Ga is calculated so as not to exceed the limit value GaL. More specifically, at time t8, if the target intake air volume Ga reaches the limit value GaL, the target value Ga is calculated to increase to match the limit value GaL. Subsequently, if it is determined that the accelerator opening A is maintained at a constant level at time t9, maintenance control is initiated, and the target intake air volume Ga is maintained at the target value Ga(t9) at time t9, when the limit value GaL is reached.

[0036] Thus, when the intake control unit 25 is performing maintenance control (times t6 to t7), it determines whether the change in accelerator opening A |ΔA| is less than or equal to the threshold α. If it determines that the accelerator opening A has increased and the change in |ΔA| has exceeded the threshold α (time t7), it stops the maintenance control. Furthermore, when the intake control unit 25 is performing maintenance control, it also determines whether the accelerator opening A has decreased to approximately 0 (for example, around 0-3%). If it determines that the accelerator opening A has become approximately 0, it also stops the maintenance control. In other words, even if the driver is only resting their foot on the accelerator pedal and not pressing the accelerator, the maintenance control is stopped. In this case, while the maintenance control is stopped (times t7 to t9), the target intake volume Ga can be increased up to the limit value GaL corresponding to the most recent rise in engine water temperature. Then, when the maintenance control is resumed (time t9), maintenance control can be performed with the target intake volume Ga(t9) corresponding to the most recent rise in engine water temperature. This allows the system to meet the torque requirements corresponding to the driver's accelerator pedal input (accelerator opening A) to the maximum extent possible, depending on the latest elevated engine water temperature.

[0037] In the example in Figure 6, at time t10 the accelerator is pressed and the accelerator opening A is maintained at a constant level. Then, at time t12 the accelerator is released from the state where the accelerator opening A is constant, and the accelerator opening A decreases. Subsequently, at time t13 the accelerator opening A is maintained at a constant level again. In this case, at time t11 the target intake air volume Ga reaches the limit value GaL, and if it is determined that the accelerator opening A is maintained at a constant level, maintenance control is started, and the target intake air volume Ga is maintained at the target value Ga(t11) at time t11 when it reached the limit value GaL. Subsequently, at time t12 the accelerator is released and if it is determined that the accelerator opening A is not maintained at a constant level, maintenance control is stopped, and the target intake air volume Ga is calculated so as not to exceed the limit value GaL. Subsequently, if the accelerator is pressed at time t13, and the target intake air volume Ga reaches the limit value GaL at time t14, and it is determined that the accelerator opening A is being maintained at a constant level, maintenance control is initiated, and the target value Ga(t14) at time t14, which reached the limit value GaL, is maintained.

[0038] Thus, when the intake control unit 25 is performing maintenance control (times t11-t12), it determines whether the change in accelerator opening A |ΔA| is less than or equal to the threshold α. If it determines that the accelerator opening A has decreased and the change in |ΔA| has exceeded the threshold α (time t12), it stops the maintenance control. It also determines whether the accelerator opening A has decreased to approximately 0, and if it determines that the accelerator opening A has become approximately 0, it also stops the maintenance control. In this case, while the maintenance control is stopped (times t12-t14), the target intake volume Ga can be increased up to the limit value GaL corresponding to the most recent rise in engine water temperature. After that, when the maintenance control is resumed (time t14), maintenance control can be performed with the target intake volume Ga(t14) corresponding to the most recent rise in engine water temperature. This makes it possible to satisfy the torque requirement corresponding to the driver's accelerator pedal depression (accelerator opening A) to the maximum extent possible according to the most recent rise in engine water temperature.

[0039] As thresholds α for the change in accelerator opening A |ΔA|, a start threshold α may be set separately for initiating maintenance control when the accelerator opening A is maintained at approximately a constant level, and a stop threshold α may be set separately for discontinuing maintenance control when the accelerator opening A increases or decreases. The start threshold α and the stop threshold α may be different values ​​or the same value. Furthermore, an increase-trigger stop threshold α may be set separately for discontinuing maintenance control when the accelerator is pressed and the accelerator opening A increases, and a decrease-trigger stop threshold α may be set separately for discontinuing maintenance control when the accelerator is released and the accelerator opening A decreases. The increase-trigger stop threshold α and the decrease-trigger stop threshold α may be different values ​​or the same value.

[0040] Figure 7 is a flowchart showing an example of a process performed by the ECU20. The process shown in this flowchart starts when the vehicle is started and the ECU20 is started, and is repeated at predetermined intervals. As shown in Figure 7, first in step S1, it is determined whether or not maintenance control is being performed. If maintenance control is not being performed, step S1 is affirmed, and the process proceeds to step S2. If maintenance control is being performed, step S1 is denied, and the process proceeds to step S7.

[0041] In step S2, it is determined whether the target intake volume Ga is greater than or equal to the limit value GaL. If the target volume Ga has reached the limit value GaL, step S2 is affirmed and the process proceeds to step S3. If the target volume Ga has not reached the limit value GaL, step S2 is denied and the process ends without limiting the target volume Ga.

[0042] In step S3, it is determined whether the change in accelerator opening A |ΔA| is less than or equal to the threshold α. If the accelerator opening A is not maintained at approximately constant, step S3 is rejected, and the process proceeds to step S4, where the target intake air volume Ga is limited to the limit value GaL corresponding to the most recent rise in engine water temperature, and the process ends. If the accelerator opening A is maintained at approximately constant, step S3 is affirmed, and the process proceeds to steps S5 and S6, where maintenance control is started, and the target intake air volume Ga 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 change in accelerator opening A |ΔA| is greater than the threshold α, or whether accelerator opening A is approximately 0. If accelerator opening A is maintained at approximately a constant level and accelerator opening A is not approximately 0, step S7 is rejected, and the process proceeds to step S6, where the target intake air volume Ga is maintained (limited) to the target value Ga(t) at the point t when the limit value GaL is reached, and the process ends. If accelerator opening A is not maintained at approximately a constant level, or if accelerator opening A becomes approximately 0, step S7 is affirmed, and 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 starting the engine, the intake air volume is not restricted until the target value Ga reaches the limit value GaL, and the torque requirement corresponding to the driver's accelerator pedal depression (accelerator opening A) is met (NO in S2). Furthermore, even when the target value Ga reaches the limit value GaL and the intake air volume is restricted, the limit value GaL increases with the rise in engine water temperature, so the torque requirement can be met to the maximum extent according to the latest rise in engine water temperature (S4). In addition, when the accelerator opening A is kept constant, the intake air volume is kept constant, so acceleration contrary to the driver's intention can be prevented (S5, S6).

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

[0046] (2) Engine 1 is mounted in the vehicle. The intake control unit 25 calculates a target value Ga according to the accelerator opening A of the vehicle. When the target value Ga reaches the limit value GaL, the intake control unit 25 determines whether the change amount |ΔA| of the accelerator opening A is less than or equal to the threshold α (start threshold α). If it determines that the change amount |ΔA| is less than or equal to the threshold α (start threshold α), it starts maintenance control to maintain the target value Ga(t) at the time t when the limit value GaL is reached (Figures 4 to 6). As a result, even if the output limit is relaxed and the intake volume limit value GaL increases, the intake volume is kept constant when the accelerator opening A is kept approximately constant, and acceleration contrary to the driver's intention can be prevented.

[0047] (3) After starting maintenance control, the intake control unit 25 determines whether the accelerator opening A has increased and the amount of change |ΔA| has exceeded the threshold α (increase stop threshold α). If it determines that the amount of change |ΔA| has exceeded the threshold α (increase stop threshold α), it stops maintenance control and calculates a target value Ga according to the accelerator opening A (Figure 5). Also, after starting maintenance control, the intake control unit 25 determines whether the accelerator opening A has decreased and the amount of change |ΔA| has exceeded the threshold α (decrease stop threshold α), or whether the accelerator opening A has become approximately 0. If it determines that the amount of change |ΔA| has exceeded the threshold α (decrease stop threshold α), or that the accelerator opening A has become approximately 0, it stops maintenance control and calculates a target value Ga according to the accelerator opening A (Figure 6). In this case, when maintenance control is stopped and then restarted, the torque requirement corresponding to the accelerator opening A can be met to the maximum extent possible according to the latest relaxed power 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. However, the internal combustion engine is not limited to such an example, and may also be an internal combustion engine mounted on a vehicle supplied with either gasoline fuel or alcohol-containing fuel (FFV (Flexible-Fuel Vehicle)), or an internal combustion engine mounted on a vehicle supplied with only gasoline fuel (gasoline vehicle).

[0049] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications 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 Position Sensor, 23 Water Temperature Sensor, 24 Intake Air Volume 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 for Internal Combustion Engine

Claims

1. A correction coefficient calculation unit that calculates a correction coefficient for increasing the standard injection amount of fuel injected into the combustion chamber of a spark-ignition internal combustion engine, calculated according to the operating state of the internal combustion engine, over a predetermined period from the start of the internal combustion engine; A limit value calculation unit that calculates a limit value for the intake amount of the internal combustion engine over the predetermined period, The system includes an intake control unit that calculates a target value for the intake volume so as not to exceed the limit value, and controls the intake volume based on the calculated target value so as not to exceed the limit 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 is characterized in that the limit value calculation unit calculates the limit value such that it gradually increases as the correction coefficient decreases.

2. In the control device for an internal combustion engine according to claim 1, The aforementioned internal combustion engine is mounted in the vehicle, The control device for an internal combustion engine is characterized in that the intake control unit calculates the target value according to the accelerator opening of the vehicle.

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

4. In the control device for an internal combustion engine according to claim 3, The control device for an internal combustion engine is characterized in that, after starting the maintenance control, the intake control unit determines whether the accelerator opening has increased and whether the amount of change has exceeded the threshold for stopping when it increases, and if it determines that the amount of change has exceeded the threshold for stopping when it increases, it stops the maintenance control and calculates the target value according to the accelerator opening.

5. In the control device for an internal combustion engine according to claim 3 or 4, The control device for an internal combustion engine is 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 the threshold for stopping when the change occurs, or whether the accelerator opening has become approximately zero, and if it determines that the amount of change has exceeded the threshold for stopping when the change occurs, or that the accelerator opening has become approximately zero, it stops the maintenance control and calculates the target value according to the accelerator opening.

6. In the control device for an internal combustion engine according to claim 1, A control device for an internal combustion engine, characterized in that the fuel is an alcohol-containing fuel containing alcohol.

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