Control device for internal combustion engine

Abstract

To quickly solve a problem relating to combustion abnormality when the abnormality occurs in a certain cylinder of an internal combustion engine and to suppress unreasonable reduction of engine torque.SOLUTION: A control device 0 of an internal combustion engine for controlling the internal combustion engine having a plurality of cylinders 1 and burning a fuel injected from an injector 11 in each of the cylinders 1, performs correction to temporarily stop the injection of the fuel to the cylinder 1 when combustion abnormality is detected in the certain cylinder 1 and to increase engine torque output by the other cylinders 1 at this time more than before. More concretely, the injection of the fuel to the cylinder 1 is temporarily stopped, and at least one of an intake valve timing of the other cylinder 1 at this time, a fuel injection amount to the other cylinder 1, and an ignition timing of the other cylinder 1 is corrected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to control of an internal combustion engine mounted on a vehicle or the like. [Background technology]

[0002] Reducing carbon dioxide emissions, which have a greenhouse effect, is recognized as a global issue. Recently, attempts have been made to use hydrogen as fuel instead of carbon-containing fossil fuels for internal combustion engines, which are used as various power sources.

[0003] Hydrogen is a gas at room temperature and pressure. Therefore, a hydrogen fuel tank can store ultra-high pressure hydrogen of up to approximately 70 MPa. The hydrogen discharged from this fuel tank is reduced and adjusted to a predetermined pressure of approximately 10 MPa to 20 MPa via a pressure regulator before being supplied to an injector. The fuel injected from the injector is then combusted in the cylinder, rotating the crankshaft, which is the output shaft of the internal combustion engine (see, for example, the following patent document).

[0004] The basic structure of a four-stroke internal combustion engine that uses hydrogen fuel is not much different from existing engines that use gasoline or diesel. However, compared to gasoline or diesel, hydrogen has smaller molecules, is more susceptible to leakage, and has a wider range of flammable concentrations. If combustion in the cylinder becomes unstable and misfires occur, leaving unburned fuel, there is a concern that this could leak into the intake passage, causing a backfire, or into the exhaust passage, causing an afterfire. Alternatively, if the temperature inside the combustion chamber of the cylinder is significantly high, there is a risk of knocking or pre-ignition, in which the fuel self-ignites at a timing that is different from the desired timing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-105088 Summary of the Invention [Problem to be solved by the invention]

[0006] When misfire occurs in a cylinder, or when knocking or pre-ignition occurs, it is desirable to temporarily suspend fuel injection and ignition combustion for that cylinder and perform scavenging by circulating air that does not contain fuel components. This dilutes and removes unburned fuel components remaining in the combustion chamber of that cylinder, or cools the combustion chamber of that cylinder to lower its temperature.

[0007] However, by suspending fuel injection to a particular cylinder, the total engine torque output by the internal combustion engine may decrease, which may cause fluctuations in engine rotation.

[0008] The present invention was developed with the above points in mind, and its intended purpose is to quickly resolve any problems related to combustion abnormalities that occur in a particular cylinder, and to prevent an unduly large drop in engine torque. [Means for solving the problem]

[0009] The present invention controls an internal combustion engine having a plurality of cylinders, in which fuel injected from an injector is burned in each cylinder. When an abnormality in combustion is detected in a certain cylinder, fuel injection to that cylinder is temporarily stopped, and a correction is made to increase the engine torque output by other cylinders at the same time compared to before. In the correction when an abnormality in combustion is detected in a certain cylinder, fuel injection to that cylinder is temporarily stopped, and the intake valve timing of other cylinders at the same time is advanced from before, the throttle valve opening is widened from before, the fuel injection amount to other cylinders is increased from before, or the ignition timing of other cylinders is advanced from before, thereby suppressing an unduly lowered engine torque of the internal combustion engine without increasing the engine speed. The control device for an internal combustion engine is configured. Here, the abnormal combustion includes at least one of unstable combustion or misfire, knocking, pre-ignition, and the like.

[0010] More specifically It is also preferable that when a combustion abnormality is detected in a certain cylinder, it is determined whether the abnormality is a misfire or abnormal combustion other than a misfire, and then the number of cycles for executing the correction when a combustion abnormality is detected in a certain cylinder is made different depending on whether the abnormality is a misfire or abnormal combustion other than a misfire. . [Effects of the Invention]

[0011] According to the present invention, when a combustion abnormality occurs in a cylinder of an internal combustion engine, the problem related to the abnormality can be quickly resolved and an unduly low drop in engine torque can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle internal combustion engine and a control device according to an embodiment of the present invention; [Figure 2] 3 is a flowchart showing an example of a procedure of a process executed by the control device for the internal combustion engine according to a program of the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine according to this embodiment. The internal combustion engine according to this embodiment is a four-stroke, direct-injection, spark-ignition engine having a plurality of cylinders 1 (one of which is shown in FIG. 1). Each cylinder 1 is provided with an injector 11 for injecting fuel directly into the combustion chamber of that cylinder 1. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 generates a spark discharge between a center electrode and a ground electrode when an induced voltage generated in an ignition coil is applied to it. The ignition coil is integrally housed in a coil case together with an igniter, which is a semiconductor switching element.

[0014] The internal combustion engine of this embodiment uses fuel containing hydrogen (which may be extremely high-purity hydrogen) as fuel and burns the fuel in cylinder 1. A fuel tank 16 stores ultra-high-pressure hydrogen fuel. The fuel discharged from the fuel tank 16 is delivered to the injector 11 via a fuel pipe 13, and is injected into the combustion chamber of cylinder 1 when the injector 11 opens. In this embodiment, a regulator that reduces and adjusts the pressure of the hydrogen fuel to a predetermined level is not provided on the fuel pipe 13 from the tank 16 to the injector 11. Instead, a control valve 14 that can block the flow of fuel through the fuel pipe 13 is provided. The control valve 14 serves as a safety valve and is a flow control valve that can open and close the fuel pipe 13 or increase or decrease the flow rate of fuel flowing through the fuel pipe 13.

[0015] An intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. In the intake passage 3, an air cleaner 31, an electronically controlled throttle valve 32 which is an intake throttle valve, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream.

[0016] An exhaust passage 4 for discharging exhaust gases guides exhaust gases generated as a result of fuel combustion in the cylinders 1 to the outside through the exhaust ports of each cylinder 1. An exhaust manifold 42 and an exhaust purification device 41 are arranged on this exhaust passage 4. The exhaust purification device 41 includes a three-way catalyst that promotes oxidation / reduction reactions of hydrocarbons, carbon monoxide, and nitrogen oxides, and a selective catalytic reduction device that reduces nitrogen oxides using a reducing agent such as urea water. In addition, an exhaust bypass passage 43 that bypasses the exhaust turbine 52 and a wastegate valve 44 that is a bypass valve that opens and closes the inlet of this bypass passage 43 are provided.

[0017] The exhaust turbocharger 5 is configured so that an exhaust turbine 52 and a compressor impeller 51 are coaxially connected and interlocked via a shaft 53. The turbine 52 and impeller 51 are rotationally driven using exhaust energy, and the rotational force causes the compressor to perform a pumping action, thereby pressurizing and compressing (supercharging) the intake air and sending it into the cylinder 1.

[0018] In the internal combustion engine of this embodiment, a timing chain (or belt) is wound around the crank sprocket (or pulley), intake sprocket (or pulley), and exhaust sprocket (or pulley), and this timing chain transmits engine torque from the crankshaft to the intake camshaft via the intake sprocket and to the exhaust camshaft via the exhaust sprocket. The intake camshaft drives the intake valves of each cylinder 1 to open and close, and the exhaust camshaft drives the exhaust valves of each cylinder to open and close.

[0019] Additionally, a VVT mechanism 6 is interposed between the intake sprocket and the intake camshaft. The VVT mechanism 6 variably controls the opening and closing timing of the intake valve of cylinder 1 by changing the rotational phase of the intake camshaft relative to the crankshaft. The VVT mechanism 6 may be a vane-type VVT that uses the lubricating oil (engine oil) of the internal combustion engine as its working fluid and displaces the phase angle of the camshaft relative to the cam sprocket using the lubricating oil pressure, or it may be a motor-driven VVT that displaces the phase angle of the camshaft relative to the cam sprocket using an electric motor.

[0020] Note that a similar VVT mechanism may be interposed between the exhaust sprocket and the exhaust camshaft to variably control the opening and closing timing of the exhaust valve of cylinder 1. Furthermore, the specific form of VVT mechanism 6 for changing the opening and closing timing of the intake valve and / or exhaust valve of cylinder 1 of an internal combustion engine is arbitrary and is not limited to a single one. In addition to mechanisms that advance / retard the rotational phase of the intake camshaft and / or exhaust camshaft relative to the crankshaft, mechanisms that provide multiple cams to open the intake valve and / or exhaust valve and use these cams appropriately, mechanisms that change the lever ratio of a rocker arm via an electric motor, and mechanisms that use electromagnetic solenoid valves as the intake valve and / or exhaust valve are also known, and it is permissible to select and employ one of these various mechanisms.

[0021] The electronic control unit 0 that controls the operation of the internal combustion engine in this embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, etc. The ECU 0 may be configured by connecting a plurality of ECUs or controllers so that they can communicate with each other via an electric communication line such as a CAN (Controller Area Network).

[0022] The input interface of the ECU 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal by the driver of the vehicle as the accelerator opening (in other words, the engine load rate or engine torque required for the internal combustion engine), an intake air temperature / intake air temperature sensor that detects the temperature and pressure of the intake air in the intake passage 3 (particularly, the surge tank 33 or the intake manifold 34) connected to the cylinder 1, and a pressure sensor that detects the pressure and pressure of the intake air in the intake passage 3 (particularly, the surge tank 33 or the intake manifold 34). The signals input to the exhaust passage 4 include an intake air temperature and intake pressure signal d output from a pressure sensor, a coolant temperature signal e output from a water temperature sensor that detects the coolant temperature of the internal combustion engine, a fuel temperature and fuel pressure signal f output from a fuel temperature and fuel pressure sensor 15 that detects the temperature and pressure of the hydrogen fuel in the fuel pipe 13 connected to the injector 11 (particularly downstream of the control valve 14 and immediately upstream of the injector 11), a vibration signal g output from a vibration-type knock sensor that detects the magnitude of vibration of the cylinder block that contains the cylinders 1 of the internal combustion engine, and a gas property signal h output from a sensor that detects the properties of the gas flowing through the exhaust passage 4. Sensors that detect gas properties include an O2 sensor or linear A / F sensor that measures the oxygen concentration contained in the gas, in other words the air-fuel ratio, and a hydrogen sensor that measures the hydrogen concentration contained in the gas.

[0023] The output interface of ECU0 outputs an ignition signal i to the igniter of the spark plug 12, a fuel injection signal j to the solenoid of the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the control valve 14, a valve timing control signal m to the VVT mechanism 6, and the like.

[0024] The processor of ECU0 interprets and executes programs stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine. ECU0 acquires various pieces of information a, b, c, d, e, f, g, and h required for controlling the operation of the internal combustion engine via an input interface, and based on this, determines various operating parameters such as the required fuel injection amount, fuel injection timing (including the number of fuel injections per cycle for cylinder 1), fuel injection pressure, ignition timing (including the number of spark ignitions per cycle for cylinder 1), and intake valve opening and closing timing. ECU0 applies various control signals i, j, k, l, and m corresponding to the operating parameters via an output interface.

[0025] When determining the amount of fuel to be injected from the injector 11 into cylinder 1, the ECU 0 first calculates the amount of air taken into cylinder 1 and then determines the basic amount TP of fuel injection required to achieve the target air-fuel ratio, which is appropriate for that amount of intake air. The amount of intake air is estimated based on the actually measured engine speed and intake pressure. If necessary, the estimated value can be corrected according to the intake temperature, atmospheric pressure, etc. If an air flow meter is installed in the intake passage 3, the amount of intake air can be directly measured via the air flow meter. The target air-fuel ratio can be set to the stoichiometric air-fuel ratio or close to it, or it can be set leaner than the stoichiometric air-fuel ratio.

[0026] Next, this basic injection amount TP is corrected by a feedback correction coefficient FAF corresponding to the deviation between the air-fuel ratio of the gas flowing into the catalyst 41 and its target value, and various correction coefficients K determined according to environmental conditions and other circumstances (correction coefficients FAF and K are each positive numbers that increase or decrease around 1). The required fuel injection amount TD is TD=TP×FAF×K This becomes:

[0027] In the internal combustion engine of this embodiment, no pressure regulator is provided on the fuel pipe 13 between the fuel tank 16 and the injector 11. Therefore, the pressure of the fuel immediately upstream of the injector 11 fluctuates depending on the amount of fuel currently stored in the fuel tank 16. This is because as the fuel stored in the tank 16 is consumed and reduced, the pressure inside the tank 16, and therefore the pressure of the fuel discharged from the tank 16, decreases. This means that the amount of fuel injected when the injector 11 is open for a certain unit time fluctuates from time to time.

[0028] Map data defining the relationship between the temperature and pressure of fuel supplied to the injector 11 and the amount of fuel injected from the injector 11 when the injector 11 is open for a unit time is stored in advance in the memory of the ECU 0. The effective amount of fuel injected from the injector 11 per unit time increases as the temperature of the fuel supplied to the injector 11 decreases because the density of the fuel increases, and also increases as the pressure of the fuel increases. The ECU 0 measures the current temperature and pressure of the fuel via a sensor 15 installed on the fuel pipe 13, and searches the map using the temperature and pressure as keys to determine the amount of fuel injected from the injector 11 per unit time.

[0029] Then, based on the injection amount per unit time, the ECU 0 determines the length of the valve opening time of the injector 11 that will enable the required injection amount TD of fuel to be injected. Incidentally, the injector 11 has an invalid injection time during which the injector 11 does not open or does not inject fuel even when the solenoid that drives the needle valve is energized. In step S4, the valve opening time of the injector 11 is calculated taking into account the invalid injection time. The ECU 0 energizes the fuel injection signal j to the injector 11 for the determined valve opening time, thereby opening the injector 11 and injecting fuel.

[0030] In cylinder 1 of an internal combustion engine, fuel combustion can sometimes become unstable, causing a misfire. When a misfire occurs, unburned fuel components remain in the combustion chamber of cylinder 1, which can lead to concerns that the unburned fuel components may leak into the intake passage 3 and cause a backfire, or leak into the exhaust passage 4 and cause an afterfire. Furthermore, if the temperature in the combustion chamber of cylinder 1 is significantly high, knocking or pre-ignition may occur, in which fuel self-ignites and burns at a timing that is different from the desired timing. Both of these can damage the internal combustion engine.

[0031] As shown in FIG. 2, when the ECU 0 of this embodiment detects a combustion abnormality such as misfire, knocking, pre-ignition, etc. in any cylinder 1 of the internal combustion engine (step S1), it executes a fuel cut to temporarily suspend fuel injection from the injector 11 to that cylinder 1 (step S2).

[0032] In step S1, the ECU 0 determines whether a misfire is occurring in each cylinder 1, for example, based on the output signal b of the crank angle sensor. The ECU 0 normally monitors the rotational speed of the crankshaft of the internal combustion engine by referring to the crank angle signal b. Specifically, the ECU 0 repeatedly measures the time required for the crankshaft to rotate a predetermined crank angle, typically 30° CA, by referring to the pulse train of the crank angle signal b. At the same time, the ECU 0 subtracts the previously measured required time from the currently measured required time to obtain a change in the required time for 30° CA, which is an index of the amount of decrease in the rotational speed for each 30° CA. A positive value for the change in the required time for 30° CA indicates that the rotational speed of the internal combustion engine is decreasing (deceleration), whereas a negative value indicates that the rotational speed of the internal combustion engine is increasing (acceleration). The crankshaft rotation speed per 30° CA or the time required for each 30° CA is not constant; it is fastest during the expansion stroke of each cylinder 1 and slowest midway between the expansion strokes of one cylinder 1 and the next. Even if fuel is burning normally and no misfire occurs, the time series of the time required for each 30° CA pulsates at the cycle of each cylinder 1's expansion stroke. Conversely, if a misfire occurs during the expansion stroke of cylinder 1, the crankshaft rotation does not accelerate properly, causing the crankshaft rotation speed per 30° CA to drop unduly, i.e., the time required for each 30° CA to become unduly long. ECU0 determines that a sudden drop in crankshaft rotation speed, or in other words, a misfire, has occurred when the change in the time required for each 30° CA (= current required time - previous required time) is positive and exceeds the misfire determination value. Alternatively, the time required for each 30° CA rotation may be compared with a misfire determination value, and if the time required exceeds the misfire determination value, it may be determined that a misfire has occurred.

[0033] Also, in step S1, the ECU 0 determines, based on the vibration signal g output by the knock sensor, whether knocking or pre-ignition is occurring in each cylinder 11. The ECU 0 compares the currently sampled value of the vibration signal g, which indicates the intensity of vibration of a cylinder 1 or a cylinder block of the internal combustion engine, with a knock determination value, and when the former exceeds the latter, determines that knocking or pre-ignition has occurred in that cylinder 1.

[0034] When ECU0 detects a combustion abnormality in any of the cylinders 1, it temporarily suspends fuel injection from the injector 11 for that cylinder 1 in step S2, circulates air that does not contain fuel components into that cylinder 1, and performs scavenging that does not burn fuel in the combustion chamber of that cylinder 1. As a result, even if unburned fuel components remain in the combustion chamber of that cylinder 1, they can be diluted with air and discharged to the exhaust passage 4 side, preventing the occurrence of backfire or afterfire. Alternatively, the temperature inside the combustion chamber of that cylinder 1 can be cooled and lowered to prevent repeated occurrences of knocking or pre-ignition.

[0035] However, simply pausing fuel injection and ignition combustion in the cylinder 1 may result in a drop in the total engine torque output by all cylinders 1 of the internal combustion engine, which may lead to undesirable fluctuations in engine speed. Therefore, in synchronization with the temporary suspension of fuel injection for the cylinder 1 with abnormal combustion, the ECU 0 performs correction control to increase the engine torque output by the other cylinders 1 compared to before (step S3). In step S3, for example, In order to increase the amount of intake air to the other cylinders 1 where no combustion abnormality is occurring, the opening timing of the intake valves of those other cylinders 1 is further advanced. Alternatively, the opening of the throttle valve 32 is further widened so that the amount of air taken into those other cylinders 1 increases. Increasing the amount of fuel injected from the injector 11 to other cylinders 1 where no combustion abnormalities are occurring - Further advance the spark ignition timing in other cylinders 1 where combustion abnormalities are not occurring, to bring them closer to MBT (Minimum Advance for Best Torque). At least one of the following is executed.

[0036] The correction controls in steps S2 and S3 end when it appears that the problem in the cylinder 1 where the combustion abnormality was detected has been resolved (step S4). After this, fuel injection and ignition combustion are resumed in the cylinder 1 where the combustion abnormality was detected. In addition, the intake air amount, fuel injection amount, and ignition timing of the other cylinders 1 are returned to normal control amounts. In other words, the engine torque output by the other cylinders 1, which had been increased up to that point, is reduced to a normal magnitude.

[0037] Regarding step S4, if the abnormality that has occurred in a certain cylinder 1 is a misfire (not knocking or pre-ignition), it is thought that scavenging in that cylinder 1 can be completed in one cycle (one cycle is the series of intake stroke-compression stroke-expansion stroke-exhaust stroke of one cylinder 1) or two cycles.If the abnormality that has occurred in a certain cylinder 1 is knocking or pre-ignition (not misfire), it is thought that cooling by scavenging in that cylinder 1 can be completed in a few cycles.

[0038] According to this embodiment, when a combustion abnormality occurs in a cylinder 1 of an internal combustion engine, it is possible to quickly resolve the problem related to the abnormality and suppress an unduly decrease in engine torque. Since the engine speed can be maintained without unnecessarily increasing or decreasing, there is no adverse effect on the drivability or NV (Noise and Vibration) performance of the vehicle.

[0039] Corrections that increase engine speed are not required (avoid significantly increasing engine speed as this may have a negative impact on NV performance and drivability). The present invention is not limited to the above-described embodiment. For example, although the internal combustion engine in the above embodiment is of a direct injection type, the present invention may also be applied to a port injection type internal combustion engine in which fuel is injected from an injector toward the intake port of each cylinder.

[0040] Furthermore, the method of determining whether a combustion abnormality has occurred in any cylinder is not limited to that described in the above embodiment. For example, if the internal combustion engine is equipped with sensors that measure the temperature (in-cylinder temperature) or pressure (in-cylinder pressure) inside the combustion chamber of cylinder 1, or the ion current generated inside the combustion chamber of cylinder 1 during fuel combustion, it can be determined in step S1 whether a combustion abnormality has occurred based on the changes in the in-cylinder temperature, in-cylinder pressure, or in-cylinder current.

[0041] In addition, the specific configuration of each part can be modified in various ways without departing from the spirit of the present invention. [Industrial Applicability]

[0042] The present invention can be applied to an internal combustion engine mounted on a vehicle or the like. [Explanation of symbols]

[0043] 0...Control unit (ECU) 1...cylinder 11...Injector 12...Spark plug 3...Intake passage 32...Throttle valve 6...VVT intake mechanism b...Crank angle signal c...Accelerator opening signal i…Ignition signal j…Fuel injection signal k...Throttle valve opening operation signal m...Intake valve timing control signal

Claims

1. An internal combustion engine having a plurality of cylinders, in which fuel injected from an injector is combusted in each cylinder, When an abnormality in combustion is detected in a certain cylinder, fuel injection to that cylinder is temporarily stopped, and a correction is made to increase the engine torque output by other cylinders at the same time compared to before. In the correction when an abnormality in combustion is detected in a certain cylinder, a control device for an internal combustion engine temporarily suspends fuel injection into that cylinder, and advances the intake valve timing of other cylinders at the same time from before, widens the throttle valve opening from before, increases the fuel injection amount into other cylinders from before, or advances the ignition timing of other cylinders from before, thereby suppressing an unduly decrease in engine torque of the internal combustion engine without increasing engine speed.

2. When an abnormality in combustion is detected in a certain cylinder, it is determined whether the abnormality is a misfire or abnormal combustion other than a misfire, 2. The control device for an internal combustion engine according to claim 1, wherein the number of cycles for performing said correction when a combustion abnormality is detected in a certain cylinder is made different depending on whether the abnormality is a misfire or abnormal combustion other than a misfire.

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