Control device for internal combustion engine

Abstract

Provided is a control device of an internal combustion engine capable of determining occurrence of abnormal combustion by using a parameter that has little angle dependency and that is strongly affected by occurrence of abnormal combustion. A control device (50) for an internal combustion engine calculates an increase amount in gas pressure torque due to combustion on the basis of crank angle acceleration (αd) at each crank angle (θd), calculates an increase amount (ΔPcyl_brn) in gas pressure due combustion on the basis of an increase amount (ΔTgas_brn) in gas pressure torque due combustion at each crank angle, and determines whether or not abnormal combustion has occurred in the internal combustion engine on the basis of the increase amount (ΔPcyl_brn) in gas pressure due to combustion at each crank angle (θd) of a determination angle section (Δθdet).

Description

[Technical Field]

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

[0002] Pre-ignition, also known as abnormal combustion, is a phenomenon in which deposits remaining in the spark plug or cylinder become so hot that they become a heat source and self-ignite before ignition by the spark plug. The technology in Patent Document 1 detects pre-ignition by the range of fluctuations in the rotational speed of the internal combustion engine.

[0003] For example, if the ignition timing of a specific cylinder is retarded by a certain angle, the output of the internal combustion engine decreases, causing the rotational speed of the internal combustion engine to fluctuate. If pre-ignition occurs in this case, a flame will be generated in the combustion chamber earlier than the ignition timing, thereby reducing the fluctuation range of the rotational speed of the internal combustion engine. Therefore, the occurrence of pre-ignition is detected by determining whether the fluctuation range of this rotational speed is smaller than a predetermined range (fluctuation range for pre-ignition detection). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-136566 Summary of the Invention [Problem to be solved by the invention]

[0005] Pre-ignition, including low-speed pre-ignition (LSPI), which occurs in turbocharged internal combustion engines, particularly at low revolutions and high loads, not only advances the timing of the start of combustion but also involves rapid combustion, resulting in an earlier increase in gas pressure inside the cylinder and a sudden increase in gas pressure inside the cylinder. The conversion of the force acting on the piston due to the increase in gas pressure caused by pre-ignition into crank angular acceleration is angle-dependent. Near top dead center, where pre-ignition occurs, the conversion coefficient approaches 0, and the impact of pre-ignition on crank angular acceleration is small. For this reason, it is difficult to accurately detect the occurrence of pre-ignition using detection methods that capture rotational fluctuations. Furthermore, adding an in-cylinder pressure sensor to directly detect gas pressure inside the cylinder increases costs.

[0006] Therefore, an object of the present application is to provide a control device for an internal combustion engine that can determine the occurrence of abnormal combustion using parameters that have little angle dependency and that strongly reflect the influence of the occurrence of abnormal combustion. [Means for solving the problem]

[0007] The control device for an internal combustion engine according to the present application comprises an angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion out of a gas pressure torque applied to a crankshaft by gas pressure in a cylinder based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure torque due to combustion based on the increase in gas pressure torque due to combustion and the crank angle; and an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on the increase in gas pressure due to combustion at each crank angle in a determination angle interval set corresponding to a combustion period, The gas pressure calculation unit calculates the gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, at each crank angle based on the current state of the amount of gas intake gas in the cylinder and the crank angle, and calculates the gas pressure in the cylinder at each crank angle based on the gas pressure in the cylinder when uncombusted and the increase in gas pressure due to the combustion.The abnormal combustion judgment unit judges the peak value of the increase in gas pressure due to the combustion in the judgment angle range, and judges whether pre-ignition has occurred by comparing the gas pressure in the cylinder at the crank angle corresponding to the peak value with a gas pressure threshold for pre-ignition. [Effects of the Invention]

[0008] According to the control device for an internal combustion engine of the present application, unlike the crank angular acceleration, the increase in gas pressure due to combustion has little angle dependency and is a good indicator of the impact of abnormal combustion. Therefore, the occurrence of abnormal combustion can be accurately determined based on the increase in gas pressure due to combustion. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an internal combustion engine and a control device for the internal combustion engine according to a first embodiment. [Figure 2] 1 is a schematic configuration diagram of an internal combustion engine and a control device for the internal combustion engine according to a first embodiment. [Figure 3] 1 is a block diagram of a control device for an internal combustion engine according to a first embodiment. [Figure 4] 1 is a hardware configuration diagram of a control device for an internal combustion engine according to a first embodiment. [Figure 5] 4 is a time chart for explaining angle information detection processing according to the first embodiment. [Figure 6] FIG. 3 is a diagram for explaining the determination of the occurrence of pre-ignition according to the first embodiment. [Figure 7] FIG. 3 is a diagram for explaining the determination of the occurrence of pre-ignition according to the first embodiment. [Figure 8] FIG. 4 is a diagram for explaining the behavior of gas pressure in a cylinder during normal combustion according to the first embodiment. [Figure 9] FIG. 4 is a diagram for explaining the behavior of gas pressure in a cylinder when pre-ignition occurs according to the first embodiment. [Figure 10] FIG. 3 is a diagram for explaining the determination of the occurrence of pre-ignition according to the first embodiment. [Figure 11] FIG. 3 is a diagram for explaining the determination of the occurrence of pre-ignition according to the first embodiment. [Figure 12] FIG. 4 is a diagram for explaining misfire occurrence determination according to the first embodiment. [Figure 13] FIG. 4 is a diagram for explaining misfire occurrence determination according to the first embodiment. [Figure 14]FIG. 4 is a diagram for explaining the behavior of gas pressure in a cylinder when a misfire occurs according to the first embodiment. [Figure 15] FIG. 3 is a diagram for explaining the behavior of gas pressure in a cylinder according to the first embodiment. [Figure 16] FIG. 10 is a diagram for explaining the determination of the occurrence of pre-ignition according to the second embodiment. [Figure 17] FIG. 10 is a diagram for explaining a misfire occurrence determination according to the second embodiment. [Figure 18] FIG. 10 is a diagram for explaining the determination of the occurrence of pre-ignition according to the second embodiment. [Figure 19] FIG. 10 is a diagram for explaining a misfire occurrence determination according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. First Embodiment A control device 50 for an internal combustion engine 1 according to a first embodiment (hereinafter simply referred to as the control device 50) will be described with reference to the drawings. Fig. 1 and Fig. 2 are schematic configuration diagrams of the internal combustion engine 1 and the control device 50 according to this embodiment, and Fig. 3 is a block diagram of the control device 50 according to this embodiment. The internal combustion engine 1 and the control device 50 are mounted on a vehicle, and the internal combustion engine 1 serves as a driving force source for the vehicle (wheels).

[0011] 1-1. Configuration of internal combustion engine 1 First, the configuration of the internal combustion engine 1 will be described. As shown in Fig. 1, the internal combustion engine 1 has cylinders 7 that burn a mixture of air and fuel. The internal combustion engine 1 has intake pipes 23 that supply air to the cylinders 7, and an exhaust pipe 17 that discharges exhaust gas burned in the cylinders 7. The internal combustion engine 1 is a gasoline engine. The internal combustion engine 1 has a throttle valve 4 that opens and closes the intake pipe 23. The throttle valve 4 is an electronically controlled throttle valve that is driven to open and close by an electric motor controlled by a control device 50. The throttle valve 4 is provided with a throttle opening sensor 19 that outputs an electric signal corresponding to the opening of the throttle valve 4.

[0012] An air flow sensor 3 is provided in the intake pipe 23 upstream of the throttle valve 4, and outputs an electric signal corresponding to the amount of intake air taken into the intake pipe 23. The internal combustion engine 1 is equipped with an exhaust gas recirculation device 20. The exhaust gas recirculation device 20 has an EGR flow path 21 that recirculates exhaust gas from the exhaust pipe 17 to the intake manifold 12, and an EGR valve 22 that opens and closes the EGR flow path 21. The intake manifold 12 is the portion of the intake pipe 23 downstream of the throttle valve 4. The EGR valve 22 is an electronically controlled EGR valve that is driven to open and close by an electric motor controlled by the control device 50. The exhaust pipe 17 is equipped with an air-fuel ratio sensor 18 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust gas in the exhaust pipe 17.

[0013] The intake manifold 12 is provided with a gas pressure sensor 8 that outputs an electric signal corresponding to the pressure inside the intake manifold 12. An injector 13 that injects fuel is provided downstream of the intake manifold 12. The injector 13 may be provided so as to inject fuel directly into the cylinders 7. The internal combustion engine 1 is provided with an atmospheric pressure sensor 33 that outputs an electric signal corresponding to the atmospheric pressure Patm. The internal combustion engine 1 is provided with a water temperature sensor 34 that detects the coolant temperature.

[0014] A spark plug that ignites the air-fuel mixture and an ignition coil 16 that supplies ignition energy to the spark plug are provided at the top of each cylinder 7. Also provided at the top of each cylinder 7 are an intake valve 14 that adjusts the amount of intake air drawn into the cylinder 7 from an intake pipe 23, and an exhaust valve 15 that adjusts the amount of exhaust gas discharged from the cylinder to an exhaust pipe 17. The intake valve 14 is provided with an intake variable valve timing mechanism that varies the valve opening and closing timing. The exhaust valve 15 is provided with an exhaust variable valve timing mechanism that varies the valve opening and closing timing. The variable valve timing mechanisms 14 and 15 have electric actuators.

[0015] As shown in FIG. 2, the internal combustion engine 1 has a plurality of cylinders 7 (three in this example). Each cylinder 7 has a piston 5 inside. The piston 5 of each cylinder 7 is connected to the crankshaft 2 via a connecting rod 9 and a crank 32. The crankshaft 2 is rotationally driven by the reciprocating motion of the piston 5. Combustion gas pressure generated in each cylinder 7 presses against the top surface of the piston 5, rotating the crankshaft 2 via the connecting rod 9 and the crank 32. The crankshaft 2 is connected to a power transmission mechanism that transmits driving force to the wheels. The power transmission mechanism is composed of a transmission, a differential gear, etc. Note that a vehicle equipped with the internal combustion engine 1 may be a hybrid vehicle equipped with a motor generator in the power transmission mechanism.

[0016] The internal combustion engine 1 is equipped with a signal plate 10 that rotates integrally with the crankshaft 2. The signal plate 10 has a plurality of teeth at a plurality of predetermined crank angles. In this embodiment, the signal plate 10 has teeth arranged at 10-degree intervals. The teeth of the signal plate 10 have missing tooth portions where some of the teeth are missing. The internal combustion engine 1 is equipped with a crank angle sensor 11 that is fixed to the engine block 24 and detects the teeth of the signal plate 10.

[0017] The internal combustion engine 1 is equipped with a camshaft 29 connected to the crankshaft 2 by a chain 28. The camshaft 29 drives the intake valve 14 and the exhaust valve 15 to open and close. The camshaft 29 rotates once while the crankshaft 2 rotates twice. The internal combustion engine 1 is equipped with a cam signal plate 31 that rotates integrally with the camshaft 29. The cam signal plate 31 has a plurality of teeth at a plurality of predetermined camshaft angles. The internal combustion engine 1 is equipped with a cam angle sensor 30 that is fixed to the engine block 24 and detects the teeth of the cam signal plate 31.

[0018] Based on two types of output signals from the crank angle sensor 11 and the cam angle sensor 30, the control device 50 detects the crank angle relative to the top dead center of each piston 5 and determines the stroke of each cylinder 7. The internal combustion engine 1 is a four-stroke engine having an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke.

[0019] The crank angle sensor 11 and the cam angle sensor 30 output electrical signals in response to changes in the distance between each sensor and the teeth due to the rotation of the crankshaft 2. The output signal of each angle sensor 11, 30 is a square wave that turns on and off depending on whether the sensor is close to the teeth or far from them. Each angle sensor 11, 30 may be, for example, an electromagnetic pickup type sensor.

[0020] 1-2. Configuration of the control device 50 Next, the control device 50 will be described. The control device 50 is a control device that controls the internal combustion engine 1. As shown in Fig. 3, the control device 50 includes control units such as an angle information detection unit 51, a gas pressure calculation unit 52, an abnormal combustion determination unit 53, an avoidance control unit 54, and a basic control unit 55. The control units 51 to 55 of the control device 50 are realized by processing circuits included in the control device 50. Specifically, as shown in Fig. 4, the control device 50 includes, as processing circuits, an arithmetic processing device 90 (computer) such as a CPU (Central Processing Unit), a storage device 91 connected to the arithmetic processing device 90 via a signal line such as a bus, an input circuit 92 that inputs external signals to the arithmetic processing device 90, and an output circuit 93 that outputs signals from the arithmetic processing device 90 to the outside.

[0021] The arithmetic processing device 90 may be an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), various logic circuits, various signal processing circuits, etc. Furthermore, a plurality of the same or different types of arithmetic processing device 90 may be provided, and each process may be shared and executed.

[0022] The storage device 91 includes volatile and non-volatile storage devices such as RAM (Random Access Memory), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable ROM), etc. The input circuit 92 is connected to various sensors and switches and includes an A / D converter and the like that inputs output signals from these sensors and switches to the arithmetic processing device 90. The output circuit 93 is connected to electrical loads and includes a drive circuit and the like that outputs control signals from the arithmetic processing device 90 to these electrical loads.

[0023] The functions of the control units 51 to 55 of the control device 50 are realized by an arithmetic processing device 90 executing software (programs) stored in a storage device 91 such as a ROM or EEPROM, in cooperation with other hardware of the control device 50, such as the storage device 91, an input circuit 92, and an output circuit 93. Setting data such as threshold values ​​used by the control units 51 to 55 is stored in the storage device 91 such as a ROM or EEPROM. Data such as calculated values ​​and detected values ​​calculated by the control units 51 to 55, including the crank angular velocity ωd, crank angular acceleration αd, in-cylinder gas pressure Pcyl, in-cylinder gas pressure Pcyl_unbrn when uncombusted, and increment in gas pressure due to combustion ΔPcyl_brn, are stored in a rewritable storage device 91 such as a RAM.

[0024] In this embodiment, the input circuit 92 is connected to the crank angle sensor 11, cam angle sensor 30, water temperature sensor 34, air flow sensor 3, throttle opening sensor 19, gas pressure sensor 8, atmospheric pressure sensor 33, air-fuel ratio sensor 18, accelerator position sensor 26, etc. The output circuit 93 is connected to the throttle valve 4 (electric motor), EGR valve 22 (electric motor), injector 13, ignition coil 16, intake variable valve timing mechanism 14, exhaust variable valve timing mechanism 15, etc. Note that various sensors, switches, actuators, etc. (not shown) are connected to the control device 50. Based on output signals from the various sensors, the control device 50 detects the operating conditions of the internal combustion engine 1, such as the intake air amount, pressure in the intake manifold, atmospheric pressure Patm, air-fuel ratio, and accelerator opening.

[0025] 1-2-1. Basic control unit 55 As a basic control function, the basic control unit 55 calculates the fuel injection amount, ignition timing, etc. based on the input output signals of various sensors, and controls the injector 13, the ignition coil 16, etc. The basic control unit 55 calculates the output torque of the internal combustion engine 1 requested by the driver based on the output signal of the accelerator position sensor 26, etc., and controls the throttle valve 4, etc., so as to obtain an intake air amount that realizes the requested output torque. Specifically, the basic control unit 55 calculates a target throttle opening and controls the operation of the electric motor of the throttle valve 4 so that the throttle opening detected based on the output signal of the throttle opening sensor 19 approaches the target throttle opening. The basic control unit 55 also calculates a target opening of the EGR valve 22 based on the input output signals of various sensors, and controls the operation of the electric motor of the EGR valve 22. The basic control unit 55 calculates the target opening / closing timing of the intake valve and the target opening / closing timing of the exhaust valve based on the output signals of various sensors input thereto, and controls the operation of the intake and exhaust variable valve timing mechanisms 14, 15 based on the target opening / closing timing.

[0026] 1-2-2. Angle information detection unit 51 The angle information detection unit 51 detects the crank angle θd based on the output signal of the crank angle sensor 11, and calculates the crank angular velocity ωd, which is the time rate of change of the detected crank angle θd, and the crank angular acceleration αd, which is the time rate of change of the crank angular velocity ωd. The crank angular velocity ωd corresponds to the rotation speed.

[0027] 5, in this embodiment, the angle information detection unit 51 detects the crank angle θd and also detects the detection time Td at which the crank angle θd is detected based on the output signal of the crank angle sensor 11. Then, the angle information detection unit 51 calculates the angle interval Δθd and the time interval ΔTd corresponding to the detected angle θd, based on the detected crank angle θd and the detection time Td.

[0028] For example, angle information detection unit 51 determines crank angle θd when detecting the falling edge (or rising edge) of the output signal (rectangular wave) of crank angle sensor 11. Using a known method, angle information detection unit 51 detects crank angle θd relative to the top dead center of piston 5 of first cylinder #1, based on two types of output signals from crank angle sensor 11 and cam angle sensor 30, and determines the stroke of each cylinder 7.

[0029] <Calculation of crank angular velocity ωd and crank angular acceleration αd> The angle information detection unit 51 calculates the crank angular velocity ωd based on each crank angle θd and the detection time Td at which each crank angle θd was detected. For example, as shown in the following equation, the angle information detection unit 51 calculates the crank angular velocity ωd(n) of the currently detected angle based on the angle interval Δθd(n) between the currently detected crank angle θd(n) and the previously detected crank angle θd(n-1) and the time interval ΔTd(n) between the currently detected time Td(n) and the previously detected time Td(n-1). Note that various other well-known methods may also be used.

number

[0030] The angle information detection unit 51 calculates the crank angular acceleration αd(n) based on the crank angular velocity ωd. For example, as shown in the following equation, the angle information detection unit 51 calculates the crank angular acceleration αd(n) of the currently detected angle based on the crank angular velocity ωd(n) calculated for the currently detected angle, the crank angular velocity ωd(n-1) calculated for the previously detected angle, and the time interval ΔTd(n) of the currently detected angle. Note that various other well-known methods may also be used.

number

[0031] The angle information detection unit 51 associates the calculated angle information such as the crank angular velocity ωd and the crank angular acceleration αd with the corresponding crank angle θd and stores it in a storage device 91 such as a RAM for at least a period equal to or greater than a determination angle range described below.

[0032] 1-2-3. Gas pressure calculation unit 52 The gas pressure calculation unit 52 calculates, at each crank angle θd, an increase in gas pressure torque ΔTgas_brn due to combustion, which is part of the gas pressure torque applied to the crankshaft by the gas pressure in the cylinder, based on the crank angle θd and the crank angular acceleration αd. The gas pressure calculation unit 52 also calculates, at each crank angle θd, an increase in gas pressure torque ΔTgas_brn due to combustion, based on the crank angle θd and the gas pressure torque increase ΔPcyl_brn. This will be described in detail below.

[0033] <Calculation of shaft torque Tcrk_unbrn when combustion is not yet complete> At each crank angle θd, the gas pressure calculation unit 52 calculates the gas pressure Pcyl_unbrn in the cylinder when uncombusted, assuming that uncombusted fuel is present, and the axial torque Tcrk_unbrn when uncombusted fuel is applied to the crankshaft due to the reciprocating motion of the piston, based on the crank angle θd, crank angular velocity ωd, and the state of the intake gas amount in the cylinder.

[0034] In this embodiment, the gas pressure calculation unit 52 calculates, at each crank angle θd, a gas pressure torque Tgas_unbrn during uncombustion, which is an axial torque applied to the crankshaft due to gas pressure in the cylinder during uncombustion, assuming that uncombustion occurs, based on the crank angle θd and the state of the intake gas amount in the cylinder. The gas pressure calculation unit 52 also calculates a reciprocating inertia torque Tpstn, which is an axial torque applied to the crankshaft due to the reciprocating motion of the piston, based on the crank angle θd and the crank angular velocity ωd. The gas pressure calculation unit 52 calculates, at each crank angle θd, a axial torque Tcrk_unbrn during uncombustion by adding the gas pressure torque Tgas_unbrn during uncombustion and the reciprocating inertia torque Tpstn. This will be described in detail below.

[0035] The gas pressure calculation unit 52 calculates the gas pressure Pcyl_unbrn in the cylinder when uncombusted, assuming that combustion is not occurring, based on the current state of the intake gas amount in the cylinder (in this example, the current gas pressure Pin in the intake pipe) and the crank angle θd at each crank angle θd.

[0036] In this embodiment, the gas pressure calculation unit 52 calculates the gas pressure Pcyl_unbrn_i in each cylinder i when uncombusted using the following equation: For cylinder i whose intake valve and exhaust valve are closed, the gas pressure calculation unit 52 uses an equation for calculating gas pressure using a polytropic change to calculate the gas pressure Pcyl_unbrn_i in each cylinder i when uncombusted, based on the gas pressure Pin in the intake pipe and the crank angle θd. For cylinder i whose intake valve is open and whose exhaust valve is closed, the gas pressure calculation unit 52 calculates the gas pressure Pcyl_unbrn_i in the cylinder when uncombusted, based on the gas pressure Pin in the intake pipe, and for cylinder i whose exhaust valve is open, calculates the gas pressure Pcyl_unbrn_i in the cylinder when uncombusted, based on the gas pressure Pex in the exhaust pipe.

number

[0037] Here, Nply is a polytropic index, and a preset value is used. Vcyl0 is the cylinder volume of the combustion cylinder when the intake valve is closed. A preset value may be used, or it may be changed according to the intake valve closing timing set by the intake variable valve timing mechanism 14. Vcly_θ_i is the cylinder volume of each cylinder at the crank angle θd_i of each cylinder i, and is a function of the crank angle θd_i of each cylinder i. Note that in the case of an offset crank, the offset may be taken into account in calculating the cylinder volume Vcly_θ. For example, the cylinder volume Vcly_θ_i of each cylinder i may be set based on the third and fourth equations of equation (3). Here, Vcyltop is the cylinder volume when the piston is positioned at top dead center, Sp is the projected area of ​​the piston top, r is the crank length, L is the connecting rod length, and φ_i is the connecting rod angle of each cylinder i. The crank angle θd_i of each cylinder i used in the calculation of the trigonometric functions is a crank angle obtained by shifting the crank angle θd so that the top dead center of the compression stroke for each cylinder i is 0 degrees.

[0038] The gas pressure calculation unit 52 calculates, at each crank angle θd, the gas pressure torque Tgas_unbrn during uncombustion, which is the axial torque applied to the crankshaft due to the gas pressure in the cylinder during uncombustion, assuming that uncombustion occurs, based on the gas pressure Pcyl_unbrn in the cylinder during uncombustion and the crank angle θd.

[0039] In this embodiment, the gas pressure calculation unit 52 uses the following equation to convert gas pressure into torque, and calculates the gas pressure torque Tgas_unbrn in the uncombusted state based on the gas pressure Pcyl_unbrn_i in each cylinder i in the uncombusted state and the crank angle θd_i of each cylinder i.

number

[0040] Here, R_i is a conversion coefficient for converting the force acting on the piston of each cylinder i into torque, and is a function of the crank angle θd_i of each cylinder i. For example, the conversion coefficient R_i of each cylinder i may be set based on the third and fourth equations of equation (4). Alternatively, map data in which the relationship between the crank angle θd and the conversion coefficient R is preset may be used. In the case of an offset crank, the offset may be taken into consideration when calculating the conversion coefficient R_i of each cylinder i. N is the number of cylinders, and in this embodiment, N=3.

[0041] The gas pressure calculation unit 52 calculates, at each crank angle θd, a reciprocating inertia torque Tpstn, which is an axial torque applied to the crankshaft by the reciprocating motion of the piston, based on the crank angle θd and the crank angular velocity ωd.

[0042] In this embodiment, the gas pressure calculation unit 52 calculates the reciprocating inertia torque Tpstn using the following equation.

number

[0043] Here, mp is the mass of the piston. Ka_i is a coefficient for calculating the acceleration of the piston based on the crank angular velocity ωd, and is a function of the crank angle θd_i of each cylinder i. For example, the acceleration calculation coefficient Ka_i of each cylinder i may be set based on the third equation of equation (5). Although the third equation of equation (5) is an approximation, an exact value may be calculated. Alternatively, map data in which the relationship between the crank angle θd and the acceleration calculation coefficient Ka is preset may be used. In the case of an offset crank, an offset may be taken into account in calculating the acceleration calculation coefficient Ka_i of each cylinder i. The conversion coefficient R_i of each cylinder i is the same as that of equation (4). In addition, an inertia torque generated by the inertia of the connecting rod, etc. may be added to the inertia torque Tin.

[0044] As shown in the following equation, the gas pressure calculation section 52 calculates the uncombusted axial torque Tcrk_unbrn by adding the uncombusted gas pressure torque Tgas_unbrn and the reciprocating inertia torque Tpstn at each crank angle θd.

number

[0045] Alternatively, the gas pressure calculation unit 52 may refer to uncombusted map data in which the relationship between the crank angle θd, crank angular velocity ωd, and state of the intake gas amount in the cylinder and the uncombusted axial torque Tcrk_unbrn is set, and calculate the uncombusted axial torque Tcrk_unbrn corresponding to each crank angle θd, crank angular velocity ωd, and state of the intake gas amount in the cylinder.

[0046] For example, the uncombusted state map data is set for each operating state (in this example, the state of the crank angular velocity ωd and the amount of intake gas in the cylinder) that affects the gas pressure torque and reciprocating inertia torque during uncombusted state. The gas pressure calculation unit 52 refers to the uncombusted state map data corresponding to the current operating state and calculates the uncombusted state axial torque Tcrk_unbrn corresponding to each crank angle θd. The uncombusted state map data may be set in advance based on experimental data or may be set in advance based on the theoretical formulas (3) to (6). Furthermore, the uncombusted state map data may be updated based on the actual axial torque Tcrkd that is actually calculated during uncombusted state.

[0047] <Calculation of actual shaft torque Tcrkd> The gas pressure calculation unit 52 calculates the actual torque Tcrkd acting on the crankshaft at each crank angle θd based on the crank angular acceleration αd.

[0048] In this embodiment, the gas pressure calculation unit 52 calculates the actual torque Tcrkd at each crank angle θd by multiplying the crank angular acceleration αd by the moment of inertia Icrk of the crankshaft system, as shown in the following equation.

number

[0049] <Calculation of external load torque Tload> The gas pressure calculation unit 52 calculates an external load torque Tload, which is a torque applied to the crankshaft from outside the internal combustion engine, based on the actual torque Tcrkd_tdc calculated at the crank angle θd_tdc near top dead center and the uncombusted torque Tcrk_unbrn_tdc. Here, the vicinity of top dead center is, for example, within an angle interval from 10 degrees before top dead center to 10 degrees after top dead center. For example, the crank angle θd_tdc near top dead center is set in advance to the crank angle at top dead center.

[0050] The gas pressure calculation unit 52 calculates the external load torque Tload during combustion by subtracting the actual axial torque Tcrkd_tdc near the top dead center from the axial torque Tcrk_unbrn_tdc during uncombusted combustion near the top dead center, as shown in the following equation.

number

[0051] Since the gas pressure torque of the combustion cylinder becomes almost zero near the top dead center of the combustion stroke, the external load torque Tload can be calculated with a small calculation load based on the uncombusted axial torque Tcrk_unbrn_tdc near the top dead center and the actual axial torque Tcrkd_tdc near the combusted axial torque near the top dead center.

[0052] <Calculation of the increase in gas pressure torque due to combustion ΔTgas_brn> The gas pressure calculation unit 52 calculates the increase in gas pressure torque due to combustion ΔTgas_brn based on the actual shaft torque Tcrkd, the uncombusted shaft torque Tcrk_unbrn, and the external load torque Tload at each crank angle θd. In this embodiment, the gas pressure calculation unit 52 calculates the increase in gas pressure torque due to combustion ΔTgas_brn by subtracting the uncombusted shaft torque Tcrk_unbrn from the actual shaft torque Tcrkd and adding the external load torque Tload, as shown in the following equation.

number

[0053] <Calculation of the increase in gas pressure due to combustion ΔPcyl_brn> The gas pressure calculation unit 52 calculates the increase in gas pressure due to combustion ΔPcyl_brn at each crank angle θd based on the increase in gas pressure torque due to combustion ΔTgas_brn and the crank angle θd. In this embodiment, the gas pressure calculation unit 52 calculates the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn using the following equation: The conversion coefficient R_brn is the conversion coefficient for the combustion cylinder among the conversion coefficients R_i for each cylinder i in equation (4).

number

[0054] At the crank angle θd at top dead center, the conversion coefficient R_brn of the combustion cylinder becomes 0, resulting in a division by 0. Therefore, the gas pressure calculation unit 52 may calculate the average value of ΔPcyl_brn calculated at the crank angles before and after the top dead center as ΔPcyl_brn at the top dead center.

[0055] <Calculation of in-cylinder gas pressure Pcyl> The gas pressure calculation unit 52 calculates the gas pressure Pcyl in the cylinder by adding the gas pressure Pcyl_unbrn in the cylinder when uncombusted and the increase in gas pressure ΔPcyl_brn in the cylinder due to combustion at each crank angle θd, as shown in the following equation.

number

[0056] The gas pressure calculation unit 52 stores each calculated value, such as the actual axial torque Tcrkd calculated at each crank angle θd, the axial torque Tcrk_unbrn in the uncombusted state, the increase in gas pressure torque due to combustion ΔTgas_brn, the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn, and the gas pressure Pcyl in the cylinder, together with the corresponding angle identification number n and angle information such as the crank angle θd, in a storage device 91 such as a RAM.

[0057] 1-2-4. Abnormal combustion determination unit 53 <Principles for determining abnormal combustion> The principle of abnormal combustion determination will be explained below. 6 plots the relationship between the peak value dQ / dθ_max of the actual heat release rate and the peak value α_max of the crank angular acceleration in each combustion cycle when pre-ignition occurs in some combustion cycles and pre-ignition in others does not occur in other combustion cycles. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder), and the peak value α_max of the crank angular acceleration is a value calculated by the control device 50.

[0058] The increase in the peak value α_max of the crank angular acceleration is not proportional to the increase in the peak value dQ / dθ_max of the actual heat release rate. Therefore, to the right of the dashed-dotted line, which is the region of the peak value dQ / dθ_max of the actual heat release rate where it is desired to determine that pre-ignition has occurred, the peak value α_max of the crank angular acceleration does not increase proportionally, making it difficult to set a determination threshold (the dashed line in FIG. 6) that accurately determines the occurrence of pre-ignition.

[0059] This is because the conversion of the force acting on the piston due to the increase in gas pressure caused by pre-ignition into crank angular acceleration α is angle-dependent, and near the top dead center where pre-ignition occurs, the conversion coefficient R_brn of the combustion cylinder becomes close to 0, and the impact of pre-ignition on the crank angular acceleration α is small.

[0060] Figure 7 plots the relationship between the peak value dQ / dθ_max of the actual heat release rate in each combustion cycle and the peak value Pcyl_max of the gas pressure in the cylinder calculated by the control device 50, when there is a mixture of combustion cycles in which pre-ignition occurs and combustion cycles in which pre-ignition does not occur.

[0061] Since it is not possible to clearly separate the peak value Pcyl_max of the gas pressure in the cylinder to the right of the dotted-dash line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that pre-ignition has occurred (above the dashed line in Figure 7), from the peak value Pcyl_max of the gas pressure in the cylinder to the left of the dotted-dash line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that pre-ignition has not occurred (below the dashed line in Figure 7), it is difficult to set a judgment threshold (dashed line in Figure 7) that accurately determines the occurrence of pre-ignition.

[0062] Figure 8 shows an example of changes in the gas pressure Pcyl in the cylinder relative to the crank angle θd during a combustion cycle (compression stroke and combustion stroke) when pre-ignition is not occurring. The peak value Pcyl_max of the gas pressure in the cylinder is the gas pressure Pcyl in the cylinder at the position indicated by the dashed-dotted line A. The gas pressure Pcyl in the cylinder at the position indicated by the dashed-dotted line A is the same as the gas pressure Pcyl_unbrn (dashed line) in the cylinder when combustion is not occurring, assuming that no combustion is occurring.

[0063] Figure 9 shows an example of changes in the gas pressure Pcyl in the cylinder relative to the crank angle θd in a combustion cycle (compression stroke and combustion stroke) in which pre-ignition occurs. The peak value Pcyl_max of the gas pressure in the cylinder is the gas pressure Pcyl in the cylinder at the position of the two-dot chain line B. Since the difference between the peak value Pcyl_max of the gas pressure in the cylinder in Figure 9 and Figure 8 is small, it becomes difficult to determine whether pre-ignition has occurred.

[0064] 10 plots the relationship between the peak value dQ / dθ_max of the actual heat release rate and the in-cylinder gas pressure Pcyl_Δbrnmax at the crank angle corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn in each combustion cycle when both combustion cycles in which pre-ignition occurs and combustion cycles in which pre-ignition does not occur are present. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual in-cylinder gas pressure (for example, a value measured by a gas pressure sensor in the cylinder), and ΔPcyl_brn and Pcyl_Δbrnmax are values ​​calculated by the control device 50.

[0065] Since it is possible to clearly separate the gas pressure Pcyl_Δbrnmax (above the dashed line in FIG. 10) in the cylinder at the crank angle corresponding to the peak value of ΔPcyl_brn to the right of the dashed-dotted line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that pre-ignition is occurring, and the gas pressure Pcyl_Δbrnmax (below the dashed line in FIG. 10) in the cylinder at the crank angle corresponding to the peak value of ΔPcyl_brn to the left of the dashed-dotted line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that pre-ignition is not occurring, it is possible to set a determination threshold (dashed line in FIG. 10) that accurately determines the occurrence of pre-ignition. This is because, unlike the crank angular acceleration α, ΔPcyl_brn has little angle dependency and is able to clearly indicate the impact of the occurrence of pre-ignition.

[0066] As shown in Figures 8 and 9, the gas pressure Pcyl_Δbrnmax in the cylinder at the crank angle corresponding to the peak value of the increase ΔPcyl_brn in gas pressure in the cylinder due to combustion is the gas pressure Pcyl in the cylinder at the position of the two-dot chain line B. There is a large difference between the gas pressure Pcyl_Δbrnmax in the cylinder corresponding to the peak value of ΔPcyl_brn in Figures 8 and 9. Therefore, as shown in Figure 10, it is possible to determine pre-ignition.

[0067] 11 plots the relationship between the crank angle θ_dQ / dθmax corresponding to the peak value dQ / dθ_max of the actual heat release rate and the crank angle θd_Δbrnmax corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn, for each combustion cycle, when some combustion cycles have pre-ignition and others do not. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder), and the crank angle θd_Δbrnmax corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn is a value calculated by the control device 50.

[0068] Since it is possible to clearly separate the crank angle θd_Δbrnmax (above the dashed line in FIG. 11) corresponding to the peak value of ΔPcyl_brn to the right of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition has occurred, and the crank angle θd_Δbrnmax (below the dashed line in FIG. 11) corresponding to the peak value of ΔPcyl_brn to the left of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition has not occurred, it becomes possible to set a determination threshold (dashed line in FIG. 11) that accurately determines the occurrence of pre-ignition. This is because ΔPcyl_brn has little angle dependency and clearly reflects the influence of the occurrence of pre-ignition.

[0069] Figure 12 plots the relationship between the peak value dQ / dθ_max of the actual heat release rate and the in-cylinder gas pressure Pcyl_Δbrnmax at the crank angle corresponding to the peak value of the in-cylinder gas pressure increase ΔPcyl_brn due to combustion in each combustion cycle, when some combustion cycles cause misfires and others do not. Note that the scales of the horizontal and vertical axes in Figure 12 are larger than those of the horizontal and vertical axes in Figure 10. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual in-cylinder gas pressure (for example, a value measured by a gas pressure sensor in the cylinder), and ΔPcyl_brn and Pcyl_Δbrnmax are values ​​calculated by the control device 50.

[0070] The cylinder gas pressure Pcyl_Δbrnmax (below the dashed line in FIG. 12) at the crank angle corresponding to the peak value of ΔPcyl_brn to the left of the dashed-dotted line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that a misfire is occurring, can be clearly separated from the cylinder gas pressure Pcyl_Δbrnmax (above the dashed line in FIG. 12) at the crank angle corresponding to the peak value of ΔPcyl_brn to the right of the dashed-dotted line, which is the region of the actual heat release rate peak value dQ / dθ_max where it is desired to determine that a misfire is not occurring. This makes it possible to set a determination threshold (dashed line in FIG. 12) that accurately determines the occurrence of a misfire. This is because, unlike the crank angular acceleration α, ΔPcyl_brn has little angle dependency and is therefore more sensitive to the effects of misfire occurrence.

[0071] Figure 13 plots the relationship between the crank angle θ_dQ / dθmax corresponding to the peak value dQ / dθ_max of the actual heat release rate and the crank angle θd_Δbrnmax corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn, for each combustion cycle, when some combustion cycles have misfires and some do not. Note that the scales of the horizontal and vertical axes in Figure 13 are larger than those of the horizontal and vertical axes in Figure 11. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder), and the crank angle θd_Δbrnmax corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion ΔPcyl_brn is a value calculated by the control device 50.

[0072] The crank angle θd_Δbrnmax (below the dashed line in FIG. 13) corresponding to the peak value of ΔPcyl_brn to the left of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate for which it is desired to determine that a misfire is occurring, can be clearly separated from the crank angle θd_Δbrnmax (above the dashed line in FIG. 13) corresponding to the peak value of ΔPcyl_brn to the right of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate for which it is desired to determine that a misfire is not occurring. This makes it possible to set a determination threshold (dashed line in FIG. 13) that accurately determines the occurrence of a misfire. This is because, unlike the crank angular acceleration α, ΔPcyl_brn has little angle dependency and is therefore able to clearly reflect the impact of the occurrence of a misfire.

[0073] As described above, the occurrence of abnormal combustion such as pre-ignition and misfire can be determined based on the increase ΔPcyl_brn in gas pressure in the cylinder due to combustion that has little angle dependency.

[0074] <Determining abnormal combustion> Therefore, the abnormal combustion determination unit 53 determines whether abnormal combustion has occurred in the internal combustion engine based on the increase ΔPcyl_brn in gas pressure due to combustion at each crank angle θd in the determination angle section Δθdet set corresponding to the combustion period.

[0075] As described above, unlike the crank angular acceleration α, the increase in gas pressure due to combustion ΔPcyl_brn has little angle dependency and is a good indicator of the impact of abnormal combustion. Therefore, the occurrence of abnormal combustion can be accurately determined based on the increase in gas pressure due to combustion ΔPcyl_brn.

[0076] The determination angle section Δθdet is set to an angle section within the compression stroke and combustion stroke so that it can be determined whether or not abnormal combustion has occurred. Note that the determination angle section does not have to include the compression stroke.

[0077] <Preignition Judgment> In this embodiment, the abnormal combustion determination unit 53 determines the peak value of the increase in gas pressure due to combustion ΔPcyl_brn in the determination angle interval Δθdet, and determines whether pre-ignition has occurred by comparing the gas pressure Pcyl_Δbrnmax in the cylinder at the crank angle θd corresponding to the peak value with the gas pressure threshold value ThP_pre for pre-ignition.

[0078] As explained using Fig. 10, a difference in tendency of Pcyl_Δbrnmax occurs between when pre-ignition has occurred and when it has not. Therefore, by setting the gas pressure threshold value ThP_pre for pre-ignition between Pcyl_Δbrnmax when pre-ignition has occurred and Pcyl_Δbrnmax when pre-ignition has not occurred, it is possible to accurately determine whether pre-ignition has occurred.

[0079] The abnormal combustion determination unit 53 determines that pre-ignition has occurred if the gas pressure Pcyl_Δbrnmax in the cylinder corresponding to the peak value of ΔPcyl_brn exceeds the gas pressure threshold value ThP_pre for pre-ignition, and determines that pre-ignition has not occurred if Pcyl_Δbrnmax falls below the gas pressure threshold value ThP_pre for pre-ignition.

[0080] The abnormal combustion determination unit 53 sets the gas pressure threshold value ThP_pre for pre-ignition based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold value data for pre-ignition in which the relationship between the operating state and the gas pressure threshold value ThP_pre is set, and sets the gas pressure threshold value ThP_pre for pre-ignition that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotation angular velocity), etc.

[0081] Alternatively, the abnormal combustion determination unit 53 may determine the peak value of the increase in gas pressure due to combustion ΔPcyl_brn in the determination angle interval Δθdet, and determine whether pre-ignition has occurred by comparing the crank angle θd_Δbrnmax corresponding to the peak value with the angle threshold value Thθ_pre for pre-ignition.

[0082] As explained using Fig. 11, a difference in tendency of θd_Δbrnmax occurs between when pre-ignition has occurred and when it has not. Therefore, by setting the angle threshold value Thθ_pre for pre-ignition between θd_Δbrnmax when pre-ignition has occurred and θd_Δbrnmax when pre-ignition has not occurred, it is possible to accurately determine whether pre-ignition has occurred.

[0083] The abnormal combustion determination unit 53 determines that pre-ignition has occurred if the crank angle θd_Δbrnmax corresponding to the peak value of ΔPcyl_brn exceeds the angle threshold value Thθ_pre for pre-ignition, and determines that pre-ignition has not occurred if θd_Δbrnmax is below the angle threshold value Thθ_pre for pre-ignition.

[0084] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_pre for pre-ignition based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for pre-ignition in which the relationship between the operating state and the angle threshold value Thθ_pre is set, and sets the angle threshold value Thθ_pre for pre-ignition that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotation angular velocity), etc.

[0085] <Judgment of misfire> The abnormal combustion determination unit 53 determines the peak value of the increase in gas pressure due to combustion ΔPcyl_brn in the determination angle interval Δθdet, and determines whether or not a misfire has occurred by comparing the gas pressure Pcyl_Δbrnmax in the cylinder at the crank angle corresponding to the peak value with the gas pressure threshold value ThP_mf for misfire.

[0086] As explained using Figure 12, there is a difference in the tendency of Pcyl_Δbrnmax between when a misfire occurs and when a misfire does not occur. Therefore, by setting the gas pressure threshold value ThP_mf for misfire between Pcyl_Δbrnmax when a misfire occurs and Pcyl_Δbrnmax when a misfire does not occur, it is possible to accurately determine whether a misfire has occurred.

[0087] The abnormal combustion determination unit 53 determines that a misfire has occurred when the gas pressure Pcyl_Δbrnmax in the cylinder corresponding to the peak value of ΔPcyl_brn falls below the gas pressure threshold value ThP_mf for misfire, and determines that a misfire has not occurred when Pcyl_Δbrnmax exceeds the gas pressure threshold value ThP_mf for misfire.

[0088] The abnormal combustion determination unit 53 sets the gas pressure threshold value ThP_mf for misfire based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold value data for misfire in which the relationship between the operating state and the gas pressure threshold value ThP_mf is set, and sets the gas pressure threshold value ThP_mf that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotational angular velocity), etc.

[0089] Alternatively, the abnormal combustion determination unit 53 may determine the peak value of the increase in gas pressure due to combustion ΔPcyl_brn in the determination angle interval Δθdet, and compare the crank angle θd_Δbrnmax corresponding to the peak value with the angle threshold value Thθ_mf for misfire to determine whether or not a misfire has occurred.

[0090] As explained using Figure 13, there is a difference in the tendency of θd_Δbrnmax between when a misfire occurs and when a misfire does not occur. Therefore, by setting the angle threshold value Thθ_mf for misfire between θd_Δbrnmax when a misfire occurs and θd_Δbrnmax when a misfire does not occur, it is possible to accurately determine whether a misfire has occurred.

[0091] The abnormal combustion determination unit 53 determines that a misfire has occurred if the crank angle θd_Δbrnmax corresponding to the peak value of ΔPcyl_brn is below the angle threshold value Thθ_mf for misfire, and determines that a misfire has not occurred if θd_Δbrnmax is above the angle threshold value Thθ_mf for misfire.

[0092] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_mf for misfire based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for misfire in which the relationship between the operating state and the angle threshold value Thθ_mf is set, and sets the angle threshold value Thθ_mf for misfire that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotational angular velocity), etc.

[0093] <Calculation of the peak value of ΔPcyl_brn taking misfire into account> 14 shows an example of changes in the gas pressure Pcyl in the cylinder relative to the crank angle θd in a combustion cycle (compression stroke and combustion stroke) in which a misfire occurs. When a misfire occurs, the increase in gas pressure ΔPcyl_brn in the cylinder due to combustion approaches zero, making it difficult to determine its peak value. The crank angle θd_Δbrnmax corresponding to the peak value fluctuates for each combustion cycle, making it more likely that an error will occur in determining whether or not a misfire has occurred.

[0094] Therefore, the abnormal combustion judgment unit 53 judges the peak value of the increase in gas pressure due to combustion ΔPcyl_brn in the judgment angle interval Δθdet, and if the peak value is smaller than the misfire state corresponding threshold value ThΔP_mf, sets the angle θd_mf corresponding to the misfire state, which is preset within the judgment angle interval Δθdet, as the crank angle θd_Δbrnmax corresponding to the peak value.

[0095] According to this configuration, even when a misfire occurs and the increase in gas pressure in the cylinder due to combustion, ΔPcyl_brn, approaches 0, making it difficult to determine its peak value, the angle θd_mf corresponding to the misfire state can be set as the crank angle θd_Δbrnmax corresponding to the peak value, so that θd_Δbrnmax does not fluctuate with each combustion cycle, thereby suppressing errors in misfire determination.

[0096] The misfire state threshold value ThΔP_mf is set to a value greater than 0, taking into consideration the fluctuation range of ΔPcyl_brn due to noise, variation factors, etc. when a misfire occurs. For example, the misfire state angle θd_mf may be set to the end angle of the determination angle interval Δθdet, or may be preset to correspond to the crank angle θd_Δbrnmax corresponding to the peak value when no misfire occurs.

[0097] <Measures to deal with fluctuations in ΔPcyl_brn> 15 shows an example of changes in the gas pressure Pcyl in the cylinder relative to the crank angle θd during a combustion cycle (compression stroke and combustion stroke) in which no misfire occurs. In this example, due to variations in the tooth angle of the signal plate 10, the increase in gas pressure ΔPcyl_brn in the cylinder due to combustion is greater than 0 (hatched portion) before the start of combustion. Even in this case, the peak value of ΔPcyl_brn after the start of combustion is greater, so no error in determining abnormal combustion occurs. However, it is preferable not to have an increase in ΔPcyl_brn before the start of combustion due to noise, variations, etc. Furthermore, this would deteriorate the accuracy of calculating the heat release rate dQ / dθ in the second embodiment and the mass fraction burned MFB in the third embodiment, which will be described later.

[0098] Therefore, when the crank angle θd is changed to the retard side (changed in the rotation direction) during the compression stroke and the combustion stroke, the gas pressure calculation unit 52 determines the crank angle θd at which the increase in gas pressure due to combustion ΔPcyl_brn becomes greater than the above-zero determination threshold ThΔP_0 for the first time during the compression stroke as the first crank angle θd1, determines the crank angle θd at which the increase in gas pressure due to combustion ΔPcyl_brn becomes equal to or less than the above-zero determination threshold ThΔP_0 after the first crank angle θd1 as the second crank angle θd2, and determines the crank angle θd at which the increase in gas pressure due to combustion ΔPcyl_brn becomes greater than the above-zero determination threshold ThΔP_0 after the second crank angle θd2 during the combustion stroke following the compression stroke as the third crank angle θd3. Then, when the first crank angle θd1 and the third crank angle θd3 exist, the gas pressure calculation unit 52 sets the increase in gas pressure ΔPcyl_brn due to combustion in the angle section corresponding to the first crank angle θd1 to the second crank angle θd2 to 0.

[0099] According to this configuration, even if ΔPcyl_brn before the start of combustion increases above 0 due to noise, variation factors, etc., it is possible to correct ΔPcyl_brn before the start of combustion to 0. The above-zero determination threshold value ThΔP_0 is set to a value equal to or greater than 0.

[0100] 1-2-4. Avoidance control unit 54 When the abnormal combustion determination unit 53 determines that abnormal combustion has occurred, the avoidance control unit 54 controls the internal combustion engine by changing control parameters of the internal combustion engine so as to suppress the occurrence of abnormal combustion. The control parameters to be changed include one or more of the fuel injection amount, the amount of intake gas in the cylinder, the ignition timing, the EGR amount, and the control amount of the variable valve timing mechanism.

[0101] <When pre-ignition occurs> For example, if the control parameters to be changed include the fuel injection amount, and if it is determined that pre-ignition has occurred, the avoidance control unit 54 enriches (increases) the fuel injection amount from a reference injection amount, thereby suppressing the occurrence of pre-ignition by cooling the fuel. If the control parameters to be changed include the intake gas amount in the cylinder, and if it is determined that pre-ignition has occurred, the avoidance control unit 54 reduces the intake gas amount in the cylinder from a reference intake gas amount, thereby suppressing the occurrence of pre-ignition by lowering the temperature of the compressed gas near top dead center. For example, the throttle valve 4 is controlled to close. If the control parameters to be changed include the ignition timing, and if it is determined that pre-ignition has occurred, the avoidance control unit 54 changes the ignition timing to a retarded side from the reference ignition timing, thereby suppressing the occurrence of pre-ignition by lowering the combustion temperature.

[0102] If the control parameters to be changed include the EGR amount, when it is determined that pre-ignition has occurred, the avoidance control unit 54 increases the EGR amount above the reference EGR amount, thereby reducing the ignitability of the air-fuel mixture and the combustion temperature, thereby suppressing the occurrence of pre-ignition. For example, the avoidance control unit 54 controls the EGR valve 22 to the open side. If the control parameters to be changed include the control amount of the variable valve timing mechanism, when it is determined that pre-ignition has occurred, the avoidance control unit 54 changes the control amount of the variable valve timing mechanism above the reference control amount to suppress the occurrence of pre-ignition, thereby suppressing the occurrence of pre-ignition. The control amount of the variable valve timing mechanism is the exhaust valve opening / closing timing when controlling the variable valve timing mechanism of the exhaust valve, and is the intake valve opening / closing timing when controlling the variable valve timing mechanism of the intake valve. For example, the control amount is changed to increase the overlap period between the exhaust valve opening period and the intake valve opening period, thereby increasing the internal EGR amount, thereby reducing the ignitability of the air-fuel mixture and the combustion temperature, thereby suppressing the occurrence of pre-ignition.

[0103] When it is determined that pre-ignition has occurred, the avoidance control unit 54 changes the reference control parameter calculated by the basic control unit 55 for the control parameter to be changed, transmits the changed control parameter to the basic control unit 55, and reflects it in the control of the basic control unit 55. When it is determined that pre-ignition has occurred, the avoidance control unit 54 gradually changes the control parameter to be changed toward a side that suppresses the occurrence of pre-ignition, and when it is determined that pre-ignition has not occurred, gradually returns the control parameter to be changed toward the side opposite to the side that suppresses the occurrence of pre-ignition. Furthermore, the avoidance control unit 54 may increase the amount of change in the control parameter to be changed toward a side that suppresses the occurrence of pre-ignition as the intensity of the occurrence of pre-ignition increases. When the control parameter to be changed can be changed for each cylinder, the control parameter to be changed for the cylinder in which pre-ignition has occurred may be changed.

[0104] <When a misfire occurs> For example, if the control parameters to be changed include the fuel injection amount, and if it is determined that a misfire has occurred, the avoidance control unit 54 enriches (increases) the fuel injection amount from a reference injection amount to suppress the occurrence of a misfire. If the control parameters to be changed include the intake gas amount in the cylinder, and if it is determined that a misfire has occurred, the avoidance control unit 54 increases the intake gas amount in the cylinder from a reference intake gas amount to suppress the occurrence of a misfire. For example, the throttle valve 4 is controlled to open. If the control parameters to be changed include the ignition timing, and if it is determined that a misfire has occurred, the avoidance control unit 54 advances the ignition timing from the reference ignition timing to suppress the occurrence of a misfire.

[0105] If the control parameters to be changed include the EGR amount, and if it is determined that a misfire has occurred, the avoidance control unit 54 reduces the EGR amount below a reference EGR amount to suppress the occurrence of the misfire. For example, the EGR valve 22 is controlled to close. If the control parameters to be changed include the control variable of the variable valve timing mechanism, and if it is determined that a misfire has occurred, the avoidance control unit 54 changes the control variable of the variable valve timing mechanism to a value that suppresses the occurrence of the misfire from the reference control variable, thereby suppressing the occurrence of the misfire. The control variable of the variable valve timing mechanism is the exhaust valve opening / closing timing when controlling the variable valve timing mechanism of the exhaust valve, and is the intake valve opening / closing timing when controlling the variable valve timing mechanism of the intake valve. For example, the control variable is changed to reduce the overlap period between the exhaust valve opening period and the intake valve opening period, thereby reducing the internal EGR amount and suppressing the occurrence of the misfire.

[0106] When it is determined that a misfire has occurred, the avoidance control unit 54 changes the reference control parameter calculated by the basic control unit 55 for the control parameter to be changed, transmits the changed control parameter to the basic control unit 55, and reflects it in the control of the basic control unit 55. When it is determined that a misfire has occurred, the avoidance control unit 54 gradually changes the control parameter to be changed toward a side that suppresses the occurrence of misfire, and when it is determined that a misfire has not occurred, gradually returns the control parameter to the side opposite to the side that suppresses the occurrence of misfire. Furthermore, the avoidance control unit 54 may increase the amount by which the control parameter to be changed toward a side that suppresses the occurrence of misfire as the frequency of misfires increases. When the control parameter to be changed can be changed for each cylinder, the control parameter to be changed for the cylinder where a misfire has occurred may be changed.

[0107] 2. Second Embodiment A control device 50 according to a second embodiment will be described with reference to the drawings. Description of components similar to those of the first embodiment will be omitted. The basic configuration of the control device 50 according to this embodiment is similar to that of the first embodiment. This embodiment differs from the first embodiment in that a gas pressure calculation unit 52 calculates the heat release rate dQ / dθd, and an abnormal combustion determination unit 53 determines whether or not abnormal combustion has occurred using the heat release rate dQ / dθd.

[0108] <Calculation of actual heat release rate dQ / dθ> The gas pressure calculation unit 52 calculates the heat release rate dQ / dθd per unit crank angle at each crank angle θd based on the gas pressure Pcyl in the cylinder and the crank angle θd.

[0109] In this embodiment, the gas pressure calculation unit 52 uses the following equation to calculate the heat release rate dQ / dθd per unit crank angle at each crank angle θd.

number

[0110] Here, κ is the specific heat ratio, and Vcly_θ is the cylinder volume of the combustion cylinder at each crank angle θd, which are calculated as described above using equation (3). The calculated heat release rate dQ / dθd at each crank angle θd is stored in a storage device 91 such as a RAM, similar to other calculated values.

[0111] <Principles for determining abnormal combustion> The principle of determining abnormal combustion based on the heat release rate dQ / dθd will be explained below. 16 plots the relationship between the crank angle θ_dQ / dθmax corresponding to the peak value dQ / dθ_max of the actual heat release rate and the crank angle θd_dQ / dθdmax corresponding to the peak value dQ / dθd_max of the heat release rate calculated by the control device 50, in each combustion cycle when pre-ignition occurs in some combustion cycles and pre-ignition in others does not occur in other combustion cycles. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder).

[0112] Since it is possible to clearly separate the crank angle θd_dQ / dθdmax (above the dashed line in FIG. 16) corresponding to the peak value of the heat release rate to the right of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition is occurring, and the crank angle θd_dQ / dθdmax (below the dashed line in FIG. 16) corresponding to the peak value of the heat release rate to the left of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition is not occurring, it becomes possible to set a determination threshold (dashed line in FIG. 16) that accurately determines the occurrence of pre-ignition. This is because, unlike the crank angular acceleration α, the heat release rate dQ / dθd has little angle dependency and is therefore able to clearly indicate the influence of the occurrence of pre-ignition.

[0113] Figure 17 plots the relationship between the crank angle θ_dQ / dθmax corresponding to the peak value dQ / dθ_max of the actual heat release rate and the crank angle θd_dQ / dθdmax corresponding to the peak value dQ / dθd_max of the heat release rate calculated by the control device 50, in each combustion cycle when there is a mixture of combustion cycles in which misfires occur and combustion cycles in which misfires do not occur. Note that the scales of the horizontal and vertical axes in Figure 17 are larger than those of the horizontal and vertical axes in Figure 16. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder).

[0114] The crank angle θd_dQ / dθdmax (below the dashed line in FIG. 17) corresponding to the peak value of the heat release rate to the left of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate for which it is desired to determine that a misfire is occurring, can be clearly separated from the crank angle θd_dQ / dθdmax (above the dashed line in FIG. 17) corresponding to the peak value of the heat release rate to the right of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate for which it is desired to determine that a misfire is not occurring. This makes it possible to set a determination threshold (dashed line in FIG. 17) that accurately determines the occurrence of a misfire. This is because, unlike the crank angular acceleration α, the heat release rate dQ / dθd has little angle dependency and is therefore more sensitive to the influence of the occurrence of a misfire.

[0115] As described above, the occurrence of abnormal combustion such as pre-ignition and misfire can be determined based on the heat release rate dQ / dθd, which has little angle dependency.

[0116] <Determining abnormal combustion> Therefore, the abnormal combustion judgment unit 53 judges whether or not abnormal combustion has occurred in the internal combustion engine based on the heat release rate dQ / dθd at each crank angle θd in the judgment angle range Δθdet, which is calculated based on the increase ΔPcyl_brn in gas pressure due to combustion at each crank angle θd.

[0117] As described above, unlike the crank angular acceleration α, the heat release rate dQ / dθd has little angle dependency and is highly susceptible to the effects of abnormal combustion. Therefore, the occurrence of abnormal combustion can be accurately determined based on the heat release rate dQ / dθd calculated based on the gas pressure increase ΔPcyl_brn due to combustion.

[0118] <Preignition Judgment> In this embodiment, the abnormal combustion determination unit 53 determines the peak value of the heat release rate dQ / dθd in the determination angle interval Δθdet, and determines whether or not pre-ignition has occurred by comparing the crank angle θd_dQ / dθdmax corresponding to the peak value with the angle threshold value Thθ_pre for pre-ignition.

[0119] As explained using Fig. 16, a difference in tendency of θd_dQ / dθdmax occurs between when pre-ignition has occurred and when it has not. Therefore, by setting the angle threshold value Thθ_pre for pre-ignition between θd_dQ / dθdmax when pre-ignition has occurred and θd_dQ / dθdmax when pre-ignition has not occurred, it is possible to accurately determine whether pre-ignition has occurred.

[0120] The abnormal combustion determination unit 53 determines that pre-ignition has occurred if the crank angle θd_dQ / dθdmax corresponding to the peak value of dQ / dθd exceeds the angle threshold value Thθ_pre for pre-ignition, and determines that pre-ignition has not occurred if θd_dQ / dθdmax is below the angle threshold value Thθ_pre for pre-ignition.

[0121] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_pre for pre-ignition based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for pre-ignition in which the relationship between the operating state and the angle threshold value Thθ_pre is set, and sets the angle threshold value Thθ_pre for pre-ignition that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotation angular velocity), etc.

[0122] <Judgment of misfire> The abnormal combustion determination unit 53 determines the peak value of the heat release rate dQ / dθd in the determination angle interval Δθdet, and determines whether or not a misfire has occurred by comparing the crank angle θd_dQ / dθdmax corresponding to the peak value with the angle threshold value Thθ_mf for misfire.

[0123] As explained using Figure 17, there is a difference in the tendency of θd_dQ / dθdmax between when a misfire occurs and when it does not. Therefore, by setting the angle threshold value Thθ_mf for misfire between θd_dQ / dθdmax when a misfire occurs and θd_dQ / dθdmax when a misfire does not occur, it is possible to accurately determine whether a misfire has occurred.

[0124] The abnormal combustion determination unit 53 determines that a misfire has occurred if the crank angle θd_dQ / dθdmax corresponding to the peak value of the heat release rate dQ / dθd is below the angle threshold value Thθ_mf for misfire, and determines that a misfire has not occurred if θd_dQ / dθdmax is above the angle threshold value Thθ_mf for misfire.

[0125] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_mf for misfire based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for misfire in which the relationship between the operating state and the angle threshold value Thθ_mf is set, and sets the angle threshold value Thθ_mf for misfire that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotational angular velocity), etc.

[0126] <Calculating the peak value of dQ / dθd taking misfire into account> In addition, the abnormal combustion judgment unit 53 judges the peak value of the heat release rate dQ / dθd in the judgment angle interval Δθdet, and if the peak value is smaller than the misfire state corresponding threshold value ThdQ_mf, sets the misfire state corresponding angle θd_mf, which is previously set within the judgment angle interval Δθdet, as the crank angle θd_dQ / dθdmax corresponding to the peak value.

[0127] According to this configuration, even if a misfire occurs and the heat release rate dQ / dθd approaches 0, making it difficult to determine its peak value, the angle θd_mf corresponding to the misfire state can be set as the crank angle θd_dQ / dθdmax corresponding to the peak value, preventing θd_dQ / dθdmax from fluctuating with each combustion cycle and suppressing errors in misfire determination.

[0128] 3. Embodiment 3 A control device 50 according to a third embodiment will be described with reference to the drawings. Description of the same components as those in the first embodiment will be omitted. The basic configuration of the control device 50 according to this embodiment is the same as that of the first embodiment. This embodiment differs from the first embodiment in that a gas pressure calculation unit 52 calculates the heat release rate dQ / dθd and the mass fraction burned MFB, and an abnormal combustion determination unit 53 determines whether or not abnormal combustion has occurred using the mass fraction burned MFB.

[0129] <Calculation of actual heat release rate dQ / dθ> As in the second embodiment, the gas pressure calculation unit 52 calculates the heat release rate dQ / dθd per unit crank angle at each crank angle θd based on the gas pressure Pcyl in the cylinder and the crank angle θd.

[0130] The gas pressure calculation unit 52 uses the formula (12) to calculate the heat release rate dQ / dθd per unit crank angle at each crank angle θd.

[0131] <Calculation of mass fraction burned (MFB)> The gas pressure calculation unit 52 calculates the mass fraction burned MFB for each crank angle θd by integrating the heat release rate dQ / dθd during the combustion period.

[0132] In this embodiment, the gas pressure calculation unit 52 uses the following equation to calculate the mass fraction burned MFB for each crank angle θd by dividing the interval integral value obtained by integrating the heat release rate dQ / dθd from the start angle θ0 to each crank angle θd by the total integral value Q0 obtained by integrating the heat release rate dQ / dθd over the entire combustion period. The gas pressure calculation unit 52 performs a calculation process to calculate the mass fraction burned MFB at each crank angle θd. The calculated mass fraction burned MFB for each crank angle θd is stored in the storage device 91, such as a RAM, along with other calculated values.

number

[0133] The crank angle θd_MFB90 (above the dashed line in FIG. 18) at which the mass fraction burned MFB reaches the determination percentage (90%) on the right side of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition is occurring, and the crank angle θd_MFB90 (below the dashed line in FIG. 18) at which the mass fraction burned MFB reaches the determination percentage (90%) on the left side of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that pre-ignition is not occurring, can be clearly separated, making it possible to set a determination threshold (dashed line in FIG. 18) that accurately determines the occurrence of pre-ignition. This is because, unlike the crank angular acceleration α, the mass fraction burned MFB has little angle dependency and is therefore more clearly affected by the occurrence of pre-ignition.

[0134] Figure 19 plots the relationship between the crank angle θ_dQ / dθmax corresponding to the peak value dQ / dθ_max of the actual heat release rate and the crank angle θd_MFB90 at which the mass fraction burned MFB calculated by the control device 50 reaches the determination rate (90%) in each combustion cycle when there is a mixture of combustion cycles in which misfires occur and combustion cycles in which misfires do not occur. Note that the scales of the horizontal and vertical axes in Figure 19 are larger than those of the horizontal and vertical axes in Figure 18. Here, the peak value dQ / dθ_max of the actual heat release rate is a value calculated from the actual gas pressure in the cylinder (for example, a value measured by a gas pressure sensor in the cylinder).

[0135] The crank angle θd_MFB90 (below the dashed line in FIG. 19 ) at which the mass fraction burned MFB reaches the determination percentage (90%) on the left side of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that a misfire is occurring, can be clearly separated from the crank angle θd_MFB90 (above the dashed line in FIG. 19 ) at which the mass fraction burned MFB reaches the determination percentage (90%) on the right side of the dashed-dotted line, which is the region of the crank angle θ_dQ / dθmax corresponding to the peak value of the actual heat release rate at which it is desired to determine that a misfire is not occurring. This makes it possible to set a determination threshold (dashed line in FIG. 19 ) that accurately determines the occurrence of a misfire. This is because, unlike the crank angular acceleration α, the mass fraction burned MFB has little angle dependency and is therefore more sensitive to the influence of the occurrence of a misfire.

[0136] As described above, the occurrence of abnormal combustion such as pre-ignition and misfire can be determined by the mass fraction burned MFB, which has little angle dependency.

[0137] <Determining abnormal combustion> Therefore, the abnormal combustion judgment unit 53 judges whether or not abnormal combustion has occurred in the internal combustion engine based on the mass combustion fraction MFB at each crank angle θd in the judgment angle range Δθdet, which is calculated based on the increase ΔPcyl_brn in gas pressure due to combustion at each crank angle θd.

[0138] As described above, unlike the crank angular acceleration α, the mass fraction burned MFB has little angle dependency and is more sensitive to the influence of abnormal combustion. Therefore, the occurrence of abnormal combustion can be accurately determined based on the mass fraction burned MFB calculated based on the increase in gas pressure ΔPcyl_brn due to combustion.

[0139] <Preignition Judgment> In this embodiment, the abnormal combustion determination unit 53 determines the crank angle θd_MFB90 at which the mass fraction burned MFB becomes a determination percentage (for example, 90%) in the determination angle interval Δθdet, and determines whether pre-ignition has occurred by comparing the crank angle θd_MFB90 corresponding to the determination percentage with the angle threshold value Thθ_pre for pre-ignition. The determination percentage may be set to a percentage other than 90%.

[0140] As explained using Fig. 18, a difference in tendency of θd_MFB90 occurs between when pre-ignition has occurred and when it has not. Therefore, by setting the angle threshold value Thθ_pre for pre-ignition between θd_MFB90 when pre-ignition has occurred and θd_MFB90 when pre-ignition has not occurred, it is possible to accurately determine whether pre-ignition has occurred.

[0141] The abnormal combustion determination unit 53 determines that pre-ignition has occurred if the crank angle θd_MFB90 at which the mass combustion fraction MFB becomes the determination ratio (90%) exceeds the angle threshold value Thθ_pre for pre-ignition, and determines that pre-ignition has not occurred if θd_MFB90 is below the angle threshold value Thθ_pre for pre-ignition.

[0142] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_pre for pre-ignition based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for pre-ignition in which the relationship between the operating state and the angle threshold value Thθ_pre is set, and sets the angle threshold value Thθ_pre for pre-ignition that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotation angular velocity), etc.

[0143] <Judgment of misfire> The abnormal combustion determination unit 53 determines the crank angle θd_MFB90 at which the mass fraction burned MFB becomes a determination ratio (for example, 90%) in the determination angle interval Δθdet, and determines whether or not a misfire has occurred by comparing the crank angle θd_MFB90 corresponding to the determination ratio with the angle threshold value Thθ_mf for misfire.

[0144] As explained using Figure 19, there is a difference in the tendency of θd_MFB90 between when a misfire occurs and when a misfire does not occur. Therefore, by setting the angle threshold value Thθ_mf for misfire between θd_MFB90 when a misfire occurs and θd_MFB90 when a misfire does not occur, it is possible to accurately determine whether a misfire has occurred.

[0145] The abnormal combustion determination unit 53 determines that a misfire has occurred if the crank angle θd_MFB90 at which the mass fraction burned MFB becomes the determination rate (90%) is below the angle threshold value Thθ_mf for misfire, and determines that a misfire has not occurred if θd_MFB90 is above the angle threshold value Thθ_mf for misfire.

[0146] The abnormal combustion determination unit 53 sets the angle threshold value Thθ_mf for misfire based on the operating state of the internal combustion engine. For example, the abnormal combustion determination unit 53 references gas pressure threshold data for misfire in which the relationship between the operating state and the angle threshold value Thθ_mf is set, and sets the angle threshold value Thθ_mf for misfire that corresponds to the current operating state. The operating state of the internal combustion engine may include the state of the amount of intake gas in the cylinder (for example, the gas pressure Pin in the intake pipe, the amount of intake air, etc.), the air-fuel ratio, the rotation speed (rotational angular velocity), etc.

[0147] <Other embodiments> (1) In the above embodiments, the angle information detection unit 51 has been described as using the output signal of the crank angle sensor 11. However, another crank angle sensor that detects the teeth of a link gear or the like may be provided, and the angle information detection unit 51 may use the output signal of the other crank angle sensor.

[0148] (2) In the above embodiments, a three-cylinder engine is used as an example. However, an engine with any number of cylinders (for example, one, two, four, or six) may be used.

[0149] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment. [Explanation of symbols]

[0150] 1: internal combustion engine, 11: crank angle sensor, 50: control device for internal combustion engine, 51: angle information detection unit, 52: gas pressure calculation unit, 53: abnormal combustion determination unit, 54: avoidance control unit, dQ / dθd: heat release rate, Pcyl: gas pressure in cylinder, Pcyl_Δbrnmax: gas pressure in cylinder at crank angle corresponding to peak value of increase in gas pressure in cylinder due to combustion, Pcyl_unbrn: gas pressure in cylinder when uncombusted, ThΔP_0: exceeding zero determination threshold, ThΔP_mf: misfire state corresponding threshold, Thθ_mf: angle threshold for misfire, Thθ_pre: angle threshold for pre-ignition, ThP_mf: gas pressure threshold for misfire, ThP _pre: gas pressure threshold for pre-ignition, ThdQ_mf: misfire state threshold, ΔPcyl_brn: increase in gas pressure due to combustion, Δθdet: judgment angle interval, αd: crank angular acceleration, θd: crank angle, θd1: first crank angle, θd2: second crank angle, θd3: third crank angle, θd_Δbrnmax: crank angle corresponding to the peak value of the increase in gas pressure in the cylinder due to combustion, θd_MFB90: crank angle at which the mass burn rate reaches the judgment rate, θd_dQ / dθdmax: crank angle corresponding to the peak value of the heat release rate, θd_mf: angle corresponding to the misfire state, ωd: crank angular velocity

Claims

1. an angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of the crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, The gas pressure calculation unit calculates the gas pressure inside the cylinder when uncombusted, assuming that uncombusted fuel is present, at each crank angle based on the current state of the amount of gas intake gas into the cylinder and the crank angle, and calculates the gas pressure inside the cylinder at each crank angle based on the gas pressure inside the cylinder when uncombusted and the increase in gas pressure due to the combustion.The abnormal combustion judgment unit judges the peak value of the increase in gas pressure due to the combustion in the judgment angle range, and compares the gas pressure inside the cylinder at the crank angle corresponding to the peak value with a gas pressure threshold for pre-ignition, thereby determining whether or not pre-ignition has occurred.

2. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, The abnormal combustion determination unit is a control device for an internal combustion engine that determines whether pre-ignition has occurred by determining the peak value of the increase in gas pressure due to the combustion in the determination angle interval and comparing the crank angle corresponding to the peak value with an angle threshold value for pre-ignition.

3. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, the gas pressure calculation unit calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, based on a current state of an intake gas amount in the cylinder and the crank angle, and calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, based on the gas pressure in the cylinder when uncombusted and an increase in gas pressure due to the combustion; The abnormal combustion determination unit determines the peak value of the increase in gas pressure due to the combustion in the determination angle interval, and determines whether or not a misfire has occurred by comparing the gas pressure in the cylinder at the crank angle corresponding to the peak value with a gas pressure threshold value for a misfire.

4. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, The abnormal combustion determination unit determines the peak value of the increase in gas pressure due to the combustion in the determination angle interval, and compares the crank angle corresponding to the peak value with an angle threshold value for misfire, thereby determining whether or not a misfire has occurred.

5. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, the gas pressure calculation unit calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, based on a current state of an intake gas amount in the cylinder and the crank angle, and calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, based on the gas pressure in the cylinder when uncombusted and an increase in gas pressure due to the combustion; At each crank angle, a heat release rate per unit crank angle is calculated based on the gas pressure in the cylinder and the crank angle; The abnormal combustion determination unit is a control device for an internal combustion engine that determines whether pre-ignition has occurred by determining the peak value of the heat release rate in the determination angle interval and comparing the crank angle corresponding to the peak value with an angle threshold value for pre-ignition.

6. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, the gas pressure calculation unit calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, based on a current state of an intake gas amount in the cylinder and the crank angle, and calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, based on the gas pressure in the cylinder when uncombusted and an increase in gas pressure due to the combustion; At each crank angle, a heat release rate per unit crank angle is calculated based on the gas pressure in the cylinder and the crank angle; The abnormal combustion determination unit determines a peak value of the heat release rate in the determination angle interval, and compares the crank angle corresponding to the peak value with an angle threshold value for misfire, thereby determining whether or not a misfire has occurred.

7. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, the gas pressure calculation unit calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, based on a current state of an intake gas amount in the cylinder and the crank angle, and calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, based on the gas pressure in the cylinder when uncombusted and an increase in gas pressure due to the combustion; At each crank angle, a heat release rate per unit crank angle is calculated based on the gas pressure in the cylinder and the crank angle; A control device for an internal combustion engine that calculates a mass combustion rate for each crank angle by integrating the heat generation rate over the combustion period, and the abnormal combustion judgment unit judges the crank angle in the judgment angle interval at which the mass combustion rate becomes a judgment rate, and judges whether or not pre-ignition has occurred by comparing the crank angle corresponding to the judgment rate with an angle threshold for pre-ignition.

8. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, the gas pressure calculation unit calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, assuming that uncombusted fuel is present, based on a current state of an intake gas amount in the cylinder and the crank angle, and calculates, at each crank angle, a gas pressure in the cylinder when uncombusted, based on the gas pressure in the cylinder when uncombusted and an increase in gas pressure due to the combustion; At each crank angle, a heat release rate per unit crank angle is calculated based on the gas pressure in the cylinder and the crank angle; calculating a mass combustion fraction for each crank angle by integrating the heat release rate over the combustion period; The abnormal combustion determination unit determines the crank angle at which the mass combustion rate becomes a determination rate within the determination angle range, and compares the crank angle corresponding to the determination rate with an angle threshold value for misfire, thereby determining whether or not a misfire has occurred.

9. An angle information detection unit that detects a crank angle and a crank angular acceleration based on an output signal of a crank angle sensor; a gas pressure calculation unit that calculates, at each crank angle, an increase in gas pressure torque due to combustion, out of a gas pressure torque applied to the crankshaft by gas pressure in a cylinder, based on the crank angle and the crank angular acceleration, and calculates, at each crank angle, an increase in gas pressure due to combustion, based on the increase in gas pressure torque due to combustion and the crank angle; an abnormal combustion determination unit that determines whether or not abnormal combustion has occurred in the internal combustion engine based on an increase in gas pressure due to the combustion at each crank angle within a determination angle section that is set corresponding to a combustion period, The gas pressure calculation unit When the crank angle is changed to the retard side in the compression stroke and the combustion stroke, determining, as a first crank angle, the crank angle at which the increase in gas pressure due to the combustion becomes greater than a zero-exceeding determination threshold during a compression stroke; determining, after the first crank angle, the crank angle at which the increase in gas pressure due to the combustion becomes equal to or less than the over-zero determination threshold, as a second crank angle; determining, as a third crank angle, the crank angle at which an increase in gas pressure due to the combustion becomes greater than the over-zero determination threshold value after the second crank angle in a combustion stroke after the compression stroke; A control device for an internal combustion engine that, when the first crank angle and the third crank angle exist, sets the increase in gas pressure due to the combustion in the angle section corresponding to the first crank angle to the second crank angle to zero.

10. 5. The control device for an internal combustion engine according to claim 1, wherein the abnormal combustion determination unit determines a peak value of the increase in gas pressure due to the combustion in the determination angle interval, and if the peak value is smaller than a misfire state corresponding threshold value, sets an angle corresponding to a misfire state that is preset within the determination angle interval as the crank angle corresponding to the peak value.

11. 10. The control device for an internal combustion engine according to claim 1, further comprising an avoidance control unit that, when it is determined that abnormal combustion has occurred, changes control parameters of the internal combustion engine and controls the internal combustion engine so as to suppress the occurrence of abnormal combustion.

Images