Control device for an internal combustion engine

Abstract

The processors (B705, B706) of the control device for the internal combustion engine (1) of the present invention calculate the first combustion moment (MFB50) or the first combustion period (IG100_1) in the cylinder of the internal combustion engine (1) based on the crankshaft angle detected by the crankshaft angle sensor (20). The processor (B702) calculates the heat generation rate based on the first combustion moment or the first combustion period. The processor (B703) calculates the cylinder pressure and the unburned gas temperature in the cylinder based on the heat generation rate. The processor (B704) calculates the first combustion rate (laminar combustion rate SL1) based on the cylinder pressure and the unburned gas temperature in the cylinder. The processor (B707) learns the correspondence between the first combustion rate and the first combustion moment or the first combustion period.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] Combustion control technology is currently known to improve the combustion performance of internal combustion engines by recirculating a portion of the exhaust gas diverted from the exhaust manifold back to the intake manifold (recirculation). This control technology enables a system that controls the amount of air drawn into the engine and the proportion of exhaust gas recirculation by adjusting valve opening, while simultaneously controlling fuel injection quantity and ignition timing based on the relationship between the amount of fresh air detected by an intake air quantity sensor and the exhaust gas recirculation ratio. Additionally, lean-burn systems using a leaner fuel-air mixture than the stoichiometric mixture are known. Lean-burn engines enable a system that controls the amount of air drawn into the engine by adjusting valve opening, while simultaneously controlling fuel injection quantity and ignition timing based on the relationship between the amount of fresh air detected by an intake air quantity sensor and the target air-fuel ratio.

[0003] Increasing the exhaust gas recirculation (EGR) rate can improve pump losses caused by throttle valve throttling during partial load operation and reduce knocking during high load operation. However, excessively increasing the EGR rate can lead to unstable combustion and misfires. Furthermore, in lean-burn engines, pump losses caused by throttle valve throttling during partial load operation can also be reduced. Additionally, the increased specific heat ratio due to lean combustion and the resulting temperature drop improves thermal efficiency. However, excessively lean conditions can also lead to unstable combustion and misfires.

[0004] The aforementioned combustion control technologies exhibit the following trend: the greater the amount of exhaust gas recirculation to dilute the fuel, or the greater the amount of fuel injection to lean the fuel, the more significant the combustion instability becomes. Therefore, combustion state detection feedback control becomes crucial as a technology for appropriately detecting / preventing excessive dilution or leaning. As a means of this, techniques such as in-cylinder pressure estimation based on crankshaft angle sensors (e.g., see Patent Document 1) and techniques for detecting combustion instability by installing direct pressure sensors within the cylinder (e.g., see Patent Document 2) have been disclosed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-53742

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-219005 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] The control system described in Patent Document 1 discloses that, based on information about the crankshaft angle and angular acceleration obtained from a crankshaft angle sensor, it estimates the torsional vibration torque generated in the crankshaft mechanism. Based on this, it calculates the combustion pressure in the cylinder derived from the mechanical relationship of the crankshaft mechanism and uses it for correction control of ignition timing and EGR rate. However, the method of calculating the combustion pressure in the cylinder using the mechanical relationship of the crankshaft mechanism based on crankshaft angle sensor information involves a large amount of computation and requires very high accuracy from the crankshaft angle sensor, thus increasing the cost of the controller and sensor.

[0011] On the other hand, Patent Document 2 discloses a lean-burn control system that uses a sensor to directly measure combustion pressure within the cylinder. It detects the combustion rate based on the in-cylinder pressure measurement during the initial combustion period immediately following ignition, and adjusts the air-fuel ratio accordingly. However, the increased cost associated with using a combustion pressure sensor is a concern.

[0012] The purpose of this invention is to provide a control device for an internal combustion engine that can detect the combustion state inside the cylinder without using in-cylinder sensors, thereby reducing manufacturing costs.

[0013] Technical means for solving technical problems

[0014] To achieve the above objectives, the control device for the internal combustion engine of the present invention includes a processor that calculates a first combustion moment or a first combustion period in the cylinder of the internal combustion engine based on the crankshaft angle detected by a crankshaft angle sensor, calculates a heat generation rate based on the first combustion moment or the first combustion period, calculates the cylinder pressure and the unburned gas temperature based on the heat generation rate, calculates a first combustion speed based on the cylinder pressure and the unburned gas temperature, and learns the correspondence between the first combustion speed and the first combustion moment or the first combustion period.

[0015] Invention Effects

[0016] According to the present invention, the combustion state inside the cylinder can be detected without using an in-cylinder sensor, thereby reducing manufacturing costs. Other issues, features, and effects not described above will become clear from the following description of embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic structural diagram of the engine system as the control object of the engine control system, which is one embodiment of the present invention.

[0018] Figure 2 This is a block diagram representing an example of the hardware structure of an ECU.

[0019] Figure 3 This diagram illustrates the control module used to calculate the throttle valve opening command value, the EGR valve opening command value, and the fuel injection valve drive pulse command value.

[0020] Figure 4 This diagram illustrates the intake metering control module used to calculate the current values ​​of fill efficiency and EGR rate.

[0021] Figure 5 This is a diagram illustrating the physical model considered when constructing the opening control model for the throttle valve and EGR valve used to achieve the target filling efficiency and target EGR rate.

[0022] Figure 6 This diagram uses a valve cross-section schematic to illustrate the method for calculating the target valve opening based on a valve flow calculation model.

[0023] Figure 7 This diagram illustrates the overall situation of the control module that corrects the fuel injection quantity and EGR valve opening based on the combustion state detected by the crankshaft angle sensor.

[0024] Figure 8 It is a graph illustrating a typical heat generation rate curve and a representative combustion period / moment commonly found in engines.

[0025] Figure 9A This is a diagram illustrating a method for detecting the moment of the combustion center of gravity based on crankshaft angle sensor signals.

[0026] Figure 9B It is a graph showing the relationship between the maximum angular acceleration and the moment of combustion center of gravity.

[0027] Figure 10 This diagram illustrates the relationship between IG50, IG10, and IG90.

[0028] Figure 11A It is a graph illustrating the rate of heat generation from combustion.

[0029] Figure 11B This is a diagram illustrating the method for calculating cylinder pressure.

[0030] Figure 11C This is a diagram illustrating the method for calculating in-cylinder temperature and unburned gas temperature.

[0031] Figure 12A It is a graph illustrating the relationship between combustion rate and combustion duration.

[0032] Figure 12B This is a graph illustrating the impact of differences during combustion on the heat generation rate.

[0033] Figure 12C This is a graph illustrating the effect of differences during combustion on cylinder pressure.

[0034] Figure 12D This is a graph illustrating the effect of differences in temperature during combustion.

[0035] Figure 13A This is a graph illustrating the effects of pressure, unburned gas temperature, and equivalence ratio (0.6) on the laminar combustion rate of gasoline.

[0036] Figure 13B This is a graph illustrating the effects of pressure, unburned gas temperature, and equivalence ratio (1.0) on the laminar combustion rate of gasoline.

[0037] Figure 13C This is a graph illustrating the effects of pressure, unburned gas temperature, and equivalence ratio (1.3) on the laminar combustion rate of gasoline.

[0038] Figure 14 This is a graph illustrating the effect of EGR rate on the laminar combustion rate of gasoline.

[0039] Figure 15 This is a diagram illustrating the relationship between combustion rate and combustion duration.

[0040] Figure 16 This is a diagram illustrating the method and flowchart for learning the relationship between combustion rate and combustion period based on recursive least squares.

[0041] Figure 17 This is a graph illustrating the tendency of IG50 relative to rotational speed and filling efficiency.

[0042] Figure 18 This is a flowchart illustrating a combustion control method that uses combustion detection information based on a crankshaft angle sensor in a lean-burn system.

[0043] Figure 19 It is a timing diagram illustrating the actions performed in a lean-burn system when combustion control is implemented using combustion detection information based on a crankshaft angle sensor.

[0044] Figure 20 This is a flowchart illustrating a combustion control method using combustion detection information based on a crankshaft angle sensor in an EGR system.

[0045] Figure 21 It is a timing diagram illustrating the actions performed in the EGR combustion system when combustion control is implemented using combustion detection information based on the crankshaft angle sensor. Detailed Implementation

[0046] Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The purpose of this embodiment is to maintain high EGR control accuracy and air-fuel ratio, preventing poor combustion in the internal combustion engine due to control errors in these parameters. Furthermore, in this specification and the accompanying drawings, components having substantially the same function or structure are labeled with the same reference numerals, and repeated descriptions are omitted.

[0047] First, refer to Figure 1 The structure of the engine system as the control object of the engine control system, which is one embodiment of the present invention, is described.

[0048] Figure 1 This section illustrates a schematic structural example of an engine system as the control object of an engine control system according to one embodiment of the present invention. The engine system includes an internal combustion engine 1, an accelerator pedal position sensor 2, an airflow sensor 3, a throttle valve 4, an intake manifold 5, a flow enhancement valve 7, an intake valve 8, an exhaust valve 10, a fuel injection valve 12, spark plugs 13, and a crankshaft angle sensor 20. Furthermore, the engine system also includes an air-fuel ratio sensor 14, an EGR (Exhausted Gas Recirculation) pipe 15, an EGR cooler 16, an EGR temperature sensor 17, an EGR valve upstream pressure sensor 18, an EGR valve 19, and an ECU (Electronic Control Unit) 21.

[0049] A throttle valve 4 is located upstream of the intake manifold 5 formed in the intake pipe 31, and controls the amount of intake air flowing into the cylinders of the internal combustion engine 1 by throttling the intake flow path. In this embodiment, the throttle valve 4 is an electronically controlled butterfly valve whose valve opening can be controlled independently of the driver's accelerator pedal depressor. Downstream of the throttle valve 4, it is connected to the intake manifold 5, on which the intake manifold pressure sensor 6 is mounted.

[0050] The flow enhancement valve 7 is located downstream of the intake manifold 5 and enhances the turbulence of the flow inside the cylinder by deflecting the intake air drawn into the cylinder. During exhaust gas recirculation combustion, as described later, the flow enhancement valve 7 is closed to promote and stabilize turbulent combustion.

[0051] An intake valve 8 and an exhaust valve 10 are provided in the internal combustion engine 1. The intake valve 8 and exhaust valve 10 each have a variable valve mechanism for continuously changing the phase of valve opening and closing. An intake valve position sensor 9 and an exhaust valve position sensor 11 for detecting the opening and closing phase of the valves are respectively assembled in the variable valve mechanisms of the intake valve 8 and exhaust valve 10. A direct fuel injection valve 12 for directly injecting fuel into the cylinder is provided in the cylinder of the internal combustion engine 1. Alternatively, the fuel injection valve 12 can also be an intake port injection type, injecting fuel into the intake port.

[0052] A spark plug 13 is installed in the cylinder of the internal combustion engine 1. The spark plug 13 exposes its electrode part inside the cylinder and ignites the combustible mixture by spark. A crankshaft angle sensor 20 is installed on the crankshaft and outputs a signal corresponding to the rotation angle of the crankshaft as a signal indicating the engine speed to the ECU 21. An air-fuel ratio sensor 14 is located in the exhaust pipe 32 and outputs a signal indicating the detected exhaust gas components, i.e., the air-fuel ratio, to the ECU 21.

[0053] In this embodiment, an EGR system is configured including an EGR pipe 15 and an EGR valve 19 disposed within the EGR pipe 15. The EGR pipe 15 connects the exhaust flow path (intake pipe 31) and the intake flow path (exhaust pipe 32), diverting exhaust gas from the exhaust flow path and recirculating it downstream of the throttle valve 4. An EGR cooler 16 disposed on the EGR pipe 15 cools the exhaust gas. The EGR valve 19 is disposed downstream of the EGR cooler 16 and controls the flow rate of the exhaust gas. An EGR temperature sensor 17 for detecting the temperature of the exhaust gas flowing upstream of the EGR valve 19 and an EGR valve upstream pressure sensor 18 for detecting the pressure upstream of the EGR valve 19 are provided in the EGR pipe 15.

[0054] ECU 21 is an example of an electronic control unit that controls various components of the engine system or performs various data processing tasks. The engine system and ECU 21 constitute the engine control system. The various sensors and actuators mentioned above are connected to ECU 21 in a communicative manner. ECU 21 controls the operation of actuators such as the throttle valve 4, fuel injection valve 12, intake valve 8, exhaust valve 10, and EGR valve 19. Furthermore, based on signals input from various sensors, ECU 21 detects the operating state of the internal combustion engine 1 and ignites the spark plug 13 at a timing determined according to the operating state. Moreover, if ECU 21 detects an abnormality or malfunction in the engine system, including the internal combustion engine 1, it illuminates the corresponding warning indicator 22 (MIL).

[0055] Figure 2This is a block diagram illustrating an example of the hardware structure of ECU 21. ECU 21 has a control unit 23, a storage unit 24, and an input / output interface 25 interconnected via a system bus 26. The control unit 23 consists of a CPU (Central Processing Unit) 23a, a ROM (Read Only Memory) 23b, and a RAM (Random Access Memory) 23c. The CPU 23a loads the control program stored in the ROM 23b into the RAM 23c and executes it, thereby implementing the various functions of ECU 21. The storage unit 24, which serves as an auxiliary storage device and is composed of semiconductor memory or the like, records state-space models, parameters, data obtained from executing the control program, etc. Additionally, the control program can also be stored in the storage unit 24.

[0056] Input / output interface 25 is the interface for communication of signals and data with various sensors and actuators. ECU 21 has an A / D (Analog / Digital) converter (not shown), driver circuitry, etc., that processes the input and output signals from various sensors. Input / output interface 25 can also function as an A / D converter. Furthermore, while a CPU is used as the processor, other processors such as an MPU (Micro Processing Unit) can also be used.

[0057] Figure 3 This diagram illustrates the control module used to calculate the throttle valve opening command value, the EGR valve opening command value, and the fuel injection valve drive pulse command value. Additionally, in Figure 3 In the diagram, a B is appended to the beginning of the reference numerals for each functional module (the same applies below).

[0058] In the target torque calculation unit 301, the target torque of the engine is calculated based on the engine speed, the driver's accelerator pedal depressor, and the externally required torque. In the target filling efficiency calculation unit 302, the amount of air drawn into the cylinder in one cycle, i.e., the filling efficiency, is calculated based on the engine speed and the target torque. Here, filling efficiency is defined as the proportion of the actual amount of air drawn in when the mass of air at standard conditions (25°C, 1 atmosphere) fills the stroke volume, using 1.0 as a baseline.

[0059] In the target throttle valve opening calculation unit 303, the airflow through the throttle valve is calculated based on the target filling efficiency and rotational speed. The target throttle valve opening to achieve the aforementioned airflow is then calculated based on the states before and after throttling. A throttle valve opening command value is output based on this target throttle valve opening.

[0060] In the target EGR rate calculation unit 304, the EGR rate, pre-adjusted by engine calibration considering fuel consumption and exhaust performance, is set on the control map for each engine speed / target fill efficiency. The target EGR rate is then calculated based on the engine speed and target fill efficiency using this control map. In the target EGR valve opening calculation unit 305, the target EGR valve opening is calculated based on the current fill efficiency value, engine speed, target EGR rate, and the combustion speed prediction result (described later). An EGR valve opening command value is output based on this target EGR valve opening. Details of the current fill efficiency value will be provided using... Figure 4 To be described later.

[0061] In the target equivalence ratio calculation unit 306, the target equivalence ratio is calculated based on the target fill efficiency and engine speed. Here, the equivalence ratio is an indicator of the fuel-air mixture concentration based on the stoichiometric air-fuel ratio. The stoichiometric air-fuel ratio is set to 1, becoming a value greater than 1 under rich conditions and a value less than 1 under lean conditions. In the target fuel injection quantity calculation unit 307, the target fuel injection quantity is calculated based on the current fill efficiency value, the target equivalence ratio, and the combustion rate prediction result described later. Based on this fuel injection quantity, an injector drive pulse command value is output.

[0062] In the fuel center-of-gravity time calculation unit 308, the combustion center-of-gravity time (MFB50: 50% Mass Fraction Burned, fuel mass fraction) as the first combustion moment is calculated based on the crankshaft angle sensor signal. In the combustion speed prediction unit 309, the combustion speed is predicted based on the combustion center-of-gravity time, engine speed, current fill efficiency value, current EGR rate value, and current equivalence ratio value. Based on this combustion speed prediction result or a combustion period prediction result that is related to the combustion speed, the target EGR rate and target fuel injection quantity are corrected. Furthermore, details of the current EGR rate value will be obtained using... Figure 4 To be described later.

[0063] By adopting such a control structure, the torque required by the driver can be accurately controlled, and combustion instability caused by errors in EGR rate and air-fuel ratio control can be appropriately prevented, thereby achieving low fuel consumption and low exhaust performance.

[0064] Figure 4This diagram illustrates the intake metering control module used to calculate the current values ​​of fill efficiency and EGR rate. In the EGR valve flow calculation unit 401, the EGR valve flow rate is calculated based on the EGR valve opening, the upstream state of the EGR valve, and the downstream state. The upstream state of the EGR valve is directly detected by pressure and temperature sensors, or it can be calculated using a control mapping diagram based on engine speed and load information. In the intake manifold pressure, temperature, and EGR rate calculation unit 402, the intake manifold pressure, temperature, and EGR rate are calculated based on the cylinder intake flow rate, the sensor value of the airflow sensor, and the EGR valve flow rate.

[0065] In the fill efficiency and EGR rate calculation unit 403, the current values ​​of fill efficiency and EGR rate are calculated and output based on the intake manifold pressure, temperature, EGR rate, and engine speed. In the cylinder intake flow calculation unit 404, the cylinder intake flow rate is calculated based on engine speed, fill efficiency, EGR rate, and engine speed. By employing such a control structure, the current state inside the cylinder can be accurately measured, and the fuel injection quantity and ignition timing can be controlled with high precision, achieving low fuel consumption and low exhaust performance.

[0066] Figure 5 This is a diagram illustrating the physical model considered when constructing the throttle valve and EGR valve opening control model for achieving the target fill efficiency and target EGR rate. As state variables within the intake manifold, the pressure (hereinafter referred to as "intake manifold pressure") pm and the EGR rate ξm within the intake manifold (e.g., intake manifold 5) are defined as follows, which can be obtained by the following equations (1) and (2), respectively.

[0067] [Formula 1]

[0068]

[0069] [Equation 2]

[0070]

[0071] Here, mth (marked with a dot) represents the flow rate through the throttle valve, megr (marked with a dot) represents the flow rate through the EGR valve, mcyl (marked with a dot) represents the cylinder intake flow rate, κ represents the polytropic exponent, R represents the gas constant, Vm represents the intake manifold volume, Ta represents the atmospheric temperature, Tegr represents the EGR temperature, and Tm represents the intake manifold temperature. The dotted symbols above indicate the first derivative of time.

[0072] The flow rate through the throttle valve (mth marked with a dot) can be calculated using the following formula (3). Furthermore, the flow rate through the throttle valve is approximately equivalent to the detection value of the airflow sensor 3 (mafs marked with a dot).

[0073] [Formula 3]

[0074]

[0075] Here, ρa is the atmospheric density, μth is the throttle valve flow coefficient, Dth is the throttle valve outer diameter, φth is the throttle valve opening, φth0 is the throttle valve minimum opening, and pa is the atmospheric pressure.

[0076] The flow rate (megr marked with a dot above) of the EGR valve can be calculated using the following formula (4).

[0077] [Formula 4]

[0078]

[0079] Here, ρe is the EGR density (recirculated exhaust gas density), μegr is the EGR valve flow coefficient, Degr is the EGR valve outer diameter, φegr is the EGR valve opening, and φegr0 is the EGR valve minimum opening.

[0080] The cylinder intake flow rate (mcyl marked with a dot) is calculated by the following formula (5).

[0081] [Formula 5]

[0082]

[0083] Here, Ne is the speed of internal combustion engine 1 (revolutions per minute), ηin is the intake efficiency, and Vd is the total stroke volume of internal combustion engine 1. The intake efficiency is a value representing the proportion of the mass of gas actually drawn into the cylinder, based on the mass of gas in the intake manifold equivalent to the stroke volume of all cylinders (e.g., 4 cylinders) (1.0).

[0084] The filling efficiency ηch of the new gas drawn into the cylinder is defined by the following formula (6).

[0085] [Formula 6]

[0086]

[0087] Here, p0 and T0 are the temperature and pressure under standard atmospheric conditions (e.g., 25°C, 101.325 Pa).

[0088] The net mean effective pressure (BMEP), which is an indicator of torque, is obtained by the following equation (7).

[0089] [Formula 7]

[0090]

[0091] Here, HL represents the lower heating value of the fuel, ηite represents the thermal efficiency shown in the figure, φ represents the equivalence ratio, L0 represents the stoichiometric air-fuel ratio, and pf represents the frictional mean effective pressure with respect to frictional torque. Frictional torque is the torque that acts due to friction and opposes the motion between contacting objects.

[0092] Here, refer to Figure 6 This section explains the calculation of the target valve opening based on the valve flow rate calculation model.

[0093] Figure 6 This diagram illustrates the method for calculating the target valve opening based on a valve flow rate calculation model, using a schematic diagram of the valve cross-section. In the diagram, the dotted symbol at the top represents the valve flow rate, pup represents the gas pressure upstream (in) of the valve, pdown represents the gas pressure downstream (out) of the valve, ρup represents the gas density upstream of the valve, D represents the valve's outer diameter, and φ represents the valve opening. The slanted section represents the flow path of the gas through the valve. The cross-sectional area of ​​this flow path, i.e., the opening area S, is represented by the following equation (8).

[0094] [Formula 8]

[0095]

[0096] When the above valve is a throttle valve Figure 6 pup is equivalent to atmospheric pressure patm, pdown is equivalent to intake manifold pressure pm, ρup is equivalent to atmospheric density ρatm, and D is equivalent to the outer diameter of the throttle valve Dth. The throttle valve of equation (3) is modified by the flow rate formula to achieve the throttle valve opening φth of the target air volume (mth,d marked with dots above) specified by the target torque and speed, as shown in equation (9), by performing an inverse operation on the throttle valve using the flow rate formula.

[0097] [Formula 9]

[0098]

[0099] Replacing equation (9) with a table of throttle valve opening degree and opening area allows it to be used for Figure 5 The target throttle valve opening calculation unit 503 performs the calculation of the target throttle valve opening.

[0100] Similarly, in the case where the valve described above is an EGR valve, Figure 6pup is equivalent to the upstream pressure pegr of the EGR valve, pdown is equivalent to the intake manifold pressure pm, ρup is equivalent to the EGR density ρegr, and D is equivalent to the outer diameter of the EGR valve Degr. The EGR valve in equation (4) is modified by flow rate to achieve the EGR valve opening φegr of the target EGR flow rate (megr,d marked with a dot symbol above) specified by the target torque and speed, as shown in equation (10), by performing an inverse operation on the EGR valve using flow rate.

[0101] [Formula 10]

[0102]

[0103] Replacing equation (10) with a table of EGR valve opening degree and opening area allows it to be used for... Figure 5 The target EGR rate calculation unit 504 performs the calculation of the target EGR valve opening.

[0104] Figure 7 This diagram illustrates the main components of a control module that corrects the fuel injection quantity and EGR valve opening based on the combustion state detected by a crankshaft angle sensor. In the fill efficiency and EGR rate calculation unit 701, the current fill efficiency and EGR rate are calculated based on the engine speed, the value sensed by the airflow sensor, the throttle valve opening, and the EGR valve opening. Figure 5 and Figure 4 The model for calculation by the computation unit is explained in detail.

[0105] In the heat generation rate calculation unit 702, the heat generation rate is calculated based on the current fill efficiency and EGR rate, equivalence ratio, and the combustion period described later. The heat generation rate refers to the heat generated per crankshaft angle out of the total heat generated through combustion. The heat generation rate curve varies due to factors such as combustion rate, combustion chamber shape, and ignition timing.

[0106] In the in-cylinder pressure, in-cylinder temperature, and unburned gas temperature calculation unit 703, the in-cylinder pressure, in-cylinder temperature, and unburned gas temperature are calculated using the equation of state and polynomial state change formulas, based on the aforementioned relationship between heat generation rate and combustion chamber volume. In the laminar combustion rate calculation unit 704, the laminar combustion rate is calculated based on the in-cylinder pressure, unburned gas temperature, equivalence ratio, and EGR rate. The laminar combustion rate is a state variable determined by the fuel type, mixture composition, temperature, and pressure.

[0107] In the MFB50 calculation unit, the moment when the combustion mass ratio reaches 50% of the total supplied mass (the moment of combustion center of gravity) is calculated based on the crankshaft angle sensor signal, i.e., MFB50. In the combustion period calculation unit 706, the total combustion period from ignition to the end of combustion is calculated based on the correlation with MFB50.

[0108] In the combustion rate / combustion period learning unit 707, the relationship between the combustion period information obtained from the crankshaft angle sensor signal (crankshaft angle sensor information) and the laminar combustion rate estimated based on the in-cylinder pressure is learned. The recursive least squares method, described later, is applied during the learning process. Since learning can be performed on-board using the recursive least squares method, vehicle-specific correlations can be considered in the control. Factors contributing to the vehicle's inherent state include deviations in fuel properties, changes in fuel type (e.g., ethanol concentration in the fuel), deposits on the EGR valve and / or throttle valve, actuator and sensor errors, etc.

[0109] The aforementioned deviations, when implemented in EGR combustion systems and lean-burn systems near the combustion limits, can lead to excessive increases in combustion intensity. Therefore, they need to be properly considered. Through detection based on crankshaft angle sensors and on-board learning, an adaptation mechanism for these deviations can be implemented.

[0110] In the laminar combustion rate prediction unit 708, the laminar combustion rate under the target control state is predicted based on the target equivalence ratio, the target EGR rate, and the current in-cylinder pressure and unburned gas temperature. In the combustion period prediction unit 709, the combustion period corresponding to the target equivalence ratio, the target EGR rate, and the current in-cylinder pressure and unburned gas temperature is predicted based on the aforementioned laminar combustion rate prediction results and the correlation between combustion rate and combustion period.

[0111] In the target equivalence ratio / target EGR rate correction unit 710, if the predicted value during combustion is above a predetermined value, the target equivalence ratio or target EGR rate is corrected towards the side where the combustion period decreases (the side where the combustion rate increases). That is, in the equivalence ratio, if the combustion period is above a predetermined value, a correction is performed towards the rich side. In the fuel injection quantity correction calculation unit 711, the fuel injection quantity is corrected towards the incremental side by an amount equivalent to the rich correction, and a correction amount is added to the injector pulse width command value.

[0112] Furthermore, regarding the EGR rate, if the combustion period is above a predetermined value, the target value is corrected towards reducing EGR. In the EGR valve opening correction calculation unit 712, an EGR valve opening correction amount equivalent to the aforementioned EGR reduction correction is added to the EGR valve opening command value. In the ignition timing advance correction calculation unit 713, if the combustion period increases, the ignition timing is corrected towards the advance angle side; if the combustion period decreases, the ignition timing is corrected towards the lag angle side. The ignition timing is output as a command value. With the control structure described above, combustion instability caused by errors in EGR rate and air-fuel ratio control can be appropriately prevented, achieving low fuel consumption and low exhaust performance. In addition, since the combustion state detection feedback mechanism can be implemented without using an in-cylinder pressure sensor, costs can be reduced.

[0113] Figure 8 This diagram illustrates typical heat generation rate curves and representative combustion periods / moments common in engines. In gasoline engines, combustion occurs shortly after ignition during flame nucleation, a period of minimal heat release. The time before the 10% combustion mass percentage point (MFB10) is referred to as the initial combustion period. The period from ignition to MFB10 is called IG10. Between MFB10 and MFB90, combustion is propelled by turbulent flame propagation, exhibiting the majority of the heat generation rate; this period is called the main combustion period. Here, MFB50 is defined as the combustion center of gravity moment, detected based on the crankshaft angle sensor signal.

[0114] Figure 9A , 9B This is a diagram illustrating the method for detecting the MFB50 moment based on the crankshaft angle sensor signal. Figure 9A The graph shows the crankshaft angular acceleration calculated from the crankshaft angle sensor signal relative to the crankshaft angle. As can be seen from the graph, the crankshaft angular acceleration exhibits a peak value at the combustion moment of each cylinder. The following graph shows the relationship between the maximum crankshaft angular acceleration and the combustion center of gravity moment of each cylinder. There is a high correlation between the maximum crankshaft angular acceleration (maximum angular acceleration) and MFB50, allowing the combustion center of gravity moment to be indirectly detected based on the crankshaft angle sensor signal. By employing such a control structure, the computational load can be significantly reduced compared to methods that estimate the in-cylinder pressure at each crankshaft angle based on the shift in torque at each crankshaft angle obtained from the crankshaft angle sensor signal. Furthermore, while the system configuration of this embodiment detects MFB50 as the combustion center of gravity moment, the invention is not limited to this; similar or identical effects can be achieved by detecting combustion mass ratios representing other combustion mass proportions.

[0115] Figure 10This diagram illustrates the relationship between IG50, IG10, and IG90. IG50 represents the combustion period from ignition to MFB50, and the aforementioned MFB50 based on the crankshaft angle sensor signal can be applied. As shown in the diagram, there is a high correlation between IG50, IG10, and IG90, allowing for the indirect detection of IG10 and IG90 from IG50.

[0116] Information about the initial combustion period can be obtained from IG10, information about the full combustion period can be obtained from IG90, and information about the main combustion period can be obtained based on the information from MFB10 to MFB90. Furthermore, the system configuration of the embodiment of the present invention uses a linear function of IG50, IG10, and IG90, but the present invention is not limited to this; the same or similar effects can be achieved by using a quadratic function, etc.

[0117] Figure 11A , 11B Figure 11C illustrates the method for calculating in-cylinder pressure, in-cylinder temperature, and unburned gas temperature based on the heat generation rate from combustion. The in-cylinder pressure and temperature at the moment the intake valve closes (IVC) can be determined based on the pressure and temperature in the intake manifold. Regarding the in-cylinder pressure and temperature at the ignition point, it can be assumed that the state change from IVC to ignition point (SPK) is a polytropic change, and can be calculated using the following formula.

[0118] [Equation 11]

[0119]

[0120] [Equation 12]

[0121]

[0122] Here, κ is the multivariate exponent, determined by the specific heat ratio and heat loss, which depend on temperature / gas composition. Vz is the cylinder volume corresponding to the crankshaft angle. Then, the pressure and temperature from ignition to the end of combustion are obtained in stages by discretizing and integrating the differential equations for each crankshaft angle θ. The entire combustion period is divided into N parts, and the in-cylinder pressure Pz in the nth part... n It can be calculated based on the rate of volume change and the rate of heat generation using the following formula.

[0123] [Equation 13]

[0124]

[0125] Furthermore, the in-cylinder temperature Tz of the nth cylinder nIt can be obtained using the following formula. Here, θ is the crankshaft angle, and Qz is the heat generation. dQz / dθ can be calculated using an empirical formula known as the Wiebe function. Alternatively, a table storing the results of pre-calculated Wiebe functions can be used.

[0126] [Formula 14]

[0127]

[0128] Furthermore, the temperature Tu of the nth unburned gas n It can be based on the pressure and temperature at the ignition point and the pressure Pz in the nth cylinder. n It can be obtained by the following formula.

[0129] [Formula 15]

[0130]

[0131] By executing equations (13), (14), and (15) up to n = 1, 2, ..., N, the pressure, temperature, and unburned gas temperature of the entire combustion process are calculated. A larger number of segments N improves accuracy but increases computational load, resulting in a trade-off. The optimal value for the number of segments N is selected during design based on this trade-off. This structure reduces costs compared to structures with pressure sensors that directly detect cylinder pressure.

[0132] Figures 12A-12D This is a graph illustrating the relationship between combustion rate and combustion duration, and the impact of differences in combustion duration on cylinder pressure and temperature. The relationship between combustion rate and combustion duration is shown below. Figure 12A The relationship is roughly inversely proportional; the lower the combustion rate, the longer the combustion period. Regarding the impact of combustion period on cylinder pressure, a shorter combustion period shifts cylinder pressure towards the increasing side. Furthermore, cylinder pressure temperature and unburned gas temperature also tend to increase with a shorter combustion period.

[0133] As described above, in-cylinder pressure and temperature are affected by changes in combustion rate, and the combustion rate itself is also affected by pressure and temperature. Therefore, it is theoretically difficult to predict the combustion rate and duration of the cycle in advance at the start of combustion. Thus, in order to control the EGR rate, air-fuel ratio, and ignition timing based on combustion rate and duration, a means for predicting combustion rate and duration is needed. As this prediction means, the system configuration of the embodiments of the present invention is a learning unit having combustion rate and duration, which makes current or future predictions based on past learning results.

[0134] Figure 13A , 13BFigure 13C illustrates the effects of pressure, unburned gas temperature, and stoichiometry on the laminar combustion rate of gasoline. The pressure and temperature ratios are proportions relative to standard atmospheric pressure and temperature. Pressure, unburned gas temperature, and stoichiometry all influence the laminar combustion rate, and their sensitivity varies due to interactions. This relationship is maintained as a mapping or function. Figure 7 In the laminar combustion rate calculation unit 704, the laminar combustion rate can be calculated based on pressure, unburned gas temperature and stoichiometry.

[0135] Figure 14 This is a graph illustrating the effect of EGR rate on the laminar combustion rate of gasoline. The vertical axis of the graph represents the laminar combustion rate ratio with a baseline of 1.0, using an EGR rate of zero as a reference, indicating the sensitivity to EGR mole fraction. As the EGR rate increases, the laminar combustion rate decreases. This relationship is maintained as a table or function. Figure 7 In the laminar combustion rate calculation unit 704, the laminar combustion rate can be obtained based on the EGR rate.

[0136] Figure 15 This diagram illustrates the method for learning the relationship between combustion rate and combustion period. Here, a method is used to approximate this relationship using a polynomial. Combustion rate is affected not only by laminar combustion rate but also by turbulence, etc., therefore, rotational speed and filling efficiency must be considered when learning the relationship between combustion rate and combustion period. Furthermore, the combustion mechanism differs during the initial combustion period (ignition period to MFB10) and the main combustion period (MFB10 to MFB90), therefore, the laminar combustion rate during both periods must be considered. The following polynomial is defined with these as variables.

[0137] [Formula 16]

[0138]

[0139] Here, y is the output, set to IG50. x1 is the rotational speed, x2 is the fill efficiency, x3 is the laminar combustion rate during initial combustion, and x4 is the laminar combustion rate during main combustion. Rearranging the above equation, it can be expressed using the following partial regression coefficient vector and explanatory variable vector.

[0140] [Equation 17]

[0141]

[0142] As a result, using four variables as input elements to define 13 variables, the relationship between IG50 and combustion rate was learned by identifying 14 partial regression coefficients that included a constant term. This function was maintained within... Figure 7The combustion rate / combustion period learning unit 707 and the combustion period prediction unit 709 are capable of learning and prediction. The system in the embodiment shown here is configured with a 4-variable quadratic polynomial, but the present invention is not limited to this, and other polynomials may be used. Furthermore, as alternatives to polynomials, neural networks, control maps, etc., can also achieve the same or similar effects as polynomial-based learning and prediction.

[0143] Figure 16 This is a diagram illustrating the method and flowchart for learning the relationship between combustion rate and combustion period based on recursive least squares. It shows the method of successively updating the partial regression coefficient vector θ^ based on the relationship between input and output. The symbol ^ is placed above (or to the upper right of) θ to represent the partial regression coefficient vector. When executing the recursive least squares method, in S1601, it is determined whether the recursive least squares method can be executed. The criteria for determining whether execution is possible consider the sensor state and the prediction range of the state equation as a prerequisite. The following specifically shows the calculations executed in S1602~S1606.

[0144] Here, the relationship between combustion period and combustion rate, which is the object of study, is a time-varying system affected by fuel properties, deposit adhesion, and actuator / sensor errors. To address this, a Sequential Identification Algorithm with a variable forgetting factor is employed. The forgetting factor is a function that reduces the influence of historical data exponentially. By further employing variable forgetting, historical data is forgotten during transitional states, and the forgetting factor is brought close to 1 during steady states, thereby enabling the active utilization of historical data. The following represents the recursive least squares method with a variable forgetting factor. First, the difference between the polynomial and the output value is taken as the error ε(k) and calculated using the following equation (S1602).

[0145] [Formula 18]

[0146]

[0147] Next, based on the covariance matrix P(k-1), the input vector φ(k), and the forgetting factor λ(k), L(k) is calculated using the following formula. Based on L(k) and the error ε(k), the partial regression coefficient vector θ^(k) is updated using the following formula (S1603, S1604).

[0148] [Formula 19]

[0149]

[0150] At this point, the forgetting factor λ(k) and the covariance matrix P(k) are obtained by the following equations (S1605, S1606).

[0151] [Formula 20]

[0152]

[0153] Here, σ is the adjustment parameter during learning. Furthermore, the parameter identification algorithm in this embodiment uses the recursive least squares method, but the invention is not limited to this. That is, other optimization methods such as genetic algorithms can achieve the same or similar results as parameter identification algorithms.

[0154] Figure 17 This graph illustrates the trend of IG50 relative to rotational speed and filling efficiency. Under low-load conditions with reduced filling efficiency, IG50 tends to increase due to the increased residual gas ratio and decreased pressure / temperature conditions, primarily resulting in a decrease in laminar combustion velocity during the initial combustion phase. On the other hand, turbulence intensity increases with rotational speed, leading to an increase in turbulent combustion velocity. Therefore, even if the laminar combustion velocity does not increase, its impact on combustion is relatively minimal.

[0155] Equation (16) approximates the aforementioned tendency of IG50 relative to engine speed and fill efficiency. In EGR combustion, when deposits cause EGR to increase relative to the same EGR valve opening, IG50 also increases. Furthermore, in lean combustion, when fuel properties and fuel type cause laminar combustion speed to decrease for the same target equivalence ratio, IG50 also increases. For each of these engine variations, adaptive control based on onboard learning can be achieved by employing Equation (16) and a recursive least-squares approximation of the partial regression coefficients of this model.

[0156] Figure 18 This is a flowchart illustrating a combustion control method using combustion detection information based on a crankshaft angle sensor in a lean-burn system. In S1801, the target torque is calculated based on factors such as the driver's accelerator pedal input. In S1802, the fill efficiency used to achieve the target torque is calculated. In S1803, the throttle valve opening used to achieve the required air volume for the engine is calculated.

[0157] In S1804, the target equivalence ratio is calculated based on engine speed and fill efficiency. In S1805, the injector fuel injection pulse width for achieving the target equivalence ratio is calculated. In S1806, MFB50 is detected based on the crankshaft angle sensor signal. In S1807, each combustion period, including the initial combustion period, main combustion period, and full combustion period, is calculated based on MFB50 and ignition timing.

[0158] In S1808, considering the heat generation rate curve determined based on the entire combustion period and the combustion chamber volume change rate, the in-cylinder pressure, temperature, and unburned gas temperature corresponding to the crankshaft angle are calculated. In S1809, based on the in-cylinder pressure, unburned gas temperature, EGR rate, and equivalence ratio corresponding to the initial combustion period and main combustion period mentioned above, the laminar combustion rate for each period is calculated.

[0159] In S1810, whether learning can be performed is determined by considering factors such as whether the system is in a stable state and the sensor's operating conditions. If learning is deemed possible, a statistical model regarding combustion rate and combustion duration is learned in S1811. In S1812, the target equivalence ratio is predicted (in... Figure 18 In the example, the combustion rate is lean. In S1813, based on the predicted combustion rate, the above statistical model is used to predict the combustion period. In S1814, based on the predicted combustion period, if the combustion period is greater than the specified value, the equivalence ratio is corrected towards the rich side in S1815.

[0160] By implementing the controls described above, combustion instability caused by excessive combustion during lean burn can be appropriately prevented.

[0161] Figure 19 This is a timing diagram illustrating the operation of combustion control using combustion detection information based on a crankshaft angle sensor in a lean-burn system. When MFB50 is delayed under lean conditions, and the combustion period becomes longer than a predetermined value (time: ii), MFB50 is corrected to the desired time by temporarily advancing the ignition timing. Furthermore, the stoichiometry is adjusted towards the rich side to increase the combustion rate, so that the combustion period reaches the predetermined value.

[0162] The relationship between combustion period and combustion rate is studied. After the study, the combustion rate corresponding to the target equivalence ratio is predicted, and the combustion period corresponding to the predicted combustion rate is predicted. The target equivalence ratio (equivalence ratio A→B) is corrected so that the predicted combustion period becomes the specified value. In the subsequent lean combustion mode (time: iv), lean combustion can be implemented by using the corrected equivalence ratio as the new target equivalence ratio to appropriately prevent combustion instability.

[0163] Figure 20 This is a flowchart illustrating a combustion control method using combustion detection information based on a crankshaft angle sensor in an EGR system. In S2001, the target torque is calculated based on factors such as the driver's accelerator pedal input. In S2002, the fill efficiency used to achieve the target torque is calculated. In S2003, the throttle valve opening used to achieve the required air volume for the engine is calculated.

[0164] In S2004, the target EGR rate is calculated based on engine speed and fill efficiency. In S2005, the EGR valve opening for achieving the target equivalence ratio is calculated. In S2006, MFB50 is detected based on the crankshaft angle sensor signal. In S2007, each combustion period, including the initial combustion period, main combustion period, and full combustion period, is calculated based on MFB50 and ignition timing.

[0165] In S2008, considering the heat generation rate curve determined based on the entire combustion period and the combustion chamber volume change rate, the in-cylinder pressure, temperature, and unburned gas temperature corresponding to the crankshaft angle are calculated. In S2009, based on the in-cylinder pressure, unburned gas temperature, EGR rate, and equivalence ratio corresponding to the initial combustion period and the main combustion period, the laminar combustion rate for each period is calculated.

[0166] In S2010, the system considers factors such as whether it is in a stable state and the sensor's operating conditions to determine if learning is possible. If learning is deemed possible, a statistical model regarding combustion rate and combustion duration is learned in S2011. In S2012, the combustion rate at the target EGR rate is predicted. In S2013, based on the predicted combustion rate, the combustion duration is predicted using the aforementioned statistical model. In S2014, based on the predicted combustion duration, if the combustion duration exceeds a predetermined value, the EGR rate is corrected towards a decrease in S2015.

[0167] By implementing the controls described above, combustion instability caused by excessive combustion during EGR combustion can be appropriately prevented.

[0168] Figure 21 This is a timing diagram illustrating the actions of combustion control implemented using combustion detection information based on a crankshaft angle sensor in an EGR combustion system. When MFB50 is delayed under EGR conditions, and the combustion period becomes greater than the specified value (time: ii), MFB50 is corrected to the desired time by temporarily advancing the ignition timing. Furthermore, the EGR rate is corrected towards the decreasing side to increase the combustion rate, so that the combustion period reaches the specified value.

[0169] The relationship between combustion period and combustion rate is studied. After the study, the combustion rate corresponding to the target EGR rate is predicted, and the combustion period corresponding to the predicted combustion rate is predicted. The target EGR rate is then corrected (EGR rate A→B) so that the predicted combustion period becomes the specified value. In the subsequent EGR combustion mode (time: iv), by using the corrected EGR rate as the new target EGR rate, EGR combustion can be implemented to appropriately prevent combustion instability.

[0170] As described above, the electronic control device (ECU21) of this embodiment is an electronic control device for controlling an engine, which includes: an EGR system having an EGR pipe (EGR pipe 15) that allows a portion of the exhaust gas from the internal combustion engine to flow back to the intake manifold, and an EGR valve (EGR valve 19) disposed within the EGR pipe; an airflow sensor (airflow sensor 3) that detects the flow rate of air taken into the intake manifold; a throttle valve (throttle valve 4) disposed downstream of the airflow sensor; an intake manifold pressure sensor (intake manifold pressure sensor 6) disposed downstream of the throttle valve and located downstream of the connection between the intake manifold and the EGR pipe, detecting the pressure downstream of the throttle valve in the intake manifold, i.e., the intake manifold pressure; and a crankshaft angle sensor that detects the engine speed, combustion center of gravity moment (MFB50), etc.

[0171] The electronic control unit (ECU21) includes the following components that perform the following processing: calculate the in-cylinder pressure, temperature and unburned gas temperature based on the combustion period calculated from the MFB50 detected by the crankshaft angle sensor, calculate the combustion rate based on them, the equivalence ratio and the EGR rate, learn the correlation between the combustion period and the combustion rate, and correct the target values ​​of the EGR rate and the equivalence ratio based on the learned correlation.

[0172] Furthermore, in this embodiment, the recursive least squares method is applied at least to the learning unit described above. According to this embodiment configured as described above, when combustion instability occurs due to excessive reduction in combustion rate or prolonged combustion period during EGR combustion or lean combustion, this situation can be appropriately detected and controlled to achieve a more suitable EGR rate and equivalence ratio for combustion, thus achieving combustion stabilization and improving engine thermal efficiency.

[0173] Furthermore, the present invention is not limited to the embodiments described above. Various other applications and modifications can be made without departing from the spirit of the claimed invention. For example, in the embodiments described above, the structures of the electronic control device and the engine control system have been explained in detail and specifically for the purpose of easily understanding the invention, but it is not limited to having all the structural elements described. Additionally, other structural elements can be added, substituted, or deleted from a portion of the structure of the above embodiments.

[0174] In the above embodiments, an example of applying the present invention to an engine system without a turbocharger has been described, but the present invention is not limited to this example. For example, by generating a control model of an engine system with a turbocharger, the present invention can be applied to an engine system with a turbocharger.

[0175] Furthermore, the structures, functions, and processing units of the above-described embodiments can also be partially or entirely implemented in hardware, for example, through integrated circuit design. As hardware, FPGAs (Field Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits) can be used.

[0176] In addition, Figure 18 and Figure 20 As shown in the flowchart, multiple processes can be executed in parallel without affecting the processing results, or the processing order can be changed.

[0177] The main features of this embodiment can also be summarized as follows.

[0178] Control unit of internal combustion engine 1 (ECU21, Figure 2 The processors (B705, B706) Figure 7 The processor calculates the first combustion moment (MFB50, i.e., the moment of combustion center of gravity) or the first combustion period (IG100_1) in the cylinder of the internal combustion engine 1 based on the crankshaft angle detected by the crankshaft angle sensor 20. In this embodiment, the processor calculates the first combustion moment (MFB50) and then the first combustion period (IG100_1), but it can also directly calculate one or both depending on the object being learned.

[0179] The processor (B702) calculates the heat generation rate based on the first combustion moment (MFB50) or the first combustion period (IG100_1). The processor (B703) calculates the in-cylinder pressure and the in-cylinder unburned gas temperature based on the heat generation rate. The processor (B704) calculates the first combustion rate (laminar combustion rate SL1) based on the in-cylinder pressure and the in-cylinder unburned gas temperature. Therefore, the combustion state (in-cylinder pressure, in-cylinder unburned gas temperature, combustion rate) can be detected without using in-cylinder sensors, reducing manufacturing costs. Furthermore, compared to existing methods (methods for calculating in-cylinder pressure based on the mechanical relationships of the crankshaft mechanism), the computational load on in-cylinder pressure calculation can be reduced.

[0180] The processor (B707) learns the correspondence between the first combustion rate (laminar combustion rate SL1) and the first combustion period (IG100_1). In this embodiment, the processor (B707) learns the correspondence between the first combustion rate (laminar combustion rate SL1) and the first combustion period (IG100_1), but it can also learn the correspondence between the first combustion rate (laminar combustion rate SL1) and the first combustion moment (MFB50). This allows it to adapt to deviations (fluctuations) in the correspondence caused by the inherent operating environment of the vehicle (fuel, onboard equipment, sensors, actuators, etc.).

[0181] Processor (B708, Figure 7 Based on the target values ​​(target equivalence ratio, target EGR rate) of the control parameters of the feedback control of the internal combustion engine 1, a second combustion rate (laminar combustion rate SL2) is predicted when the control parameters reach the target values. Thus, the combustion rate (laminar combustion rate SL2) when the control parameters reach the target values ​​can be obtained.

[0182] The processors (B709, B710) adjust the target values ​​of the internal combustion engine's control parameters (target equivalence ratio, target EGR rate) based on the predicted second combustion rate (laminar combustion rate SL2). This enables feedback control without using in-cylinder sensors.

[0183] In detail, the processor (B709) predicts the second combustion period (IG100_2) corresponding to the second combustion rate (laminar combustion rate SL2) based on the learned correspondence. Alternatively, the processor (B709) may not predict the second combustion period (IG100_2), but instead predict the second combustion moment corresponding to the second combustion rate (laminar combustion rate SL2). Thus, it is possible to obtain the combustion period (IG100_2) or combustion moment in which the control parameters reach the target value under each vehicle's operating environment.

[0184] The processor (B710) adjusts the target values ​​of the control parameters (target equivalence ratio, target EGR rate) of the internal combustion engine 1 based on the second combustion period (IG100_2). The processor (B710) can also adjust the target values ​​of the control parameters (target equivalence ratio, target EGR rate) of the internal combustion engine 1 based on the predicted second combustion time. This enables feedback control without using in-cylinder sensors.

[0185] Control parameters include, for example, EGR rate, EGR valve opening, air-fuel ratio, fuel injection period (representing the injector's drive pulse width), ignition timing, ignition energy, or the opening of a flow-enhancing valve that causes the intake air to deflect. This prevents poor combustion in the internal combustion engine. Furthermore, ignition energy is controlled, for example, by changing the energizing time of the spark plug.

[0186] The processor (B707) can also stop learning the correspondence based on the operating state of the internal combustion engine 1 or the operating state of the actuators or sensors mounted on the internal combustion engine 1. For example, it can stop learning the correspondence when the ECU 21 has just started or when the sensor detection values ​​are fluctuating. As a result, the accuracy of learning is improved.

[0187] (Modified example)

[0188] The processor can also diagnose faults by comparing the first combustion rate (laminar combustion rate SL1), the first combustion time (MFB50), or the first combustion period (IG100_1) with a threshold used to determine the fault state, based on the learned correspondence between the first combustion rate (laminar combustion rate SL1) and the first combustion time or the first combustion period (IG100_1). This allows for fault diagnosis without using in-cylinder sensors.

[0189] Furthermore, the processor can also predict the time required to reach a fault state based on the temporal changes in the learning results of the correspondence and the threshold used to determine the fault state. Thus, users can, for example, perform maintenance on the internal combustion engine or control unit by taking into account the predicted time required to reach the fault state.

[0190] In addition, the embodiments of the present invention can also be carried out in the following ways.

[0191] (1). A control device (ECU21) for an internal combustion engine 1, wherein a crankshaft angle sensor 20 for detecting the crankshaft angle is provided on the crankshaft of the internal combustion engine 1, and a unit for detecting the moment of combustion center of gravity (MFB50) in the cylinder based on the detection value of the crankshaft angle sensor, the control device for the internal combustion engine being characterized in that it includes: a unit (B703) for calculating the in-cylinder pressure and the temperature of unburned gas in the cylinder based on the information of the combustion moment; a unit (B704) for calculating the combustion speed based on the calculated in-cylinder pressure and the temperature of unburned gas in the cylinder; and a unit (B707) for learning the relationship between the calculated combustion speed and the detected combustion moment or combustion period.

[0192] (2). The control device for the internal combustion engine according to (1) is characterized in that it includes a unit (B708) for predicting the combustion speed based on the target value of the control parameters of the internal combustion engine (target equivalence ratio, target EGR rate, etc.).

[0193] (3). The control device for the internal combustion engine according to (2) is characterized in that it includes a unit (B710) for correcting the target value of the control parameters of the internal combustion engine based on the predicted combustion speed.

[0194] (4). The control device for the internal combustion engine according to (1) is characterized in that it includes: a unit (B708, B709) that predicts the combustion speed based on the target value of the control parameters of the internal combustion engine, and predicts the combustion time or combustion period based on the predicted combustion speed according to the learning result of the relationship between the combustion speed and the combustion time or combustion period.

[0195] (5). The control device for the internal combustion engine according to (4) is characterized in that it includes: a unit (B710) for correcting the target value of the control parameters of the internal combustion engine based on the predicted combustion time or combustion period.

[0196] (6). The control device for an internal combustion engine according to any one of (3)-(5), characterized in that the control parameter is the EGR rate or the EGR valve opening.

[0197] (7). The control device for an internal combustion engine according to any one of (3)-(5), characterized in that the control parameter is the air-fuel ratio or the injection period of the injector.

[0198] (8). The control device for an internal combustion engine according to any one of (3)-(5), characterized in that the control parameter is ignition timing or ignition energy.

[0199] (9). The control device for an internal combustion engine according to any one of (3)-(5), characterized in that the control parameter is the opening degree of the flow enhancement valve.

[0200] (10). The control device for the internal combustion engine according to (1) is characterized in that it includes: a unit that stops the learning unit of the relationship between the combustion speed and the combustion time or combustion period based on the operating state of the internal combustion engine 1 or the operating state of the actuator or sensor mounted on the internal combustion engine 1.

[0201] (11). The control device for the internal combustion engine according to (1) is characterized in that it includes an abnormality diagnosis unit, which compares the combustion speed, combustion time or combustion period with a threshold for judging an abnormal state based on the learning result of the relationship between the combustion speed and the combustion time or combustion period, and diagnoses the abnormality based on the comparison result.

[0202] (12). The control device for the internal combustion engine according to (1) is characterized in that it includes an abnormality diagnosis unit, which predicts the period during which the learning value will reach an abnormal state based on the learning result of the relationship between the combustion speed and the combustion time or combustion period, and based on the time change of the learning result and a threshold for judging the abnormal state.

[0203] According to at least one of the above methods, the relationship between in-cylinder combustion speed and combustion period is learned based on the combustion center of gravity moment detected by the crankshaft angle sensor, and the EGR control or air-fuel ratio control is corrected based on the above relationship. Therefore, the accuracy of EGR control and air-fuel ratio control can be maintained at a high level, and poor combustion of the internal combustion engine (e.g., combustion instability, misfire) caused by errors in EGR control and air-fuel ratio control can be appropriately prevented.

[0204] Explanation of reference numerals in the attached figures

[0205] 1...Internal combustion engine, 3...Airflow sensor, 4...Throttle valve, 5...Intake manifold, 6...Intake manifold pressure sensor, 12...Fuel injection valve, 13...Spark plug, 15...EGR pipe, 17...EGR temperature sensor, 18...EGR valve upstream pressure sensor, 19...EGR valve, 21...ECU, 22...Warning indicator light, 23...Control unit, 24...Storage unit.

Claims

1. A control device for an internal combustion engine, characterized in that: This includes a processor that calculates the first combustion moment or first combustion period in the cylinder of the internal combustion engine based on the crankshaft angle detected by a crankshaft angle sensor. The heat generation rate is calculated based on the first combustion moment or during the first combustion period. The cylinder pressure and unburned gas temperature are calculated based on the heat generation rate. The first combustion rate is calculated based on the cylinder pressure and the temperature of the unburned gas in the cylinder. Learn the correspondence between the first combustion rate and the first combustion time or the first combustion period.

2. The control device for an internal combustion engine according to claim 1, characterized in that: The processor predicts a second combustion rate based on the target value of the control parameters of the feedback control of the internal combustion engine, in which the control parameters are in the state of the target value.

3. The control device for an internal combustion engine according to claim 2, characterized in that: The processor adjusts the target value of the control parameters of the internal combustion engine based on the predicted second combustion rate.

4. The control device for an internal combustion engine according to claim 2, characterized in that: The processor predicts the second combustion moment or second combustion period corresponding to the second combustion rate based on the learned correspondence.

5. The control device for an internal combustion engine according to claim 4, characterized in that: The processor corrects the target values ​​of the control parameters of the internal combustion engine based on the second combustion time or the second combustion period.

6. The control device for an internal combustion engine according to claim 2, characterized in that: The control parameters are: EGR rate, EGR valve opening, air-fuel ratio, fuel injection period representing the width of the injector's drive pulse, ignition timing, ignition energy, or the opening of a flow enhancement valve that causes the intake air to deflect.

7. The control device for an internal combustion engine according to claim 1, characterized in that: The processor stops learning the corresponding relationship based on the operating state of the internal combustion engine or the operating state of the actuators or sensors mounted on the internal combustion engine.

8. The control device for an internal combustion engine according to claim 1, characterized in that: Based on the learning results of the correspondence, the processor compares the first combustion rate, the first combustion time, or the first combustion period with a threshold used to determine the fault state, and diagnoses the fault based on the comparison results. Alternatively, based on the time variation of the learning results of the aforementioned correspondence and the threshold used to determine the fault state, the period required to reach the fault state can be predicted.

Images