JP2015001156A - Device for creating waveform of heat generation rate of internal combustion engine, and combustion state diagnosing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To create a waveform of a heat generation rate of a high-temperature oxidation reaction due to premix-combustion at high accuracy.SOLUTION: When fuel is injected into a cylinder in a temperature range of not less than reference reaction starting temperature (900 K) of a high-temperature oxidation reaction due to premix-combustion, a reaction starting timing is set to a retard angle side as a progress degree is smaller according to the progress degree of a thermal decomposition reaction occurring before the high-temperature oxidation reaction due to the premix-combustion, so as to produce a waveform of a heat generation rate of the high-temperature oxidation reaction due to the premix-combustion. By such processing, the reaction starting timing of the high-temperature oxidation reaction due to the premix-combustion can be precisely defined, so as to produce an ideal waveform of a heat generation rate of a low-temperature oxidation reaction at high accuracy. Also, when a combustion state is diagnosed using the ideal waveform of the heat generation rate, accuracy of diagnosis can be improved.

Description

  The present invention relates to a heat generation rate waveform generating device that generates a heat generation rate waveform of an internal combustion engine such as a diesel engine, and combustion of an internal combustion engine that diagnoses an actual combustion state using the generated heat generation rate waveform The present invention relates to a state diagnosis apparatus.

  Conventionally, the combustion state of a diesel engine (hereinafter, simply referred to as “engine”) used as an automobile engine or the like is evaluated. Specifically, this combustion state evaluation method uses a heat generation rate waveform that is a change in the heat generation rate (heat generation amount per unit rotation angle of the crankshaft) in the combustion chamber, and the waveform is an ideal waveform. The combustion state in the combustion chamber is evaluated by judging whether or not (see, for example, Patent Document 1). In addition, as the reaction form (combustion form) constituting the heat release rate waveform, there are a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, a high temperature oxidation reaction, etc. The combustion state of each reaction form is diagnosed using the heat release rate waveform.

JP 2011-106334 A JP 2010-138712 A

  Although the reaction start timing of each reaction described above can be controlled by temperature, sufficient accuracy may not be obtained only by temperature control. The inventor of the present invention examined this point, and found that the reaction start timing of the high-temperature oxidation reaction by premixed combustion is affected by the degree of progress of the thermal decomposition reaction occurring before that. Then, in order to further increase the accuracy of creating the heat release rate waveform of the high-temperature oxidation reaction by premixed combustion, it is necessary to grasp the reaction start timing with high accuracy, leading to the invention of the present invention. It was.

  That is, the present invention has been made in view of the above points, and an object of the present invention is an internal combustion engine capable of creating a heat generation rate waveform of a high-temperature oxidation reaction by premixed combustion with higher accuracy. An object of the present invention is to provide a heat generation rate waveform generation apparatus and a combustion state diagnosis apparatus.

-Solution principle of the invention-
The solution principle of the present invention taken in order to achieve the above object is that the heat generated before the high temperature oxidation reaction by the premixed combustion is generated when the ideal heat generation rate waveform of the high temperature oxidation reaction by the premixed combustion is created. By taking into account the influence of the progress of the decomposition reaction, the heat release rate waveform of the high temperature oxidation reaction by premixed combustion can be created with high accuracy.

-Solution-
Specifically, the present invention is premised on a heat generation rate waveform generation device that generates a heat generation rate waveform of a fuel reaction in an internal combustion engine that burns fuel injected into a cylinder from a fuel injection valve. In such a heat generation rate waveform creation device, among the reactions of the fuel injected from the fuel injection valve, when creating an ideal heat generation rate waveform of a high temperature oxidation reaction by premixed combustion, high temperature oxidation by the premixed combustion is performed. It is characterized in that the reaction start time is set according to the progress degree of the thermal decomposition reaction that occurs before the reaction, and an ideal heat generation rate waveform of the high-temperature oxidation reaction by the premixed combustion is created. More specifically, when fuel is injected into the cylinder in a temperature range where the in-cylinder gas temperature is equal to or higher than the reference reaction start temperature of the high-temperature oxidation reaction by premixed combustion, the fuel decomposition is performed according to the degree of progress of the pyrolysis reaction. As the degree of progress is smaller, the reaction start timing of the high temperature oxidation reaction by premixed combustion is set to the retard side.

  In the present invention, the degree of progress of the pyrolysis reaction (pyrolysis achievement rate) can be determined based on the in-cylinder gas temperature at the start of fuel injection.

  In the present invention, focusing on the fact that the reaction start timing of the high-temperature oxidation reaction by premixed combustion is affected by the progress of the thermal decomposition reaction that occurs before that, the above-described configuration, that is, premixing When creating the ideal heat release rate waveform of the high temperature oxidation reaction by combustion, adopt a configuration that sets the reaction start time according to the degree of progress of the thermal decomposition reaction that occurs before the high temperature oxidation reaction by the premixed combustion Yes. With such a configuration, it is possible to accurately define the reaction start timing of the high temperature oxidation reaction by premixed combustion, and an ideal heat generation rate waveform of the high temperature oxidation reaction by premixed combustion can be created with high accuracy.

  Here, the “ideal heat generation rate waveform” in the present invention means that the fuel injection amount according to the command injection amount, the fuel injection pressure according to the command injection pressure, and the fuel injection period according to the command injection period are secured. This is the state of the heat release rate waveform that should be obtained theoretically assuming that the combustion efficiency is sufficiently high.

  Further, the “creation of an ideal heat generation rate waveform” in the present invention is not limited to the one that actually draws an ideal heat generation rate waveform. It is a concept that includes a state in which the heat generation amount for each unit rotation angle is defined.

  In the heat generation rate waveform creation device of the present invention, in addition to creating an ideal heat generation rate waveform of a high temperature oxidation reaction by premixed combustion, a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, a high temperature oxidation reaction by diffusion combustion, etc. An ideal heat generation rate waveform of each reaction may be created. In this way, by obtaining ideal heat release rate waveforms for vaporization reaction, low-temperature oxidation reaction, thermal decomposition reaction, high-temperature oxidation reaction by premixed combustion, and high-temperature oxidation reaction by diffusion combustion, each reaction form can be determined. It can be defined individually. For example, when used for diagnosis of a combustion state to be described later, it is possible to determine in which reaction an abnormality has occurred by comparing the ideal heat generation rate waveform and the actual heat generation rate waveform. Become. In particular, the vaporization reaction and the thermal decomposition reaction are endothermic reactions (the thermal decomposition reaction may be an exothermic reaction), but there are abnormalities in the reaction rate, reaction amount, and reaction period for this endothermic reaction. It is possible to diagnose whether or not there is any, and it is possible to improve the diagnostic accuracy.

  Note that the utilization form of the ideal heat release rate waveform obtained for each of the reactions includes not only the diagnosis of the combustion state but also the design of the internal combustion engine and the acquisition of the appropriate value of the control parameter.

  In addition, as a procedure for creating an ideal heat release rate waveform of each reaction including the high-temperature oxidation reaction by the premixed combustion, the reaction rate is the slope of the hypotenuse, the reaction amount is the area, and the reaction period is the base, based on the start time of the reaction. An ideal heat release rate waveform model consisting of triangles with a length of is created, and the ideal heat release rate waveform model of each reaction is made smooth by filtering.

  By creating a heat release rate waveform model that approximates a triangle in this way and creating an ideal heat release rate waveform using this heat release rate waveform model, the calculation process for the creation is simplified. It is possible to reduce the load on the calculation means such as the ECU.

  Specific examples of the apparatus for diagnosing the combustion state using the ideal heat generation rate waveform obtained by the above-described heat generation rate waveform generating apparatus for an internal combustion engine include the following configuration. That is, the ideal heat generation rate waveform is compared with the actual heat generation rate waveform when the fuel actually reacts in the cylinder, and the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform becomes a predetermined amount or more. In this case, it is configured to diagnose that an abnormality has occurred in the fuel reaction.

  More specifically, the ideal heat generation rate waveform is compared with the actual heat generation rate waveform when the fuel actually reacts in the cylinder, and the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is determined. When there is a reaction that is more than a fixed amount, it is configured to diagnose that an abnormality has occurred in the reaction.

  The “reaction abnormality” here is not limited to a reaction abnormality (such as equipment failure) that hinders the operation of the internal combustion engine, but can correct (or learn) the control parameters of the internal combustion engine (for example, exhaust gas). This includes the case where there is a deviation in the heat generation rate waveform to the extent that it is possible to correct emissions and combustion noise within the limits of regulation.

  With this specific matter, when the actual heat generation rate waveform deviates from the ideal heat generation rate waveform by a predetermined amount or more in a plurality of fuel reactions (reaction forms), it is diagnosed that the reaction is abnormal. It will be. In other words, each reaction of the fuel has different characteristics (reaction start temperature, reaction rate, etc.), so that each ideal characteristic and the actually obtained (actually measured) actual heat generation rate waveform By comparing with the characteristics, it is possible to identify the reaction in which an abnormality has occurred with high accuracy. For this reason, improvement of diagnostic accuracy can be aimed at. Then, by taking improvement measures (for example, correction of control parameters of the internal combustion engine) for the reaction form diagnosed as abnormal, a control parameter suitable for the reaction form diagnosed as abnormal is selected, The control parameter can be corrected. For this reason, the controllability of the internal combustion engine can be greatly improved.

  Specific operations when it is diagnosed that an abnormality has occurred in the reaction include the following. That is, when there is a reaction in which the deviation of the actual heat generation rate waveform with respect to the ideal heat generation rate waveform is equal to or greater than a predetermined abnormality determination deviation amount, and when it is diagnosed that the reaction is abnormal, When the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is equal to or less than a predetermined correctable deviation amount, the control parameter of the internal combustion engine is corrected so that the deviation is less than the abnormality determination deviation amount. On the other hand, when the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform exceeds the correctable deviation amount, the internal combustion engine is diagnosed as having a failure.

  In this way, when it is diagnosed that an abnormality has occurred in the reaction, whether or not the abnormality can be resolved is determined based on the deviation amount of the actual heat generation rate waveform from the ideal heat generation rate waveform. I am doing so. For this reason, it is possible to accurately discriminate between a state in which a normal reaction state is obtained by correcting the control parameter and a state in which maintenance such as component replacement is required.

  In addition, as the control parameter when the control parameter of the internal combustion engine is corrected so that the deviation is less than the abnormality determination deviation amount, an oxygen amount and a fuel amount in the cylinder are exemplified. The amount of oxygen in the cylinder is determined by the oxygen density and can be adjusted by the EGR rate, the intake air supercharging rate, and the like. The amount of fuel in the cylinder is determined by the fuel density and can be adjusted by the fuel injection timing, the fuel injection pressure, and the fuel injection amount.

  On the other hand, an example of diagnosing that a failure has occurred in the internal combustion engine is a case where the deviation of the actual heat generation rate waveform exceeds the correctable deviation amount. In this case, the control parameter of the internal combustion engine Since the correction amount exceeds a predetermined guard value, it is possible to diagnose that a failure has occurred in the internal combustion engine. Specifically, when a lower limit is set in advance for each of the in-cylinder gas temperature, oxygen density, and fuel density, and any of these in-cylinder gas temperature, oxygen density, or fuel density is below the lower limit value. If the control parameter correction amount of the internal combustion engine exceeds a predetermined guard value, it is diagnosed that the internal combustion engine has failed.

  Here, the usage pattern of the heat generation rate waveform generating device for the internal combustion engine specifically includes mounting on a vehicle or mounting on an experimental device.

  Further, the usage state of the combustion state diagnostic device for the internal combustion engine includes mounting on a vehicle or mounting on an experimental device.

  According to the present invention, when creating an ideal heat generation rate waveform of a high temperature oxidation reaction by premixed combustion, the reaction start timing is set according to the progress degree of the thermal decomposition reaction that occurs before the high temperature oxidation reaction by the premixed combustion. Since it is set, the reaction start time of the high temperature oxidation reaction by the premixed combustion can be accurately defined. As a result, an ideal heat generation rate waveform of the high-temperature oxidation reaction by premixed combustion can be created with higher accuracy. Further, when the combustion state is diagnosed using this ideal heat generation rate waveform, the accuracy of the diagnosis can be increased.

It is a figure which shows schematic structure of the diesel engine which concerns on embodiment, and its control system. It is sectional drawing which shows the combustion chamber of a diesel engine, and its peripheral part. It is a block diagram which shows the structure of control systems, such as ECU. It is a schematic diagram of the intake / exhaust system and the combustion chamber for explaining the outline of the combustion mode in the combustion chamber. FIG. 6 is a waveform diagram showing an example of a relationship between a fuel injection rate (fuel injection amount per unit rotation angle of crankshaft) waveform and a heat generation rate (heat generation amount per unit rotation angle of crankshaft) waveform. It is a flowchart which shows the procedure of a combustion state diagnosis and control parameter correction | amendment. It is a figure which shows a rotational speed correction coefficient map. It is a figure which shows an example of the correction | amendment retardation amount map which uses oxygen density as a parameter. It is a figure which shows an example of the map which calculates | requires the progress degree of thermal decomposition reaction. It is a figure which shows an example of the map which calculates | requires the correction | amendment retardation amount of the reference temperature arrival time of the high temperature oxidation reaction by premixed combustion. 11A shows an ideal heat generation rate waveform model, FIG. 11A shows a case where the ideal heat generation rate waveform model is an isosceles triangle, and FIG. 11B shows a case where the ideal heat generation rate waveform model is an unequal triangle. FIG. FIG. 12A shows the relationship between the elapsed time and the amount of fuel supplied into the cylinder when fuel is injected from the injector, and FIG. 12B shows the reaction of the fuel injected during each injection period. It is a figure which shows quantity. It is a figure which shows an example of the ideal heat release rate waveform model in each reaction form when one fuel injection is performed. It is a figure which shows the ideal heat release rate waveform produced by synthesize | combining each waveform obtained by smoothing the ideal heat release rate waveform model of FIG. 13 by a filter process. It is a figure which shows an example of the ideal heat release rate waveform (solid line) at the time of one fuel injection, and an actual heat release rate waveform (a broken line and a dashed-dotted line).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the combustion state diagnosis apparatus (heat generation rate waveform generation) of the present invention is applied to a common rail in-cylinder direct injection multi-cylinder (for example, in-line 4-cylinder) diesel engine (compression self-ignition internal combustion engine) mounted on a vehicle. A case where a device is also mounted will be described.

-Engine configuration-
FIG. 1 is a schematic configuration diagram of a diesel engine 1 (hereinafter simply referred to as “engine 1”) and its control system according to the present embodiment.

  As shown in FIG. 1, the engine 1 according to the present embodiment is configured as a diesel engine system having a fuel supply system 2, a combustion chamber 3, an intake system 6, an exhaust system 7 and the like as main parts.

  The fuel supply system 2 includes a supply pump 21, a common rail 22, an injector (fuel injection valve) 23, an engine fuel passage 27, and the like.

  The supply pump 21 increases the pressure of the fuel pumped from the fuel tank and then supplies the fuel to the common rail 22 via the engine fuel passage 27. The common rail 22 has a function as a pressure accumulating chamber that holds (accumulates) high-pressure fuel at a predetermined pressure, and distributes the accumulated fuel to the injectors 23. The injector 23 is a piezo injector provided with a piezoelectric element (piezo element) inside.

  The intake system 6 includes an intake manifold 63 connected to an intake port 15 a formed in the cylinder head 15 (see FIG. 2), and an intake pipe 64 is connected to the intake manifold 63. The intake system 6 is provided with an air cleaner 65, an air flow meter 43, and an intake throttle valve (diesel throttle) 62 in order from the upstream side.

  The exhaust system 7 includes an exhaust manifold 72 connected to an exhaust port 71 formed in the cylinder head 15, and an exhaust pipe 73 is connected to the exhaust manifold 72. The exhaust system 7 is provided with an exhaust purification unit 77. The exhaust purification unit 77 is provided with an NSR (NOx Storage Reduction) catalyst 75 and a DPF (Diesel Particle Filter) 76 as NOx storage reduction type catalysts.

  As shown in FIG. 2, the cylinder block 11 is formed with a cylinder bore 12 for each cylinder (four cylinders), and a piston 13 is accommodated in each cylinder bore 12 so as to be slidable in the vertical direction. .

  The combustion chamber 3 is formed above the top surface 13 a of the piston 13. That is, the combustion chamber 3 is defined by the lower surface of the cylinder head 15 attached to the upper portion of the cylinder block 11, the inner wall surface of the cylinder bore 12, and the top surface 13 a of the piston 13. A cavity (concave portion) 13 b is formed in a substantially central portion of the top surface 13 a of the piston 13, and this cavity 13 b also constitutes a part of the combustion chamber 3.

  As the shape of the cavity 13b, the concave dimension is small in the central portion (on the cylinder center line P), and the concave dimension is increased toward the outer peripheral side.

  The piston 13 is connected to a crankshaft that is an engine output shaft by a connecting rod 18. Further, a glow plug 19 is disposed toward the combustion chamber 3. The energization of the glow plug 19 is controlled by the ECU 100.

  The cylinder head 15 is provided with an intake valve 16 for opening and closing an intake port 15a and an exhaust valve 17 for opening and closing an exhaust port 71.

  Further, as shown in FIG. 1, the engine 1 is provided with a supercharger (turbocharger) 5. The turbocharger 5 includes a turbine wheel 52 and a compressor wheel 53 that are connected via a turbine shaft 51. The turbocharger 5 in the present embodiment is a variable nozzle type turbocharger, and a variable nozzle vane mechanism (not shown) is provided on the turbine wheel 52 side.

  The intake pipe 64 is provided with an intercooler 61 for forcibly cooling the intake air whose temperature has been raised by supercharging in the turbocharger 5.

  Further, the engine 1 is provided with an exhaust gas recirculation passage (EGR passage) 8 for appropriately returning a part of the exhaust gas to the intake system 6. The EGR passage 8 is provided with an EGR valve 81 and an EGR cooler 82.

-Sensors-
Various sensors are attached to each part of the engine 1, and signals related to the environmental conditions of each part and the operating state of the engine 1 are output.

  For example, the air flow meter 43 outputs a detection signal corresponding to the flow rate (intake air amount) of the intake air upstream of the intake throttle valve 62 in the intake system 6. The rail pressure sensor 41 outputs a detection signal corresponding to the fuel pressure stored in the common rail 22. The throttle opening sensor 42 detects the opening of the intake throttle valve 62. The intake pressure sensor 48 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the intake air pressure. The intake air temperature sensor 49 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the temperature of the intake air. The A / F (air-fuel ratio) sensors 44a and 44b are arranged on the upstream side and the downstream side of the NSR catalyst 75, respectively, and output detection signals that change continuously according to the oxygen concentration in the exhaust gas.

-ECU-
The ECU 100 includes a microcomputer (not shown) such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and an input circuit and an output circuit.

  As shown in FIG. 3, the input circuit of the ECU 100 includes the rail pressure sensor 41, the throttle opening sensor 42, the air flow meter 43, the A / F sensors 44a and 44b, the exhaust temperature sensors 45a and 45b, the intake pressure sensor 48, An intake air temperature sensor 49 is connected. Further, the input circuit includes a water temperature sensor 46 that outputs a detection signal corresponding to the cooling water temperature of the engine 1, an accelerator opening sensor 47 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, and an output shaft (crank) of the engine 1. A crank position sensor 40 that outputs a detection signal (pulse) every time the shaft rotates a certain angle, an in-cylinder pressure sensor (CPS (Combustion Pressure Sensor)) 4A that detects the pressure in the cylinder (combustion chamber 3), the outside air temperature A sensor 4B, an external air pressure sensor 4C, and the like are connected.

  On the other hand, the output circuit of the ECU 100 includes the supply pump 21, the injector 23, the intake throttle valve 62, the EGR valve 81, the variable nozzle vane mechanism (actuator for adjusting the opening degree of the variable nozzle vane) 54 of the turbocharger 5 and the like. It is connected.

  Then, the ECU 100 executes various controls of the engine 1 based on outputs from the various sensors described above, calculated values obtained by arithmetic expressions using the output values, or various maps stored in the ROM. .

  For example, the ECU 100 executes pilot injection (sub-injection) and main injection (main injection) as fuel injection control of the injector 23. Since the functions of the pilot injection and the main injection are well known, description thereof is omitted here.

  The fuel injection pressure when executing the fuel injection is determined by the internal pressure of the common rail 22. As the common rail internal pressure, generally, the target value of the fuel pressure supplied from the common rail 22 to the injector 23, that is, the target rail pressure, increases as the engine load (engine load) increases and the engine speed (engine speed) increases. It will be expensive.

  In addition to the pilot injection and the main injection described above, after injection and post injection are performed as necessary. Since the function of these injections is also well-known, explanation here is omitted.

  Further, the ECU 100 controls the opening degree of the EGR valve 81 according to the operating state of the engine 1 to adjust the exhaust gas recirculation amount (EGR amount) toward the intake manifold 63.

-Outline of combustion mode-
Next, the outline of the combustion mode in the combustion chamber 3 in the engine 1 according to the present embodiment will be described.

  As shown in FIG. 4, the gas sucked into the cylinder includes fresh air sucked from the intake pipe 64 and EGR gas sucked from the EGR passage 8.

  The fresh air and EGR gas sucked into the cylinder in this way are sucked into the cylinder as the piston 13 (not shown in FIG. 4) descends via the intake valve 16 which is opened in the intake stroke. It becomes in-cylinder gas. This in-cylinder gas is sealed in the cylinder (inside the combustion chamber 3) by closing the intake valve 16 when the valve is closed according to the operating state of the engine 1 (in-cylinder gas confinement state). In the subsequent compression stroke, the piston 13 is compressed as it rises. When the piston 13 reaches the vicinity of the compression top dead center, the injector 23 is opened for a predetermined time by the injection amount control by the ECU 100 described above, so that fuel is directly injected into the combustion chamber 3 (pilot injection or main injection). Run).

-Heat release rate waveform-
FIG. 5 shows an example of the heat release rate waveform and the fuel injection rate waveform. As shown in FIG. 5, each reaction form (combustion form) of the fuel injected into the cylinder (combustion chamber 3) of the engine 1 is separated into a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and a high temperature oxidation reaction. can do. These combustion forms occur in the order of a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and a high temperature oxidation reaction. In addition, FIG. 5 is a figure which shows the heat release rate waveform in each reaction form when one fuel injection (pilot injection) is performed. Details of each reaction mode will be described later.

−Calculation of in-cylinder environmental parameters−
When creating an ideal heat release rate waveform used for the combustion state diagnosis described later, it is necessary to define the fuel reaction start timing, reaction rate, and reaction amount. And in order to prescribe | regulate these waveform components (reaction start time, reaction rate, reaction amount), it is necessary to obtain | require the oxygen density in a cylinder, a fuel density, and in-cylinder gas temperature.

  Hereinafter, a method for calculating these in-cylinder environmental parameters (oxygen density, fuel density, in-cylinder gas temperature) will be described.

(Oxygen density)
The oxygen density is an index representing the oxygen supply capacity (temporal oxygen supply capacity) for the fuel, whether or not EGR is performed, the EGR amount (including the residual gas amount in the cylinder (so-called internal EGR amount)), It fluctuates according to the altitude of the road that is running. And if this oxygen density changes, it will affect the reaction start time, reaction rate, and reaction amount in each reaction of fuel. That is, the lower the oxygen density, the more the reaction start timing shifts to the retarded side, the reaction rate becomes lower (the reaction becomes slower), and the reaction amount decreases. In particular, the effects of low-temperature oxidation reaction, thermal decomposition reaction, and high-temperature oxidation reaction among fuel reactions appear.

  Even if fuel multi-stage injection (for example, pilot injection and main injection) is performed, the amount of oxygen consumed by combustion of fuel injected by fuel injection for preheating (pilot injection) is It is very small compared to the amount of oxygen. For this reason, it is assumed here that the oxygen densities of the space in the cavity (hereinafter referred to as the cavity area) and the space outside the cavity (hereinafter referred to as the cavity area) constituting the cylinder space are substantially the same. (For example, even when combustion is performed only in the region outside the cavity, it is assumed that they are substantially the same.) A case will be described in which the oxygen density is obtained for the entire cylinder.

The oxygen density ρo ₂ for the entire cylinder is obtained by the following equation (1) or (2).

Oxygen density ρo ₂ = Oxygen amount in intake air / clearance volume (1)
Oxygen density ρo ₂ = Oxygen amount in intake / stroke volume at start of reaction (2)
Here, the oxygen amount (mass) in the intake air can be calculated from the intake air amount detected by the air flow meter 43, the outside air temperature detected by the outside air temperature sensor 4B, the outside air pressure detected by the outside air pressure sensor 4C, and the like. An example of the clearance volume is a stroke volume (compression end volume) when the piston 13 reaches the compression top dead center. According to this, since the gap volume can be handled as a fixed value, the calculation of the oxygen density ρo ₂ can be simplified, and the reliability thereof is increased. The gap volume used in Formula (1) is not limited to this.

When the oxygen density ρo ₂ is calculated by the above equation (2), in each fuel reaction (vaporization reaction, low temperature oxidation reaction, thermal decomposition reaction, high temperature oxidation reaction by premixed combustion, high temperature oxidation reaction by diffusion combustion) The reaction start time, reaction rate, and reaction amount vary depending on the oxygen density ρo ₂ at the time of the reaction. For this reason, in order to obtain the reaction start time, reaction rate, and reaction amount in each reaction, it is necessary to individually specify the oxygen density ρo ₂ at the time of the reaction.

In this embodiment, the calculation timing of the oxygen density ρo ₂ corresponding to each reaction of the fuel is set, and the oxygen density ρo ₂ corresponding to each reaction is specified individually using the stroke volume at this timing. I can do it.

Note that the oxygen density ρo ₂ at a predetermined timing set in advance may be obtained, and the oxygen density ρo ₂ at the start of each reaction may be individually specified by calculating backward from the oxygen density ρo ₂ .

In calculating the oxygen density ρo _2, which one of the formula (1) and the formula (2) is adopted is appropriately determined in consideration of simplification of arithmetic processing, high reliability of the oxygen density ρo ₂ , and the like. Selected.

(Fuel density)
Next, a method for obtaining the fuel density in the cylinder will be described.

  Here, in order to facilitate understanding, description will be made on the assumption that the fuel densities in the cavity inner region and the outer cavity region are substantially the same.

  The fuel density ρfuel is calculated by the following formula (3) or formula (4).

Fuel density ρfuel = fuel injection amount / stroke volume at the start of reaction (3)
Fuel density ρfuel = fuel injection amount / stroke volume at the start of fuel injection (4)
Here, the fuel injection amount is a fuel amount injected from the injector 23 (for example, a fuel amount in main injection). This fuel injection amount can be calculated from the fuel injection pressure detected by the rail pressure sensor 41 and the valve opening period (command injection period) of the injector 23. The stroke volume at the start of the reaction is the in-cylinder volume (the sum of the volume in the cavity area and the volume in the outside cavity area) when the in-cylinder gas temperature reaches the reaction temperature described later. The relationship between the in-cylinder gas temperature and the in-cylinder volume is based on experiments and simulations in advance using parameters such as the outside air temperature detected by the outside air temperature sensor 4B, the compression ratio, and the amount of preheating in the cylinder (preheating amount by pilot injection, etc.). It is prescribed by. The reaction start timing, reaction rate, and reaction amount in each reaction of fuel vary according to the fuel density ρfuel at the time of the reaction. For this reason, in order to obtain the reaction start time, reaction rate, and reaction amount in each reaction, it is necessary to individually specify the fuel density ρfuel at the time of the reaction.

  In the present embodiment, the calculation timing of the fuel density ρfuel corresponding to each reaction of fuel is set, and the fuel density ρfuel corresponding to each reaction can be individually specified using the stroke volume at this timing. I have to.

  Alternatively, the fuel density ρfuel at a predetermined timing set in advance may be obtained, and the fuel density ρfuel at the time of each reaction may be individually specified by calculating backward from the fuel density ρfuel. The stroke volume at the start of fuel injection is the in-cylinder volume at the time when fuel injection from the injector 23 is started (when the fuel injection command signal is transmitted from the ECU 100). Since the in-cylinder volume is determined according to the crank angle position, the in-cylinder volume can be obtained based on the crank angle position at the time when fuel injection from the injector 23 is started.

  Furthermore, if the time point when the piston 13 reaches the compression top dead center (TDC) is set as the calculation timing of the fuel density ρfuel, the volume in the cylinder is determined in advance, so that the stroke volume is easily specified. For this reason, the calculation of the fuel density ρfuel can be simplified, and the reliability thereof is increased.

  In calculating the fuel density ρfuel, which one of the above formulas (3) and (4) is to be adopted is selected as appropriate in consideration of the simplification of arithmetic processing and the high reliability of the fuel density ρfuel. Is done.

(In-cylinder gas temperature)
As a method for obtaining the in-cylinder gas temperature, parameters such as the intake air temperature, the piston position (compression degree of the intake gas), the preheating state by pilot injection, etc. are used as parameters. These maps are obtained and mapped, and this map is stored in the ROM of the ECU 100. That is, the in-cylinder gas temperature is obtained by fitting parameters such as the intake air temperature, piston position, preheat state, etc. to the map.

  Further, the in-cylinder gas temperature may be calculated from the thermal energy equation Q = mcT. Here, Q is the heat energy input into the cylinder, m is the mass of the gas in the cylinder, c is the specific heat of the gas, and T is the in-cylinder gas temperature.

-Creation of heat release rate waveform, combustion state diagnosis, and control parameter correction-
Next, creation of a heat release rate waveform (creation of an ideal heat release rate waveform), which is a feature of this embodiment, combustion state diagnosis (diagnosis of each reaction mode of fuel in a cylinder), and the diagnosis result The control parameter correction executed in this way will be described.

  In the creation of the heat generation rate waveform, the combustion state diagnosis, and the control parameter correction, as shown in FIG. 6, (1) creation of an ideal heat generation rate waveform and (2) creation of an actual heat generation rate waveform (3) The combustion state diagnosis is performed by comparing the ideal heat generation rate waveform and the actual heat generation rate waveform. (4) The control parameters of the engine 1 are corrected according to the result of the combustion state diagnosis. All of the configurations for performing the operations (1) to (4) may be mounted (implemented) on the vehicle, or only the operation (1) is performed by a laboratory or the like, and the result (creation) The ideal heat generation rate waveform) is stored in the ROM of the ECU 100, and the configuration for performing the operations (2) to (4) may be mounted on the vehicle. The operations (processes) (1) to (4) or the operations (processes) (2) to (4) may be executed every cycle, or may be executed every predetermined multiple cycles. Also good.

  Further, in the creation of the (1) ideal heat release rate waveform, (1-A) separation of fuel reaction forms, (1-B) ideal heat release rate waveform models for the separated reaction forms, respectively. Creation of an ideal heat release rate waveform by filtering (filter processing) of (1-C) ideal heat release rate waveform model is sequentially performed.

  Each operation will be specifically described below.

(1) Creation of ideal heat release rate waveform The creation of the ideal heat release rate waveform will be described. First, an outline of creating an ideal heat generation rate waveform will be described.

  As the rate-limiting conditions for the reaction (chemical reaction, etc.) of the fuel injected into the cylinder from the injector 23, the in-cylinder gas temperature, the oxygen amount in the cylinder (a value correlated with the oxygen density in the cylinder), Examples include the amount of fuel (a value that correlates with the fuel density in the cylinder) and the distribution of fuel in the cylinder. Among these, the order of low control freedom is the order of the temperature in the cylinder (cylinder gas temperature), the amount of oxygen in the cylinder, the amount of fuel in the cylinder, and the distribution of fuel in the cylinder.

  That is, the in-cylinder gas temperature is substantially determined by the intake air temperature and the compression ratio of the engine 1 before the fuel reacts, and the degree of freedom of control is the lowest. The in-cylinder gas temperature also varies depending on the amount of preheating caused by combustion of the fuel when fuel injection is performed in advance (for example, when fuel injection for preheating is performed).

  Further, since the amount of oxygen in the cylinder can be adjusted by the opening of the intake throttle valve 62 and the opening of the EGR valve 81, the degree of freedom of control is higher than the in-cylinder gas temperature. Further, the oxygen amount in the cylinder also varies depending on the supercharging rate by the turbocharger 5.

  Further, the amount of oxygen in the cylinder also varies depending on the amount of oxygen consumed by combustion of the fuel when fuel injection (fuel injection for preheating or the like) is performed in advance. Further, the amount of fuel in the cylinder can be adjusted by controlling the fuel injection pressure (common rail pressure) by the supply pump 21 and controlling the injection period of each of the multistage injections of fuel from the injector 23. The degree of freedom of control is higher than that. In addition, since the fuel distribution in the cylinder can be adjusted by controlling the fuel injection pressure and the injection period of each of the multistage fuel injections, the degree of freedom in control is high.

  And in this embodiment, the priority of the conditions which determine the reaction state of a fuel is set high in order with the said low degree of freedom of control. Here, the quantitative conditions of the temperature in the cylinder (in-cylinder gas temperature), the amount of oxygen in the cylinder, and the amount of fuel in the cylinder are given higher priority than the fuel distribution in the cylinder. That is, the start timing (reaction start timing) of each reaction of the fuel is determined using the in-cylinder gas temperature as an axis. That is, the reference temperature arrival angle (crank angle position at the reaction start timing of each reaction mode) is determined from the in-cylinder gas temperature (compressed gas temperature). In the present embodiment, when determining the start time of each reaction, the start time is corrected according to the oxygen density. Details will be described later.

  The oxygen density is an index representing the oxygen supply capability for the fuel, and becomes a rate-limiting condition for combustion when oxygen supply shortage occurs. The fuel density is an index representing the reaction heat supply capacity for the unburned region, and is a rate-limiting condition for combustion when fuel supply is insufficient.

  Then, using this reaction start time as a base point, the reaction rate, the reaction amount, and the reaction period are obtained, and an ideal heat release rate waveform model is created for each reaction mode. That is, the reaction speed, the reaction amount, and the reaction period of each of the plurality of reaction forms of the fuel injected into the cylinder are defined as the in-cylinder environment (cylinder gas temperature that determines the reaction start timing) and the fuel composition (the fuel that contributes to the reaction). The ideal heat release rate waveform model for each reaction is created.

As an operation for creating the ideal heat release rate waveform model, specifically, the reference reaction rate efficiency [J / CA ² / mm ³ ] corresponding to the in-cylinder gas temperature (reference temperature), the fuel composition, and the like at the reaction start time and The reference reaction amount efficiency [J / mm ³ ] is determined for each reaction form, and the reference reaction rate efficiency and the reference reaction amount efficiency are corrected based on the oxygen supply capacity (oxygen density) to the combustion field. The reaction rate and reaction amount are determined from the efficiency and the fuel amount. Further, the reaction speed is corrected according to the engine speed described later. The “reaction rate efficiency” is also referred to as “reaction rate gradient coefficient”, and the “reaction amount efficiency” is also referred to as “combustion efficiency”.

  Then, an ideal heat release rate waveform model (triangle model) described later is created from the reaction start timing, reaction rate, and reaction amount, thereby determining the reaction period. This reaction period is determined by the following equation (5).

Reaction period = 2 × (reaction amount / reaction rate) ^1/2 (5)
Details of creation of the ideal heat release rate waveform model (triangle model) will be described later.

(1-A) Separation of Fuel Reaction Form Next, separation of fuel reaction form, which is the first procedure for creating the ideal heat release rate waveform, will be described.

  When fuel is injected from the injector 23, a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and a high temperature oxidation reaction are performed in the cylinder according to the in-cylinder environment. Furthermore, the high temperature oxidation reaction can be separated into a high temperature oxidation reaction by premixed combustion and a high temperature oxidation reaction by diffusion combustion. Hereinafter, each reaction mode will be described.

(A) Vaporization reaction In the vaporization reaction, the fuel injected from the injector 23 is vaporized by receiving heat in the cylinder. This reaction is generally a spray-controlled reaction that starts when the fuel spray spreads to some extent in a state where the fuel is exposed to an environment where the gas temperature in the cylinder is 500K or higher. .

  The boiling point of light oil used in the diesel engine 1 is generally 453K to 623K, and the practical range where fuel injection is performed in the cylinder (for example, the timing when the pilot injection is performed) is BTDC (before compression top dead center). ) 40 ° CA. Since the in-cylinder gas temperature at this timing generally rises to about 550K to 600K (other than in cold regions), it is not necessary to consider the temperature-limiting condition in this vaporization reaction.

The reference reaction amount efficiency in this vaporization reaction is, for example, −1.14 [J / mm ³ ].

  In addition, the effective injection amount in this vaporization reaction (the amount of fuel that contributes to the vaporization reaction) is determined from the fuel injection amount to the amount of wall surface adhesion and the amount of unburned floating fuel (the fuel that exists outside the spray lump and does not contribute to the reaction) Is the amount obtained by subtracting. Hereinafter, these fuel amounts are referred to as unburned fuel amounts. These unburned fuel amounts can be obtained experimentally according to the injection amount (which has a correlation with fuel penetration force) and the injection timing (which has a correlation with cylinder pressure).

  And as reaction amount in the said vaporization reaction, it calculates | requires by the following formula | equation (6).

Reaction amount in vaporization reaction = −1.14 × effective injection amount (6)
Since this vaporization reaction is an endothermic reaction, the reaction amount (generated heat amount) is a negative value. This vaporization reaction is hardly affected by the oxygen density because the amount of oxygen required for the reaction is small.

(B) Low-temperature oxidation reaction In the low-temperature oxidation reaction, a low-temperature oxidation reaction component (such as a fuel having a linear single bond composition such as n-cetane (C ₁₆ H ₃₄ )) contained in the diesel oil that is the fuel of the diesel engine 1 is burned. It is a reaction to. This low-temperature oxidation reaction component is a component that can be ignited even when the in-cylinder gas temperature is relatively low. The larger the amount of n-cetane or the like (the higher the cetane fuel), the more the inside of the cylinder. Thus, the low temperature oxidation reaction easily proceeds, and the ignition delay is suppressed. Specifically, the low temperature oxidation reaction component such as n-cetane starts combustion (low temperature oxidation reaction) when the in-cylinder gas temperature reaches about 750K. Note that fuel components (high temperature oxidation reaction components) other than n-cetane do not start combustion (high temperature oxidation reaction) until the in-cylinder gas temperature reaches about 900K.

The standard reaction rate efficiency in this low-temperature oxidation reaction is, for example, 0.294 [J / CA ² / mm ³ ]. The standard reaction amount efficiency is, for example, 5.0 [J / mm ³ ].

The reaction rate and reaction amount of the low-temperature oxidation reaction are calculated based on the reference reaction rate efficiency and the reference reaction amount efficiency (for example, calculated by multiplying the effective injection amount). Further, in calculating the reaction rate of the low temperature oxidation reaction, a coefficient (rotational speed correction coefficient = (rotational speed correction coefficient) = (reference reaction speed) obtained by multiplying the reference reaction speed efficiency by the effective injection amount (reference reaction speed). The reference rotation speed / actual rotation speed) ² ) is multiplied. An arbitrary rotation speed (for example, 2000 rpm) can be set as the reference rotation speed for obtaining the rotation speed correction coefficient. Thereby, even if a gas composition etc. change, reaction rate can be calculated | required as a value depending on time.

The rotation speed correction coefficient may be obtained from the rotation speed correction coefficient map shown in FIG. The rotation speed correction coefficient map shown in FIG. 7 is obtained by setting the reference rotation speed to 2000 rpm. In a region where the actual rotational speed of the engine 1 is equal to or higher than the reference rotational speed (2000 rpm), a value corresponding to “(reference rotational speed / actual rotational speed) ² ” (a value corresponding to the engine rotational speed indicated by a one-dot chain line in the figure). ) As the rotation speed correction coefficient. On the other hand, in a region where the actual rotational speed of the engine 1 is less than the reference rotational speed (2000 rpm), the value corresponding to “(reference rotational speed / actual rotational speed) ² ” is corrected by a predetermined ratio (to the lower side). The corrected value is obtained as the rotation speed correction coefficient (see the solid line in the region below the reference rotation speed). In this case, the correction ratio is obtained by experiment or simulation.

  The reference rotation speed is not limited to the above-described value, and is preferably set to a rotation speed range where the engine 1 is used most frequently.

  Since this low-temperature oxidation reaction is an exothermic reaction, the reaction amount (generated heat amount) is a positive value.

(C) Thermal decomposition reaction The thermal decomposition reaction is a reaction that performs thermal decomposition (breakage of chain bonds of carbon chains) of a fuel component, and the reaction temperature is about 800K, for example.

The reference reaction rate efficiency in this thermal decomposition reaction is, for example, 0.384 [J / CA ² / mm ³ ]. The standard reaction amount efficiency is, for example, 5.0 [J / mm ³ ].

  Further, the reaction rate and reaction amount of the thermal decomposition reaction are also calculated based on the reference reaction rate efficiency and the reference reaction amount efficiency (for example, calculated by multiplying the effective injection amount). Further, even when calculating the reaction rate of the thermal decomposition reaction, the value obtained by multiplying the reference reaction rate efficiency by the effective injection amount (reference reaction rate) is multiplied by the rotation speed correction coefficient corresponding to the engine rotation speed. The

  Here, as a parameter representing the state of the thermal decomposition reaction, there is a degree of progress of the thermal decomposition reaction (thermal decomposition achievement rate) [%]. The degree of progress of this thermal decomposition reaction is a value (the amount of thermal decomposition / the total amount of fuel component) that has undergone thermal decomposition (cutting of chain bonds of carbon chains) with respect to the entire fuel component injected into the cylinder. Fuel component amount (total carbon amount) [%]), for example, the degree of progress of the pyrolysis reaction when reaching half of the reaction period of the pyrolysis reaction (details will be described later) is 50% .

  In the present embodiment, this thermal decomposition reaction is treated as an endothermic reaction. That is, the reaction amount (generated heat amount) is a negative value.

(D) High-temperature oxidation reaction by premixed combustion The reaction temperature of the high-temperature oxidation reaction by premixed combustion is, for example, about 900K. That is, the reaction that starts combustion when the in-cylinder gas temperature reaches 900 K is a high-temperature oxidation reaction by this premixed combustion.

The reference reaction rate efficiency in the high temperature oxidation reaction by the premixed combustion is, for example, 4.3 [J / CA ² / mm ³ ]. The standard reaction amount efficiency is, for example, 30.0 [J / mm ³ ].

  Further, the reaction rate and reaction amount of the high-temperature oxidation reaction by this premixed combustion are also calculated based on the reference reaction rate efficiency and the reference reaction amount efficiency (for example, calculated by multiplying the effective injection amount). Further, even when calculating the reaction rate of the high temperature oxidation reaction by the premixed combustion, the rotation speed correction according to the engine rotation speed with respect to the value obtained by multiplying the reference reaction speed efficiency by the effective injection amount (reference reaction speed). The coefficient is multiplied.

  Here, as described above, in the high temperature oxidation reaction by the premixed combustion, it is influenced by the progress degree of the thermal decomposition reaction that occurs before that. If the degree of progress of the pyrolysis reaction has reached a pyrolysis achievement reference value (for example, 50%), a high-temperature oxidation reaction by premixed combustion can be started at the reference reaction start temperature (900 K). On the other hand, when the degree of progress of the pyrolysis reaction does not reach the reference value for achieving pyrolysis (for example, when the degree of progress is less than 50%), the reaction of the high-temperature oxidation reaction by premixed combustion starts according to the degree of progress. The temperature shifts to a higher temperature side than the reference reaction start temperature (900K) (the reaction start timing is delayed to the retard side).

  Since the high temperature oxidation reaction by this premixed combustion is an exothermic reaction, the reaction amount (generated heat amount) is a positive value.

(E) High temperature oxidation reaction by diffusion combustion The reaction temperature of the high temperature oxidation reaction by diffusion combustion is about 1000K, for example. In other words, the reaction in which the fuel injected toward the cylinder having a temperature of 1000 K or more starts combustion immediately after the injection is a high temperature oxidation reaction by this diffusion combustion.

  Moreover, the reaction rate in the high temperature oxidation reaction by this diffusion combustion changes according to the common rail pressure, and is obtained from the following equations (7) and (8).

GrdB = A × common rail pressure + B (7)
Grd = GrdB × (reference engine speed / actual engine speed) ²
X (d / reference d) x (N / reference N) (8)
GrdB: reference reaction rate, Grd: reaction rate, d: nozzle hole diameter of the injector 23, N: number of nozzle holes of the injector 23, A, B: constants obtained by experiments, etc. Multiplying the ratio of the actual nozzle hole diameter to the reference nozzle hole diameter and the ratio of the actual nozzle hole number to the reference nozzle hole number of the injector 23 is a generalized equation. Further, the equation (8) is obtained by multiplying the rotation speed correction coefficient, thereby obtaining a response speed corrected in accordance with the engine rotation speed.

The standard reaction amount efficiency of the high temperature oxidation reaction by diffusion combustion is, for example, 30.0 [J / mm ³ ], and the reaction amount of the high temperature oxidation reaction by diffusion combustion is also equal to the reference reaction amount efficiency. Calculated based on (e.g., calculated by multiplying the effective injection amount).

  Since the high temperature oxidation reaction by diffusion combustion is also an exothermic reaction, the reaction amount (generated heat amount) is a positive value.

  As described above, the reaction form of the fuel can be separated.

(1-B) Creation of Ideal Heat Release Rate Waveform Model for Each Separated Reaction Form Next, creation of ideal heat release rate waveform models for each separated reaction form will be described.

  By separating the reaction forms as described above, it is possible to create an ideal heat release rate waveform model in each reaction form. That is, an ideal heat release rate waveform model can be created for each of a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, a high temperature oxidation reaction by premixed combustion, and a high temperature oxidation reaction by diffusion combustion.

  In this embodiment, the ideal heat release rate waveform model is approximated to an isosceles triangle for each reaction. That is, with the reaction start temperature (reaction start time) as a base point, the reaction rate is the slope of the hypotenuse of the isosceles triangle, the reaction amount is the area of the isosceles triangle, and the reaction period is the length of the base of the isosceles triangle. Create an ideal heat release rate waveform model.

  Hereinafter, the creation of the ideal heat release rate waveform model will be specifically described.

(A) Reaction start time (vaporization reaction)
As described above, since the boiling point of light oil used in the diesel engine 1 is 453K to 623K, the crank angle position [° CA] when the in-cylinder gas temperature reaches 623K is set as the reaction start time of the vaporization reaction. To do. When the temperature field (in-cylinder gas temperature) at which fuel is injected is 623 K or more, the reaction start timing of the vaporization reaction is the same as the fuel injection start timing (the reaction start timing of the vaporization reaction = fuel injection start) season). Further, as described above, since the vaporization reaction is hardly affected by the oxygen density, the reaction start timing of the vaporization reaction is not corrected by the oxygen density.

(Pyrolysis reaction, low temperature oxidation reaction, high temperature oxidation reaction)
As described above, the thermal decomposition reaction, the low temperature oxidation reaction, the high temperature oxidation reaction by premixed combustion, and the high temperature oxidation reaction by diffusion combustion are affected by the oxygen density, and the reaction start timing is delayed as the oxygen density decreases. Therefore, the reaction start temperature of each reaction, that is, the reaction start timing is corrected using the oxygen density. The reaction start timing of each reaction in this case can be calculated by the following equation (9).

Reaction start time = reference temperature arrival time + oxygen density decrease correction retardation amount (9)
Here, the reference temperature arrival time of the above formula (9) will be described. As described above, the reaction start temperature of the low-temperature oxidation reaction is about 750 K, so the in-cylinder gas temperature reaches 750 K (reference reaction start temperature). The crank angle position [° CA] of the timing to perform is set as the reference temperature reaching timing of the low temperature oxidation reaction. Since the reaction start temperature of the thermal decomposition reaction is about 800K, the crank angle position [° CA] when the in-cylinder gas temperature reaches 800K (reference reaction start temperature) is set as the reference temperature arrival time of the pyrolysis reaction. Since the reaction start temperature of the high temperature oxidation reaction by premix combustion is about 900K, the crank angle position [° CA] when the in-cylinder gas temperature reaches 900K (reference reaction start temperature) is set to the high temperature oxidation reaction by premix combustion. The reference temperature is reached. Since the reaction start temperature of the high temperature oxidation reaction by diffusion combustion is about 1000 K, the crank angle position [° CA] when the in-cylinder gas temperature reaches 1000 K (reference reaction start temperature) is used as a reference for the high temperature oxidation reaction by diffusion combustion. Time to reach temperature.

  In addition, the oxygen density decrease correction retardation amount in the above formula (9) is a correction amount of the reaction start timing due to the influence of the oxygen density. The relationship between the oxygen density and the oxygen concentration decrease correction retardation amount is stored in the ROM of the ECU 100 as a correction retardation amount map that is obtained in advance by experiments and simulations. The density reduction correction retardation amount is extracted.

  FIG. 8 shows an example of a corrected retardation amount map for a certain reaction (for example, a high temperature oxidation reaction by premixed combustion). Similar maps are stored in the ROM of the ECU 100 for other reactions (low-temperature oxidation reaction, thermal decomposition reaction, and high-temperature oxidation reaction by diffusion combustion).

  This correction retardation amount map is obtained by simplifying the change in the retardation amount of the reaction start timing (oxygen density decrease correction retardation amount) with respect to the change in oxygen density by the Wiebe function.

  In the case shown in FIG. 8, when the oxygen density changes from ρ1 to ρ2, the retardation amount when the oxygen density is ρ1 is CA1, and the retardation amount when the oxygen density is ρ2 is “0”. The terms a and m, which are the shape parameters of the Wiebe function, are set.

  The correction retardation amount map shown in FIG. 8 represents the change in the oxygen density decrease correction retardation amount with respect to the change in oxygen density by the Wiebe function, but is not limited thereto, and the oxygen density with respect to the change in oxygen density. You may make it utilize the correction | amendment retardation amount map which represented the change of the fall correction | amendment retardation amount by the linear function.

  In addition, when considering the amount of retardation of the reaction start time due to the influence of the spray distribution (for example, the influence of the spray distribution resulting from the change in the fuel injection pressure), A corrected retardation amount map that prescribes the change is created in advance, and the retardation amount of the reaction start time is obtained according to this corrected retardation amount map.

(Correcting the arrival time of the reference temperature for high temperature oxidation reaction by premixed combustion)
First, as described above, the reaction start timing of each reaction can be controlled by temperature. That is, the reaction start timing of each reaction can be managed as an independent phenomenon depending on the in-cylinder gas temperature, but the high-temperature oxidation reaction by premixed combustion is affected by the progress of the thermal decomposition reaction that occurs before that. Focusing on these points, in this embodiment, the reaction start time (reference temperature arrival time) of the high-temperature oxidation reaction by premixed combustion is variably set according to the degree of progress of the thermal decomposition reaction. Make it possible to accurately define the start time. An example of the processing will be described below.

  [ST1] The progress degree [%] of the thermal decomposition reaction that occurs before the high-temperature oxidation reaction by premixed combustion is calculated based on the in-cylinder gas temperature at the start of fuel injection. Specifically, the in-cylinder gas temperature at the start of fuel injection is calculated by the above-described calculation method, and thermal decomposition is performed with reference to the map of FIG. 9 based on the calculated in-cylinder gas temperature at the start of fuel injection. Determine the degree of progress [%] of the reaction.

  The progress degree map of FIG. 9 shows that when the fuel is injected into the cylinder in the temperature region where the in-cylinder gas temperature is 900K or higher, the in-cylinder gas temperature at the start of the fuel injection is 900K (reference reaction start temperature). Focusing on the fact that the higher the temperature, the smaller the progress of the pyrolysis reaction, and the change in the progress of the pyrolysis reaction [%] is simplified by the Wiebe function using the in-cylinder gas temperature at the start of fuel injection as a parameter. It has become.

  Specifically, in the progress degree map shown in FIG. 9, when the in-cylinder gas temperature at the start of fuel injection changes from 900K to 1000K, the in-cylinder gas temperature at the start of fuel injection is 900K. The a term and m term, which are the shape parameters of the Wiebe function, are set so that the degree of progress is 50% and the degree of progress when the in-cylinder gas temperature is 1000 K is “0”. The progress degree map of FIG. 9 is stored in the ROM of the ECU 100.

  In the progress degree map shown in FIG. 9, the reference value (typical value: KPYR) of the degree of thermal decomposition when the high-temperature oxidation reaction by premixed combustion starts at 900 K (reference reaction start temperature) is 50%. Without being limited thereto, a value other than 50% may be applied to the reference value.

  Moreover, when not using the progress degree map of such a thermal decomposition reaction, the progress degree of a thermal decomposition reaction can be calculated | required also from the following formula | equation (10).

Degree of progression = KPYR × exp (a × X ^{m + 1} ) (10)
Here, X = (in-cylinder gas temperature at the start of fuel injection [K] −900 [K]) / 100 [K] ≧ 0, KPYR = 50 [%] a = −8.06, m = 2.54 It is. In addition, also when using such Formula (10), you may apply values other than 50% about KPYR which is a representative value (reference value).

  [ST2] Using the degree of progress [%] of the thermal decomposition reaction obtained in the process of [ST1], the thermal decomposition progress degree change correction retardation amount [° CA] is calculated with reference to the map of FIG. Using the calculated pyrolysis progress degree change correction retardation amount [° CA], the reference temperature arrival time is corrected by the following equation (11).

Reference temperature arrival time after correction = reference temperature arrival time + thermal decomposition progress degree change correction retardation amount (11)
Then, using the calculated reference temperature arrival time after correction, the reaction start time [° CA] of the high temperature oxidation reaction by premixed combustion is calculated by the above equation (9) [reaction start time = (reference temperature reached). Timing + pyrolysis progress change correction retardation amount) + oxygen density decrease correction retardation amount]. The reaction start timing [° CA] of the high-temperature oxidation reaction by the premixed combustion calculated in this way is used for an ideal heat generation rate waveform creation process to be described later. When the in-cylinder gas temperature at the start of fuel injection is lower than the reference reaction start temperature (900K) of the high-temperature oxidation reaction by premixed combustion, and the degree of progress of the thermal decomposition reaction is 50% or more, The crank angle position at which the internal gas temperature reaches 900K is defined as the reaction start timing [° CA] of the high temperature oxidation reaction by premixed combustion.

  Note that the reaction start timing [° CA] of the high-temperature oxidation reaction by premixed combustion calculated as described above may be corrected using a reference engine rotation speed (for example, 1000 rpm). Specifically, by multiplying the reaction start timing [° CA] of the high-temperature oxidation reaction by the premixed combustion obtained in the above calculation process by the engine speed ratio (reference engine speed / actual engine speed NE). Then, the rotational speed of the reaction start time [° CA] of the high temperature oxidation reaction by the premixed combustion is corrected.

  Here, the corrected retardation amount map shown in FIG. 10 is based on the case where the degree of progress of the thermal decomposition reaction is 50% (representative value), and the actual degree of progress of the thermal decomposition reaction is smaller than the reference degree of progress. Focusing on the fact that the reference temperature arrival time to reach the reaction start temperature of the high temperature oxidation reaction by premix combustion is delayed (the reaction start time of the high temperature oxidation reaction by premix combustion changes to the retard side) The change in the thermal decomposition progress degree change correction retardation amount [° CA] is simplified by the Wiebe function using the progress degree [%] of the decomposition reaction as a parameter.

  Specifically, in the corrected retardation amount map shown in FIG. 10, when the degree of progress of the pyrolysis reaction changes from 50% to 0%, the degree of progress of the pyrolysis reaction is 50%. The terms a and m, which are the shape parameters of the Wiebe function, are set so that the amount of retardation is “0” and the amount of retardation when the degree of progress of the thermal decomposition reaction is 0% is CA2. The corrected retardation amount map of FIG. 10 is stored in the ROM of the ECU 100.

  In the corrected retard amount map shown in FIG. 10, the retard amount is set to a larger value as the progress degree [%] of the thermal decomposition reaction is smaller. That is, the reaction start timing of the high-temperature oxidation reaction by premixed combustion obtained by performing correction using the retardation amount calculated from the corrected retardation amount map of FIG. 10 is smaller as the progress degree of the thermal decomposition reaction is smaller. The value is on the retard side.

  The correction retardation amount map shown in FIG. 10 represents the change in the thermal decomposition progress degree change correction retardation amount with respect to the change in the progress degree of the thermal decomposition reaction by the Wiebe function. You may make it utilize the correction | amendment retardation amount map which represented the change of the correction | amendment retardation amount with respect to the change of the progress degree of decomposition reaction by the linear function. Further, a correction retardation amount map as shown in FIG. 10 may be created by experiments, simulations, or the like.

  As described above, according to the present embodiment, when the fuel is injected into the cylinder in the temperature range equal to or higher than the reference reaction start temperature (900K) of the high temperature oxidation reaction by the premixed combustion (the fuel has been injected by 900K). If not, the reaction start time is set to the retarded side as the progress degree of the thermal decomposition reaction that occurs before the high temperature oxidation reaction by the premix combustion is smaller. The reaction start time of the oxidation reaction can be accurately determined. Thereby, the ideal heat release rate waveform mentioned later can be created with high accuracy.

  In this correction processing example, the reference temperature arrival time is corrected based on the degree of progress of the thermal decomposition reaction. However, the present invention is not limited to this, and high-temperature oxidation by premixed combustion calculated by the above equation (9) is not limited thereto. You may make it correct | amend the reaction start time of reaction. Specifically, the pyrolysis progress degree calculated based on the progress degree of the pyrolysis reaction is calculated based on the start stage of the high temperature oxidation reaction by the premixed combustion calculated by the equation (9) (the reaction start time after the oxygen density correction). Correction may be performed using the change correction retardation amount (reaction start time after oxygen density correction + pyrolysis progress degree change correction retardation amount).

  In the above correction processing, the correction delay amount is obtained from the degree of progress of the thermal decomposition reaction, and the reaction start time of the high temperature oxidation reaction by the premixed combustion is set. However, the present invention is not limited to this. A map (calculation formula) that directly calculates the reaction start timing of the high-temperature oxidation reaction by premixed combustion based on the degree of progress of pre-combustion is created by experiments and simulations, etc., and the degree of progress of the pyrolysis reaction using that map etc. Accordingly, the reaction start timing of the high-temperature oxidation reaction by premixed combustion may be set to the retard side as the progress degree is smaller.

(B) Reaction rate (gradient)
The reaction rate is set based on the reference reaction rate efficiency. When the ideal heat generation rate waveform model is approximated to an isosceles triangle, the rising rate during the period in which the heat generation rate increases and the heat generation rate decrease. Their absolute values are consistent with the descending slope of the period.

  In addition, when the reaction rate in the period in which the heat generation rate decreases is lower than the reaction rate in the period in which the heat generation rate increases (when the ideal heat generation rate waveform model is an inequilateral triangle), The descending gradient is obtained by multiplying the ascending gradient by a predetermined value α (<1).

  In the ideal heat release rate waveform model in the high temperature oxidation reaction by diffusion combustion, the reaction rate is proportional to the injection rate waveform gradient, and the reaction rate is constant if the fuel injection pressure (common rail internal pressure) is constant. In the ideal heat release rate waveform model in other reactions (for example, high temperature oxidation reaction by premixed combustion), the reaction speed is proportional to the fuel injection amount.

  The reaction rate may be corrected using the oxygen density or fuel density described above.

(C) Generated heat (area)
The thermal efficiency [J / mm ³ ] in each reaction can be regarded as a constant (for example, 30 J / mm ^{3 in} the case of a high temperature oxidation reaction) if the combustion period is optimized. For this reason, the generated heat amount is obtained by multiplying the thermal efficiency by the fuel injection amount (the effective injection amount).

  However, the low-temperature oxidation reaction is completed together with the high-temperature oxidation reaction, and the high-temperature oxidation reaction by diffusion combustion is completed alone.

  The amount of heat generated in this way corresponds to the area of a triangle that is an ideal heat generation rate waveform model. The amount of generated heat may be corrected using the oxygen density.

(D) Combustion period (base)
The combustion period corresponding to the length of the base of the triangle is obtained from the gradient of the triangle (reaction rate) and the area of the triangle (heat generation amount).

  As shown in FIG. 11, the triangular area (corresponding to the amount of generated heat) is S, the base length (corresponding to the combustion period) is L, and the height (corresponding to the heat generation rate at the peak of the heat generation rate) is H. , A is the period from the start of combustion to the peak of the heat generation rate, and B is the period from the peak of the heat generation rate to the end of combustion (B = A when the ideal heat generation rate waveform model is an isosceles triangle), G is the ascending gradient (corresponding to the reaction rate during the period when the heat generation rate increases), and α (≦ 1) is the ratio of the descending gradient (corresponding to the reaction rate during the period when the heat generation rate decreases) to this ascending gradient. In this case, the following relationship holds. FIG. 11A shows a case where the ideal heat generation rate waveform model is an isosceles triangle, and FIG. 11B shows a case where the ideal heat generation rate waveform model is an unequal triangle.

H = A × G = B × α × G
From this, B = A / α.

S = A ² × G / 2 + A × G × B / 2 = (1 + 1 / α) × A ² × G / 2
Therefore, A = SQRT [2S / {(1 + 1 / α) G}].

Therefore, the base length L is
L = A + B = A (1 + 1 / α)
= (1 + 1 / α) × SQRT [2S / {(1 + 1 / α) G}]
When the ideal heat release rate waveform model is an isosceles triangle, α = 1.
L = 2 × SQRT (S / G) = 2 × SQRT (30 × Fq / G).

(Fq is the fuel injection amount (effective injection amount). As described above, when the heat generation amount per 1 mm ^{3 of} fuel is 30 J, “30 × Fq” is the triangular area S)
In this way, the combustion period is determined when the injection amount (injection amount command value: a value correlated with the generated heat amount) and the gradient (reaction rate) are given.

  Hereinafter, the reason why the ideal heat generation rate waveform model can be approximated to a triangle (especially an isosceles triangle) will be described. FIG. 12A shows the relationship between the elapsed time when fuel is injected from the injector 23 and the amount of fuel supplied into the cylinder in one reaction mode (the amount of fuel used in that reaction mode). ing. In FIG. 12A, the fuel injection period in which the fuel supply amount is obtained is divided into ten periods. That is, the fuel injection period is divided into ten periods with the same fuel supply amount, and the period numbers from the first period to the tenth period are assigned to each period. That is, after the fuel injection in the first period is completed, the fuel injection in the second period is started without interruption, and after the fuel injection in the second period is completed, the fuel injection is not interrupted. The fuel injection is continued until the end of the tenth period in the injection mode in which the fuel injection in the three periods is started.

  FIG. 12B shows the reaction amount of the fuel injected in each period (the one shown in FIG. 12B is the exothermic amount in the exothermic reaction). As shown in FIG. 12B, fuel injection in the first period is started and fuel injection in the second period is started (period t1 in FIG. 12B). Only the reaction of the fuel injected in the period takes place. Then, during the period from the start of fuel injection in the second period to the start of fuel injection in the third period (period t2 in FIG. 12B), the reaction of the fuel injected in the first period and The reaction of the fuel injected in the second period is performed together. In this way, every time a new injection period is reached, the total reaction amount of fuel gradually increases (the total reaction amount increases by the amount of fuel in the period during which new injection is started). This increase period corresponds to the positive gradient period (advanced period relative to the peak position of the reaction) of the ideal heat release rate waveform model.

  Thereafter, the reaction of the fuel injected in the first period ends. At this time (timing T1 in FIG. 12B), the reaction of the fuel injected in the second period and thereafter is not completed, and the reaction of the fuel injected in the second period to the tenth period continues. Yes. When the reaction of the fuel injected in the second period is completed (timing T2 in FIG. 12B), the reaction of the fuel injected in the third period and thereafter is not completed. The reaction of the fuel injected in the period will continue. In this way, the reaction of the fuel injected in each period ends in sequence, so that the total reaction amount of the fuel gradually decreases (the total reaction amount decreases by the amount of fuel for which the reaction has ended). Go). This decrease period (a period in which the reaction amount is indicated by a broken line in FIG. 12B) is a period of a negative gradient of the ideal heat release rate waveform model (a period on the retard side from the peak position of the reaction). Equivalent to.

  Since the fuel reaction is performed in the above-described manner, the ideal heat generation rate waveform model can be approximated as a triangle (isosceles triangle).

  The above is the procedure for creating the ideal heat release rate waveform model for each reaction mode of fuel.

(1-D) Creation of ideal heat release rate waveform by filtering of ideal heat release rate waveform model After creating an ideal heat release rate waveform model as described above, this ideal heat release rate waveform model is subjected to well-known filter processing ( For example, an ideal heat generation rate waveform is created by performing smoothing by processing using a Wiebe filter. This will be specifically described below.

  FIG. 13 shows an ideal heat generation rate waveform model (an isosceles triangle corresponding to each reaction) when one fuel injection is performed. In FIG. 13, in order to facilitate understanding of the present invention, an ideal heat generation rate waveform model when a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and each high temperature oxidation reaction are sequentially performed by one fuel injection. (Isosceles triangles corresponding to each reaction) are shown. Specifically, I in the figure is an ideal heat release rate waveform model of a vaporization reaction, II is an ideal heat release rate waveform model of a low-temperature oxidation reaction, and III is an ideal heat release rate of a thermal decomposition reaction (a thermal decomposition reaction that is endothermic). A waveform model IV is an ideal heat release rate waveform model of a high temperature oxidation reaction by premixed combustion. V is an ideal heat release rate waveform model of the high temperature oxidation reaction by diffusion combustion.

  FIG. 14 shows an ideal heat generation rate waveform obtained by smoothing the ideal heat generation rate waveform model by filtering. In this way, the ideal heat release rate waveform model (isosceles triangle) corresponding to each reaction (vaporization reaction, low temperature oxidation reaction, thermal decomposition reaction, each high temperature oxidation reaction) is smoothed by the filter processing, and the ideal heat release rate A waveform will be created.

  In the actual engine 1, pilot injection, after injection, and the like are performed in addition to the main injection. Therefore, for these pilot injections and after-injections, an ideal heat release rate waveform model is created in the cylinder in the same way as described above, and this is smoothed by filtering to create an ideal heat release rate waveform. Is done.

  Then, an ideal heat generation rate waveform for the entire cylinder in the main injection and these ideal heat generation rate waveforms (ideal heat generation rate waveforms for pilot injection and after injection) are combined for one cycle. An ideal heat generation rate waveform for the target is created.

  Even when the main injection is divided into a plurality of times and executed (divided main injection), the ideal heat generation rate for one cycle is obtained by synthesizing the ideal heat generation rate waveforms in each main injection. A waveform will be created.

  When multiple injections are performed in this way, in order to synthesize each ideal heat generation rate waveform, in-cylinder gas temperature at the timing of fuel injection at the preceding stage (advance side), and thereafter It is necessary to consider that the in-cylinder gas temperature at the timing of fuel injection (on the retard side) is different from each other.

  Specifically, in the steady operation state of the engine, when the preheating or the like is not performed at the timing of fuel injection on the advance side, fresh air sucked from the outside, residual gas in the cylinder, and EGR The reaction is started based on the compressed gas temperature resulting from the temperature rise of the gas such as gas as the piston 13 moves. When starting the engine or returning the fuel injection from the fuel cut, the reaction starts based on the compressed gas temperature due to the rise in temperature of the fresh air drawn from the outside as the piston 13 moves. Will be.

  On the other hand, when the fuel is injected at the retarded angle side, the temperature rises by adding the temperature of burned gas (combustion gas of fuel injected at the advanced angle side) to the compressed gas temperature. Since the fuel is injected with respect to the temperature field, the reaction start timing shifts to the advance side as compared with the case where there is no temperature increase due to the burned gas. Considering this, the ideal heat generation rate waveform due to the reaction of fuel injected on the advance side and the ideal heat generation rate waveform due to the reaction of fuel injected on the retard side are considered the temperature changes described above. Ask. That is, the start time of each reaction in each injection is defined by temperature management. Thereby, it is possible to appropriately obtain the start time of each reaction in each injection. As a result, it is possible to properly define the reaction start order, the period in which the reactions are paralleled, etc., and the ideal heat generation rate waveform by synthesizing the ideal heat generation rate waveform created for each injection Can be created with high accuracy.

(2) Creation of actual heat generation rate waveform The actual heat generation rate waveform to be compared with the ideal heat generation rate waveform is generated according to a change in the in-cylinder pressure detected by the in-cylinder pressure sensor 4A. In other words, there is a correlation between the heat generation rate in the cylinder and the in-cylinder pressure (the higher the heat generation rate, the higher the in-cylinder pressure). Therefore, from the in-cylinder pressure detected by the in-cylinder pressure sensor 4A. An actual heat generation rate waveform can be created. Since the process of creating the actual heat generation rate waveform from the detected in-cylinder pressure is known, the description thereof is omitted here.

(3) Diagnosis of combustion state by comparing ideal heat generation rate waveform and actual heat generation rate waveform As a diagnosis of combustion state (diagnosis of reaction mode), the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform Done based on size. For example, when there is a reaction form in which the divergence is equal to or greater than a preset threshold value (abnormality judgment divergence amount in the present invention), it is diagnosed that the reaction form is abnormal. Become. For example, when there is a reaction form in which the deviation of the heat generation rate is 10 [J / ° CA] or more, or the deviation of the actual heat generation rate waveform to the crank angle side (advance side or When there is a reaction form in which the delay angle deviation is 3 ° CA or more, it is diagnosed that the reaction form is abnormal. These values are not limited to this, and are set as appropriate through experiments and simulations.

  For example, the case where the ideal heat generation rate waveform shown in FIG. 14 is created will be described as an example. Like the actual heat generation rate waveform shown by a broken line in FIG. The actual heat generation rate waveform in each high-temperature oxidation reaction (high-temperature oxidation reaction by premixed combustion and high-temperature oxidation reaction by diffusion combustion) is shifted to the retard side with respect to the waveform shown in FIG. If it exceeds, it is diagnosed that an abnormality has occurred in each high-temperature oxidation reaction, that is, an abnormality has occurred in the reaction start timing of each high-temperature oxidation reaction.

  In addition, as shown in the actual heat generation rate waveform indicated by the alternate long and short dash line in FIG. 15, the peak value of the heat generation rate waveform in each high-temperature oxidation reaction is higher than the ideal heat generation rate waveform indicated by the solid line, and the deviation exceeds the threshold value. If it exceeds, it is diagnosed that an abnormality has occurred in each high-temperature oxidation reaction, that is, an abnormality has occurred in the reaction amount in each high-temperature oxidation reaction. Such diagnosis is not limited to the high temperature oxidation reaction, but is similarly performed for the vaporization reaction, the low temperature oxidation reaction, and the thermal decomposition reaction.

  The parameters for diagnosing whether or not an abnormality has occurred in the reaction form are not limited to the above-described reaction time deviation (ignition delay, etc.) or the peak value deviation of the heat release rate waveform, but the reaction rate. Deviation, reaction period deviation, peak phase, and the like.

(4) Correction of control parameter of engine 1 according to diagnosis result In the diagnosis of the combustion state by comparing the ideal heat generation rate waveform and the actual heat generation rate waveform, the actual heat generation rate with respect to the ideal heat generation rate waveform as described above. When there is a reaction form in which the waveform deviation exceeds a preset threshold, it is diagnosed that an abnormality has occurred in the reaction form, and the control parameter of the engine 1 is corrected so as to reduce this deviation. .

  For example, when the actual heat generation rate waveform is shown by a broken line in FIG. 15, it is determined that fuel ignition delay has occurred and oxygen is insufficient, and the intake air cooling capacity by the intercooler 61 is determined. The shortage of oxygen is eliminated by reducing the EGR gas amount by decreasing the opening degree of the EGR valve 81 or by increasing the intake supercharging rate.

  Further, when the actual heat generation rate waveform is shown by a one-dot chain line in FIG. 15, it is determined that the reaction amount of the fuel is too large, and the fuel injection amount reduction correction, the EGR gas increase correction, etc. I do.

  As other corrective action, when the reaction start time in the actual heat generation rate waveform is on the retard side with respect to the ideal heat generation rate waveform, the intake supercharging rate is increased or the pilot in the cylinder is piloted. It is also possible to make corrections such as increasing the amount of preheating by injection.

  Control parameters for bringing the actual heat generation rate waveform closer to the ideal heat generation rate waveform are not limited to those described above, but include fuel injection timing, gas composition in the cylinder, intake air amount (gas amount), and various learning values. (A learned value of the fuel injection amount or fuel injection timing) may be used. For example, when the oxygen density in the cylinder is excessive or insufficient, learning is performed so as to correct the EGR gas or the intake supercharging rate as the learning value. Further, when the fuel density in the cylinder is excessive or insufficient, learning is performed such that the fuel injection timing, the fuel injection pressure, and the fuel injection amount are corrected as the learning value.

  Such correction of the control parameter is executed when the actual heat generation rate waveform can be substantially matched with the ideal heat generation rate waveform by the correction of the control parameter. Specifically, it is executed when the deviation amount of the actual heat generation rate waveform with respect to the ideal heat generation rate waveform is equal to or less than a predetermined correctable deviation amount. This correctable deviation amount is set in advance by experiment or simulation. When the deviation amount of the actual heat generation rate waveform with respect to the ideal heat generation rate waveform exceeds the correctable deviation amount, the correction amount of the control parameter exceeds the predetermined guard value. Diagnose that a failure has occurred in a part of the devices constituting the system 1. Specifically, when the lower limit values of the in-cylinder gas temperature, oxygen density, and fuel density are set in advance, and any of these in-cylinder gas temperature, oxygen density, and fuel density is below the lower limit value, If the correction amount of the control parameter of the engine 1 exceeds a predetermined guard value, it is diagnosed that the engine 1 has failed.

  In this case, without correcting the control parameter, for example, the MIL (warning lamp) on the meter panel in the passenger compartment is turned on to urge the driver to give a warning, and abnormality information is provided to the diagnosis provided in the ECU 100. Will be written.

  As described above, according to the present embodiment, when the ideal heat generation rate waveform of the high temperature oxidation reaction by the premixed combustion is created, the progress degree of the thermal decomposition reaction that occurs before the high temperature oxidation reaction by the premixed combustion is performed. Since the reaction start time is set according to the above, the reaction start time of the high temperature oxidation reaction by the premixed combustion can be accurately defined. As a result, an ideal heat generation rate waveform of a high-temperature oxidation reaction by premixed combustion can be created with high accuracy.

  And in this embodiment, the ideal heat generation rate waveform of the high temperature oxidation reaction by such premixed combustion, and the ideal heat generation rate waveform of each of the high temperature oxidation reaction by vaporization reaction, low temperature oxidation reaction, thermal decomposition reaction, and diffusion combustion Is used to create an ideal heat release rate waveform for the entire cylinder, and the combustion state is diagnosed using this ideal heat release rate waveform. For this reason, when the actual heat generation rate waveform deviates from the ideal heat generation rate waveform by a predetermined amount or more for each of the plurality of fuel reaction forms, it is possible to diagnose that the reaction form is abnormal. it can. That is, each reaction form can be handled individually and the presence or absence of abnormality can be diagnosed for each. For this reason, it is possible to specify the reaction form in which an abnormality has occurred with high accuracy, and to improve the diagnostic accuracy.

  And by taking improvement measures (correction of control parameters) for the reaction form diagnosed as abnormal (when the divergence is equal to or less than a predetermined correctable deviation amount), the reaction state of the reaction form is optimized. Therefore, it is possible to correct the optimal control parameter for performing the correction, and an effective correction operation can be performed. As a result, it becomes possible to bring the entire reaction of the fuel closer to the ideal reaction (the actual heat generation rate waveform of each reaction approaches the ideal heat generation rate waveform), and the controllability of the engine 1 is greatly improved. be able to.

  Further, when it is diagnosed that an abnormality has occurred in the reaction, whether or not the abnormality can be resolved is determined based on a deviation amount of the actual heat generation rate waveform from the ideal heat generation rate waveform. Therefore, it is possible to accurately determine a state in which a normal reaction state is obtained by correcting the control parameter and a state in which maintenance such as component replacement is necessary.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to the in-line four-cylinder diesel engine 1 mounted on an automobile has been described. The present invention is applicable not only to automobiles but also to engines used for other purposes. Further, the number of cylinders and the engine type (separate type engine, V-type engine, horizontally opposed engine, etc.) are not particularly limited.

  In the above embodiment, the combustion state diagnosis apparatus according to the present invention is stored in the ROM of the in-vehicle ECU 100 (mounted on the vehicle), and the combustion state is diagnosed in the operating state of the engine 1. The present invention is not limited to this, and the combustion state diagnosis device is provided in an experimental device (engine bench tester), and the combustion state is diagnosed when the engine 1 is tested on the experimental device in the design stage of the engine 1. It is also possible to apply to a usage pattern in which an appropriate value of the control parameter is obtained by performing the above.

  In the above embodiment, an ideal heat generation rate waveform model for the entire cylinder is created on the assumption that the oxygen density and the fuel density in the outer cavity region and the inner cavity region are substantially the same. The ideal heat release rate waveform was created by filtering the rate waveform model. The present invention is not limited to this, and it is assumed that at least one of the oxygen density and the fuel density in the region outside the cavity and the region in the cavity is different, and an ideal heat release rate waveform model is created for each region. An ideal heat generation rate waveform for the entire cylinder may be created by filtering the heat generation rate waveform model and synthesizing each ideal heat generation rate waveform.

  Further, in the above-described embodiment, the engine 1 to which the piezo injector 23 that changes the fuel injection rate by being in a fully opened valve state only during the energization period is described. However, the present invention applies a variable injection rate injector. Application to engines is also possible.

  INDUSTRIAL APPLICABILITY The present invention can be applied to creation of a heat release rate waveform of each reaction of fuel and diagnosis of each reaction in a diesel engine or the like mounted on an automobile.

1 engine (internal combustion engine)
12 Cylinder bore 13 Piston 23 Injector (fuel injection valve)
3 Combustion chamber 40 Crank position sensor 49 Intake air temperature sensor 4A In-cylinder pressure sensor 100 ECU
I Ideal heat release rate waveform model of vaporization reaction II Ideal heat release rate waveform model of low temperature oxidation reaction III Ideal heat release rate waveform model of pyrolysis reaction IV Ideal heat release rate waveform model of high temperature oxidation reaction by premixed combustion V Diffusion combustion Model of ideal heat release rate for high temperature oxidation reaction

Claims (10)

An apparatus for creating a heat release rate waveform of the fuel reaction in an internal combustion engine that burns fuel injected into a cylinder from a fuel injection valve,
Among the reactions of fuel injected from the fuel injection valve, when creating an ideal heat generation rate waveform of a high temperature oxidation reaction by premixed combustion, the progress of a thermal decomposition reaction that occurs before the high temperature oxidation reaction by the premixed combustion An apparatus for creating a heat release rate waveform of an internal combustion engine, characterized in that a reaction start time is set according to the degree and an ideal heat release rate waveform of a high temperature oxidation reaction by the premixed combustion is created. In the internal combustion engine heat release rate waveform creation device according to claim 1,
When fuel is injected into the cylinder in a temperature range where the in-cylinder gas temperature is equal to or higher than the reference reaction start temperature of the high-temperature oxidation reaction by premixed combustion, the degree of progress is smaller according to the degree of progress of the thermal decomposition reaction. An apparatus for generating a heat release rate waveform of an internal combustion engine, characterized in that a reaction start time of a high-temperature oxidation reaction by premixed combustion is set to a retard side. In the internal combustion engine heat release rate waveform creation device according to claim 1 or 2,
The progress rate of the thermal decomposition reaction is obtained based on the in-cylinder gas temperature at the start of fuel injection. In the internal combustion engine heat release rate waveform creation device according to any one of claims 1 to 3,
A heat of an internal combustion engine characterized by creating ideal heat generation rate waveforms for each of a vaporization reaction, a low temperature oxidation reaction, the thermal decomposition reaction, a high temperature oxidation reaction by the premixed combustion, and a high temperature oxidation reaction by diffusion combustion Incidence waveform creation device. In the internal combustion engine heat release rate waveform creation device according to any one of claims 1 to 4,
The ideal heat release rate waveform is created by creating an ideal heat release rate waveform model consisting of triangles with the reaction rate as the base point, the reaction rate as the slope of the hypotenuse, the reaction amount as the area, and the reaction period as the base length. An apparatus for creating a heat release rate waveform of an internal combustion engine, wherein the heat release rate waveform model is created by smoothing an ideal heat release rate waveform model by filtering.   An ideal heat generation rate waveform created by the heat generation rate waveform creation device for an internal combustion engine according to any one of claims 1 to 5, and an actual heat generation rate waveform when fuel actually reacts in the cylinder, When the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is equal to or greater than a predetermined amount, the fuel reaction is diagnosed as having an abnormality. A combustion state diagnostic device for an internal combustion engine. The combustion state diagnosis apparatus for an internal combustion engine according to claim 6,
The combustion state diagnosis apparatus for an internal combustion engine, wherein the actual heat generation rate waveform is obtained based on an in-cylinder pressure detected by an in-cylinder pressure sensor. The combustion state diagnosis apparatus for an internal combustion engine according to claim 6 or 7,
When the divergence of the actual heat generation rate waveform with respect to the ideal heat generation rate waveform is equal to or greater than a predetermined abnormality determination divergence amount, and it is diagnosed that an abnormality has occurred in the fuel reaction, When the deviation of the actual heat generation rate waveform is equal to or less than a predetermined correctable deviation, the control parameter of the internal combustion engine is corrected to control the deviation to be less than the abnormality determination deviation, while the ideal heat A combustion state diagnosis apparatus for an internal combustion engine that diagnoses that a failure has occurred in the internal combustion engine when the deviation of the actual heat generation rate waveform from the generation rate waveform exceeds the correctable deviation amount. In the internal combustion engine heat release rate waveform creation device according to any one of claims 1 to 5,
An apparatus for creating a heat release rate waveform of an internal combustion engine, which is mounted on a vehicle or mounted on an experimental device. The combustion state diagnosis apparatus for an internal combustion engine according to any one of claims 6 to 8,
A combustion state diagnostic device for an internal combustion engine, which is mounted on a vehicle or mounted on an experimental device.

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