JP5949676B2 - Heat generation rate waveform creation device and combustion state diagnostic device for internal combustion engine - Google Patents

Description

  The present invention relates to an apparatus for creating a heat release rate waveform of an internal combustion engine such as a diesel engine, and an apparatus for diagnosing an actual combustion state using the created heat release rate waveform.

  As is well known in the art, in a diesel engine (hereinafter sometimes simply referred to as an engine) used as an automobile engine or the like, each control parameter such as a fuel injection amount is corrected according to the engine operating state. In this case, it is desirable to recognize the reaction state of the fuel in the cylinder (hereinafter sometimes referred to as a combustion state) and correct each control parameter accordingly so as to obtain a desired reaction state.

  As one of means for correcting each control parameter according to the reaction state of the fuel in the cylinder in this way, a heat release rate waveform during combustion is obtained, and the heat release rate waveform is an ideal waveform (hereinafter referred to as ideal heat). It is known to correct each control parameter so as to obtain an occurrence rate waveform (Patent Document 1).

JP 2011-106334 A JP 2011-050661 A Japanese Patent Laying-Open No. 2005-233107

  Incidentally, as disclosed in, for example, Patent Document 2 and Patent Document 3, a part of the fuel supplied into the cylinder of the internal combustion engine adheres to the inner wall surface of the cylinder or floats in the vicinity of the inner wall surface. Thus, unburned fuel does not contribute to combustion. In consideration of this point, when creating an ideal heat generation rate waveform as in Patent Document 1, the amount of fuel contributing to combustion is obtained by subtracting the unburned fuel from the injected fuel (hereinafter referred to as effective It is conceivable to use an injection amount).

  However, the technique disclosed in Patent Document 1 is performed without interruption of fuel injection into the cylinder, and various types such as low-temperature oxidation reaction, thermal decomposition, and high-temperature oxidation reaction occur as the temperature of the combustion field increases in the air-fuel mixture formed. This is based on the assumption that the reaction is performed continuously. Consideration is given to the case where the continuity of the injected fuel is not maintained and the combustion is discontinuous, for example, when the fuel is injected in multiple batches. It has not been.

  Similarly, the continuity of the injected fuel is not maintained even when there is a fuel injection period in which the fuel injected at one time is injected separately into the inner region and the outer region of the cavity provided in the piston. Combustion may be discontinuous. Even in such a case, the conventional technology does not disclose how much the amount of unburned fuel is.

  For this reason, for example, when the amount of unburned fuel increases in a low-temperature environment such as when the internal combustion engine is warming up or in a cold region, an ideal heat generation rate waveform is created in a situation where the effective injection amount decreases accordingly. It is inevitable that the accuracy of this will decrease. As a result, the accuracy of the combustion diagnosis by comparing the ideal heat generation rate waveform with the actual heat generation rate waveform also decreases.

  In view of this point, the inventor of the present invention needs to accurately estimate the amount of unburned fuel even when the combustion of the injected fuel becomes discontinuous in order to increase the creation accuracy of the ideal heat release rate waveform. Focusing on this, the present invention has been achieved.

  That is, the present invention has been made in view of the above points, and an object of the present invention is to provide a heat generation rate of the internal combustion engine that can define the combustion state of the fuel in the cylinder of the internal combustion engine with high accuracy. The object is to provide a waveform creation device and a combustion state diagnosis device.

-Solution principle of the invention-
The solution principle of the present invention taken to achieve the above object is to estimate the amount of unburned fuel for each injected fuel that performs this discontinuous combustion when the combustion of the injected fuel becomes discontinuous. This increases the accuracy of creating the ideal heat release rate waveform.

-Solution-
Specifically, the present invention is directed to an apparatus for creating a heat release rate waveform of combustion in an internal combustion engine that performs combustion of fuel injected into a cylinder from a fuel injection valve. When the combustion of the injected fuel becomes discontinuous with respect to the heat generation rate waveform creation device, the unburned fuel amount is estimated individually for each injected fuel that performs the discontinuous combustion, and the estimation result The ideal heat release rate waveform of the combustion is created based on the effective injection amount obtained from the above.

  The “ideal heat generation rate waveform” here refers to a state in which a fuel injection amount corresponding to the command injection amount, a fuel injection pressure corresponding to the command injection pressure, and a fuel injection period corresponding to the command injection period are secured. It is a heat generation rate waveform that should be theoretically obtained assuming that the combustion efficiency is sufficiently high. Further, as a method of obtaining the effective injection amount from the estimation result of the unburned fuel amount, the unburned fuel amount (estimated value) may be subtracted from the fuel injection amount, or the ratio of the unburned fuel amount in the injected fuel The effective injection amount may be calculated based on (estimated value). Furthermore, a method of obtaining an effective injection amount with reference to a preset map from the estimation result of the unburned fuel amount is also conceivable.

  According to the specific matter, for example, when fuel is injected in a plurality of times and the combustion becomes discontinuous, the amount of unburned fuel is estimated individually for each injected fuel that performs this discontinuous combustion. Therefore, by subtracting the estimated unburned fuel amount, the effective injection amount that actually contributes to combustion can be accurately calculated, and the accuracy of the ideal heat release rate waveform created based on this can be increased. .

  The “creation of the ideal heat generation rate waveform” in the present invention is not limited to the one that actually draws the 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.

  Here, the “case where the combustion of fuel is discontinuous” is not limited to the case where the fuel is injected in a plurality of times as described above, but the injected fuel is injected into the cavity provided in the piston. For example, there may be a fuel injection period that is divided into an internal region and an external region.

  That is, for example, when a piston is provided with a cavity like a diesel engine, the volume in the internal region and the external region are greatly different, and the environment in the region such as temperature is also different. It is more accurate to regard them as being independent of each other. Therefore, the inside of the cylinder is divided into the inner region and the outer region of the cavity, the amount of unburned fuel is estimated in each, and the ideal heat generation rate waveform of combustion for each region based on the effective injection amount obtained from this estimation result It is preferable to create a configuration.

  Thus, by synthesizing the ideal heat generation rate waveform created for each region, an ideal heat generation rate waveform for the entire cylinder can be created. Thereby, the creation accuracy of the ideal heat release rate waveform for the entire inside of the cylinder can be increased.

  For example, the amount of fuel injected into each of these regions is calculated based on the fuel injection ratio to the inner region and the outer region of the cavity, and unburned using a different calculation formula for each region. It is preferable to estimate the fuel amount. Different formulas are used to calculate the amount of unburned fuel using multiple parameters (variables) when the terms do not match and when the terms match but the coefficients (constants) do not match. , Including both.

  That is, the inner area of the cavity is narrower than the outer area, and the injected fuel tends to adhere to the inner wall surface, while the amount of floating fuel is smaller than that of the outer area. For this reason, it is preferable to calculate the amount of unburned fuel by increasing the weight of the parameter that affects the fuel wall adhesion in the inner area of the cavity, while in the outer area, not only the wall adhesion but also the unburned floating fuel. This is because it is preferable to increase the weighting of the parameter that affects the quantity.

  More specifically, first, a calculation formula using at least the product of the fuel injection amount and the injection pressure and the injection timing as parameters for each of the discrete injected fuels such as the fuel spray inside and outside the cavity is provided. Use it to estimate the amount of unburned fuel. This is because the larger the product of the fuel injection amount and the injection pressure, the more the fuel adheres to the inner wall surface of the cavity and the outer region, and more the fuel that floats in the outer region. In addition, it is preferable to use parameters such as in-cylinder pressure, in-cylinder temperature, and engine speed for estimation of the amount of unburned fuel.

  Then, the combustion of the fuel excluding the unburned component is defined by at least a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and a high temperature oxidation reaction, and the reaction rate, reaction amount, and reaction period are calculated for each reaction, and the ideal What is necessary is just to set it as the structure which produces a heat release rate waveform. At this time, for each of the reactions, it is preferable to use an effective injection amount excluding the unburned component at least for calculating the reaction rate and the reaction amount.

  Moreover, the following is mentioned as a preparation procedure of the said ideal heat release rate waveform. First, based on the start time of each reaction of the fuel, an ideal heat release rate waveform model composed of triangles with the reaction rate as the slope of the hypotenuse, the reaction amount as the area, and the reaction period as the base length, and The ideal heat release rate waveform model of the reaction is synthesized and then smoothed 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 internal combustion engine heat generation rate waveform generation apparatus 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 burns in the cylinder, and the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is a predetermined amount or more. In this case, it is configured to diagnose that an abnormality has occurred in the reaction related to the combustion of fuel.

  The “abnormality in the reaction” as used herein is not limited to a reaction abnormality (such as equipment failure) that hinders the operation of the internal combustion engine, but the correction (or learning) of the control parameter of the internal combustion engine. This includes the case where the heat generation rate waveform has a divergence to the extent possible (for example, correction can be made to suppress exhaust emission and combustion noise within the regulation range).

  By this specific matter, if the actual heat generation rate waveform deviates from the ideal heat generation rate waveform by a predetermined amount or more in the reaction related to the combustion of fuel (reaction form), it is diagnosed that the reaction is abnormal. Will do. For example, when diagnosis is performed for each of a plurality of reactions, the characteristics (reaction start temperature, reaction rate, etc.) of each fuel reaction are different from each other. By comparing the characteristics of the actual heat release rate waveform (measured), 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 value is set in advance for each of the in-cylinder temperature, the oxygen density, and the fuel density, and any of these in-cylinder temperature, oxygen density, and fuel density is lower than the lower limit value, If the correction amount of the control parameter of the internal combustion engine exceeds a predetermined guard value, it is diagnosed that a failure has occurred in the internal combustion engine.

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

  In the present invention, when the combustion of the fuel injected into the cylinder of the internal combustion engine becomes discontinuous, this estimation is performed by estimating the amount of unburned fuel individually for each injected fuel that performs this discontinuous combustion. It becomes possible to improve the creation accuracy of the ideal heat release rate waveform created based on the effective injection amount obtained by subtracting the value. Further, when the abnormality diagnosis of the combustion state is performed using the ideal heat generation rate waveform, the diagnosis accuracy can be improved.

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. It is sectional drawing which shows a combustion chamber at the time of main injection execution, and its peripheral part. It is a top view of a combustion chamber at the time of main injection execution. FIG. 7A is a schematic diagram around the combustion chamber showing a state in which substantially the entire amount of injected fuel is injected toward the cavity inner region, and FIG. 7A shows the fuel in the compression stroke in which the piston moves toward the compression top dead center. FIG. 7B is a diagram showing the time of fuel injection during the expansion stroke in which the piston moves toward the bottom dead center. FIG. 8A is a schematic diagram of the vicinity of the combustion chamber showing a state in which substantially the entire amount of injected fuel is injected toward the region outside the cavity, and FIG. 8A shows the fuel in the compression stroke in which the piston moves toward the compression top dead center. FIG. 8B is a diagram showing the time of fuel injection during the expansion stroke in which the piston moves toward the bottom dead center. FIG. 9A is a schematic diagram of the periphery of the combustion chamber showing a state in which a part of the injected fuel is injected toward the area inside the cavity and the other is injected toward the area outside the cavity. FIG. FIG. 9B is a view showing the time of fuel injection in the expansion stroke in which the piston moves toward the bottom dead center, respectively, during the fuel injection in the compression stroke that moves toward the point. It is a figure which shows the relationship between a crank angle position and the fuel distribution rate in a cavity. It is a figure for demonstrating the calculation method of the fuel distribution rate in a cavity. 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 figure which shows the procedure of a combustion state diagnosis and control parameter correction | amendment. It is a schematic diagram of the combustion chamber periphery which shows the state in which the spray of the fuel injected toward the area | region outside a cavity reaches | attains a cylinder bore inner wall surface. It is a figure which shows an example of the injection timing correction coefficient map used for calculation of the amount of unburned fuel. It is a figure which similarly shows an example of a rotational speed correction coefficient map. It is a figure which similarly shows an example of a cylinder pressure correction coefficient map. It is a figure which similarly shows an example of a water temperature correction coefficient map. 19A shows an ideal heat generation rate waveform model. FIG. 19A shows a case where the ideal heat generation rate waveform model is an isosceles triangle, and FIG. 19B shows a case where the ideal heat generation rate waveform model is an unequal triangle. FIG. FIG. 20 (a) 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. 20 (b) shows the reaction of the fuel injected in 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 to the area | region outside a cavity. 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. 21 by a filter process. 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 to the area | region in a cavity. 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. 23 by a filter process. This figure shows the ideal heat release rate waveform for the entire cylinder created by combining the ideal heat release rate waveform for the region outside the cavity and the ideal heat release rate waveform for the region inside the cavity. is there. It is a figure which shows an example of an ideal heat release rate waveform (solid line) 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, a case where the combustion state diagnosis device according to the present invention is mounted on 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 an automobile. explain.

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

  As shown in FIG. 1, the engine 1 according to this 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 raises the fuel pumped from the fuel tank to a high pressure 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 accumulation chamber that holds (accumulates) high pressure fuel at a predetermined pressure, and distributes the accumulated fuel to the injectors 23, 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 occlusion 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 piston 13 is connected to a crankshaft (not shown) as an engine output shaft by a connecting rod 18 and reciprocates in the cylinder in synchronization with the rotation.

  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, for example, as shown in the figure, the concave dimension (that is, the depth of the cavity 13b) is small in the central portion (on the cylinder centerline P), and the concave dimension gradually increases from the outer side toward the outer side. It is getting bigger. In addition, the outer peripheral edge portion of the cavity 13b has a shape in which the lower portion has a larger diameter than the upper portion, and the lower portion of the inner wall of the cavity 13b is removed in an annular shape.

  In other words, the upper portion of the inner wall of the cavity 13b is formed so as to protrude inward (that is, close to the central injector 23). As a result, the cavity facing the upper combustion chamber 3 is formed. The opening diameter of 13b is smaller than the bottom of the cavity 13b. That is, as is clear from FIGS. 7 and 9, the distance from the injection hole of the injector 23 to the cavity inner wall surface in the fuel injection direction is shorter on the upper side than on the lower side.

  The cylinder head 15 is provided with an intake valve 16 that opens and closes the intake port 15a and an exhaust valve 17 that opens and closes the exhaust port 71 facing the top surface 13a of the piston 13 that opens in the cavity 13b. Thus, the valve is operated by a valve mechanism (not shown). The cylinder head 15 is provided with a glow plug 19 obliquely from the side where the intake port 15a is located toward the combustion chamber 3 below.

  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.

  Further, 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, and a part of the exhaust gas is appropriately returned to the intake manifold 63. Thus, an exhaust gas recirculation passage (EGR passage) 8 is connected. An EGR valve 81 and an EGR cooler 82 are provided in the EGR passage 8.

-Sensors-
Various sensors are attached to each part of the engine 1. For example, the air flow meter 43 outputs a detection signal corresponding to the intake air amount. 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 outputs a detection signal corresponding to the opening of the intake throttle valve 62. The intake pressure sensor 48 outputs a detection signal corresponding to the intake air pressure. The intake air temperature sensor 49 outputs a detection signal corresponding to the intake air temperature.

-ECU-
The ECU 100 includes a microcomputer including a CPU, a ROM, a RAM, and the like (not shown) and an input / output circuit. As shown in FIG. 3, the input circuit of the ECU 100 includes a crank position sensor 40, the rail pressure sensor 41, a throttle opening sensor 42, an air flow meter 43, A / F sensors 44a and 44b, exhaust temperature sensors 45a and 45b, A water temperature sensor 46, an accelerator opening sensor 47, an intake pressure sensor 48, an intake air temperature sensor 49, an in-cylinder pressure sensor 4A, an outside air temperature sensor 4B, an outside air pressure sensor 4C, and the like are connected.

  On the other hand, the output circuit of the ECU 100 is connected to the supply pump 21, the injector 23, the intake throttle valve 62, the EGR valve 81, the variable nozzle vane mechanism 54 of the turbocharger 5, and the like.

  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 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) is lowered through 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).

  FIG. 5 is a cross-sectional view showing the combustion chamber 3 and its periphery when the main injection is performed, and FIG. 6 is a plan view of the combustion chamber 3 when the fuel is injected (a view showing the upper surface of the piston 13).

(Fuel injection mode)
Next, the form in the cylinder of the fuel injected from the injector 23 will be described.

  The fuel sprays A, A,... Injected from the injection holes of the injector 23 diffuse in a substantially conical shape. In general, the pilot injection is performed at a crank angle position that is more advanced than the crank angle position at which the piston 13 reaches the compression top dead center, and almost all of the injected fuel is in the region outside the cavity 13b (the top surface of the piston 13). 13a and the lower surface of the cylinder head 15; hereinafter, this space is injected toward the “outside cavity region”). This contributes to preheating of the area outside the cavity.

  Further, depending on the injection period of this pilot injection, fuel is injected toward the region outside the cavity in the first half of the injection period, and in the second half of the injection period, the internal space of the cavity 13b (hereinafter, this space is referred to as “intracavity region”). In some cases, fuel is injected toward the At this time, the area outside the cavity and the area inside the cavity are each preheated.

  Further, the main injection is executed at a crank angle position where the piston 13 reaches the vicinity of the compression top dead center. For example, FIG. 7 (FIG. 7A) is a compression stroke in which the piston 13 moves toward the compression top dead center. In general, as shown in FIG. 7B, the fuel is injected during the expansion stroke in which the piston 13 moves toward the bottom dead center. The whole amount will be injected toward the cavity area.

  Note that the fuel injected by the main injection is not necessarily injected entirely into the cavity region. If early injection is performed or the injection period is long, the injection of the main injection is performed. Depending on the start timing and the injection end timing, some fuel may be injected into the region outside the cavity. This will be specifically described below.

  For example, as shown in FIG. 8A (when fuel is injected during the compression stroke in which the piston 13 moves toward the compression top dead center), the piston 13 advances by a predetermined amount from the crank angle position at which the compression top dead center is reached. When main injection is started in a state where the crank angle position is on the corner side, the fuel injected at the beginning of the injection period of the main injection is injected toward the region outside the cavity. Further, for example, as shown in FIG. 8B (when fuel is injected during the expansion stroke in which the piston 13 moves toward the bottom dead center), a predetermined amount is obtained from the crank angle position at which the piston 13 has reached the compression top dead center. When the main injection is continued until the crank angle position is on the retard side, the fuel injected at the end of the injection period of the main injection is injected toward the outside of the cavity. .

  In addition, at the piston position shown in FIG. 7A, when fuel injection is performed on the advance side of the piston position, a part of the injected fuel is injected toward the region outside the cavity. Therefore, the piston position shown in FIG. 7A can be called an intra-cavity injection advance limit. Further, at the piston position shown in FIG. 7 (b), when fuel injection is performed on the retard side from the piston position, a part of the injected fuel is injected toward the region outside the cavity. Therefore, the piston position shown in FIG. 7B can be called an intra-cavity injection retardation limit.

  Further, at the piston position shown in FIG. 8A, when fuel injection is performed on the retard side from the piston position, a part of the injected fuel is injected toward the cavity inner region. Therefore, the piston position shown in FIG. 8A can be called an out-cavity injection retardation limit. Further, at the piston position shown in FIG. 8 (b), when fuel injection is performed on the advance side of the piston position, a part of the injected fuel is injected toward the cavity inner region. Therefore, the piston position shown in FIG. 8B can be referred to as an outside-cavity injection advance limit.

  The crank angle position corresponding to each limit described above can be defined in advance by the engine specifications, the spray angle of fuel injected from the injector 23, and the like. As an example, the outside-cavity injection retardation limit (FIG. 8A) is the crank angle at a position of 28 ° CA before compression top dead center, and the in-cavity injection advance limit (FIG. 7A) is the crank angle. The position is 18 ° CA before compression top dead center. Further, the injection delay limit in the cavity (FIG. 7B) is a position at 18 ° CA after compression top dead center in the crank angle, and the injection advance limit in the cavity (FIG. 8B) is compressed at the crank angle. The position is 28 ° CA after top dead center. These values are not limited.

  When fuel injection is performed only during the period between the intra-cavity injection advance limit (FIG. 7A) and the intra-cavity injection retard limit (FIG. 7B), Substantially the entire amount is injected toward the cavity region. Further, when the fuel injection is performed in a period on the advance side of the outside-cavity injection delay limit (FIG. 8A), or more retarded than the outside-cavity injection advance limit (FIG. 8B). When fuel injection is performed during this period, the fuel injected during that period is injected toward the region outside the cavity.

  Further, for example, as shown in FIG. 9A (when the fuel is injected in the compression stroke in which the piston 13 moves toward the compression top dead center), from the outside-cavity injection delay limit (FIG. 8A), When fuel injection is performed over the injection advance limit (FIG. 7 (a)), for example, in FIG. 9 (b) (at the time of fuel injection in the expansion stroke in which the piston 13 moves toward the bottom dead center). As shown, when fuel injection is performed from the intra-cavity injection retardation limit (FIG. 7B) to the outside-cavity injection advance limit (FIG. 8B), a part of the injected fuel is It will be injected toward the area inside the cavity, and the other will be injected toward the area outside the cavity. That is, fuel is injected separately into the cavity inner region and the cavity outer region.

  In this way, when the fuel is sprayed into the area outside the cavity and the area inside the cavity, as long as the amount of fuel existing in each area does not exceed the predetermined amount, the spray of each area and most of the burned gas Stays in its injected area and has little amount to flow into the other area. For this reason, each combustion of the area | region outside a cavity and the area | region in a cavity can be handled separately.

  As described later, in order to create an ideal heat release rate waveform for the entire cylinder with high accuracy, create an ideal heat release rate waveform in the cavity region and an ideal heat release rate waveform in the region outside the cavity. It is necessary to keep. For this reason, it is necessary to obtain the amount of fuel to be burned in each of the in-cavity region and the out-cavity region. Hereinafter, a method for obtaining the amount of fuel present in each region will be described.

  FIG. 10 shows the relationship between the crank angle position and the ratio of the injection amount to the in-cavity region with respect to the fuel amount injected from the injector 23 at each crank angle position (hereinafter referred to as “in-cavity fuel distribution ratio”). FIG. In FIG. 10, the horizontal axis is the crank angle, and the vertical axis is the intra-cavity fuel distribution rate.

  The crank angle position α in FIG. 10 corresponds to the piston position of the outside-cavity injection delay limit (FIG. 8A). The crank angle position β in FIG. 10 corresponds to the piston position of the in-cavity injection advance limit (FIG. 7A). Further, the crank angle position γ in FIG. 10 corresponds to the piston position of the intra-cavity injection retardation limit (FIG. 7B). Further, the crank angle position δ in FIG. 10 corresponds to the piston position of the outside-cavity injection advance limit (FIG. 8B).

  As shown in FIG. 10, when the fuel injection timing from the injector 23 is on the advance side with respect to the crank angle position α in the figure, or on the retard side with respect to the crank angle position δ in the figure. Since almost all of the injected fuel is injected toward the region outside the cavity, the fuel distribution rate in the cavity becomes “0”.

  Further, when the fuel injection timing from the injector 23 is between the crank angle positions β and γ in the figure, almost the entire amount of the injected fuel is injected toward the in-cavity region. The internal fuel distribution rate is “1”.

  Further, when the fuel injection timing from the injector 23 is between the crank angle positions α and β in the drawing, or between the crank angle positions γ and δ in the drawing, the injection from the injector 23 is performed. The fuel thus injected is divided into an area outside the cavity and an area inside the cavity, so that the fuel distribution ratio in the cavity becomes a value between “0” and “1” according to the fuel injection timing.

  In the following description, a period on the more advanced side than the crank angle position α is a first period, a period between the crank angle positions α and β is a second period, and a period between the crank angle positions β and γ. A period is referred to as a third period, a period between the crank angle positions γ and δ is referred to as a fourth period, and a period retarded from the crank angle position δ is referred to as a fifth period.

  In order to obtain the amount of fuel in each of the in-cavity region and the out-cavity region, it is necessary to obtain the fuel distribution ratio in each region with respect to the total fuel amount injected from the injector 23. Hereinafter, the ratio of the fuel amount in the in-cavity region to the total fuel amount injected from the injector 23 is referred to as “in-cavity region total fuel distribution ratio”, and the ratio of the fuel amount in the region outside the cavity to the total fuel amount injected from the injector 23 is The ratio is referred to as “outside cavity region total fuel distribution ratio”.

  As described above, when the fuel injection period from the injector 23 is the third period, the fuel distribution ratio in the cavity is “1”. Therefore, the ratio of the fuel injection period in the third period to the total fuel injection period Can be calculated as the third period (the ratio of the fuel injection period in the third period to the total fuel injection period × “1”) of the total fuel distribution ratio in the cavity.

  On the other hand, since the fuel distribution rate in the cavity changes during the second period, a representative value of the fuel distribution ratio in the cavity during this period is obtained, and the fuel in the second period with respect to the total fuel injection period is obtained. The ratio of the injection period is multiplied by a representative value of the fuel distribution ratio in the cavity, and the second period of the total fuel distribution ratio in the cavity (the fuel injection period in the second period with respect to the total fuel injection period). It is necessary to calculate (ratio × representative value of intra-cavity fuel distribution ratio in the second period). The same applies to the fourth period.

  Hereinafter, a method for obtaining the representative value of the fuel distribution ratio in the cavity will be specifically described with reference to FIG. FIG. 11 shows the relationship between the crank angle position and the fuel distribution ratio in the cavity when fuel is injected during the predetermined period in the second period.

  The waveform shown in FIG. 11 is obtained by simplifying the change in the fuel distribution ratio in the cavity with respect to the change in the crank angle position by the Wiebe function, and the ACO at the beginning of the second period is set to “0 (X = 0)”. The fuel distribution rate in the cavity at the timing of “ACO = 0” is set to “0”, and the ACI at the end of the second period is set to “1 (X = 1)”. The terms a and m, which are the shape parameters of the Wiebe function, are set so that the fuel distribution rate in the cavity at the timing “1” is “1”. For example, a = 8.06 and m = 2.54 are set.

  Consider a case where fuel injection is started at the timing Ais in the drawing during the second period and the fuel injection is ended at the timing Aie.

  In this case, the length Xis of the period from the time when the crank angle reaches the angular position α (ACO = 0) to the time when the fuel injection starts, and the fuel injection ends from the time when the crank angle reaches the angular position α. The length Xie of the period up to the point in time is given by the following equations (1) and (2).

Xis = (Ais-ACO) / (ACI-ACO) (1)
Xie = (Aie-ACO) / (ACI-ACO) (2)
In this case, the representative value f (X) of the intra-cavity fuel distribution ratio is calculated by the following equation (3).

f (X) = {f (Xis) + f (Xie)} / 2 (3)
Here, f (Xis) is the fuel distribution rate in the cavity at the timing Ais and corresponds to Yis in the figure. Further, f (Xie) is the fuel distribution rate in the cavity at the timing Aie and corresponds to Yie in the drawing.

  In this way, it is possible to calculate the representative value f (X) of the intra-cavity fuel distribution ratio when the fuel is separately injected into the outer cavity region and the inner cavity region.

  Actually, fuel injection may be performed not only in the second period but also in each of the first, third, fourth, and fifth periods. Therefore, the fuel injection in these periods is also taken into consideration. Therefore, it is necessary to calculate the total fuel distribution ratio (the total fuel distribution ratio in the cavity) for the entire fuel injection period.

  Therefore, first, the fuel injection rate ΔAinj (i) in each period i (i = 1 to 5) is obtained by the following equation (4).

ΔAinj (i) = period X (i) / total fuel injection period (4)
“I” in the formula (4) is a value corresponding to the target periods 1 to 5.

  That is, the ratio of the injection period in each of the first to fifth periods to the total fuel injection period from the injector 23 is calculated as the fuel injection rate (ΔAinj (1) to ΔAinj (5)) in each period.

  Further, the intra-cavity fuel distribution ratio in the first period and the fifth period is “0”, and the intra-cavity fuel distribution ratio in the third period is “1” (see FIG. 10). For this reason, the fuel injection rates (ΔAinj (1), ΔAinj (5)) in the first period and the fifth period do not contribute to the total intra-cavity region fuel distribution ratio, and the fuel injection rates (ΔAinj ( In 3)), the total amount of injected fuel contributes to the total fuel distribution ratio in the cavity region (which affects the total fuel distribution ratio in the cavity region). Further, the intra-cavity fuel distribution ratios (ΔAinj (2), ΔAinj (4)) in the second period and the fourth period vary depending on the fuel injection period (length of the fuel injection period) in each period.

For this reason, the total fuel distribution ratio in the cavity for the entire period of fuel injection can be obtained by the following equation (5).
Total fuel distribution ratio in the cavity = ΔAinj (2) × f (X (2)) + ΔAinj (3)
+ ΔAinj (4) × f (X (4)) (5)
As a result, the total fuel distribution ratio in the cavity region for the entire fuel injection period is calculated.

  Then, by multiplying the total fuel injection amount from the injector 23 by this total intra-cavity region fuel distribution rate, the amount of fuel existing in the intra-cavity region can be calculated. Further, if the total fuel distribution ratio outside the cavity is obtained from the total fuel distribution ratio within the cavity (1−total fuel distribution ratio within the cavity), the total fuel injection rate is multiplied by the total fuel injection ratio outside the cavity. The amount of fuel existing in the area outside the cavity can be calculated. The amount of fuel existing in the region outside the cavity can also be calculated by subtracting the amount of fuel present in the region inside the cavity from the total fuel injection amount.

  Next, the relationship between the fuel injection timing and the amount of generated heat will be described. FIG. 12 shows an example of the relationship between the fuel injection rate waveform and the heat release rate waveform. TDC in the figure is a crank angle position corresponding to the compression top dead center of the piston 13. The waveform shown in the lower part of FIG. 12 shows a plurality of patterns of the injection rate waveform of the fuel injected from the injector 23. The waveform shown in the upper part of FIG. 12 shows a change in heat generation rate (heat generation rate waveform) corresponding to each fuel injection rate.

  Of the fuel injection rate waveforms shown in FIG. 12, those indicated by the solid line a, the broken line b, and the alternate long and short dash line c start fuel injection on the advance side with respect to the outside-cavity injection delay limit (FIG. 8A). In addition, the fuel injection is completed on the advance side with respect to the outside-cavity injection delay limit, and substantially the entire amount of the injected fuel is injected toward the outside-cavity region. The heat release rate waveform corresponding to the fuel injection rate waveform indicated by the solid line a is indicated by the solid line A, the heat release rate waveform corresponding to the fuel injection rate waveform indicated by the broken line b is indicated by the broken line B, and is indicated by the alternate long and short dash line c. A heat generation rate waveform corresponding to the fuel injection rate waveform is indicated by a one-dot chain line C.

  Also, among the fuel injection rate waveforms shown in FIG. 12, the solid line d and the broken line e indicate that fuel injection is started on the retard side of the intra-cavity injection advance limit (FIG. 7 (a)) and the cavity. This is a case where the fuel injection is completed on the advance side from the inner injection delay limit (FIG. 7B), and substantially the entire amount of the injected fuel is injected toward the in-cavity region. A heat generation rate waveform corresponding to the fuel injection rate waveform indicated by the solid line d is indicated by a solid line D, and a heat generation rate waveform corresponding to the fuel injection rate waveform indicated by the broken line e is indicated by a broken line E.

  As shown in the fuel injection rate waveform shown in FIG. 12, when the fuel injected into the area outside the cavity burns even though the injection amount in each fuel injection is equal, the heat per unit rotation angle of the crankshaft The amount of generation is relatively small and the combustion is slow (see heat generation rate waveforms A, B, and C in FIG. 12). This is because an air-fuel mixture having a relatively low density (low fuel density) is generated by injecting the injected fuel into the region outside the cavity having a relatively large volume.

  In contrast, when the fuel injected into the cavity region burns, the heat generation amount per unit rotation angle of the crankshaft is relatively large and the combustion is steep (the heat generation rate waveform in FIG. 12). (See D, E). This is because the injected fuel is injected into the area of the cavity with a relatively small volume, so that the temperature of the combustion field rises rapidly and a relatively high-density (high fuel density) mixture is present in this temperature field. This is because it is generated.

  The energy generated by the combustion in the combustion field in this way passes through the kinetic energy for pushing down the piston 13 toward the bottom dead center, the thermal energy for raising the temperature in the combustion chamber 3, the cylinder block 11 and the cylinder head 15. The heat energy is radiated to the outside (for example, cooling water).

  The in-cylinder gas after combustion is discharged to the exhaust port 71 and the exhaust manifold 72 as the piston 13 rises through the exhaust valve 17 that opens in the exhaust stroke, and becomes exhaust gas.

−Creation of heat release rate waveform, combustion state diagnosis, and control parameter correction−
Next, the creation of the heat release rate waveform (creation of the ideal heat release rate waveform), the combustion state diagnosis (diagnosis of each reaction mode of the fuel in the cylinder), and the diagnosis results, which are the characteristic parts of this embodiment, The correction of the control parameter executed in response will be described.

  In the generation of the heat generation rate waveform, the combustion state diagnosis, and the control parameter correction, as shown in FIG. 13, (1) generation of an ideal heat generation rate waveform and (2) generation 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, and the configuration for performing the operations (2) to (4) may be mounted on the vehicle.

  In the present embodiment, the inside of the cylinder is divided into the cavity inner region and the cavity outer region, and the combustion state in each is individually defined. For this reason, in the creation of the ideal heat generation rate waveform (1), the creation of the ideal heat generation rate waveform for the region inside the cavity and the creation of the ideal heat generation rate waveform for the region outside the cavity are individually performed. The ideal heat generation rate waveform for the entire cylinder is created by synthesizing these ideal heat generation rate waveforms.

  As described above, when the ideal heat generation rate waveform is individually created for each area inside and outside the cavity as described above, the amount of unburned fuel (unburned fuel) is estimated for each area. Then, by subtracting this, the amount of fuel actually burned (effective injection amount) is calculated. As will be described in detail later, a part of the fuel injected into each region inside and outside the cavity adheres to the inner wall surface of the cavity 13b and the inner wall surface of the cylinder bore 12, and becomes unburned fuel that does not contribute to the reaction. An ideal heat release rate waveform is created based on the effective injection amount excluding this amount.

  In the combustion state diagnosis (3), the combustion state diagnosis is performed by comparing the ideal heat generation rate waveform and the actual heat generation rate waveform for the entire cylinder.

  More specifically, in the creation of the ideal heat generation rate waveform, (1-A) division of reaction region, (1-B) separation of fuel reaction form, (1-C) each separated reaction Creation of ideal heat generation rate waveform model for each form, (1-D) generation of ideal heat generation rate waveform by filtering (filtering) of ideal heat generation rate waveform model, and synthesis of ideal heat generation rate waveform are 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. In the following, the region where the fuel injection is performed out of the region inside the cavity and the region outside the cavity will be referred to as a “target region” (if the fuel injection is performed in one region, this one region) Corresponds to the target area, and both areas correspond to the target area when fuel injection is performed in both areas).

  The rate-limiting conditions for the reaction (chemical reaction, etc.) of the fuel injected from the injector 23 into the target region include the temperature in the target region, the oxygen amount in the target region (a value correlated with the oxygen density in the target region), the target region The amount of internal fuel (a value that has a correlation with the fuel density in the target region) and the fuel distribution in the target region are listed. Among these, the order of low control freedom is the order of the temperature in the target area, the oxygen amount in the target area, the fuel quantity in the target area, and the fuel distribution in the target area.

  That is, the temperature in the target region is substantially determined by the intake air temperature and the compression ratio of the engine 1 in the stage before the fuel reacts, and the degree of freedom of control is the lowest. In addition, the temperature in the target region also varies depending on the amount of preheating due to the combustion of the fuel when fuel injection is performed in advance (for example, when fuel injection for preheating is performed). Further, since the oxygen amount (oxygen density) in the target area can be adjusted by the opening degree of the intake throttle valve 62 and the opening degree of the EGR valve 81, the degree of freedom of control is higher than the temperature in the target area. Further, the oxygen amount (fuel density) in the target region also varies depending on the supercharging rate by the turbocharger 5. Further, the amount of oxygen in the target region 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 target region 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. Further, since the fuel distribution in the target region 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.

  In the present embodiment, on the condition that the warm-up operation of the engine 1 is completed and the outside air temperature is equal to or higher than a predetermined temperature (for example, 0 ° C.), the reaction state of the fuel in ascending order of freedom of control. The priority of the condition for determining the is set high. Here, the quantitative conditions of the target region temperature, the target region oxygen amount, and the target region fuel amount are set to have a higher priority than the target region fuel distribution. That is, the start timing (reaction start timing) of each reaction of the fuel is determined using the temperature in the target region 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 temperature in the target region (compressed gas temperature in the target region).

  In this embodiment, when determining the start time of each reaction, the start time is corrected according to the oxygen density. Specifically, for example, as the oxygen density decreases, the reaction start timing shifts to the retard side, the reaction rate decreases (the reaction becomes slow), and the reaction amount decreases.

  Then, based on the reaction start time (reaction start time corrected by the oxygen density) as a base point, the reaction rate and the reaction amount reference values are obtained, respectively, and based on the oxygen density, the reaction rate and the reaction amount reference value A correction amount is obtained, and a correction based on this correction amount is performed to obtain a reaction rate, a reaction amount, and a reaction period, and an ideal heat release rate waveform model is created for the target region for each reaction form.

  Here, examples of the reaction of the fuel injected into the target region include 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. Reaction speed, reaction amount, reaction period of each form, temperature in the target region (gas temperature in the target region that determines the reaction start time), fuel composition (including fuel amount and fuel density contributing to the reaction), and target An ideal heat release rate waveform model for each reaction is created by calculating according to the oxygen density in the region.

  That is, when fuel injection is performed in one of the inner region and the outer region, an ideal heat generation rate waveform model is created for this one region (target region), and the fuel is generated in both regions. When the injection is performed, ideal heat generation rate waveform models are individually created for these two regions (both target regions). The generation of the ideal heat generation rate waveform model is performed only in the region where the spray exists among the region inside the cavity and the region outside the cavity. The determination of in which region the spray is present (or whether the spray is present in both regions) can be obtained based on the fuel injection period as described above.

More specifically, as an operation for creating an ideal heat release rate waveform model, more specifically, a reference reaction rate efficiency [J / CA ² / mm ³ corresponding to a gas temperature (reference temperature) in a target region, a fuel composition, and the like at the reaction start time. ] And the reference reaction amount efficiency [J / mm ³ ] are determined for each reaction form, and the reference reaction rate efficiency and the reference reaction amount efficiency are corrected from the oxygen supply capacity (oxygen density) to the combustion field, and these corrections are made. The reaction rate efficiency and the reaction amount efficiency are multiplied by the fuel amount (effective injection amount) to determine the reaction rate and the reaction amount.

  The reaction speed is corrected according to the engine speed described later. The “reaction rate efficiency” is also called “reaction rate gradient”, and the “reaction amount efficiency” is also called “combustion efficiency”. Hereinafter, “reaction rate efficiency” will be described as “reaction rate gradient”.

  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 obtained by the following equation (6).

Reaction period = 2 × (reaction amount / reaction rate) ^1/2 (6)
Details of creation of the ideal heat release rate waveform model (triangle model) will be described later.

(1-A) Reaction Region Division Next, the reaction region division, which is the first procedure for creating the ideal heat release rate waveform, will be described in detail.

  As described above, the region where the fuel injected from the injector 23 into the cylinder exists includes the outside-cavity region and the inside-cavity region. In each of these regions, there is a possibility that the existing fuel amount, temperature, and oxygen density are different from each other, and these must be obtained for each region. This will be specifically described below.

(A) Amount of fuel existing in the region When fuel injection is performed on the advance side with respect to the outside-cavity injection delay limit (FIG. 8 (a)), or the outside-cavity injection advance limit (FIG. 8 (b) When fuel injection is performed at a more retarded angle than)), substantially the entire amount of injected fuel is injected toward the region outside the cavity, and substantially all this fuel exists in the region outside the cavity. There will be almost no spray in the area within the cavity. For this reason, the fuel amount injected into the cylinder from the injector 23 becomes the fuel amount existing in the region outside the cavity as it is.

  In addition, when fuel injection is performed only during the period between the intra-cavity injection advance limit (FIG. 7A) and the intra-cavity injection retard limit (FIG. 7B), Substantially the entire amount will be injected toward the region inside the cavity, and the substantially whole amount of this fuel will be present in the region inside the cavity, and there will be almost no spray in the region outside the cavity. For this reason, the fuel amount injected into the cylinder from the injector 23 becomes the fuel amount existing in the cavity region as it is.

  Further, when fuel injection is performed from the outside-cavity injection delay limit (FIG. 8A) to the in-cavity injection advance limit (FIG. 7A), or within the injection delay limit (FIG. 8). 7 (b)) to the outside-cavity injection advance limit (FIG. 8 (b)), a part of the injected fuel is injected toward the outside of the cavity, and the other is the cavity. Injected toward the inner region, a part of the injected fuel exists in the region outside the cavity, and the other exists in the region inside the cavity. In this case, the ratio of the spray amount (fuel amount) existing in the region outside the cavity and the spray amount existing in the region in the cavity is, as described above, the total fuel distribution ratio in the cavity region calculated by the equation (5), etc. Can be calculated based on

  That is, the amount of fuel injected toward the in-cavity region (spray amount existing in the in-cavity region) can be calculated by multiplying the total fuel injection amount from the injector 23 by the in-cavity region total fuel distribution ratio. it can. Also, the amount of fuel injected toward the area outside the cavity (the amount of spray existing in the area outside the cavity) is calculated by subtracting the amount of fuel injected toward the area inside the cavity from the total fuel injection amount. can do.

  As described above, in the present embodiment, the inside of the cylinder is divided into the outside-cavity region and the inside-cavity region, and the amount of fuel for each is obtained individually using the total fuel distribution rate in the in-cavity region. Further, as described above, in each region inside and outside the cavity, the amount of unburned fuel that does not contribute to the reaction due to wall adhesion or the like is estimated, and this is subtracted from the fuel amount in each region to obtain the effective injection amount. Thus, the accuracy of the ideal heat generation rate waveform created as follows based on the effective injection amount can be increased. The method for estimating the amount of unburned fuel will be described later in detail.

(B) Intra-region temperature As a method for determining the temperature of each of the region outside the cavity and the region in the cavity (the temperature of each region during execution of fuel injection), the intake air temperature, the piston position (compression degree of intake gas), The preheating state of the target area by pilot injection etc. is used as a parameter, and the relationship between these parameters and the temperature of the outside area of the cavity and the inside area of the cavity is obtained by experiments and simulations in advance, and this map is stored in the ROM. ing. That is, by fitting parameters such as the intake air temperature, the piston position, and the preheating state of each region to the map, the temperatures of the outside region and the inside region of the cavity can be individually obtained. In addition, when determining the temperature in the cavity region, the total fuel distribution ratio in the cavity region may be used. Specifically, it is obtained by the product of the compressed gas temperature calculated based on the compression ratio, the amount of fuel (effective injection amount) obtained from the total fuel distribution ratio in the cavity region, and the amount of heat generated per unit mass of fuel. The sum of the calculated temperature rise is obtained as the temperature in the cavity region. The temperature in the region outside the cavity can be obtained in the same manner.

  The method for obtaining these temperatures is not limited to this, and a value obtained by subtracting the predetermined temperature from the in-cylinder average temperature is set as the temperature of the outside region of the cavity, and the value obtained by adding the predetermined temperature to the in-cylinder average temperature is set as the method. The temperature may be set as the temperature of the inner region. The predetermined temperature to be subtracted and added in this case is obtained as a map value corresponding to the operating state of the engine 1 by experiment or simulation, and is made variable according to this map value. Further, the temperature may be calculated from the thermal energy equation Q = mcT. Here, Q is the heat energy input to the target area (outer cavity area or inner cavity area), m is the mass of the gas in the target area, c is the specific heat of the gas, and T is the temperature of the target area.

(C) Oxygen density The oxygen density varies depending on whether or not EGR is performed, the amount of EGR, the altitude of the road on which the vehicle is traveling, and the like. 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, as described above, the lower the oxygen density, the more the reaction start timing shifts to the retarded side, the reaction rate decreases (the reaction becomes slow), 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. In the present embodiment, the oxygen density is obtained individually for each region inside and outside the cavity, but the oxygen density in the two regions may be treated as the same.

  As an example, the oxygen density is obtained by the following equation (7).

Oxygen density = cylinder residual oxygen amount / stroke volume (7)
Here, the in-cylinder oxygen residual amount is calculated individually for each of the in-cavity region and the out-cavity region. For example, when oxygen is consumed in the area outside the cavity due to execution of pilot injection toward the area outside the cavity, the remaining amount of oxygen in the area outside the cavity is reduced. The in-cylinder oxygen residual amount is calculated individually for each.

  As a method for calculating the oxygen remaining amount in each region, for example, 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 air flow meter 43 are detected. The amount (mass) of oxygen introduced into the cylinder is obtained based on the amount of intake air, etc., and the total amount of oxygen is distributed according to the volume ratio between the cavity inner area and the cavity outer area. The amount of oxygen consumed in this step may be subtracted (subtracted from the amount of oxygen on the region where oxygen is consumed). For example, a map for determining the amount of oxygen using the outside air temperature, the outside air pressure, the amount of intake air as a parameter, and a map for determining the amount of oxygen consumed using the injection period and the injection amount of pilot injection as parameters are stored in the ROM. What is necessary is just to obtain | require oxygen remaining amount based on these maps.

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

  When fuel injection is performed from the injector 23, 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 depend on the environment in the target region. Done. That is, when fuel is injected into each of the outer region and the inner region, these reactions are performed in each of these regions in accordance with the environment. 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 target region. 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 target region is 500K or higher. Yes.

  The boiling point of light oil used in the diesel engine 1 is generally 453K to 623K, and a practical region where fuel injection is performed in the target region (for example, the timing when the pilot injection is performed) is BTDC (compression top dead center). Previous) 40 ° CA. Since the gas temperature in the target region 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 ], and this reference reaction amount efficiency is multiplied by an effective injection amount to obtain the following equation (8). Thus, the reaction amount in the vaporization reaction is obtained.

Reaction amount in vaporization reaction = −1.14 × effective injection amount (8)
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 temperature in the target region is relatively low, and the higher the amount of n-cetane or the like (the higher the cetane fuel), the higher the target region. Thus, the low temperature oxidation reaction easily proceeds in this process, and the ignition delay is suppressed. Specifically, a low-temperature oxidation reaction component such as n-cetane generally starts combustion (low-temperature oxidation reaction) when the temperature in the target region reaches about 750K. In addition, fuel components (high temperature oxidation reaction components) other than n-cetane do not start combustion (high temperature oxidation reaction) until the temperature in the target region reaches about 900K.

The reference reaction rate gradient (reference reaction rate efficiency) in this low-temperature oxidation reaction is, for example, 4.0 [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 reaction rate gradient and reaction amount efficiency obtained by correcting the reference reaction rate gradient and reference reaction amount efficiency with the oxygen density ( For example, it is calculated by multiplying the effective injection amount). Further, in calculating the reaction rate of the low-temperature oxidation reaction, a coefficient (rotation speed correction coefficient = (reference value) corresponding to the value obtained by multiplying the reaction speed gradient by the effective injection amount (reference reaction speed). Rotation speed / actual rotation speed) ² ) is multiplied. Thereby, the reaction rate can be obtained as a value depending on time. Although an arbitrary rotation speed (for example, 2000 rpm) can be set as the reference rotation speed for obtaining the rotation speed correction coefficient, it is preferable to set the rotation speed range in which 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 of a fuel component. In general, the reaction temperature is about 800K.

The reference reaction rate gradient in this thermal decomposition reaction is, for example, −0.2 [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 reaction rate gradient and reaction amount efficiency obtained by correcting the reference reaction rate gradient and reference reaction amount efficiency with the oxygen density ( For example, it is calculated by multiplying the effective injection amount). Further, when calculating the reaction rate of the thermal decomposition reaction, a value (reference reaction rate) obtained by multiplying the reaction rate gradient by an effective injection amount is multiplied by the rotation speed correction coefficient corresponding to the engine rotation speed. The

  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 generally about 900K. That is, the reaction that starts combustion when the temperature in the target region reaches 900K is a high-temperature oxidation reaction by this premixed combustion.

Further, the reference reaction rate gradient in the high temperature oxidation reaction by this 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 based on the reaction rate gradient and reaction amount efficiency obtained by correcting the reference reaction rate gradient and reference reaction amount efficiency by the oxygen density. Calculated (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 coefficient corresponding to the engine rotation speed with respect to the value obtained by multiplying the reaction speed gradient by the effective injection amount (reference reaction speed) Is multiplied.

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

  In this high temperature oxidation reaction by premixed combustion, the reaction rate gradient changes according to the amount of fuel (fuel density) present in the target region. For this reason, the reaction rate gradient is calculated by using the total fuel distribution ratio in the cavity region by the following equation (9), and the reaction rate is calculated according to the reaction rate gradient.

Reaction velocity gradient = total fuel distribution ratio in the cavity x reference reaction velocity gradient (9)
In other words, when the total fuel distribution ratio in the cavity region is “1” because the entire amount of fuel injected from the injector 23 is injected into the cavity region, the reaction rate is based on the reference reaction rate gradient. Calculated. On the other hand, when the fuel injected from the injector 23 is divided into the cavity inner area and the cavity outer area, it is obtained by correcting the reference reaction speed gradient by the total fuel distribution ratio in the cavity area. The reaction rate is calculated based on the reaction rate gradient.

  Further, as described above, the reaction rate gradient in the high-temperature oxidation reaction by this premixed combustion also changes depending on the oxygen density. Details will be described later.

(E) High temperature oxidation reaction by diffusion combustion The reaction temperature of the high temperature oxidation reaction by diffusion combustion is generally about 1000K. That is, the reaction in which the fuel injected toward the target region having a temperature of 1000 K or more immediately starts combustion 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 (10) and (11).

GrdB = A × common rail pressure + B (10)
Grd = GrdB × (reference engine speed / actual engine speed) ²
X (d / reference d) x (Ni / reference Ni) (11)
GrdB: reference reaction rate, Grd: reaction rate, d: nozzle hole diameter of the injector 23, Ni: 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. In addition, the equation (11) is obtained by multiplying the rotation speed correction coefficient, so that the reaction speed corrected in accordance with the engine rotation speed is obtained.

The standard reaction amount efficiency of the high temperature oxidation reaction by diffusion combustion is, for example, 30.0 [J / mm ³ ]. The reaction amount of the high temperature oxidation reaction by diffusion combustion is also the above standard reaction amount efficiency. It is calculated based on the reaction amount efficiency obtained by correcting by the oxygen density (for example, it is 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.

(F) Calculation of effective injection amount Here, the method of calculating the effective injection amount in the present embodiment will be described in detail. As described above, the effective injection amount is obtained in consideration of the unburned portion due to the wall surface adhesion or the like. However, in this embodiment, as described above with reference to FIGS. It may be sprayed inside and outside. In this case, the unburned portion of the fuel injected into the cavity inner region is mainly the fuel adhering to the inner wall surface of the cavity 13b, while the unburned portion of the fuel injected into the outer region of the cavity includes the cylinder bore 12 In addition to the fuel adhering to the inner wall surface, many of those floating in the vicinity thereof are included.

  That is, as shown in FIGS. 5 and 9, the distance from each injection hole of the injector 23 to the inner wall surface of the cavity in the fuel injection direction is shorter than the distance to the inner wall surface of the cylinder bore. The amount of fuel that tends to increase. On the other hand, when fuel is injected into the area outside the cavity, the distance to the inner wall surface of the cylinder bore is relatively long, while the inner wall surface is wider and lower in temperature than the inner wall surface of the cavity. Since the volume of the area outside the cavity is larger than the area inside the cavity, it is considered that the amount of unburned fuel that is atomized and floats out of the diffused fuel spray is increased.

  In this way, the injected fuel is injected into and out of the cavity, and the continuity of the fuel spray is not maintained and the combustion becomes discontinuous, but it is not intended for a single fuel spray throughout the cylinder. If the amount of fuel is estimated, this estimation result will be inaccurate. In particular, when the amount of unburned fuel increases in the low-temperature environment such as in the middle of warming up of the engine 1 or in a cold region, the accuracy of creating the ideal heat release rate waveform decreases as a result of a decrease in the accuracy of the estimation. There was a problem that.

  In view of such problems, in the present embodiment, when the fuel injected as described above is injected into and out of the cavity to form discontinuous fuel spray, the amount of unburned fuel is estimated individually, The effective injection amount is obtained by subtracting this. In this way, the effective injection amount can be calculated with high accuracy, the accuracy of creating the ideal heat generation rate waveform can be increased, and the combustion state of the fuel in the cylinder of the engine 1 can be defined with high accuracy.

  Hereinafter, a method for estimating the amount of unburned fuel for each region inside and outside the cavity will be described in detail.

<Outside cavity area>
As schematically shown in FIG. 14, the fuel sprays A, A,... Injected from the injection holes of the injector 23 toward the region outside the cavity extend in the injection direction while diffusing each. At this time, the fuel ejected from the nozzle hole is ruptured by the friction with the high-pressure air in the cylinder while flying, and a large number of micro droplets are formed, and the vaporization proceeds from the surface of the droplets. An air-fuel mixture is formed at a portion near the outer periphery of the spray.

  In the flying fuel spray, some of the droplets reach the inner wall surface of the cylinder bore 12 without being vaporized and adhere to the inner surface of the cylinder bore 12 as it is, or once vaporized fuel is cooled and adhered to the inner wall surface. To do. Alternatively, fuel vapor and minute droplets float on the boundary layer B (shown with hatching) near the inner wall surface of the cylinder bore 12. Such wall-attached fuel and unburned floating fuel are unburned fuel that does not contribute to various reactions related to combustion such as vaporization and low-temperature oxidation described above.

  In the present embodiment, first, in order to obtain the amount of fuel flying to the vicinity of the inner wall surface of the cylinder bore 12 as described above, attention is paid to the product of the fuel injection amount and the injection pressure, which are the main factors that determine the flight distance. That is, if the injection pressure is low even if the injection amount is large, the flight distance of the fuel will not be very long. If the injection amount is small, the flight distance will not increase even if the injection pressure is high. The smaller the product of, the smaller the amount of unburned fuel. The larger the product of the injection amount and the injection pressure, the greater the amount of unburned fuel.

  In addition, as described above with reference to FIGS. 5 to 7 and FIG. 10, when fuel is injected toward the in-cavity region during a predetermined period in the vicinity of the TDC (the third period shown in FIG. 10), the cylinder bore There is almost no fuel reaching the 12 inner wall surfaces. On the other hand, it is considered that the fuel that reaches the inner surface of the cylinder bore gradually increases toward the advance side in the second period and toward the retard side in the fourth period. The amount of unburned fuel is estimated considering the effects of

  Further, since the fuel spray injected from the injector 23 receives the resistance of air in the cylinder, the higher the in-cylinder pressure, the greater the resistance and the shorter the flight distance. Similarly, the fuel spray is affected by the flow in the cylinder, and the flight distance tends to be shorter on the high engine speed side where the in-cylinder flow becomes stronger. Thus, if the flight distance is shortened, the amount of unburned fuel that reaches the vicinity of the inner wall surface of the cylinder bore 12 and floats or adheres to the inner wall surface is reduced.

  In addition, of the fuel that has reached the vicinity of the inner wall surface of the cylinder bore 12 as described above, it is considered that the amount of fuel that adheres to the inner wall surface increases as the temperature of the inner wall surface decreases, and also floats in the vicinity of the inner wall surface. It is considered that the amount of fuel increases as the temperature of the inner wall surface decreases. Therefore, if, for example, the engine water temperature is used as an index of the inner wall surface temperature of the cylinder bore 12, the unburned fuel increases as the engine water temperature decreases, and the unburned fuel decreases as the engine water temperature increases.

  In consideration of such various factors, in this embodiment, the amount of unburned fuel in the region outside the cavity is calculated by the following equation (12).

Unburned fuel amount = fuel injection amount × {F (injection amount × rail pressure) + W (injection timing)}
X N (engine speed) x P (in-cylinder pressure) x T (engine water temperature)
× R (Internal / external fuel distribution ratio) (12)
In the above equation (12), F (injection amount × rail pressure) is the fuel injection amount and the injection pressure (rail pressure, that is, the fuel pressure in the common rail 22 detected by the rail pressure sensor 41) as described above. It is a function of a product, and is set in advance by experiment or simulation so that the value of the function increases as the product value increases. For example, using the coefficient K _f that is set in advance, it may be F = K _f × fuel injection amount × rail pressure.

  In addition, W (injection timing), N (engine speed), P (cylinder pressure), and T (engine water temperature) are preferably influenced by the fuel injection timing, engine speed, cylinder pressure, and engine water temperature, respectively. These are correction coefficients for reflection, which are set as a function of injection timing, engine speed, in-cylinder pressure, engine water temperature, or by a map as described below (hereinafter, injection timing correction coefficient W , Rotation speed correction coefficient N, in-cylinder pressure correction coefficient P, and water temperature correction coefficient T).

  Further, R (internal / external fuel distribution ratio) is a distribution ratio correction coefficient R for determining the amount of fuel injected into each area inside and outside the cavity by multiplying this by the fuel injection amount. The above-mentioned “total in-cavity region fuel distribution ratio” (which may be “outside-cavity region total fuel distribution ratio”) is described as follows.

  The unburned fuel amount may be calculated by the following equation (13).

Unburned fuel amount = fuel injection amount × {F (injection amount × rail pressure) + W (injection timing)}
X N (engine speed) x P (in-cylinder pressure) x T (engine water temperature)
× R (Cavity inside / outside fuel distribution ratio)
X (d / reference d) x (Ni / reference Ni) (13)
In the equation (13), d is the diameter of the injection hole of the injector 23, and Ni is the number of injection holes of the injector 23. That is, equation (13) generalizes equation (12) by multiplying the ratio of the actual injection hole diameter to the reference injection hole diameter of injector 23 and the ratio of the actual injection hole number to the reference injection hole number of injector 23. It is a thing.

  A specific example of the correction coefficient will be described. FIGS. 15 to 18 are examples of correction coefficient maps in which an injection timing correction coefficient W, a rotation speed correction coefficient N, an in-cylinder pressure correction coefficient P, and a water temperature correction coefficient T are set. Show. These correction coefficient maps are obtained by mapping a suitable relationship between parameters such as injection timing and engine rotation speed and the amount of unburned fuel in the region outside the cavity in advance through experiments and simulations.

  For example, FIG. 15 shows the change (rate of change) in the amount of unburned fuel due to the change (advance angle or retard angle) of the injection timing, and plots this rate of change as the injection timing correction coefficient W. It is an approximation. In the example shown in FIG. 15, when the fuel is injected toward the cavity inner region in the vicinity of the TDC as described above, there is almost no fuel reaching the vicinity of the inner wall surface of the cylinder bore 12, and from this state, the injection timing is advanced or It shows a tendency that the fuel that reaches the vicinity of the wall surface increases as it changes to one of the retard side.

  On the other hand, FIG. 16 shows the tendency that the fuel reaching the inner wall surface of the cylinder bore 12 decreases as a result of the flow in the cylinder becoming stronger and the fuel spray spreading as the engine speed increases. That is, the value of the rotational speed correction coefficient N becomes, for example, the maximum value Nmax near the idle rotational speed, and gradually decreases as the engine rotational speed increases and gradually decreases gradually. In the high rotation range, the value is substantially constant.

  Similarly, FIG. 17 shows a tendency that the amount of fuel adhering to the inner wall surface of the cylinder bore 12 decreases as a result of the increase in resistance in the cylinder and the decrease in flight distance as the in-cylinder pressure increases. . That is, the value of the in-cylinder pressure correction coefficient P becomes, for example, the maximum value (1.0 in the example in the figure) when the in-cylinder pressure is close to the atmospheric pressure, and gradually decreases as the in-cylinder pressure increases. The degree of the decrease temporarily increases. After that, the degree of decrease in the value of the in-cylinder pressure correction coefficient P becomes gentle again, and when the in-cylinder pressure is further increased, it is generally performed and approaches the position.

  FIG. 18 shows a tendency that the fuel adhering to the inner wall surface of the cylinder bore 12 or the fuel floating near the inner wall surface decreases as the engine water temperature rises. In the example in the figure, the value of the water temperature correction coefficient T becomes a reference value (1.0 in the example in the figure) when the engine water temperature is around 0 ° C., for example, and the value of the water temperature correction coefficient T increases as the temperature rises from here. However, the degree of increase gradually decreases. Further, as the engine water temperature decreases from 0 ° C., the value of the water temperature correction coefficient T increases, and the degree of increase gradually decreases.

  The maps shown in FIGS. 15 to 18 are merely examples, and various other maps can be set. Further, correction coefficients (injection timing correction coefficient W, rotation speed correction coefficient N, in-cylinder pressure correction coefficient P, water temperature correction coefficient T) are obtained by calculation formulas set by experiments or simulations without using such a map. You may do it.

  Further, as described above, the map is not used in the present embodiment for the distribution rate correction coefficient R, and basically, the total fuel distribution rate in the cavity region (may be the total fuel distribution rate outside the cavity region). It is made to calculate using. As an example, the distribution rate correction coefficient R in the region outside the cavity is expressed by the following equation (14).

Distribution ratio correction coefficient R = 1-region total fuel distribution ratio in the cavity (14)
However, 0.1 <total cavity fuel distribution ratio <0.95
If the total fuel distribution ratio in the cavity region is very small, for example, less than 0.1, the distribution ratio correction coefficient R is set to R = 1. On the contrary, the distribution ratio correction coefficient R when the total fuel distribution ratio in the cavity region is very large, for example, exceeds 0.95, is R = 0.05. That is, when the amount of fuel injected into the cavity region is very small, it is assumed that substantially all of the injected fuel exists in the region outside the cavity, and the distribution rate correction coefficient is set to 1, while the fuel is injected into the region within the cavity. In the case where there is a large amount of fuel, the distribution rate correction coefficient is set to 0.05 in consideration of the fuel overflowing from the cavity.

<Cavity area>
The amount of unburned fuel can be calculated for the in-cavity region in the same way as the outside-cavity region described above. However, as described above, the unburned fuel in the cavity inner region is considered to be mainly adhered to the inner wall surface of the cavity, while the unburned fuel in the outer region of the cavity is deposited on the inner wall surface of the cylinder bore and the vicinity of the unburned fuel. It is thought to be the sum of the fuel with floating fuel.

Therefore, the unburned fuel in the cavity region is calculated by a different calculation formula even though the form is the same as the formula (12) or the formula (13). That is, for example, F (injection amount × rail pressure) may be F = K _f × fuel injection amount × rail pressure as in the above-mentioned cavity outer region, but the distance from the injector 23 to the cavity inner wall surface is the cylinder bore inner wall surface. The coefficient K _f is set to a large value because it is considerably shorter than the above.

  As for the injection timing correction coefficient W, the value of the injection timing correction coefficient W is large (for example, 1.0) when the fuel is injected toward the in-cavity region in the vicinity of the TDC, contrary to the above-mentioned region outside the cavity. On the other hand, when the injection timing changes by more than a predetermined value on either the advance side or the retard side and the fuel is injected toward the region outside the cavity, the injection timing correction coefficient W becomes a very small value. .

  Further, the injection timing correction coefficient W is a crank angle period during which the fuel is injected into the cavity region as described above, specifically, for example, in the crank angle positions α to δ described above with reference to FIG. In the second to fourth periods, compared to the third period (period of crank angle positions β to γ) including TDC, the second period on the slightly advanced side (period of crank angle positions α to β) and slightly retarded The fourth period on the side (period of crank angle positions γ to δ) is set to a larger value.

  That is, as described above with reference to FIGS. 5 to 7 and 9, the upper portion of the inner wall of the cavity 13 b is shaped so as to protrude inward (that is, close to the central injector 23), Since the distance from the injection hole of the injector 23 to the inner wall surface of the cavity in the fuel injection direction is shorter on the upper side than the lower side, the amount of fuel adhering to the inner wall surface of the cavity is smaller than the lower side. It is thought that it increases in the upper part.

  For this reason, the injection timing correction coefficient W for the in-cavity region is such that when the fuel is injected toward the in-cavity region, the fuel is injected in the third period including TDC and is directed to the lower portion of the inner wall surface of the cavity. The amount of wall surface adhesion is relatively small, and it is injected with a slight advance or retard angle, indicating the tendency that the amount of fuel wall surface adhesion toward the upper part of the inner wall surface of the cavity is relatively large. It is.

  In addition, the rotational speed correction coefficient N and the in-cylinder pressure correction coefficient P show almost the same tendency as the above-described cavity region (see FIGS. 16 and 17), but the water temperature correction coefficient T is the temperature of the cavity inner wall surface. Is higher than the inner wall surface of the cylinder bore and hardly affected by the engine water temperature, the water temperature correction coefficient T for the area inside the cavity is compared with the water temperature correction coefficient T (see FIG. 18) for the area outside the cavity. And the change due to the engine water temperature is set to be small.

  Furthermore, the distribution rate correction coefficient R for the in-cavity region may be considered to be opposite to the equation (14) for the outside-cavity region, and may be calculated by the following equation (15) as an example.

Distribution ratio correction coefficient R = Total fuel distribution ratio in the cavity region (15)
However, 0.1 <total cavity fuel distribution ratio <0.95
When the total fuel distribution ratio in the cavity region is very small, for example, less than 0.1, the distribution ratio correction coefficient R is set to R = 0. On the contrary, the distribution ratio correction coefficient R when the total fuel distribution ratio in the cavity region is very large, for example, exceeds 0.95, may be R = 0.95.

(1-C) Creation of ideal heat release rate waveform model for each separated reaction form Next, creation of ideal heat release rate waveform model for each reaction form separated in each of the in-cavity region and the outside-cavity region. 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, based on the reaction start temperature described above, the reaction rate (reaction rate corrected according to the oxygen density) is the slope of the hypotenuse of the isosceles triangle, and the reaction amount (reaction amount corrected according to the oxygen density) is An ideal heat release rate waveform model having an isosceles triangle area and a reaction period length of the base of the isosceles triangle is created for each of the intracavity region and the outer cavity region. As described above, the reaction start time is a value obtained by correcting the reference temperature arrival time by the oxygen density decrease correction delay amount. The creation of the ideal heat release rate waveform model below is applied to each of the reaction modes described above. This will be specifically described below.

(A) Reaction rate (reaction rate gradient)
The reaction rate is set based on the reaction rate gradient, and when the ideal heat generation rate waveform model is approximated to an isosceles triangle, the reaction rate during the period in which the heat generation rate increases and the period in which the heat generation rate decreases Their absolute values are consistent with the reaction rate at.

  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.

  As described above, in the present embodiment, the inside of the cylinder is divided into an outer cavity region and an inner cavity region, and ideal heat generation rate waveform models are created for each. In each reaction, the reaction rate gradient changes according to physical quantities such as oxygen density and fuel density in the combustion field. For this reason, in this embodiment, the reaction rate is obtained individually for each region, and an ideal heat release rate waveform model is created based on the obtained reaction rate.

(B) Generated heat (area)
The reaction amount 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 reaction amount 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.

(C) 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 (amount of generated heat).

  As shown in FIG. 19, the area of the triangle (corresponding to the amount of generated heat) is S, the length of the base (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. 19A shows a case where the ideal heat generation rate waveform model is an isosceles triangle, and FIG. 19B 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. 20A shows the relationship between the elapsed time when fuel injection is performed 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. 20A, the fuel injection period in which the fuel supply amount is obtained is divided into 10 periods. That is, the fuel injection period is divided into ten periods in which the fuel supply amounts are equal to each other, and the period numbers from the first period to the tenth period are assigned to each. 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 interrupted. The fuel injection is continued until the end of the tenth period in such an injection form that the fuel injection in the third period is started without any change.

  FIG. 20B shows the reaction amount of the fuel injected in each period (the one shown in FIG. 20B is the exothermic amount in the exothermic reaction). As shown in FIG. 20 (b), fuel injection in the first period is started and fuel injection in the second period is started (period t1 in FIG. 20 (b)). Only the reaction of the fuel injected in the first period is performed. The fuel injected in the first period is the period from the start of fuel injection in the second period until the start of fuel injection in the third period (period t2 in FIG. 20B). And the reaction of the fuel injected in the second period are 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. 20B), the reaction of the fuel injected in the second period and thereafter is not completed, and the reaction of the fuel injected in the tenth period from the second period is not completed. continuing. When the reaction of the fuel injected in the second period is completed (timing T2 in FIG. 20B), the reaction of the fuel injected in the third period and thereafter is not completed, so the third period The reaction of the fuel injected in the tenth 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. 20B) is a negative gradient period (a period retarded from the peak position of the reaction) of the ideal heat release rate waveform model. 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. 21 shows an example of an ideal heat release rate waveform model (isosceles triangle corresponding to each reaction) in each reaction mode when fuel injection is performed once in the region outside the cavity. In FIG. 21, an ideal heat generation rate waveform model (isosceles triangle corresponding to each reaction) in which 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 is obtained. Yes. Specifically, in the figure, I is the ideal heat release rate waveform model of the vaporization reaction, II is the ideal heat release rate waveform model of the low-temperature oxidation reaction, and III is the ideal heat release rate of the thermal decomposition reaction (pyrolysis reaction that is endothermic). A waveform model, IV is an ideal heat generation rate waveform model of a high temperature oxidation reaction by premixed combustion, and V is an ideal heat generation rate waveform model of a high temperature oxidation reaction by diffusion combustion.

  In addition, FIG. 22 was created by synthesizing each waveform obtained by smoothing the ideal heat release rate waveform model by filtering when fuel was injected once in the region outside the cavity. An ideal heat generation rate waveform (outside cavity injection ideal heat generation rate waveform) is shown. In this way, ideal heat release rate waveform models (isosceles triangles) corresponding to each reaction (vaporization reaction, low-temperature oxidation reaction, thermal decomposition reaction, each high-temperature oxidation reaction) are smoothed and synthesized by filtering. Thus, an ideal heat generation rate waveform only for the region outside the cavity is created.

  On the other hand, FIG. 23 shows an example of an ideal heat generation rate waveform model (isosceles triangle corresponding to each reaction) in each reaction mode when fuel injection is performed once in the cavity region. In FIG. 23, due to a rapid rise in the temperature in the cavity region, after a vaporization reaction and a thermal decomposition reaction are sequentially performed by one fuel injection, a low temperature oxidation reaction and a high temperature oxidation reaction by premixed combustion are performed. In parallel with this, after the start of these reactions, an ideal heat generation rate waveform model (isosceles triangle corresponding to each reaction) in which a high-temperature oxidation reaction by diffusion combustion is performed is obtained. Specifically, I 'in the figure is the ideal heat release rate waveform model for the vaporization reaction, II' is the ideal heat release rate waveform model for the low-temperature oxidation reaction, and III 'is the ideal for the thermal decomposition reaction (the thermal decomposition reaction that is endothermic). A heat generation rate waveform model, IV ′ is an ideal heat generation rate waveform model of a high temperature oxidation reaction by premixed combustion, and V ′ is an ideal heat generation rate waveform model of a high temperature oxidation reaction by diffusion combustion.

  FIG. 24 is created by synthesizing each waveform obtained by smoothing the ideal heat generation rate waveform model by filtering when fuel is injected once in the cavity region. The ideal heat release rate waveform (injection ideal heat release rate waveform in the cavity) is shown. In this way, ideal heat release rate waveform models (isosceles triangles) corresponding to each reaction (vaporization reaction, low-temperature oxidation reaction, thermal decomposition reaction, each high-temperature oxidation reaction) are smoothed and synthesized by filtering. Thus, an ideal heat generation rate waveform for only the region in the cavity is created.

  Furthermore, in one fuel injection, when a part of the fuel is injected into the area outside the cavity and another fuel is injected into the area inside the cavity, that is, the fuel is injected separately into the area outside the cavity and the area inside the cavity. In this case, an ideal heat generation rate waveform that targets these areas outside the cavity and an ideal heat generation rate waveform that covers the areas inside the cavity are created respectively. The ideal heat release rate waveform is created. For example, when the ideal heat generation rate waveform for the region outside the cavity is as shown in FIG. 22 and the ideal heat generation rate waveform for the region within the cavity is as shown in FIG. An ideal heat generation rate waveform (in-cylinder ideal heat generation rate waveform) as shown in FIG. 25 is created as an ideal heat generation rate waveform for the whole.

  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 in the target area is created in the same way as described above, and the ideal heat release rate waveform is created by smoothing this through filter processing. can do. Generally, pilot injection is performed at a crank angle position that is advanced by a predetermined angle or more from the compression top dead center of the piston 13, and after injection is performed at a crank angle position that is retarded by a predetermined angle or more from the compression top dead center of the piston 13. In order to be executed, these injections are directed towards the out-cavity region. For this reason, the ideal heat generation rate waveform targeting these injections is obtained as the ideal heat generation rate waveform outside the cavity.

  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.

(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. 25 is created will be described as an example. Like the actual heat generation rate waveform shown by the 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 high-temperature oxidation reaction (the waveform shown in FIG. 25). 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, like the actual heat generation rate waveform shown by the alternate long and short dash line in FIG. 26, the peak value of the heat generation rate waveform in each high-temperature oxidation reaction is higher than the ideal heat generation rate waveform shown by the solid line, and the deviation thereof has a 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 as shown by the broken line in FIG. 26, it is determined that fuel ignition delay has occurred and oxygen is insufficient, and the cooling capacity of the intake air 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. 26, it is determined that the reaction amount of the fuel is too large, and the fuel injection amount decrease correction, the EGR gas increase correction, etc. I do.

  As another correction operation, when the reaction start time in the actual heat generation rate waveform is on the retarded side with respect to the ideal heat generation rate waveform, the intake supercharging rate is increased or the pilot for the target region is increased. 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 target region is excessive or insufficient, the learning value is learned so as to correct the EGR gas or the intake supercharging rate. Further, when the fuel density in the target region is excessive or deficient, the learning value is learned so as to correct the fuel injection timing, the fuel injection pressure, and the fuel injection amount.

  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 temperature, oxygen density, and fuel density are set in advance and any of these in-cylinder temperature, oxygen density, and fuel density is lower than 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 lit to urge the driver to warn, and the diagnosis provided in the ECU 100 has abnormality information. Will be written.

  As described above, in the present embodiment, the inside of the cylinder is divided into the area inside the cavity and the area outside the cavity, and the heat release rate waveform is created for each area. That is, paying attention to the fact that the fuel injected into the cylinder is divided into areas inside and outside the cavity and the combustion becomes discontinuous, each area where physical quantities such as temperature and oxygen density may be different from each other On the other hand, the ideal heat release rate waveform is created by individually obtaining the combustion state of the fuel according to the environment in the region. For this reason, it becomes possible to prescribe | regulate the combustion state of a fuel more correctly.

  Further, in the present embodiment, when creating the heat generation rate waveform for each region inside and outside the cavity as described above, the unburned fuel amount is estimated individually for each fuel spray (injected fuel) in each region, The ideal heat release rate waveform is created as described above based on the effective injection amount obtained by subtracting this. Thereby, it becomes possible to further improve the accuracy of creating the ideal heat generation rate waveform.

  In this embodiment, the ideal heat generation rate waveforms are synthesized to create an ideal heat generation rate waveform for the entire cylinder, and the combustion state is diagnosed using the ideal heat generation rate waveform. ing. For this reason, when the actual heat generation rate waveform deviates from the ideal heat generation rate waveform by a predetermined amount or more, it can be diagnosed that an abnormality has occurred in the combustion mode. Therefore, the abnormality of the combustion state can be diagnosed with high accuracy, and the diagnostic accuracy can be improved.

  When it is diagnosed that there is an abnormality in the combustion state, by taking improvement measures (correction of control parameters) for the abnormal reaction mode (when the divergence is less than or equal to a predetermined correctable deviation), the reaction state It is possible to correct the optimum control parameter for optimizing the above, and an effective correction operation can be performed. As a result, it becomes possible to bring the entire reaction related to fuel combustion closer to the ideal reaction (the actual heat generation rate waveform of each reaction is brought closer to the ideal heat generation rate waveform), and the controllability of the engine 1 is greatly increased. Can be improved.

  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-
As described above, the embodiment described above has described the case where the present invention is applied to the in-line four-cylinder diesel engine 1 mounted on an automobile. 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. Further, the present invention is not limited to diesel engines using light oil as fuel, but can also be applied to engines using gasoline or other fuels.

  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, ideal heat generation rate waveforms are created for each of the region outside the cavity and the region inside the cavity, and these are combined and used for diagnosis of the combustion state. The present invention is not limited to this, and the diagnosis of the combustion state can be performed by using the ideal heat generation rate waveform created for each region individually, and the engine design and the control parameter can be adjusted. It may be used for seeking.

  Further, in the above embodiment, when the ideal heat generation rate waveform is created for each region inside and outside the cavity, individual fuel sprays (injected fuel) that are divided into these regions and perform discontinuous combustion are not yet individually obtained. The ideal heat generation rate waveform is created based on the effective injection amount obtained by subtracting the estimated value by estimating the fuel amount. However, in the present invention, “the case where the combustion of the fuel injected into the cylinder is discontinuous” is not limited to the case where the fuel spray is divided into the respective regions inside and outside the cavity as described above.

  For example, when fuel is divided into a plurality of times and injected into a cylinder in a single combustion cycle, the amount of unburned fuel is estimated separately for each discontinuous fuel spray (injected fuel). It is preferable to create the heat release rate waveform based on the effective injection amount obtained by subtracting the value.

  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 is applicable to creation of a heat release rate waveform for each reaction of fuel and diagnosis of each reaction in a diesel engine mounted on an automobile.

1 engine (internal combustion engine)
12 Cylinder bore (cylinder)
13 Piston 13b Cavity 23 Injector (fuel injection valve)
3 In-cylinder combustion chamber 100 ECU
I, I 'ideal heat release rate waveform model of vaporization reaction
II, II 'Waveform model of ideal heat release rate for low-temperature oxidation reaction
III, III 'ideal heat release rate waveform model of pyrolysis reaction
IV, IV 'Ideal heat release rate waveform model for high temperature oxidation reaction V, V' Ideal heat release rate waveform model for high temperature oxidation reaction

Claims (10)

An apparatus for generating a heat release rate waveform of the combustion in an internal combustion engine that performs combustion of fuel injected into a cylinder from a fuel injection valve,
When the combustion of the injected fuel becomes discontinuous, the amount of unburned fuel is estimated individually for each injected fuel that performs this discontinuous combustion, and based on the effective injection amount obtained from this estimation result, An apparatus for creating a heat release rate waveform of an internal combustion engine, characterized in that it is configured to create an ideal heat release rate waveform for combustion. In the internal combustion engine heat release rate waveform creation device according to claim 1,
When the combustion of the fuel is discontinuous, the fuel is injected in a plurality of times, or the injected fuel is injected into the internal region and the external region of the cavity provided in the piston Is a heat release rate waveform creation device for an internal combustion engine, characterized in that at least one of them is present. In the internal combustion engine heat release rate waveform creation device according to claim 2,
Based on the ratio of fuel injection to the inner region and the outer region of the cavity, the amount of fuel injected into each of these regions is calculated, and the amount of unburned fuel is calculated using a different calculation formula for each region. An apparatus for generating a heat release rate waveform of an internal combustion engine, characterized in that: In the internal combustion engine heat release rate waveform creation device according to claim 3,
A configuration for creating an ideal heat generation rate waveform for each region and creating an ideal heat generation rate waveform and synthesizing these ideal heat generation rate waveforms to create an ideal heat generation rate waveform for the entire cylinder; An apparatus for generating a heat release rate waveform of an internal combustion engine, characterized by comprising: In the internal combustion engine heat release rate waveform creation device according to any one of claims 1 to 4,
It is configured to estimate the amount of unburned fuel by using a calculation formula that uses at least the product of the fuel injection amount and the injection pressure and the injection timing as parameters for each discontinuous injected fuel of the combustion. An apparatus for creating a heat release rate waveform of an internal combustion engine. In the internal combustion engine heat release rate waveform creation device according to any one of claims 1 to 5,
A configuration in which combustion of the fuel is defined by at least a vaporization reaction, a low temperature oxidation reaction, a thermal decomposition reaction, and a high temperature oxidation reaction, and an ideal heat generation rate waveform is created by calculating a reaction rate, a reaction amount, and a reaction period for each reaction. And
An apparatus for generating a heat release rate waveform of an internal combustion engine, wherein the effective injection amount is used to calculate at least a reaction rate and a reaction amount for each reaction. In the internal combustion engine heat release rate waveform creation device according to claim 6,
The ideal heat generation rate waveform is an ideal heat generation rate waveform model composed of triangles with the reaction rate as the base point, the reaction rate as the slope, 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, which is created by synthesizing an ideal heat release rate waveform model of each reaction and smoothing it by filtering.   An ideal heat generation rate waveform obtained by the internal combustion engine heat generation rate waveform creation device according to any one of claims 1 to 7, and an actual heat generation rate waveform when fuel is actually burned in a cylinder. And when the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is greater than or equal to a predetermined amount, it is configured to diagnose that an abnormality has occurred in the reaction related to fuel combustion. A combustion state diagnosis apparatus for an internal combustion engine characterized by the above. The combustion state diagnosis apparatus for an internal combustion engine according to claim 8,
When there is a reaction in which the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform is greater than or equal to a predetermined abnormality determination deviation amount, and it is diagnosed that the reaction is abnormal, When the deviation of the actual heat generation rate waveform with respect to the generation rate waveform is equal to or less than a predetermined correctable deviation amount, the control parameter of the internal combustion engine is corrected to control the deviation to be less than the abnormality determination deviation amount. A combustion state diagnosis of an internal combustion engine characterized by diagnosing that a failure has occurred in the internal combustion engine when the deviation of the actual heat generation rate waveform from the ideal heat generation rate waveform exceeds the correctable deviation amount apparatus. The combustion state diagnostic apparatus for an internal combustion engine according to claim 8 or 9,
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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