JP2010196556A - Heating value calculation device, control device of internal combustion engine, and abnormality detection device of injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating value calculation device accurately calculating a gross heating value of fuel generating heat until a crank reaches a specific crank angle even when cylinder pressure includes an offset error. <P>SOLUTION: Crank angles are sequentially acquired by a crank angle sensor at S121. For each of the crank angles, a cylinder pressure is acquired by a cylinder pressure sensor at S123 and a capacity of a cylinder is acquired at S127. A heat generation rate per unit angle of a crank angle is calculated based on the cylinder pressure and the capacity at S129. Representing the specific crank angle before a top dead center as (-B), the heat generation rate is integrated in sections [-B, B] centered on the top dead center TDC and equal to each other on an advance side and a retard side at S133. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a calorific value calculation device that calculates the calorific value of fuel in an internal combustion engine, and an apparatus that uses the calorific value calculated by the calorific value calculation device.

  In recent years, automobile emission regulations have been strengthened, and efforts have been made to reduce harmful exhaust gas in order to meet the emission regulations. For example, exhaust gas recirculation (exhaust gas recirculation), which is a technology for extracting a part of exhaust gas after combustion and leading it to the intake side to re-intake air, introduces nitrogen, which is one of the harmful exhaust gases. Reduction of oxide (NOx) is aimed at.

  However, when exhaust gas recirculation is introduced, the fuel burns in a state where the temperature in the cylinder is low, so that it is easily affected by fuel properties and environmental conditions, and the combustion timing varies. Therefore, a technique is known in which an in-cylinder pressure P, which is an internal pressure of a cylinder, is detected by an in-cylinder pressure sensor, and the fuel combustion timing is controlled based on the in-cylinder pressure P. Specifically, for example, the heat release rate per unit angle of the crank angle is calculated by the method described in Patent Document 1. Next, the total heat generation amount of the fuel is calculated by integrating the heat generation rate in the section where the fuel is burned. Then, a combustion rate MFB at a predetermined timing (for example, 8 ° after top dead center (ATDC 8 °)) is calculated when the total calorific value is 100%, and the combustion rate MFB is calculated as a target combustion rate (for example, 50 %), The fuel injection timing or ignition timing is controlled. Thus, it is useful to calculate the total calorific value of the fuel.

Japanese Patent No. 3331107

  By the way, an appropriate value is not always obtained as the in-cylinder pressure P detected by the in-cylinder pressure sensor. For example, an unnecessary offset error α may be superimposed on the true in-cylinder pressure P0 due to an external factor such as a temperature change, variation in characteristics of the in-cylinder pressure sensor itself, or a secular change. In such a case, an error occurs in the heat generation rate calculated based on the in-cylinder pressure P. As a result, an error also occurs in the total heat generation amount calculated by integrating the heat generation rate in the section in which the fuel is burned.

  In addition, in an apparatus that controls the combustion timing using the total calorific value, if the total calorific value is in error, the objective of the apparatus cannot be achieved, for example, the fuel combustion timing cannot be accurately controlled. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a calorific value calculation device capable of accurately calculating the total calorific value even if the in-cylinder pressure P includes an offset error α. It is another object of the present invention to provide a device that uses the total calorific value calculated by the total calorific value calculation device.

In order to achieve the above object, a calorific value calculation device according to claim 1 is an internal combustion engine having a cylinder, a piston, and a crank, wherein the crank angle θ, which is the rotation angle of the crank with reference to the top dead center TDC, is top dead. A calorific value calculation device for calculating a total calorific value Q1 of the fuel that has generated heat up to a specific crank angle B after the point;
Crank angle acquisition means for acquiring the crank angle θ from a crank angle sensor for sequentially detecting the crank angle θ;
An in-cylinder pressure acquisition unit that acquires the in-cylinder pressure P from an in-cylinder pressure sensor that detects an in-cylinder pressure P that is an internal pressure of the cylinder, for each of the crank angles θ acquired by the crank angle acquisition unit;
Volume acquisition means for acquiring the volume V of the cylinder for each of the crank angles θ acquired by the crank angle acquisition means;
Based on the in-cylinder pressure P acquired by the in-cylinder pressure acquisition unit and the volume V acquired by the volume acquisition unit, the crank angle θ is determined for each of the crank angles θ acquired by the crank angle acquisition unit. A heat generation rate calculating means for calculating a heat generation rate dQ / dθ per unit angle of
When the specific crank angle B before the top dead center is (−B), the heat generation rate dQ / dθ calculated by the heat generation rate calculating means is set to be advanced and delayed with respect to the top dead center TDC. And integrating means for integrating in the interval [-B, B] equal to the corner side.

  The total heat generation amount Q1 can be calculated by integrating the heat generation rate dQ / dθ per unit angle of the crank angle θ. The heat generation rate dQ / dθ can be calculated based on the in-cylinder pressure P and the volume V. Therefore, in the calorific value calculation device according to the first aspect, in-cylinder pressure P and volume V are acquired for each crank angle θ in order to calculate the heat generation rate dQ / dθ. Here, the cylinder pressure P detected by the cylinder pressure sensor may include the offset error α as described above. The offset error α is the same value for any in-cylinder pressure P. The heat generation rate calculation means calculates the heat generation rate dQ / dθ based on the in-cylinder pressure P and the volume V. If the in-cylinder pressure P includes the offset error α, the calculated heat generation rate is calculated. An error F occurs in the occurrence rate dQ / dθ. Here, the present applicant has found that the error F is expressed by L × α × (dV / dθ). Note that L is a constant (κ / (κ−1)) calculated from the specific heat ratio κ, and (dV / dθ) is the rate of change of the volume V per unit angle of the crank angle θ. That is, the error F is expressed by a function with the change rate dV / dθ of the volume V as a variable. Since the rate of change dV / dθ of the volume V is a symmetric value in which the sign is opposite with respect to the top dead center TDC, the error F is opposite to the sign with respect to the top dead center TDC. It becomes a symmetrical value. For example, when the error F at 50 ° after top dead center (ATDC 50 °) is F50, the error F at 50 ° before top dead center (BTDC 50 °) is (−F50).

  Therefore, the integrating means integrates the heat generation rate dQ / dθ in the same section [−B, B] on the advance side and the retard side with the top dead center TDC as the center, and an error F of the heat generation rate dQ / dθ. This cancels the influence of Lα (dV / dθ). On the other hand, the heat generation rate dQ / dθ based on the true in-cylinder pressure P0 is considered to be zero until the start of fuel combustion. Therefore, even if the interval [-B, B] to be integrated includes the interval before the start of fuel combustion, the zero heat generation rate dQ / dθ is integrated in that interval, so the total heat generation It does not affect the calculation of the quantity Q1. Therefore, it is possible to calculate the total calorific value Q1 of the fuel that has generated heat up to the specific crank angle B while canceling the influence of the offset error α.

The heat generation amount calculation device according to claim 2 is the heat generation rate calculation device according to claim 1, wherein the heat generation rate calculation means includes a change rate of the in-cylinder pressure P per unit angle of the in-cylinder pressure P, the volume V, and the crank angle θ. The in-cylinder pressure change rate dP / dθ and the volume change rate dV / dθ, which is the change rate of the volume V per unit angle of the crank angle θ, are substituted into the following equation 1, and the heat release rate dQ / dθ Is calculated.

  The equation represented by Equation 1 is described in many documents such as Patent Document 1 and is considered to be an equation with high reliability for calculating the heat generation rate dQ / dθ. Therefore, by adopting this equation, the heat release rate dQ / dθ can be accurately calculated.

However, as described above, if the error α is included in the in-cylinder pressure P, an error F occurs in the calculated heat generation rate dQ / dθ. That is, substituting P = P0 + α into Equation 1 yields Equation 2 below.

  Κ / (κ−1) × α (dV / dθ) on the right side of Equation 2 is the error F of the heat generation rate dQ / dθ. That is, when κ / (κ−1) = L, the error F is expressed by L × α × (dV / dθ) as described above. Note that the value excluding the error F in Equation 2 is the heat generation rate dQ / dθ with respect to the true in-cylinder pressure P0. Therefore, the total calorific value Q1 is a value obtained by integrating the heat generation rate dQ / dθ with respect to the true in-cylinder pressure P0 by canceling the error F represented by κ / (κ-1) × α (dV / dθ). It is.

  The heat generation amount calculation device according to claim 3 is the heat generation amount calculation device according to claim 1 or 2, wherein the interval [-B, B] is a necessary and sufficient interval in which the total calorific value Q1 when all the injected fuel is burned can be calculated. It is provided with the section determination means which determines the said specific crank angle B so that it may become.

  Thereby, the section [−B, B] is a necessary and sufficient section in which the total calorific value Q1 when all the fuels are combusted can be calculated. That is, the section [-B, B] includes a section from the start of fuel combustion until all the fuel is combusted. Therefore, the total calorific value Q1 when all the fuels are combusted can be calculated. The section [-B, B] is a necessary and sufficient section for calculating the total calorific value Q1 when all the fuels are combusted. Therefore, in order to calculate the total calorific value Q1, the heat generation rate dQ / dθ. When the fuel is accumulated, the heat generation rate dQ / dθ after the combustion of the fuel is not accumulated more than necessary. Therefore, calculation load can be reduced.

  On the other hand, the crank angle θ detected by the crank angle sensor is an angle with respect to the top dead center TDC, but the crank angle θ is an accurate top dead center TDC due to a mounting error of the crank angle sensor. The angle may not be a reference angle. If there is an error in the detected crank angle θ, an error also occurs in the heat generation rate dQ / dθ and the total calorific value Q1 calculated corresponding to the crank angle θ.

  In consideration of such circumstances, the calorific value calculation device according to claim 4 is characterized in that in any one of claims 1 to 3, a top dead center detecting means for detecting top dead center TDC and a top dead center detecting means are provided. Top dead center angle acquisition means for acquiring the crank angle θ detected by the crank angle sensor corresponding to the detected top dead center TDC as a top dead center angle; and the crank angle θ detected by the crank angle sensor Correction means for correcting the dead center angle to be a reference, and the crank angle acquisition means acquires the crank angle θ corrected by the correction means.

  Thus, the crank angle θ acquired by the crank angle acquisition unit is an angle corrected by the correction unit, and is therefore an angle based on the true top dead center TDC. That is, since the crank angle θ acquired by the crank angle acquisition means can be said to be a highly accurate angle, the heat generation rate dQ / dθ and the total calorific value Q1 calculated corresponding to the crank angle θ are accurate. It can be said that it is a thing.

  Here, the top dead center TDC can be detected by paying attention to the change in the in-cylinder pressure P with respect to the crank angle θ. That is, the volume V changes as the crank angle θ changes, but the in-cylinder pressure P is considered to increase as the volume V decreases in a state where fuel is not injected. When the volume V is the smallest, that is, when the top dead center is TDC, the in-cylinder pressure P is considered to be the largest. In the state where the fuel is being injected, the in-cylinder pressure P may not become maximum even at the top dead center TDC due to the influence of the fuel. Therefore, in order to detect the top dead center TDC from the in-cylinder pressure P, it is desirable to pay attention to the in-cylinder pressure P in a state where fuel is not injected.

  The invention of claim 5 has been made in consideration of such circumstances. In other words, the calorific value calculation device according to claim 5 is the cylinder according to claim 4, wherein the top dead center detecting means detects the cylinder angle θ detected by the in-cylinder pressure sensor in a state where fuel is not injected. A correction cylinder pressure acquisition means for acquiring the internal pressure P as a correction cylinder pressure, and a maximum point detection means for detecting a point at which the correction cylinder pressure acquired by the correction cylinder pressure acquisition means is maximum as a top dead center. It is characterized by having. Thereby, the true top dead center TDC can be detected.

  Even when the crank angle θ is the same, the maximum value of the in-cylinder pressure P detected by the in-cylinder pressure sensor may vary over time due to electrical noise, mechanical noise, or the like. That is, the top dead center detected by the top dead center detection means may vary with time. Therefore, in the calorific value calculation device according to claim 6, the top dead center detecting means detects the top dead center TDC a plurality of times, and the top dead center angle obtaining means is detected a plurality of times by the top dead center detecting means. The top dead center angle is acquired for each top dead center, and the correction means performs the correction based on an average value of the plurality of top dead center angles acquired by the top dead center angle acquisition means. ing.

  As a result, even if the top dead center angle changes with time due to time variation of the top dead center TDC, the correction is made based on the average value of a plurality of top dead center angles. The influence of time change can be suppressed.

A control device for an internal combustion engine according to a seventh aspect includes a calorific value calculation device according to any one of the first to sixth aspects,
An actual combustion timing detecting means for detecting, as an actual combustion timing, a crank angle θ at which the total calorific value of fuel is a specific combustion ratio of the total calorific value Q1 calculated by the calorific value calculation device;
Combustion timing control means for controlling the fuel injection timing or ignition timing so that the actual combustion timing detected by the actual combustion timing detection means becomes the target combustion timing.

  If the combustion timing is appropriately controlled, it is possible to prevent knocking, reduce harmful exhaust gas, increase output efficiency, and the like. Combustion is performed by controlling the fuel injection timing or ignition timing so that the actual combustion timing becomes the target combustion timing when the crank angle θ, which is a specific combustion ratio of the total calorific value Q1, is set as the actual combustion timing. Time can be controlled appropriately. The control device for an internal combustion engine according to claim 7 is made in consideration of such a situation. In this case, the control device for the internal combustion engine according to claim 7 controls the combustion timing of the fuel based on the total calorific value Q1 calculated by the calorific value calculation device according to any one of claims 1-6. Since the calorific value calculation device according to any one of claims 1 to 6 can accurately calculate the total calorific value Q1 even when the in-cylinder pressure P includes the offset error α, the total calorific value is calculated. According to the control device for an internal combustion engine that controls the fuel combustion timing by the amount Q1, the fuel combustion timing can be accurately controlled. As a result, it is possible to prevent knocking, reduce harmful exhaust gas, increase output efficiency, and the like.

  According to an eighth aspect of the present invention, there is provided a control device for an internal combustion engine according to the seventh aspect, wherein a command injection amount which is a command value of the engine speed and the fuel injection amount acquired from the engine speed acquisition means for acquiring the engine speed. And target combustion timing determining means for determining the target combustion timing based on the above.

  How the injected fuel burns can be predicted to some extent because it is matched in advance based on the engine speed and the commanded fuel injection amount. Then, on the premise of the prediction, it is possible to predict when the combustion of the fuel is started and when the combustion is optimally performed. Therefore, the control apparatus for an internal combustion engine according to claim 8 determines the target combustion timing based on the engine speed and the fuel injection amount. As a result, the target combustion timing corresponding to the engine operating conditions determined by the engine speed and the fuel injection amount is determined, so that the fuel combustion can be appropriately controlled according to the engine operating conditions. .

An injector abnormality detection device according to claim 9 is a calorific value calculation device according to any one of claims 1 to 6,
Command injection amount acquisition means for acquiring the command value of the fuel injection amount as the command injection amount;
A planned total heat generation amount calculating means for calculating a total heat generation amount of the fuel when the fuel of the command injection amount acquired by the command injection amount acquisition means is injected;
Comparing the total calorific value Q1 and the planned total calorific value Q2, it comprises an abnormality determining means for determining whether or not the injector for injecting fuel is abnormal.

  Due to an abnormality in the injector, the fuel injection amount actually injected from the injector may not be the command injection amount. In this case, since the scheduled combustion is not performed, problems such as a decrease in output occur. On the other hand, the fuel injection amount is proportional to the total heat generation amount of the fuel. Therefore, in the injector abnormality detection apparatus according to the ninth aspect, the actual total heat generation amount Q1 is compared with the planned total heat generation amount Q2 of the fuel calculated from the command injection amount to detect the abnormality of the injector. At this time, the actual total calorific value Q1 is calculated by the calorific value calculation device according to any one of claims 1 to 6, so that even if the in-cylinder pressure P includes the offset error α. It can be said that it is an accurate value. That is, even if the in-cylinder pressure P includes the offset error α, it is possible to accurately detect the abnormality of the injector.

  Further, the planned total heat generation amount Q2 can be calculated as in claim 10. That is, the abnormality detection device for an injector according to claim 10 is characterized in that, in claim 9, the scheduled total heat generation amount calculation means calculates a value calculated from the command injection amount, fuel density, and fuel energy density as operating conditions and intake air amount. The estimated total calorific value Q2 is obtained by correcting with a correction coefficient determined based on at least one of the values of intake pressure, EGR rate, intake air temperature, engine water temperature, and common rail pressure. The planned total heat generation amount Q2 depends on how much the fuel of the command injection amount changes to heat. And how much it changes to heat differs depending on the operating conditions determined by the engine speed and the command injection amount. The correction coefficient is a coefficient indicating how much the fuel of the command injection amount changes to heat, and is determined as an appropriate value for each operating condition.

  Here, the correction coefficient is a value according to the operating conditions, and as in claim 10, is based on at least one value of the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure. Can be determined. For example, it can be said that the intake air amount is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the amount of intake increases, the amount of oxygen / oxygen concentration sucked into the cylinder increases, so that the fuel easily burns. On the other hand, as the amount of intake decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration decreases, the fuel becomes difficult to burn. Therefore, when the inhalation amount is increased with respect to the reference inhalation amount, the correction coefficient is increased so that the planned total calorific value Q2 is increased. On the contrary, when the inhalation amount is decreased, the correction coefficient is decreased. The planned total heat generation amount Q2 is made small.

  Further, it can be said that the intake pressure is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the intake pressure increases, the amount of oxygen sucked into the cylinder / oxygen concentration increases, so that the fuel easily burns. On the other hand, as the intake pressure decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration decreases, the fuel becomes difficult to burn. Therefore, when the intake pressure increases with respect to the reference intake pressure, the correction coefficient is increased so that the planned total heat generation amount Q2 increases. Conversely, when the intake pressure decreases, the correction coefficient is decreased. The planned total heat generation amount Q2 is made small.

  Further, it can be said that the EGR rate is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the EGR rate increases, the amount of oxygen sucked into the cylinder / oxygen concentration decreases, so that it becomes difficult for the fuel to combust. On the other hand, as the EGR rate decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration increases, the fuel becomes easy to burn. Therefore, when the EGR rate increases with respect to the reference EGR rate, the correction coefficient is decreased to decrease the planned total heat generation amount Q2, and conversely, when the EGR rate decreases, the correction coefficient is increased. The planned total heat generation amount Q2 is increased.

  Further, it can be said that the intake air temperature is a value reflecting the in-cylinder temperature. That is, as the intake air temperature increases, the in-cylinder temperature increases, so the fuel easily burns. On the other hand, as the intake air temperature decreases, the in-cylinder temperature decreases, so the fuel becomes difficult to burn. Therefore, when the intake air temperature increases with respect to the reference intake air temperature, the correction coefficient is increased to increase the planned total heat generation amount Q2, and conversely, when the intake air temperature decreases, the correction coefficient is decreased. The planned total heat generation amount Q2 is made small.

  Further, it can be said that the engine water temperature is a value reflecting the in-cylinder temperature. That is, as the engine water temperature increases, the in-cylinder temperature increases so that the fuel easily burns. On the other hand, as the engine water temperature decreases, the in-cylinder temperature decreases, so that the fuel becomes difficult to burn. Therefore, when the engine water temperature is increased with respect to the reference engine water temperature, the correction coefficient is increased so that the planned total heat generation amount Q2 is increased. Conversely, when the engine water temperature is decreased, the correction coefficient is decreased. The planned total heat generation amount Q2 is made small.

  The common rail pressure is related to fuel diffusion and volatilization. As the fuel is more easily diffused and volatilized, the fuel and air are more easily mixed, and as a result, the fuel is easily burned. On the contrary, the more difficult the fuel is to diffuse and volatilize, the more difficult it is to mix the fuel and the air, and as a result, the fuel becomes difficult to burn. That is, it can be said that the common rail pressure reflects the ease of mixing of fuel and air. Therefore, when the common rail pressure increases with respect to the reference common rail pressure, the correction coefficient is increased to increase the planned total heat generation amount Q2. On the contrary, when the common rail pressure decreases, the correction coefficient is decreased. The planned total heat generation amount Q2 is made small.

  As described above, the planned total calorific value Q2 obtained by correcting with the correction coefficient determined based on at least one of the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure is the operating condition. It can be said that it is an accurate value in consideration of.

It is the figure which showed schematic structure of the engine control system of 1st, 2nd embodiment. It is the conceptual diagram which showed the memory of ROM53 of 1st embodiment. It is the figure which showed the volume V for every crank angle (theta). It is the flowchart which showed the main routine of the injection timing control processing. It is the flowchart which showed the detail of the target combustion time determination process. It is the flowchart which showed the detail of the total calorific value calculation process. It is the flowchart which showed the detail of the top dead center position correction process. It is the figure which showed the waveform 201 of the cylinder pressure for correction | amendment. It is the figure which expanded the peak 202 periphery (inside the dotted-line frame of FIG. 8) of the waveform 201. It is the figure which showed the time change of crank angle (theta) x used as the maximum in-cylinder pressure. It is the figure which showed the waveform 1 of the cylinder pressure P for every crank angle (theta). It is the figure which showed the waveform 3 of the heat release rate dQ / d (theta) for every crank angle (theta). It is the figure which showed the waveform 5 of the total calorific value Q. FIG. FIG. 6 is a diagram showing a waveform 3 of a heat generation rate dQ / dθ, a waveform 4 of a heat generation rate dQ / dθ with respect to a true in-cylinder pressure P0, and a waveform 7 of an error F. It is the figure which showed the waveform 8 of the total calorific value Q. FIG. It is a figure for demonstrating the detection method of real MFB50. It is the conceptual diagram which showed the memory of ROM53 of 2nd embodiment. It is the flowchart which showed the main routine of abnormality detection processing. It is the flowchart which showed the detail of the plan total calorific value calculation process.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. This first embodiment is an embodiment that embodies a calorific value calculation device and a control device for an internal combustion engine of the present invention. The system of the present embodiment is an engine control system that controls a diesel engine equipped with a common rail fuel injection device.

  First, a schematic configuration of the engine control system of the present embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of the engine control system of the present embodiment. As the engine 10 to be controlled by this system, a multi-cylinder (for example, in-line four-cylinder) engine mounted on a four-wheeled vehicle (for example, an AT vehicle) is assumed. However, in FIG. 1, only one cylinder 15 is shown for convenience of explanation. The engine 10 is a 4-stroke (4 × piston stroke) reciprocating diesel engine (internal combustion engine). In other words, in this engine 10, the cylinders discrimination sensors (electromagnetic pickups) provided on the camshafts (not shown) of the intake valve 2 and the exhaust valve 30 are used for the target cylinders # 1 to # 4 at that time, respectively. In one combustion cycle “720 ° CA” cycle by four strokes of combustion and exhaust, specifically, for example, each cylinder is shifted by “180 ° CA” and sequentially executed in the order of cylinders # 1, # 3, # 4, and # 2. The The configuration of these four cylinders # 1 to # 4 is basically the same. Here, paying attention to one cylinder 14, the system will be described.

  As shown in FIG. 1, this system uses an engine 10 that rotates a crankshaft 43 that is an output shaft by torque generated in combustion in a cylinder 15 as an object to be controlled, and an ECU 50 and various sensors for controlling the engine 10. Etc. are built. Hereinafter, each element constituting this system including the engine 10 to be controlled will be described in detail.

  The engine 10 (diesel engine) to be controlled here basically includes a cylinder (cylinder) 15 formed by a cylinder block 14 and a cylinder head 22. The cylinder block 14 is provided with a cooling water passage (water jacket) 12 for circulating the cooling water through the engine 10 and a water temperature sensor 72 for detecting the temperature of the cooling water (cooling water temperature) in the cooling water passage 12. ing. The engine 10 is cooled by the cooling water.

  A piston 16 is housed in the cylinder 15, and a crankshaft 43 that is an output shaft of the engine 10 is rotated by the reciprocating motion of the piston 15. The crankshaft 43 is provided with a pulsar 42 that rotates together with the crankshaft. A plurality of teeth are formed on the outer periphery of the pulsar 42. A crank angle sensor 60 (for example, an electromagnetic pickup) that outputs a crank angle signal indicating a crank angle θ that is a rotation angle of the crank 18 by detecting teeth formed on the pulsar 42 on the outer peripheral side of the pulsar 42. ) Is provided. The number and interval of teeth formed on the outer periphery of the pulsar 42 are determined so that the crank angle signal output from the crank angle sensor 60 has a cycle of 1 ° CA, for example. Further, teeth for detecting the top dead center are formed on the outer periphery of the pulsar 42, and the crank angle sensor 60 outputs a top dead center signal corresponding to the top dead center TDC by detecting the teeth. Yes.

  However, because of the mounting error of the crank angle sensor 60 and the pulser 42, the crank angle sensor may output a top dead center signal even though it is not the top dead center TDC. That is, the top dead center detected by the crank angle sensor 60 is shifted. In such a case, the crank angle θ detected with reference to the top dead center TDC is not an accurate value. Therefore, in the present embodiment, the true top dead center TDC is detected and the deviation of the top dead center TDC is corrected. Details will be described later.

  A combustion chamber 20 is formed between the cylinder head 22 fixed to the upper end surface of the cylinder block 14 and the crown surface of the piston 16 in the cylinder 15. In the cylinder head 22, for example, two intake ports 22 (intake ports) and exhaust ports 26 (exhaust ports) that open to the combustion chamber 20 are formed, for example, for each cylinder (four ports in total). The intake port 22 and the exhaust port 26 are respectively driven by an intake valve 28 (intake valve) and an exhaust valve 30 (exhaust valve) driven by cams (not shown) (specifically, cams attached to a camshaft interlocked with the crankshaft 43). Valve). Further, in order to allow the combustion chamber 20 in the cylinder 15 and the outside of the vehicle (outside air) to communicate with each other through these ports 24 and 26, the intake port 24 has an intake pipe for sucking outside air (fresh air) into the cylinder 15. 32 (intake passage) is connected, and the exhaust port 26 is connected to an exhaust pipe 34 (exhaust passage) for discharging combustion gas (exhaust gas) from each cylinder.

  The intake pipe 32 constituting the intake system of the engine 10 is provided with an air cleaner (not shown) at the most upstream part, and fresh air is sucked through the air cleaner while removing foreign substances in the air. In addition, an air flow meter 74 (intake air amount sensor) that detects an electric signal Fa indicating the flow rate (fresh air amount) of the fresh air is provided in the downstream portion of the air cleaner, and the electric signal Fa is described later. To the ECU 50. As the air flow meter 74, for example, a hot wire type air flow meter is used. Further, an intake pressure sensor 68 for detecting the intake air pressure Pm and an intake air temperature sensor 70 for detecting the intake air temperature Ta are provided in the vicinity of the air flow meter 74, and the intake air pressure Pm and the intake air are detected. Are respectively input to the ECU 50.

  On the other hand, the exhaust pipe 34 constituting the exhaust system of the engine 10 is provided with an A / F sensor 76 which is a linear detection type oxygen concentration sensor for detecting the oxygen concentration Do in the exhaust gas. It is input to the ECU 50. The oxygen concentration Do detected by the A / F sensor 76 is used for, for example, EGR control.

  On the other hand, in the fuel supply system of this system, the in-cylinder injection method is adopted as the fuel supply method. That is, in the cylinder 15, high pressure fuel (for example, light oil having an injection pressure of “1000 atm” or more) supplied from the common rail 36 (pressure accumulation pipe) through the branch pipe 100 is directly input to the combustion chamber 20. Further, an injector 40 as an electromagnetically driven fuel injection valve for injecting and supplying fuel is further provided. The pressure of the high-pressure fuel is controlled based on a detection signal from a common rail pressure sensor 64 that detects the pressure in the common rail 36. In the engine 10, a required amount of fuel is injected and supplied to each cylinder 15 as needed by such valve opening drive of the injector 40. That is, when the engine 10 is in operation, intake air is introduced from the intake pipe 32 into the combustion chamber 20 of the cylinder 15 by the opening operation of the intake valve 28, and is mixed with the fuel injected and supplied from the injector 40. Compressed by the piston 16 in the cylinder 15 and ignited (self-ignited) and combusted, and the exhaust valve 30 is opened to discharge the exhausted gas to the exhaust pipe 34.

  Further, in the combustion chamber 20, an in-cylinder pressure sensor 66 that detects a pressure P (in-cylinder pressure) in the cylinder 16 by a detection unit (a tip portion of a probe inserted into the combustion chamber 20) located in the combustion chamber 20. For example, it is provided integrally with a glow plug as an ignition auxiliary device (specifically, it is fixed to the cylinder head 22). As a result, the combustion state in the cylinder 16 can be grasped, that is, the ignition timing and the combustion temperature can be estimated, knocking detection, combustion pressure peak position detection, misfire detection, and the like can be performed. The in-cylinder pressure P detected by the in-cylinder pressure sensor 66 is input to the ECU 50 after the noise is removed by the LPF 80. Similarly to the injector 40, an in-cylinder pressure sensor 66 is also provided for each combustion chamber of each cylinder (all four figures) of the engine 10.

  Further, an EGR device for recirculating a part of the exhaust gas as EGR gas to the intake system is disposed between the intake pipe 32 and the exhaust pipe 34. This EGR device basically includes an EGR pipe 90 provided so as to allow the intake pipe 32 and the exhaust pipe 34 to communicate with each other, and an EGR valve 91 including an electromagnetic valve or the like provided in the EGR pipe 90. Has been. The valve opening / closing of the EGR valve 91 is controlled by the ECU 50. The passage area of the EGR pipe 90, and thus the EGR rate (the ratio of the EGR gas returned to the cylinder 16 with respect to the entire exhaust gas) can be adjusted by the valve opening of the EGR valve 91. Incidentally, this adjustment is performed based on the output of the A / F sensor 76. For example, when the EGR valve 91 is fully closed, the EGR pipe 90 is shut off and the EGR amount becomes "zero". If necessary, an EGR cooler for cooling the EGR gas is also provided for the EGR pipe 90. In this EGR device, based on such a configuration, a part of the exhaust gas is recirculated to the intake system through the EGR pipe 90, thereby lowering the combustion temperature and reducing the generation of NOx.

  Furthermore, a vehicle (not shown) (for example, a four-wheel passenger car or a truck) that travels using the engine 10 as power is provided with various sensors for vehicle control in addition to the above-described sensors. For example, an accelerator sensor 62 that outputs an electric signal corresponding to the state (displacement amount) of the pedal is provided on an accelerator pedal corresponding to a driving operation unit for notifying the vehicle side of the torque required by the driver. It is provided to detect the operation amount (depression amount).

  In such a system, the ECU 50 is the part that functions as the calorific value calculation device and the control device for the internal combustion engine of the present embodiment. The ECU 50 grasps the operating conditions of the engine 10 and the user's request based on the detection signals of the various sensors, and operates various actuators such as the injector 40 in accordance therewith, so that the optimum according to the situation at the time. Various controls relating to the engine 10 are performed in this manner. For example, during steady operation of the engine 10, various combustion conditions (for example, injection timing, fuel injection amount, etc.) are calculated based on detection signals of the sensors, and various actuators are operated to operate the internal cylinders. The indicated torque (generated torque) generated through fuel combustion in the (combustion chamber), and consequently the shaft torque (output torque) actually output to the output shaft (crankshaft 43) is controlled.

  Further, the ECU 50 of the present embodiment functions as a “heat generation amount calculation device” and an “internal combustion engine control device” of the present invention, and is injected from the injector 40 by integrating the heat generation rate dQ / dθ for each crank angle θ. The total calorific value Q1 when all of the fuel burned is calculated, and the injection timing control process for controlling the injection timing based on the total calorific value Q1 is performed. Details of the injection timing control process will be described later with reference to a flowchart.

  The ECU 50 includes a CPU 51 for performing various calculations, a RAM 52 as a main memory for temporarily storing data and calculation results during the calculation, a ROM 53 as a program memory, and the like. In addition to the program, the ROM 53 stores various data used in the injection timing control process. FIG. 2 is a conceptual diagram showing the memory of the ROM 53. As shown in FIG. 2, the ROM 53 includes a combustion timing determination map memory 532, a section determination map memory 533, an FB amount calculation coefficient memory 534, and a volume memory 535 in addition to a program memory 531 that stores programs and the like. Is provided. Hereinafter, the memories 532 to 535 will be described.

  In the combustion timing determination map memory 532, the target MFB50 (target combustion) which is a target value of the crank angle θ at a combustion ratio of 50% of the total calorific value Q1 when all of the fuel injected from the injector 40 burns. A combustion timing determination map (not shown) for determining (timing) is stored. The target MFB 50 is determined in accordance with operating conditions determined by the engine speed and the fuel injection amount. That is, the combustion timing determination map is a map of the target MFB 50 determined in accordance with the engine speed and the fuel injection amount. The target MFB 50 is a parameter for realizing optimum combustion such as prevention of knocking, reduction of harmful exhaust gas, and improvement of output efficiency. Accordingly, if the actual value of the crank angle θ when the combustion ratio is 50% of the total calorific value Q1 is the actual MFB50 (actual combustion timing), the injection timing is controlled so that the actual MFB50 becomes the target MFB50. Therefore, it is possible to effectively prevent knocking, reduce harmful exhaust gas, increase output efficiency, and the like. Note that the reason why the target MFB 50 is determined in accordance with the operating conditions is that if the operating conditions are different, the combustion conditions are different, and the conditions for optimal combustion are different.

  In the section determination map memory 533, when the ECU 50 calculates the total heat generation amount Q1 by integrating the heat generation rate dQ / dθ, the section R (range) of the crank angle θ in which the heat generation rate dQ / dθ is integrated. A section determination map (not shown) for determination is stored. The section R is a necessary and sufficient section where the total calorific value Q1 when all the fuels are burned can be calculated. As described above, the section R is set as a necessary and sufficient section for calculating the total calorific value Q1 when all the fuels are combusted, so that the total calorific value Q1 when all the fuels are combusted can be calculated. This is to prevent the heat generation rate dQ / dθ after the fuel has been combusted from being accumulated more than necessary. The section R is determined for each operating condition determined by the fuel injection timing, the injection amount, and the like. This is because the fuel combustion start timing and combustion end timing differ depending on the operating conditions. Therefore, the section determination map is a map of the section R determined in accordance with the driving conditions.

  The FB amount calculation coefficient memory 534 stores an FB amount calculation coefficient for determining an FB amount that is a parameter for controlling the injection timing so that the actual MFB 50 becomes the target MFB 50. In this embodiment, the injection timing is controlled by feedback control. At this time, the amount of feedback indicates how much feedback should be performed. This amount of FB is a value determined according to operating conditions and the surrounding environment. For example, when it is desired to maintain the temperature of a certain device at 60 ° C. by feedback control, the amount of heat required for heating differs depending on whether the outside air temperature is 10 ° C. or 30 ° C. That is, the FB amount is different. The same can be said for engine control, and the required amount of FB varies depending on the operating conditions and the surrounding environment. Therefore, the FB amount calculation coefficient is a coefficient for calculating the FB amount according to the operating conditions and the surrounding environment.

  In this embodiment, PID control is adopted as feedback control. This PID control is a method in which an input value (injection timing) is performed by three elements: a deviation Error between an output value (actual MFB50) and a target value (target MFB50), its integration, and differentiation. More specifically, the PID control is a proportional operation that changes the input value in proportion to the deviation Error, an integration operation that changes the input value in proportion to the integral of the deviation Error, and an input value that is proportional to the derivative of the deviation Error. This is a control combined with a differential action to change the. The FB amount is determined from the proportional FB amount corresponding to the proportional operation, the integral FB amount corresponding to the integral operation, and the differential FB amount corresponding to the differential operation. The proportional FB amount is determined based on the deviation Error and the proportional gain Gp. The integral FB amount is determined based on the integral of the deviation Error and the integral gain Gi. The differential FB amount is determined based on the differential of the deviation Error and the differential gain Gd. The FB amount calculation coefficient is a proportional gain Gp, an integral gain Gi, and a differential gain Gd. These proportional gain Gp, integral gain Gi, and differential gain Gd are values that are determined so that the FB amount can be calculated according to the operating conditions and the surrounding environment. The reason why the PID control is employed is that the FB amount corresponding to the driving condition and the surrounding environment can be calculated without setting the FB amount calculating coefficient for each driving condition and the surrounding environment. .

  The volume memory 535 stores the volume V of the cylinder 16 (the volume of the combustion chamber 20) for each crank angle θ. FIG. 3 is a diagram showing the volume V for each crank angle θ. The crank angle θ at the top dead center TDC is set to “zero”, and the crank angle θ at the bottom dead center BDC is set to “180 °”. As shown in FIG. 3, the volume V becomes the smallest at the top dead center TDC, gradually increases as it approaches the bottom dead center BDC, and becomes the largest at the bottom dead center BDC. The volume V is symmetric with respect to the retard angle side ATDC and the advance angle side BTDC with respect to the top dead center TDC. That is, for example, the volume V at ATDC 50 ° is equal to the volume V at BTDC 50 °.

  Subsequently, the total heat generation amount Q1 when all of the fuel injected from the injector 40 burns is calculated by integrating the heat generation rates dQ / dθ for each crank angle θ, and based on the total heat generation amount Q1. An injection timing control process for controlling the injection timing will be described with reference to a flowchart. This injection timing control process is executed by the ECU 50. FIG. 4 is a flowchart showing a main routine of the injection timing control process. Note that the processing of the flowchart of FIG. 4 is executed at regular intervals while the engine is started.

  First, in step S10, a target combustion timing determination process for determining a target MFB50 according to the operating conditions is executed. FIG. 5 is a flowchart showing details of the target combustion timing determination process. Hereinafter, the target combustion timing determination process will be described in detail with reference to the flowchart of FIG.

  First, in step S111, the engine speed is acquired. The engine speed can be calculated based on how much the crank angle θ detected by the crank angle sensor 60 changes per unit time. That is, as the change per unit time of the crank angle θ increases, the engine speed increases. Step S111 is a process corresponding to the “rotation speed acquisition means” of the present invention.

  In the subsequent step S112, a command injection amount of fuel to be injected by the injector 40 is acquired. This command injection amount is determined based on the request from the user, the operating conditions, the ambient temperature based on the engine speed acquired in step S111 and the detected values of various sensors such as the air flow meter 74, the intake pressure sensor 68, and the intake air temperature sensor 70. This value is determined by the ECU 50 in consideration of the environment.

  The subsequent step S113 is a process corresponding to the “target combustion timing determining means” of the present invention. The target MFB 50 corresponding to the operating condition determined by the engine speed and the command injection amount is used for determining the combustion timing in FIG. It is determined from the combustion timing determination map stored in the map memory 532. Thereafter, the process of the flowchart of FIG. Thus, the reason why the target MFB 50 corresponding to the engine speed and the command injection amount is determined is to realize optimum combustion according to the engine speed and the command injection amount.

  Returning to the process of the flowchart of FIG. 4, after the process of step S10, a total calorific value calculation process for calculating the total calorific value Q1 when all the fuels are burned is executed in step S12. FIG. 6 is a flowchart showing details of the total calorific value calculation process. Details of the total heat generation calculation process will be described below with reference to the flowchart of FIG.

  First, in step S121, the crank angle θ is sequentially acquired based on the detection signal of the crank angle sensor 60. Step S121 is processing corresponding to “crank angle acquisition means” of the present invention.

  The subsequent step S123 is a process corresponding to the “in-cylinder pressure acquisition means” of the present invention. For each crank angle θ acquired in step S121, the in-cylinder pressure P detected by the in-cylinder pressure sensor 66 is acquired. The in-cylinder pressure P is stored in the RAM 52 in association with the corresponding crank angle θ. Note that an appropriate value is not always obtained as the in-cylinder pressure P detected by the in-cylinder pressure sensor 66. For example, an unnecessary offset error α may be superimposed on the true in-cylinder pressure P0 due to an external factor such as a temperature change, characteristic variation of the in-cylinder pressure sensor 66 itself, or a secular change. FIG. 11 is a diagram showing a waveform 1 of the in-cylinder pressure P stored in the RAM 52. FIG. 11 also shows a waveform 2 of the true in-cylinder pressure P0 for comparison with the waveform 1. As shown in FIG. 11, in the waveform 1 of the in-cylinder pressure P, an offset error α is superimposed on the waveform 2 of the true in-cylinder pressure P0.

  Here, as described above, the crank angle sensor 60 may output a top dead center signal due to an attachment error of the crank angle sensor 60 and the pulsar 42 even though it is not the top dead center TDC. In such a case, in step S121, a shift occurs in the crank angle θ detected with reference to the top dead center TDC. If the crank angle θ is deviated, the in-cylinder pressure P stored in association with the crank angle θ in step S123 is also deviated. As a result, the accuracy of the calculated heat generation rate dQ / dθ and the total calorific value Q1 is improved. Deteriorate. Therefore, in step S125, a top dead center position correction process is performed in which the top dead center TDC detected by the crank angle sensor 60 is corrected to a true top dead center TDC. FIG. 7 is a flowchart showing details of the top dead center position correction process. Hereinafter, the top dead center position correction process will be described in detail with reference to the flowchart of FIG.

  First, in step S31, the variable M indicating the average number of times is set to zero and stored in the RAM 52. Here, the top dead center TDC can be detected by paying attention to the change in the in-cylinder pressure P with respect to the crank angle θ. That is, the volume V changes as the crank angle θ changes, but the in-cylinder pressure P is considered to increase as the volume V decreases in a state where fuel is not injected. When the volume V is the smallest, that is, when the top dead center is TDC, the in-cylinder pressure P is considered to be the largest. In the state where fuel is injected, the in-cylinder pressure P may not become maximum even at the top dead center TDC due to the influence of combustion. Therefore, in order to detect the top dead center TDC from the in-cylinder pressure P, it is desirable to pay attention to the in-cylinder pressure P in a state where fuel is not injected.

  Therefore, in step S33, it is determined whether or not the fuel is not currently injected, that is, whether or not the fuel cut state. Since the fuel injection timing is determined by the ECU 50 itself, the ECU 50 can determine whether or not it is currently in a fuel cut state. At this time, if the fuel cut state is not established, the standby state is maintained until the fuel cut state is reached (S33: NO). In the case of the fuel cut state (S33: YES), the in-cylinder pressure detected by the in-cylinder pressure sensor 66 is acquired as the correction in-cylinder pressure for each crank angle θ in step S35 and stored in the RAM 52. Steps S33 and S35 are processes corresponding to the “correction in-cylinder pressure acquisition means” of the present invention. FIG. 8 is a diagram showing a correction in-cylinder pressure waveform 201 stored in the RAM 52. As shown in FIG. 8, the correction in-cylinder pressure waveform 201 has a peak 202 at the top dead center TDC. Therefore, when the crank angle θ corresponding to the true top dead center TDC is the top dead center angle θTDC, the crank angle θ corresponding to the peak 202 (maximum in-cylinder pressure) becomes the top dead center angle θTDC.

  Thus, in order to detect the top dead center angle θTDC, it is theoretically only necessary to read the crank angle θ corresponding to the peak 202, but actually, the cylinder pressure detected by the cylinder pressure sensor 66 is noise. It varies by the influence of etc. FIG. 9 is an enlarged view around the peak 202 of the waveform 201 (within the dotted line frame in FIG. 8). For reference, a waveform 203 of the in-cylinder pressure for correction when there is no influence of noise or the like is also shown. As shown in FIG. 9, it can be seen that the waveform 201 is not a clean waveform due to the influence of noise or the like. Therefore, the crank angle θx corresponding to the peak 202 of the waveform 201 is strictly equal to the true top dead center angle θTDC (the crank angle corresponding to the peak 204 of the correction cylinder pressure waveform 203 when there is no influence of noise or the like). Does not match. Therefore, in this embodiment, the average value θx_ave of the plurality of crank angles θx detected at different times is regarded as the top dead center angle θTDC. In FIG. 9, the top dead center position before correction detected by the crank angle sensor 60 is shown for reference.

  That is, in step S37, the peak 202 that is the maximum in-cylinder pressure is detected from the correction in-cylinder pressure waveform 201 (see FIG. 9) stored in the RAM 52. Step S37 is processing corresponding to “maximum point detecting means” of the present invention. Step S39 is processing corresponding to the “top dead center angle obtaining unit” of the present invention, and the crank angle θx corresponding to the peak 202 is stored in the RAM 52. In subsequent step S41, 1 is added to the variable M indicating the average number of times stored in the RAM 52 in step S31. In a succeeding step S43, it is determined whether or not the variable M indicating the average number is equal to or more than a predetermined specified number N. The prescribed number N is the number of crank angles θx for calculating the average value θx_ave. Therefore, it is considered that the larger the specified number N, the closer the calculated average value θx_ave is to the true top dead center angle θTDC with the influence of noise and the like being suppressed. However, if the specified number N is too large, calculation of the average value θx_ave increases the calculation load or takes time. Therefore, the specified number N is determined in consideration of the accuracy of the calculated average value θx_ave, the calculation load, and the like.

  In step S43, when the variable M indicating the average number has not yet reached the specified number N (S43: NO), the process returns to step S33. Thereafter, the in-cylinder pressure for correction is acquired again in the fuel cut state (S35), and the crank angle θx corresponding to the maximum in-cylinder pressure is accumulated and stored in the RAM 52 based on the in-cylinder pressure for correction (S39). If the number (variable M) of the crank angle θx stored in the RAM 52 is equal to or greater than the specified number N (S43: YES), the average crank angle θx stored in the RAM 52 is determined in step S45. The value θx_ave is calculated. Here, FIG. 10 is a diagram showing the change over time of the crank angle θx that is the maximum in-cylinder pressure. Thus, the in-cylinder pressure detected by the in-cylinder pressure sensor 66 changes over time due to the influence of noise and the like, and accordingly, the crank angle θx also changes over time. FIG. 10 also shows a distribution curve 210 showing the distribution of the crank angle θx. The calculation of the average value θx_ave by the above-described steps S31 to S45 is the same as the calculation of the crank angle θx corresponding to the peak of the distribution curve 210.

  In step S47, the top dead center position is set when the crank angle θ is the average value θx_ave. Accordingly, the crank angle θ acquired in step S121 in FIG. 6 has the average value θx_ave as the top dead center TDC, the delay angle ATDC of the top dead center TDC is a positive angle, and the advance angle BTDC is a negative angle. It is corrected as follows. Then, the process of the flowchart of FIG. Steps S45 and S47 are processes corresponding to “correction means” of the present invention. Steps S31 to S43 are processes corresponding to “top dead center detecting means” of the present invention.

  Returning to the process of the flowchart of FIG. 6, after the top dead center position correction process of step S <b> 125 is executed, the volume memory 535 of FIG. 2 is obtained in step S <b> 127 which is a process corresponding to the “volume acquisition unit” of the present invention. The volume V (see FIG. 3) for each crank angle θ stored in is read out.

Step S129 is a process corresponding to the “heat generation rate calculating means” of the present invention. The heat generation rate dQ / per unit angle of the crank angle θ is calculated for each crank angle θ by the following equation (3). dθ is calculated and stored in the RAM 52.

  In addition, Formula 3 is described in many documents such as Patent Document 1 and is considered to be a highly reliable formula for calculating the heat generation rate (dQ / dθ). In Equation 3, κ is the specific heat ratio, dV / dθ is the rate of change of volume V per unit angle of crank angle θ (volume change rate), and dP / dθ is the in-cylinder pressure per unit angle of crank angle θ. This is the change rate of P (in-cylinder pressure change rate). The volume change rate dV / dθ can be calculated based on the volume V (see FIG. 3) for each crank angle θ read out in step S127. The in-cylinder pressure change rate dP / dθ can be calculated based on the in-cylinder pressure P (see FIG. 11) for each crank angle θ acquired and stored in step S123. In this way, the heat generation rate dQ / dθ can be calculated by substituting the in-cylinder pressure P, the volume V, the volume change rate dV / dθ, and the in-cylinder pressure change rate dP / dθ into Equation 3. However, as described above, when the offset error α is superimposed on the in-cylinder pressure P, an error occurs in the calculated heat generation rate dQ / dθ.

  FIG. 12 is a diagram showing a waveform 3 of the heat generation rate dQ / dθ for each crank angle θ. For reference, FIG. 12 also shows a waveform 4 of the heat generation rate dQ / dθ when the offset error α is not superimposed on the in-cylinder pressure P. The heat generation rate dQ / dθ (waveform 4) when the offset error α is not superimposed on the in-cylinder pressure P is substantially zero at the advance side BTDC of the top dead center TDC. Then, it changes rapidly in the vicinity of the top dead center TDC of the retarded side ATDC, and becomes smaller when the retarded side ATDC is reached. Thus, the reason why the heat generation rate dQ / dθ is substantially zero at the advance side BTDC is that fuel combustion has not yet started at the advance side BTDC. Further, the reason why the heat generation rate dQ / dθ changes rapidly in the vicinity of the top dead center TDC of the retarded ATDC is that fuel is burned in that vicinity. After that, the crank angle has advanced and the heat generation rate dQ / dθ has a small value because most of the combustion of fuel has been completed.

  On the other hand, the heat generation rate dQ / dθ (waveform 3) in the case where the offset error α is superimposed on the in-cylinder pressure P becomes zero on the advance side BTDC even though fuel combustion has not yet started. Not. Further, in the vicinity of the top dead center TDC of the retard angle side ATDC, it is approximated to the waveform 4, but the heat generation rate dQ / dθ is achieved even though the crank angle has advanced and most of the combustion of the fuel has been completed. Takes a value above a certain level. That is, comparing the waveform 3 and the waveform 4, it can be seen that when the offset error α is superimposed on the in-cylinder pressure P, an error is generated in the heat generation rate dQ / dθ.

  In general, the total calorific value Q1 can be calculated by accumulating the heat generation rate dQ / dθ in the section where the fuel is combusted. If there is an error in the heat generation rate dQ / dθ, the heat generation rate The total calorific value Q1 calculated based on dQ / dθ also causes an error. For example, if fuel combustion is started at the top dead center angle θTDC corresponding to the top dead center TDC, the total calorific value Q of the fuel that has generated heat up to a certain crank angle θ is the heat in the section [θTDC, θ]. It can be calculated by accumulating the incidence dQ / dθ. FIG. 13 shows the integration of the heat generation rate dQ / dθ (waveform 3 in FIG. 12) in the section [θTDC, θ] when the offset error α is superimposed on the in-cylinder pressure P when the crank angle θ is a variable. It is the figure which showed the waveform 5 of the total calorific value Q computed in this way. In FIG. 13, the heat generation rate dQ / dθ (waveform 4 in FIG. 12) when the offset error α is not superimposed on the in-cylinder pressure P when the crank angle θ is a variable is shown in section [θTDC, θ]. The waveform 6 of the total calorific value Q calculated by integrating with is also shown. As shown in FIG. 13, when comparing the waveform 5 and the waveform 6, the larger the crank angle θ, the larger the error of the total calorific value Q (waveform 5) when the offset error α is superimposed on the in-cylinder pressure P. Become. This is because as the crank angle θ increases, the heat generation rate dQ / dθ including an error increases. Therefore, in order to calculate the total calorific value Q1 when all the fuels are combusted, the crank angle θ must be determined to be large to some extent, but as described above, if the crank angle θ is increased, an error in the total calorific value Q1. Becomes larger. Therefore, the calorific value calculation device of the present invention aims to solve this problem. Hereinafter, how this problem is solved will be described.

First, the error F of the heat generation rate dQ / dθ when the error α is included in the in-cylinder pressure P will be examined. When the true in-cylinder pressure is P0, the relationship P = P0 + α is established. It is assumed that the offset error α is the same value for any in-cylinder pressure P. Substituting this P = P0 + α into Equation 3, the following Equation 4 is derived.

  Κ / (κ−1) × α (dV / dθ) on the right side in Equation 4 is the error F of the heat release rate (dQ / dθ). The value excluding the error F in the equation 4 is the heat generation rate dQ / dθ with respect to the true in-cylinder pressure P0. FIG. 14 is a diagram showing a waveform 3 of the heat generation rate dQ / dθ, a waveform 4 of the heat generation rate dQ / dθ with respect to the true in-cylinder pressure P0, and a waveform 7 of the error F. From Equation 4, the heat generation rate dQ / dθ is the sum of the heat generation rate dQ / dθ and the error F with respect to the true in-cylinder pressure P0, so that the waveform 3 is decomposed into the waveform 4 and the waveform 7. Can do.

  Here, the error F represented by κ / (κ−1) × α (dV / dθ) is a function with the volume change rate dV / dθ as a variable. The volume change rate (dV / dθ) is a symmetric value in which the positive and negative are opposite with respect to the top dead center TDC. Therefore, the error F is also opposite in positive and negative with respect to the top dead center TDC. It becomes a symmetrical value. For example, when the error F at 50 ° after top dead center (ATDC 50 °) is F50, the error F at 50 ° before top dead center (BTDC 50 °) is (−F50). That is, the waveform 7 of the error F in FIG. 14 has a symmetrical shape in which the positive and negative are opposite with respect to the top dead center TDC.

  Therefore, if the section R (range) of the crank angle θ for integrating the heat generation rate dQ / dθ is made equal between the retard side ATDC and the advance side BTDC around the top dead center TDC, the heat generation rate dQ / dθ. The influence of the error F can be canceled. Therefore, in step S131, the section R of the crank angle θ for integrating the heat release rate dQ / dθ is determined by the section determination map stored in the section determination map memory 533 shown in FIG. At this time, the section R is determined so that the retard angle side ATDC and the advance angle side BTDC are equal with respect to the top dead center TDC. Further, according to the operating conditions determined by the engine speed, the fuel injection timing, the injection amount, etc., the section R is set so as to be a necessary and sufficient section in which the total calorific value Q1 when all the fuel is burned can be calculated. decide. As described above, the section R is set as a necessary and sufficient section for calculating the total calorific value Q1 when all the fuels are combusted, so that the total calorific value Q1 when all the fuels are combusted can be calculated. This is to prevent the heat generation rate dQ / dθ after the fuel has been combusted from being accumulated more than necessary. Step S131 is a process corresponding to the “section determining means” of the present invention.

  Therefore, when the crank angle θ when combustion of all fuels is completed is B and the specific crank angle B before the top dead center is −B, the section R determined in step S131 is [−B, B ].

  Step S133 is processing corresponding to the “accumulating means” of the present invention, and the heat generation rate dQ / dθ (waveform 3) shown in FIGS. 12 and 14 is determined in the section [−B, B] determined in step S131. Accumulate with. FIG. 15 shows a waveform 8 of the total calorific value Q calculated by integrating the heat generation rate dQ / dθ (waveform 3) shown in FIGS. 12 and 14 in the section [−B, θ] with the crank angle θ as a variable. FIG. FIG. 15 also shows the total heat generation amount Q calculated by integrating the heat generation rate dQ / dθ (waveform 3 in FIG. 12) in the section [θTDC, B] when the offset error α is superimposed on the in-cylinder pressure P. Waveform 5 is shown. Further, in FIG. 15, the total heat generation amount Q calculated by integrating the heat generation rate dQ / dθ (waveform 4 in FIG. 12) in the section [θTDC, B] when the offset error α is not superimposed on the in-cylinder pressure P. The waveform 6 is also shown.

  As shown in FIG. 15, the total calorific value Q (waveform 8) calculated by integrating the heat generation rate dQ / dθ in the interval [−B, θ] is a negative value in the range where θ is on the advance side BTDC. It has become. As the angle θ approaches the top dead center angle θTDC, the negative value increases. This is because the value of the heat generation rate dQ / dθ (waveform 3) is negative when θ is in the advance side BTDC (see FIGS. 12 and 14). On the other hand, in the range where θ is retarded ATDC, the value of the heat generation rate dQ / dθ (waveform 3) is positive (see FIGS. 12 and 14), so the total calorific value Q (waveform 8) is also cranked. It gradually increases as the corner advances. When θ is B, the total heat generation amount Q (waveform 8) coincides with the total heat generation amount Q1 (waveform 6) when the offset error α is not superimposed on the in-cylinder pressure P. That is, by integrating the heat generation rate dQ / dθ in the interval [−B, B], it is possible to calculate the total calorific value Q1 with high accuracy without the influence of the offset error α. Note that the total calorific value Q (waveform 5) calculated by integrating the heat generation rate dQ / dθ in the section [θTDC, B] includes an error as described above.

  Here, the heat generation rate dQ / dθ (waveform 3 in FIG. 14) is, as described above, the heat generation rate dQ / dθ (waveform 4 in FIG. 14) and the error F (waveform in FIG. 14) with respect to the true in-cylinder pressure P0. 7). Therefore, the value obtained by integrating the heat generation rate dQ / dθ (waveform 3 in FIG. 14) in the interval [−B, B] is the value of the heat generation rate dQ / dθ (waveform 4 in FIG. 14) with respect to the true in-cylinder pressure P0. It is a value obtained by adding the value accumulated in [−B, B] and the value accumulated in the section [−B, B] of the error F (waveform 7 in FIG. 14). As described above, the error F is a value in which the sign is symmetric about the top dead center TDC. Therefore, the error F (waveform 7 in FIG. 14) is integrated in the section [−B, B]. The value is zero. Therefore, integrating the heat release rate dQ / dθ (waveform 3 in FIG. 14) in the interval [−B, B] is to add the heat release rate dQ / dθ (waveform 4 in FIG. 14) to the true in-cylinder pressure P0. This is synonymous with [-B, B]. The heat generation rate dQ / dθ with respect to the true in-cylinder pressure P0 is considered to be zero until the start of fuel combustion. Therefore, even if the interval [−B, B] to be integrated includes the interval before the start of fuel combustion, the zero heat generation rate dQ / dθ is integrated in that interval, so the total heat generation It does not affect the calculation of the quantity Q1. Therefore, it is possible to calculate the total calorific value Q1 of the fuel that has generated heat up to the specific crank angle B while canceling the influence of the offset error α.

  After calculating the total heat generation amount Q1 in step S135, the total heat generation amount calculation process shown in FIG. 6 ends. Returning to the processing of the flowchart of FIG. 4, in step S14, the actual MFB 50, which is the crank angle θ when the combustion ratio is 50% of the total calorific value Q1, is detected. Step S14 is a process corresponding to the “actual combustion timing detecting means” of the present invention. FIG. 16 is a diagram for explaining a method of detecting the actual MFB 50. FIG. 16 shows the heat generation rate dQ / dθ (waveform 3 in FIG. 12) when the offset error α is superimposed on the in-cylinder pressure P when the crank angle θ is a variable in the section [θTDC, θ]. A waveform 5 of the total calorific value Q calculated by integration is shown. FIG. 13 shows the heat generation rate dQ / dθ (waveform 4 in FIG. 12) when the offset angle α is not superimposed on the in-cylinder pressure P when the crank angle θ is a variable in the section [θTDC, θ]. A waveform 6 of the total calorific value Q calculated by integration is also shown.

  A point 150 of the waveform 6 corresponding to the specific crank angle B indicates the total calorific value Q1. A point 151 of the waveform 6 corresponding to a half height of the point 150 indicates a combustion ratio of 50% of the total calorific value Q1. Therefore, although the crank angle θ corresponding to the point 151 of the waveform 6 is the actual MFB 50, it is assumed that there is an offset error α in the in-cylinder pressure P, and the waveform 6 is not actually detected. It becomes.

  Here, when the waveform 5 and the waveform 6 in FIG. 16 are compared, the waveform 5 and the waveform 6 are approximate in the vicinity of the top dead center TDC. The real MFB 50 is generally considered to be near the top dead center TDC. That is, the point 151 of the waveform 6 can be regarded as a point on the waveform 5. Therefore, in step S14, a point 151 of the waveform 5 corresponding to a half height of the point 150 indicating the total calorific value Q1 calculated in step S12 is detected. The waveform 5 indicates the total heat generation amount Q calculated by integrating the heat generation rate dQ / dθ in the section [θTDC, B], and therefore the heat generation rate dQ / dθ is integrated in the section [θTDC, B]. Then, the waveform 5 is calculated.

  Then, the crank angle θ corresponding to the point 151 of the waveform 5 is read as the actual MFB 50. In the present embodiment, the injection timing is feedback-controlled so that the actual MFB 50 becomes the target MFB 50. Then, in order to determine the amount of feedback indicating how much feedback should be made, in step S16, the deviation Error (target MFB50-actual) between the target MFB50 determined in step S10 and the actual MFB50 detected in step S14. MFB50) is calculated.

In the subsequent step S18, the deviation Error is substituted into the following equation (5) to determine the FB amount that is a parameter for controlling the injection timing so that the actual MFB50 becomes the target MFB50.

  Formula 5 is a formula for calculating the FB amount in PID control. This PID control is a method in which an input value (injection timing) is performed by three elements: a deviation Error between an output value (actual MFB50) and a target value (target MFB50), its integration, and differentiation. More specifically, the PID control is a proportional operation that changes the input value in proportion to the deviation Error, an integration operation that changes the input value in proportion to the integral of the deviation Error, and an input value that is proportional to the derivative of the deviation Error. This is a control combined with a differential action to change the. The FB amount is determined from the proportional FB amount corresponding to the proportional operation, the integral FB amount corresponding to the integral operation, and the differential FB amount corresponding to the differential operation. The proportional FB amount is determined based on the deviation Error and the proportional gain Gp. The integral FB amount is determined based on the integral of the deviation Error and the integral gain Gi. The differential FB amount is determined based on the differential of the deviation Error and the differential gain Gd. These proportional gain Gp, integral gain Gi, and differential gain Gd are adaptive values determined so that the FB amount can be calculated according to the operating conditions and the surrounding environment, and are stored in the FB amount calculating coefficient memory 534 shown in FIG. Stored in advance.

  In the subsequent step S20, the fuel injection timing is retarded or advanced based on the FB amount determined in step S18, and the main routine of the injection timing control process of FIG. 4 is ended. Thereby, since it controls so that real MFB50 may become target MFB50, optimal combustion according to operating conditions is realizable.

  As described above, according to the engine control system of the present embodiment, it is possible to calculate the total calorific value Q1 when all the fuel is burned while canceling the influence of the offset error α included in the in-cylinder pressure P. .

  Further, the interval [−B, B] in which the heat generation rate dQ / dθ is integrated is determined to be a necessary and sufficient interval in which the total calorific value Q1 when all the fuels are burned can be calculated. That is, the section [-B, B] includes a section from the start of fuel combustion until all the fuel is combusted. Therefore, the total calorific value Q1 when all the fuels are combusted can be calculated. The section [-B, B] is a necessary and sufficient section for calculating the total calorific value Q1 when all the fuels are combusted. Therefore, in order to calculate the total calorific value Q1, the heat generation rate dQ / dθ. When the fuel is accumulated, the heat generation rate dQ / dθ after the combustion of the fuel is not accumulated more than necessary. Therefore, calculation load can be reduced.

  Further, the crank angle θ acquired in step S121 of FIG. 6 is corrected to an angle based on the true top dead center TDC. That is, it can be said that the angle is accurate. Therefore, it can be said that the heat generation rate dQ / dθ and the total calorific value Q1 calculated in correspondence with the crank angle θ are high in accuracy.

  Further, according to the engine control system of this embodiment, since the injection timing is controlled so that the actual MFB 50 becomes the target MFB 50, it is possible to prevent knocking, reduce harmful exhaust gas, increase the efficiency of output, and the like. . At this time, the actual MFB 50 is detected based on the total calorific value Q1, and the total calorific value Q1 can be said to be an accurate value even when the in-cylinder pressure P includes the offset error α. Therefore, the real MFB 50 with high accuracy can be detected. Therefore, the fuel combustion timing can be accurately controlled.

  Further, since the target MFB 50 is determined according to the engine operating condition determined by the engine speed and the fuel injection amount, the fuel combustion can be appropriately controlled according to the engine operating condition.

Further, since the injection timing is controlled by the PID control so that the actual MFB 50 becomes the target MFB 50, the fuel combustion timing can be appropriately controlled even if the environment such as the ambient temperature changes.
(Second embodiment)

  Next, a second embodiment of the present invention will be described with reference to the drawings. This second embodiment is an embodiment that embodies the calorific value calculation device and injector abnormality detection device of the present invention. In the engine control system of the present embodiment, when the fuel of the command injection amount S is injected from the injector, the total heat generation amount of the fuel is set to the planned total heat generation amount Q2. Is calculated. Then, the actual total calorific value Q1 of the actual fuel calculated by the same method as in the first embodiment is compared with the planned total calorific value Q2, and it is determined whether the fuel corresponding to the command injection amount S is actually injected from the injector. is doing. When it is determined that fuel equivalent to the command injection amount S is not injected, an abnormality of the injector is output. Hereinafter, the engine control system of the present embodiment will be described focusing on differences from the first embodiment.

  First, the configuration of the engine control system of this embodiment will be described. The engine control system of this embodiment has the same configuration as that of the first embodiment shown in FIG. However, the contents of data stored in the ROM 53 and the processing executed by the ECU 50 are different from those in the first embodiment. The other elements are the same.

  FIG. 17 is a conceptual diagram showing the memory of the ROM 53 of this embodiment. In addition, the same code | symbol is attached | subjected to the memory same as 1st embodiment. As shown in FIG. 17, the ROM 53 of this embodiment has a program memory 531, a combustion timing determination map memory 532, a section determination map memory 533, an FB amount calculation coefficient memory 534, a volume memory 535, and a correction coefficient memory 536. In addition, a reference value memory 537 is provided. The program memory 531, the combustion timing determination map memory 532, the section determination map memory 533, the FB amount calculation coefficient memory 534, and the volume memory 535 store the same data as in the first embodiment.

  The correction coefficient memory 536 stores a correction coefficient H used when calculating the planned total heat generation amount Q2. The planned total heat generation amount Q2 depends on how much the fuel of the command injection amount S changes to heat. And how much it changes to heat differs depending on the operating conditions determined by the engine speed and the command injection amount S. The correction coefficient H is a coefficient indicating how much the fuel of the command injection amount S changes to heat, and is determined as an appropriate value for each operating condition.

  In the reference value memory 537, when the fuel is burned under the operating conditions determined by the engine speed and the command injection amount S, the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure are generally stored. Each reference value is stored as a possible value. That is, the reference value memory 537 stores a reference value for each operating condition.

  The ECU 50 of this embodiment functions as the “heat generation amount calculation device” and “injector abnormality detection device” of the present invention, and executes an abnormality detection process for detecting an abnormality of the injector 40. Hereinafter, the abnormality detection process will be described. FIG. 18 is a flowchart showing a main routine of the abnormality detection process. Note that the processing in the flowchart of FIG. 18 is executed at regular intervals while the engine is started. Also, the same processes as those in the first embodiment are denoted by the same reference numerals.

  First, in step S12, a total calorific value Q1 when all the fuel is burned is calculated by the same method as in the first embodiment. The subsequent step S71 is a process corresponding to the “command injection amount acquisition means” of the present invention, and acquires the command injection amount S of the fuel to be injected by the injector 40. This command injection amount S is based on the engine speed, detection values of various sensors such as the air flow meter 74, the intake pressure sensor 68, the intake air temperature sensor 70, and the like, taking into account user requests, operating conditions, and the surrounding environment. The value determined by the ECU 50 itself.

  The subsequent step S73 is a process corresponding to the “scheduled total heat generation amount calculation means” of the present invention, and executes a scheduled total heat generation amount calculation process for calculating the planned total heat generation amount Q2 from the command injection amount S. FIG. 19 is a flowchart showing details of the scheduled total heat generation calculation process. Details of the scheduled total heat generation calculation process will be described below.

  First, in step S91, the correction coefficient H corresponding to the engine speed and the command injection amount S is read from the correction coefficient map memory 536 shown in FIG. In subsequent step S93, a reference value corresponding to the engine speed and the command injection amount S is read from the reference value memory 537 shown in FIG.

  In the subsequent step S95, information that affects the calculation of the planned total heat generation amount Q2 is acquired from various sensors. Specifically, the intake air amount is acquired from the air flow meter 74. It can be said that the intake air amount is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the amount of intake increases, the amount of oxygen / oxygen concentration sucked into the cylinder increases, so that the fuel easily burns. On the other hand, as the amount of intake decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration decreases, the fuel becomes difficult to burn. Therefore, it can be said that the intake air amount is information that affects the calculation of the planned total heat generation amount Q2.

  In step S95, the intake pressure is acquired from the intake pressure sensor 68. It can be said that the intake pressure is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the intake pressure increases, the amount of oxygen sucked into the cylinder / oxygen concentration increases, so that the fuel easily burns. On the other hand, as the intake pressure decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration decreases, the fuel becomes difficult to burn. Therefore, it can be said that the intake pressure is information that affects the calculation of the planned total calorific value Q2.

  In step S95, the oxygen concentration in the exhaust gas is acquired from the A / F sensor 76 for adjusting the valve opening degree of the EGR valve 91. Then, the EGR rate is calculated from the oxygen concentration. It can be said that the EGR rate is a value reflecting the oxygen amount / oxygen concentration sucked into the cylinder. That is, as the EGR rate increases, the amount of oxygen sucked into the cylinder / oxygen concentration decreases, so that it becomes difficult for the fuel to combust. On the other hand, as the EGR rate decreases, the amount of oxygen sucked into the cylinder / Since the oxygen concentration increases, the fuel becomes easy to burn. Therefore, it can be said that the EGR rate is information that affects the calculation of the planned total heat generation amount Q2.

  In step S95, the intake air temperature is acquired from the intake air temperature sensor. It can be said that the intake air temperature is a value reflecting the in-cylinder temperature. That is, as the intake air temperature increases, the in-cylinder temperature increases, so the fuel easily burns. On the other hand, as the intake air temperature decreases, the in-cylinder temperature decreases, so the fuel becomes difficult to burn. Therefore, it can be said that the intake air temperature is information that affects the calculation of the planned total heat generation amount Q2.

  In step S95, the engine water temperature is acquired from the water temperature sensor 72. It can be said that the engine water temperature reflects the in-cylinder temperature. That is, as the engine water temperature increases, the in-cylinder temperature increases so that the fuel easily burns. On the other hand, as the engine water temperature decreases, the in-cylinder temperature decreases, so that the fuel becomes difficult to burn. Therefore, it can be said that the engine water temperature is information that affects the calculation of the planned total calorific value Q2.

  In step S95, the common rail pressure indicating the pressure in the common rail 36 is acquired from the common rail pressure sensor 64. Common rail pressure is related to fuel diffusion and volatilization. As the fuel is more easily diffused and volatilized, the fuel and air are more easily mixed, and as a result, the fuel is easily burned. On the contrary, the more difficult the fuel is to diffuse and volatilize, the more difficult it is to mix the fuel and the air, and as a result, the fuel becomes difficult to burn. Therefore, it can be said that the common rail pressure is information that affects the calculation of the planned total heat generation amount Q2.

  In the following step S97, the reference value acquired in step S93 is compared with the intake air amount, intake pressure, EGR rate, intake air temperature, engine water temperature and common rail pressure acquired in step S95, and the actual operating conditions and environmental conditions are determined. The correction coefficient H is corrected so that the reflected correction coefficient H is obtained. Specifically, when the intake air amount acquired in step S95 is larger than the reference value, the correction coefficient H is increased because the fuel is likely to burn. On the other hand, if the intake air amount acquired in step S95 is smaller than the reference value, the correction coefficient H is made smaller because the fuel is difficult to burn. Then, the correction coefficient H corrected based on the intake air amount is stored in the RAM 52 as the correction coefficient H1. The relationship between the intake air amount and the combustion of fuel can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. Then, how much the correction coefficient H is increased or decreased from the actual intake air amount can be determined based on the relationship.

  In step S97, if the intake pressure acquired in step S95 is larger than the reference value, the correction coefficient H is increased because the fuel is likely to burn. On the other hand, if the intake pressure acquired in step S95 is smaller than the reference value, the correction coefficient H is decreased because it is difficult for the fuel to burn. Then, the correction coefficient H corrected based on the intake pressure is stored in the RAM 52 as the correction coefficient H2. The relationship between intake pressure and fuel combustion can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. The extent to which the correction coefficient H is increased or decreased from the actual intake pressure can be determined based on the relationship.

  In step S97, if the EGR rate acquired in step S95 is larger than the reference value, the correction coefficient H is decreased because it is difficult for the fuel to burn. On the other hand, if the EGR rate acquired in step S95 is smaller than the reference value, the correction coefficient H is increased because the fuel is likely to burn. Then, the correction coefficient H corrected based on the EGR rate is stored in the RAM 52 as the correction coefficient H3. The relationship between the EGR rate and the combustion of fuel can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. The extent to which the correction coefficient H is increased or decreased from the actual EGR rate can be determined based on the relationship.

  In step S97, if the intake air temperature acquired in step S95 is larger than the reference value, the correction coefficient H is increased because the fuel is likely to burn. On the other hand, if the intake air temperature acquired in step S95 is smaller than the reference value, the correction coefficient H is decreased because it is difficult for the fuel to burn. Then, the correction coefficient H corrected based on the intake air temperature is stored in the RAM 52 as the correction coefficient H4. The relationship between the intake air temperature and the combustion of fuel can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. The extent to which the correction coefficient H is increased or decreased from the actual intake air temperature can be determined based on the relationship.

  In step S97, if the engine water temperature acquired in step S95 is larger than the reference value, the correction coefficient H is increased because the fuel is likely to burn. On the other hand, when the engine water temperature acquired in step S95 is smaller than the reference value, the correction coefficient H is decreased because the fuel is difficult to burn. Then, the correction coefficient H corrected based on the engine water temperature is stored in the RAM 52 as the correction coefficient H5. The relationship between the engine water temperature and the combustion of fuel can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. The extent to which the correction coefficient H is increased or decreased from the actual engine water temperature can be determined based on the relationship.

  In step S97, if the common rail pressure acquired in step S95 is larger than the reference value, the correction coefficient H is increased because the fuel is likely to burn. On the other hand, when the common rail pressure acquired in step S95 is smaller than the reference value, the correction coefficient H is decreased because it is difficult for the fuel to burn. Then, the correction coefficient H corrected based on the common rail pressure is stored in the RAM 52 as the correction coefficient H6. The relationship between the common rail pressure and fuel combustion can be obtained theoretically or empirically, and the relationship is stored in the ROM 53 in advance. The extent to which the correction coefficient H is increased or decreased from the actual common rail pressure can be determined based on the relationship.

  In step S97, the correction coefficients H1 to H6 stored in the RAM 52 are read out, and the average value thereof is used as the corrected correction coefficient H. Thus, the correction coefficient H reflects all of the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure.

なお、数６式中のＤは燃料密度、Ｋは燃料のエネルギー密度であり、それぞれ予め定められている値である。すなわち、指令噴射量Ｓと燃料密度Ｄと燃料のエネルギー密度Ｋと運転条件に応じた補正係数Ｈとを乗算することによって、予定総発熱量Ｑ２を算出する。その後、図１９のフローチャートの処理を終了する。 In the subsequent step S99, the planned total heat generation amount Q2 is calculated by the following equation (6).

In Equation 6, D is the fuel density and K is the energy density of the fuel, which are predetermined values. That is, the scheduled total heat generation amount Q2 is calculated by multiplying the command injection amount S, the fuel density D, the energy density K of the fuel, and the correction coefficient H according to the operating conditions. Then, the process of the flowchart of FIG.

  Returning to the processing of the flowchart of FIG. 18, in step S75, the planned total heat generation amount Q2 is compared with the actual total heat generation amount Q1, and it is determined whether or not the planned total heat generation amount Q2 is equivalent to the total heat generation amount Q1. By determining, it is determined whether or not the injector 40 is abnormal. For example, whether or not the planned total heat generation amount Q2 is equivalent to the total heat generation amount Q1 is determined based on whether or not the difference between the planned total heat generation amount Q2 and the total heat generation amount Q1 is equal to or less than a predetermined value. Step S75 is a process corresponding to the “abnormality judging means” of the present invention.

  If it is determined that the injector 40 is abnormal (S75: YES), in step S77, the user is notified that the injector 40 is abnormal by a not-shown alarm device (for example, a light emitting diode or a speaker). Then, the process of the flowchart of FIG. 18 is complete | finished. As a result, the user can grasp the abnormality of the injector 40 and can repair it. On the other hand, when it is determined that there is no abnormality in the injector 40 (S75: NO), the process of the flowchart of FIG.

  As described above, according to the engine control system of the present embodiment, the actual total heat generation amount Q1 is compared with the planned total heat generation amount Q2 of the fuel calculated from the command injection amount S, and the abnormality of the injector 40 is detected. Is detected. At this time, it can be said that the actual total calorific value Q1 is an accurate value even when the in-cylinder pressure P includes the offset error α. That is, even when the in-cylinder pressure P includes the offset error α, the abnormality of the injector 40 can be accurately detected.

  The planned total heat generation amount Q2 is calculated by multiplying the command injection amount S, the fuel density D, the energy density K of the fuel, and the correction coefficient H according to the operating conditions. Therefore, it can be said that the planned total calorific value Q2 reflects the type of fuel and operating conditions. Furthermore, since the correction coefficient H is a value based on the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure, the planned total heat generation amount Q2 can be calculated with higher accuracy.

  The calorific value calculation device, the internal combustion engine control device, and the injector abnormality detection device according to the present invention are not limited to the above-described embodiments, and can be modified within the scope of the invention. For example, in the first and second embodiments, the engine 10 to be controlled is a diesel engine, but a gasoline engine may be the control target. In this case, in the first embodiment, the fuel ignition timing is controlled instead of the fuel injection timing.

  In the second embodiment, the average value of the correction coefficients H1 to H6 of the intake air amount, the intake pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure is used as the corrected correction coefficient H. In this case, when the magnitudes of the correction coefficients H1 to H6 vary, the large correction coefficients H1 to H6 and the small correction coefficients H1 to H6 are averaged. Therefore, among the correction coefficients H1 to H6, the maximum correction coefficient H1 to H6 or the minimum correction coefficient H1 to H6 may be used as the corrected correction coefficient H. As a result, the planned total heat generation amount Q2 can be calculated with the most contributing information among the intake air amount, the intake air pressure, the EGR rate, the intake air temperature, the engine water temperature, and the common rail pressure.

  Moreover, in said 1st embodiment, the combustion time used as 50% of the total calorific value Q1 was controlled. This is because it is possible to effectively prevent knocking, reduce harmful exhaust gas, increase output efficiency, and the like. However, it is not limited only to the combustion time when it becomes 50% of the total calorific value Q1, as long as it can effectively prevent knocking, reduce harmful exhaust gas, increase the efficiency of output, etc. Any combustion timing (for example, combustion timing in the range of 10% to 90% of the total calorific value Q1) may be controlled.

  In the first embodiment, the combustion timing is controlled by PID control. However, the present invention is not limited to this. Moreover, in the said embodiment, although the heat release rate was calculated by several 3 Formula, it is not necessarily limited to this.

10 Engine (Internal combustion engine)
DESCRIPTION OF SYMBOLS 15 Cylinder 16 Piston 18 Crank 36 Common rail 40 Injector 50 ECU (The emitted-heat amount calculation apparatus, the control apparatus of an internal combustion engine, the abnormality detection apparatus of an injector)
66 In-cylinder pressure sensor 60 Crank angle sensor 64 Common rail pressure sensor 68 Intake pressure sensor 70 Intake temperature sensor 72 Engine water temperature sensor 74 Air flow meter 76 A / F sensor 91 EGR valve Q1 Total heat generation P In-cylinder pressure P0 True in-cylinder pressure α Offset error θ Crank angle B Specific crank angle TDC Top dead center Q2 Expected total heating value S Command injection amount D Fuel density K Fuel energy density H Correction factor S121 Crank angle acquisition means S123 In-cylinder pressure acquisition means S127 Volume acquisition means S129 Heat generation rate calculation Means S131 Section determination means S133 Accumulation means S33, S35 Correction cylinder pressure acquisition means S37 Maximum point detection means S39 Top dead center angle acquisition means S31-S43 Top dead center detection means S45, S47 Correction means S14 Actual combustion timing detection means S16- S20 When burning Control means S111 rotational speed acquiring unit S113 the target combustion timing determining means S71 command injection quantity acquiring means S73 estimated gross calorific value calculation means S75 abnormality determination means

Claims (10)

In an internal combustion engine having a cylinder, a piston, and a crank, the total amount of fuel that has generated heat until the crank angle θ, which is the rotation angle of the crank with respect to the top dead center TDC, reaches a specific crank angle B after the top dead center. A calorific value calculation device for calculating a calorific value Q1,
Crank angle acquisition means for acquiring the crank angle θ from a crank angle sensor for sequentially detecting the crank angle θ;
An in-cylinder pressure acquisition unit that acquires the in-cylinder pressure P from an in-cylinder pressure sensor that detects an in-cylinder pressure P that is an internal pressure of the cylinder, for each of the crank angles θ acquired by the crank angle acquisition unit;
Volume acquisition means for acquiring the volume V of the cylinder for each of the crank angles θ acquired by the crank angle acquisition means;
Based on the in-cylinder pressure P acquired by the in-cylinder pressure acquisition unit and the volume V acquired by the volume acquisition unit, the crank angle θ is determined for each of the crank angles θ acquired by the crank angle acquisition unit. A heat generation rate calculating means for calculating a heat generation rate dQ / dθ per unit angle of
When the specific crank angle B before the top dead center is (−B), the heat generation rate dQ / dθ calculated by the heat generation rate calculating means is set to be advanced and delayed with respect to the top dead center TDC. A calorific value calculation apparatus comprising: an integrating unit that integrates in an equal section [−B, B] on the corner side. The heat generation rate calculation means includes a cylinder pressure change rate dP / dθ that is a change rate of the cylinder pressure P per unit angle of the cylinder pressure P, the volume V, and the crank angle θ, and a unit angle of the crank angle θ. 2. The calorific value calculation according to claim 1, wherein the heat generation rate dQ / dθ is calculated by substituting a volume change rate dV / dθ, which is a rate of change of the volume V per unit, into the following equation (1): apparatus.

  A section determining means for determining the specific crank angle B is provided so that the section [-B, B] is a necessary and sufficient section in which the total calorific value Q1 when all the injected fuel burns can be calculated. The calorific value calculation device according to claim 1 or 2. Top dead center detecting means for detecting top dead center TDC;
Top dead center angle acquisition means for acquiring the crank angle θ detected by the crank angle sensor corresponding to the top dead center TDC detected by the top dead center detection means as a top dead center angle;
Correction means for correcting the crank angle θ detected by the crank angle sensor so that the top dead center angle is a reference,
The calorific value calculation device according to any one of claims 1 to 3, wherein the crank angle acquisition means acquires the crank angle θ corrected by the correction means. The top dead center detecting means includes
Corrective in-cylinder pressure acquisition means for acquiring the in-cylinder pressure P for each of the crank angles θ detected by the in-cylinder pressure sensor as a correction in-cylinder pressure in a state where fuel is not injected;
5. The calorific value calculation device according to claim 4, further comprising: a maximum point detection unit that detects, as a top dead center, a point at which the correction cylinder pressure acquired by the correction cylinder pressure acquisition unit is maximum. The top dead center detecting means detects the top dead center TDC a plurality of times,
The top dead center angle obtaining unit obtains the top dead center angle for each top dead center detected a plurality of times by the top dead center detection unit,
6. The calorific value calculation device according to claim 5, wherein the correction unit performs the correction based on an average value of the plurality of top dead center angles acquired by the top dead center angle acquisition unit. The calorific value calculation device according to claim 1,
An actual combustion timing detecting means for detecting, as an actual combustion timing, a crank angle θ at which the total calorific value of fuel is a specific combustion ratio of the total calorific value Q1 calculated by the calorific value calculation device;
A control apparatus for an internal combustion engine, comprising: combustion timing control means for controlling fuel injection timing or ignition timing so that the actual combustion timing detected by the actual combustion timing detection means becomes a target combustion timing .   Target combustion timing determining means for determining the target combustion timing based on the engine speed acquired from the engine speed acquiring means for acquiring the engine speed and a command injection amount that is a command value of the fuel injection amount; The control device for an internal combustion engine according to claim 7, further comprising: The calorific value calculation device according to claim 1,
Command injection amount acquisition means for acquiring the command value of the fuel injection amount as the command injection amount;
A planned total heat generation amount calculating means for calculating a total heat generation amount of the fuel when the fuel of the command injection amount acquired by the command injection amount acquisition means is injected;
An abnormality detecting device for an injector, comprising: an abnormality determining means for comparing the total calorific value Q1 and the planned total calorific value Q2 to determine whether or not an injector for injecting fuel is abnormal. The planned total calorific value calculation means calculates a value calculated from the command injection amount, fuel density, and fuel energy density at least among operating conditions, intake air amount, intake air pressure, EGR rate, intake air temperature, engine water temperature, and common rail pressure. 10. The injector abnormality detection device according to claim 9, wherein the planned total heat generation amount Q2 is obtained by correcting with a correction coefficient determined based on one value.

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