JP2016011600A - Internal combustion engine control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align heat generation rate gravity center positions of all cylinders to a target gravity center position even if a cylinder internal pressure sensor is not provided to correspond to each of all the cylinders.SOLUTION: A control unit of the present invention calculates a gravity center position of a reference cylinder #1 in which a cylinder internal pressure sensor is provided on the basis of an output value from the cylinder internal pressure sensor, and feedback-controls combustion parameters for controlling a combustion state of the reference cylinder #1 so as to make the gravity center position of the reference cylinder #1 equal to a target gravity center position. Furthermore, the control unit acquires a maximum crankshaft angular velocity of each cylinder on the basis of an output value from a crank angle sensor, and feedback-controls combustion parameters for controlling combustion states of remaining cylinders #2 to #4 in which no cylinder internal pressure sensor is provided so that maximum crankshaft angular velocities ω2 to ω4 of the remaining cylinders #2 to #4 coincides with a maximum crankshaft angular velocity ω1 of the reference cylinder #1.

Description

  The present invention relates to a control device for controlling the combustion state of fuel (air mixture) supplied to an internal combustion engine.

  In general, when operating an internal combustion engine such as a diesel engine (hereinafter also simply referred to as “engine”), a part of the energy generated by the combustion of the air-fuel mixture is converted into work for rotating the crankshaft, but the rest is lost. It becomes. This loss includes cooling loss, exhaust loss, pump loss caused by intake and exhaust, mechanical resistance loss, and the like. Of these, cooling loss and exhaust loss account for a large percentage of the total loss. Therefore, it is effective to reduce the cooling loss and the exhaust loss in order to improve the fuel consumption of the internal combustion engine.

  However, in general, there is a trade-off relationship between cooling loss and exhaust loss. That is, if the cooling loss is reduced, the exhaust loss increases, and if the exhaust loss is reduced, the cooling loss increases. Therefore, if the combustion state in which the sum of the cooling loss and the exhaust loss is minimized can be realized, the fuel efficiency of the engine is greatly improved.

  By the way, the combustion state changes in accordance with “many parameters affecting the combustion state” such as fuel injection timing and supercharging pressure. Hereinafter, the parameter affecting the combustion state is also simply referred to as “combustion parameter”. However, it is not easy to obtain each combustion parameter in advance by experiments, simulations, etc. so that a plurality of combustion parameters have appropriate values (combinations) for each operating state, and enormous adaptation time is required. To do. Therefore, methods for systematically determining combustion parameters have been proposed.

  For example, one of the conventional control devices (hereinafter also referred to as “conventional device”) is “a crank angle (hereinafter referred to as a crank angle at which half of the total heat generated during one combustion stroke is generated). , Referred to as “combustion barycenter angle”). Furthermore, when the combustion center-of-gravity angle deviates from a predetermined reference value, the conventional apparatus corrects the fuel injection timing or adjusts the EGR rate to adjust the oxygen concentration in the combustion chamber (cylinder). By adjusting, the combustion barycentric angle is made to coincide with the predetermined reference value (see, for example, Patent Document 1).

JP 2011-202629 A JP 2005-54753 A JP 2007-285194 A

  For example, in a diesel engine, multistage injection may be performed in which fuel is injected multiple times for one cycle of combustion. More specifically, in a diesel engine, pilot injection may be performed prior to main injection (main injection), and then main injection may be performed. Furthermore, after injection may be performed after main injection.

  The relationship between the crank angle and the heat generation rate when the pilot injection and the main injection are performed is represented by, for example, a waveform indicated by a curve C1 in FIG. The heat generation rate is the amount of heat generated by combustion of the air-fuel mixture per unit crank angle (unit change amount of the rotational position of the crankshaft), that is, the amount of heat generation per unit crank angle. This waveform is hereinafter also referred to as “combustion waveform”. The waveform shown in FIG. 1A takes a maximum value Lp by pilot injection that starts at a crank angle θ1, and takes a maximum value Lm by main injection that starts at a crank angle θ2. In this case, it is assumed that the combustion gravity center angle (the crank angle at which the heat generation ratio is 50%) is the crank angle θ3.

  On the other hand, as shown by the curve C2 in FIG. 1B, when only the pilot injection start timing is moved from the crank angle θ1 to the crank angle θ0 by Δθp, the fuel of the pilot injection The crank angle (heat generation start angle, combustion start crank angle) at which heat generation starts by the combustion of is moved to the advance side by Δθp. Even in this case, the combustion gravity center angle remains the crank angle θ3 and does not change. That is, even if the combustion waveform changes due to the pilot injection timing moving to the advance side, the combustion gravity center angle may not change. In other words, the combustion barycenter angle is not necessarily an index value that accurately reflects the combustion state of each cycle.

  Actually, when the inventor of the present application measured “the relationship between the combustion center-of-gravity angle and the fuel consumption deterioration rate” with respect to various “engine load and engine speed”, the inventor found that the engine load and / or engine speed It has been found that when the speed is different, the combustion center-of-gravity angle at which the fuel consumption deterioration rate is the minimum (combustion center-of-gravity angle at which the fuel consumption is the best) is also different. In other words, it has been found that even if the combustion state is controlled so that the combustion center-of-gravity angle coincides with a certain reference value, the fuel consumption deterioration rate is not minimized if the engine load and / or the engine rotation speed are different.

  Therefore, the inventor paid attention to the “heat generation rate gravity center position” instead of the conventional combustion gravity center angle as an index value representing the combustion state. This heat release rate gravity center position is defined by various methods as described below. The heat release rate gravity center position is represented by a crankshaft rotation position (that is, a crank angle).

(Definition 1) As shown in FIG. 1 (A), the heat generation rate gravity center position Gc is defined as “the crank angle is set on the horizontal axis and the heat generation rate (the amount of heat generated per unit crank angle) is set. This is the crank angle corresponding to the geometric gravity center G of the region surrounded by the waveform of the heat release rate drawn on the coordinate system (graph) set on the vertical axis and the horizontal axis.

(Definition 2) The heat release rate gravity center position Gc is a crank angle Gc that satisfies the following expression (1). In the equation (1), CAs is a crank angle at which fuel combustion starts (combustion start crank angle), and CAe is a crank angle at which the combustion ends (combustion end crank angle). Furthermore, θ is an arbitrary crank angle, and dQ (θ) is a heat generation rate at the crank angle θ.

(Definition 2 ′) When the above equation (1) is modified, the following equation (2) is obtained. That is, the heat release rate gravity center position Gc is a crank angle Gc that satisfies the following expression (2).

(Definition 3) Based on definition 2 and definition 2 ′, the heat release rate gravity center position Gc is defined as the crank angle Gc obtained by calculation according to the following equation (3).

(Definition 3 ')
Based on Definition 3, the heat generation rate gravity center position Gc is the difference between the arbitrary crank angle and the combustion start crank angle (A = θ−CAs), and the heat generation rate (B = dQ (θ )) And the integrated value (the numerator of the first term on the right side of the above equation (3)) of the product (A · B) with respect to the crank angle, the area of the region defined by the waveform of the heat generation rate with respect to the crank angle ( It is defined as the crank angle obtained by adding the combustion start crank angle (CAs) to the value obtained by dividing by the denominator of the first term on the right side of the above equation (3).

  This heat release rate gravity center position Gc is, for example, the crank angle θ3 in the example shown in FIG. In addition, as shown in FIG. 1B, when the start timing of pilot injection is moved from the crank angle θ1 to the advance side by Δθp and set to the crank angle θ0, the center of gravity position Gc is set to the crank angle Δθg. The crank angle θ3 ′ is obtained by moving to the advance side. As understood from these, it can be said that the center-of-gravity position Gc is an index value that more accurately reflects the combustion state as compared to the combustion center-of-gravity angle that is an index value of the conventional combustion state.

  Further, when the relationship between the heat release rate gravity center position Gc and the fuel consumption deterioration rate was measured for various combinations of engine speed and engine load (required torque), the engine speed and engine load were different. However, the center-of-gravity position Gc at which the fuel consumption deterioration rate is minimized is a specific crank angle (for example, 7 ° after compression top dead center). Further, it has been found that if the center of gravity position Gc is a value in the vicinity of this specific crank angle, the fuel consumption deterioration rate becomes a substantially constant value in the vicinity of the minimum value regardless of the engine rotation speed and the engine load.

  From these, the inventor found that the heat generation rate gravity center position Gc is an index value indicating a good combustion state. Therefore, the engine combustion is maintained by maintaining the gravity center position Gc constant regardless of the load and / or the engine rotational speed. The knowledge that a state can be maintained in a specific state was acquired. Further, the inventor sets the center-of-gravity position Gc as “a constant crank angle that minimizes the fuel consumption deterioration rate (that is, the sum of the cooling loss and the exhaust loss is minimized and the fuel consumption is improved)”. Thus, it has been found that the fuel consumption of the engine can be easily improved regardless of the operating state (load and / or engine speed) of the engine.

  On the other hand, when the engine load reaches a region close to the full load in a state where the heat generation rate gravity center position Gc is maintained at the constant crank angle (that is, when the fuel injection amount is very large), the in-cylinder pressure during combustion It has been found that the maximum value of may exceed the allowable pressure.

  Therefore, as shown in FIG. 2, the internal combustion engine control apparatus according to the present invention (hereinafter also referred to as “the present invention apparatus”) has at least the first load (Pem1) as the engine load. When it is within the range (specific range) between the second threshold value (Pem2) larger than one threshold value ", the heat release rate gravity center position (Gc) of each cylinder is constant regardless of the load. A parameter (combustion parameter) for changing the combustion state of each cylinder is feedback-controlled so as to be equal to the position (Gctgt = the constant value θa). The first threshold value (Pem1) may be a minimum value of loads that the engine can take, or may be a value larger than the minimum value.

  Further, when the load is in a range larger than the second threshold value (Pem2), the apparatus according to the present invention is configured such that the heat generation rate gravity center position (Gc) of each cylinder increases as the load increases. The combustion parameters of each cylinder are feedback-controlled so as to be equal to the target center-of-gravity position on the retard side in the range on the retard side with respect to (Gctgt = the constant value θa).

  Accordingly, it is possible to realize combustion control in which the maximum value of the in-cylinder pressure during combustion does not exceed the allowable pressure and the heat release rate gravity center position is considered as an index value indicating the combustion state. In addition, the device according to the present invention can improve fuel efficiency when the constant target center-of-gravity position (Gctgt = the constant value θa) is set to the best fuel economy crank angle or a crank angle in the vicinity thereof.

  By the way, in order to accurately control the heat generation rate gravity center position of each cylinder to the target gravity center position, the actual heat generation rate gravity center position of each cylinder is acquired, and each of these acquired heat generation rate gravity center positions is assigned to each cylinder. It is necessary to feedback-control the combustion parameter of each cylinder so as to coincide with a common target center-of-gravity position. Further, as understood from the above equations (1) to (3), the heat generation rate gravity center position is calculated based on the heat generation rate (dQ (θ)) calculated using the in-cylinder pressure. Therefore, when the engine has a plurality of cylinders, if it is intended to implement feedback control of the combustion parameters based on the position of the center of gravity of the heat generation rate of each cylinder, it is necessary to provide an in-cylinder pressure sensor corresponding to each cylinder. Occurs. However, since the in-cylinder pressure sensor is expensive, providing one in-cylinder pressure sensor for each cylinder may cause a significant increase in cost.

  On the other hand, most engines are usually equipped with a crank angle sensor to obtain the engine speed. Accordingly, one of the objects of the present invention is to provide an internal combustion engine that uses the crank angle sensor to match the heat generation rate gravity center position of each cylinder to the target gravity center position even if the number of in-cylinder pressure sensors is small. It is to provide a control device.

  In order to achieve this object, the device of the present invention includes a plurality of cylinders, one in-cylinder pressure sensor disposed corresponding to only one of these cylinders, and one crank angle sensor. It is applied to the internal combustion engine provided. The device of the present invention is a device that controls the center of gravity position of the heat release rate of each cylinder, and includes a center-of-gravity position calculation unit, a first feedback control unit, a maximum crankshaft angular velocity acquisition unit, and a second feedback control unit. It has.

  The center-of-gravity position calculation unit calculates the heat release rate center-of-gravity position of the cylinder (reference cylinder) in which the in-cylinder pressure sensor is provided based on the output value of the in-cylinder pressure sensor.

  The first feedback control unit feedback-controls the combustion parameter of the reference cylinder so that the “heat generation rate gravity center position of the reference cylinder” calculated by the gravity center position calculation unit is equal to the target gravity center position.

  The maximum crankshaft angular velocity acquisition unit acquires “the maximum value of the crankshaft angular velocity during the combustion period of each cylinder” calculated based on the output value of the crank angle sensor as the maximum crankshaft angular velocity of the cylinder.

  The second feedback control unit is configured so that the maximum crankshaft angular speed of a cylinder (remaining cylinder) in which the in-cylinder pressure sensor is not disposed approaches the maximum crankshaft angular speed of the reference cylinder. Feedback control of combustion parameters.

  The maximum value of the crankshaft angular velocity during a combustion period of a cylinder (hereinafter also referred to as “maximum angular velocity”) increases as the heat release rate gravity center position of the cylinder is advanced. Therefore, when the maximum angular velocity of the “cylinder in which the in-cylinder pressure sensor is not disposed (the remaining cylinders)” is larger than the maximum angular velocity of the “cylinder in which the in-cylinder pressure sensor is disposed (the reference cylinder)”, The heat generation rate gravity center positions of the remaining cylinders are on the more advanced side than the heat generation rate gravity center positions of the reference cylinders. In this case, the combustion parameters of the remaining cylinders are feedback-controlled so that the maximum angular velocity of the remaining cylinders becomes smaller (approaching the maximum angular velocity of the reference cylinder). Thereby, the maximum angular velocity of the remaining cylinders matches the maximum angular velocity of the reference cylinder. As a result, the heat release rate gravity center position of the remaining cylinders coincides with the heat release rate gravity center position of the reference cylinder, that is, the target gravity center position.

  Conversely, when the maximum angular velocity of the remaining cylinder is smaller than the maximum angular velocity of the reference cylinder, the maximum angular velocity of the remaining cylinder is increased (so as to approach the maximum angular velocity of the reference cylinder). Feedback control of combustion parameters. Thereby, the maximum angular velocity of the remaining cylinders matches the maximum angular velocity of the reference cylinder. As a result, the heat release rate gravity center position of the remaining cylinders coincides with the heat release rate gravity center position of the reference cylinder, that is, the target gravity center position.

  Thus, the device according to the present invention matches the heat generation rate gravity center of the cylinder (reference cylinder) in which the in-cylinder pressure sensor is provided with the target center-of-gravity position based on the output value of the in-cylinder pressure sensor. Furthermore, the device of the present invention matches the maximum angular velocity of the remaining cylinders with the maximum angular velocity of the reference cylinder. As a result, even if the in-cylinder pressure sensors are not provided corresponding to all the cylinders, the heat release rate gravity center positions of all the cylinders can coincide with the target gravity center positions. Therefore, an increase in the cost of the engine can be avoided.

FIG. 1 is a graph for explaining the heat generation rate gravity center position (heat generation rate gravity center crank angle), and (A) shows a combustion waveform when pilot injection and main injection are performed at a predetermined timing. (B) shows a combustion waveform when pilot injection is advanced compared to (A). FIG. 2 is a graph showing the relationship between the engine load and the target heat generation rate gravity center position. FIG. 3 is a schematic configuration diagram of “a control device according to an embodiment of the present invention” and “an internal combustion engine to which the control device is applied”. FIG. 4 shows the relationship between the maximum crankshaft angular velocity (maximum angular velocity) and the heat release rate gravity center position. FIG. 5 is a flowchart showing a combustion state control routine executed by the CPU of the control device shown in FIG. FIG. 6 is a flowchart showing a heat generation rate gravity center position feedback control routine executed by the CPU of the control device shown in FIG. FIG. 7 is a flowchart showing a maximum angular velocity feedback control routine executed by the CPU of the control device shown in FIG.

  Hereinafter, a control device for an internal combustion engine according to an embodiment of the present invention (hereinafter, also referred to as “the present control device”) will be described with reference to the drawings.

(Constitution)
This control apparatus is applied to the internal combustion engine (engine) 10 shown in FIG. The engine 10 is a multi-cylinder (in this example, in-line four cylinders), four-cycle, piston reciprocating type, and diesel engine. The engine 10 includes an engine body 20, a fuel supply system 30, an intake system 40, an exhaust system 50, and an EGR system 60.

  The engine main body 20 includes a main body 21 including a cylinder block, a cylinder head, a crankcase, and the like. The main body 21 is formed with four cylinders (combustion chambers) # 1 to # 4. A fuel injection valve (injector) 23 is disposed above each cylinder. The fuel injection valve 23 opens in response to an instruction from an engine ECU (electronic control unit) 70 described later, and directly injects fuel into the cylinder.

  The fuel supply system 30 includes a fuel pressurization pump (supply pump) 31, a fuel delivery pipe 32, and a common rail (pressure accumulation chamber) 33. The discharge port of the fuel pressurization pump 31 is connected to the fuel delivery pipe 32. The fuel delivery pipe 32 is connected to the common rail 33. The common rail 33 is connected to the fuel injection valve 23.

  The fuel pressurizing pump 31 pumps up fuel stored in a fuel tank (not shown), pressurizes the fuel, and supplies the pressurized high-pressure fuel to the common rail 33 through the fuel delivery pipe 32. The pump 31 is operated by a drive shaft that is linked to the crankshaft of the engine 10. The pump 31 can adjust the pressure of the fuel in the common rail 33 (that is, the fuel injection pressure and the common rail pressure) in response to an instruction from the ECU 70.

  The intake system 40 includes an intake manifold 41, an intake pipe 42, an air cleaner 43, a compressor 44a of a supercharger 44, an intercooler 45, a throttle valve 46, and a throttle valve actuator 47.

  The intake manifold 41 includes branch portions connected to the cylinders # 1 to # 4 and a collective portion in which the branch portions are gathered. The intake pipe 42 is connected to the collecting portion of the intake manifold 41. The intake manifold 41 and the intake pipe 42 constitute an intake passage. In the intake pipe 42, an air cleaner 43, a compressor 44a, an intercooler 45, and a throttle valve 46 are sequentially arranged from the upstream side to the downstream side of the flow of intake air. The throttle valve actuator 47 changes the opening degree of the throttle valve 46 in accordance with an instruction from the ECU 70.

  The intercooler 45 is adapted to lower the intake air temperature. The intercooler 45 includes a bypass passage (not shown) and a bypass valve interposed in the bypass passage. Further, the intercooler 45 can adjust the amount of cooling water (refrigerant) flowing between the intercooler 45 and a cooler (not shown). Accordingly, the intercooler 45 adjusts the opening degree of the bypass valve and / or the amount of cooling water in response to an instruction from the ECU 70, thereby reducing the cooling efficiency of the cooler 45 (the temperature of the inflow gas of the cooler 45 and the outflow of the cooler 45). The efficiency expressed by the ratio to the gas temperature can be changed.

  The exhaust system 50 includes an exhaust manifold 51, an exhaust pipe 52, a turbine 44 b of the supercharger 44, and an exhaust gas purification device (for example, a diesel oxidation catalyst and a particulate filter) 53.

  The exhaust manifold 51 includes branch portions connected to the cylinders # 1 to # 4 and a collective portion in which the branch portions are gathered. The exhaust pipe 52 is connected to a collecting portion of the exhaust manifold 51. The exhaust manifold 51 and the exhaust pipe 52 constitute an exhaust passage. In the exhaust pipe 52, a turbine 44b and an exhaust gas purification device 53 are arranged from the upstream to the downstream of the flow of the exhaust gas.

  The supercharger 44 is a known variable capacity supercharger, and a plurality of nozzle vanes (variable nozzles) (not shown) are provided in the turbine 44b. The opening degree of the nozzle vane is changed in accordance with an instruction from the ECU 70, and as a result, the supercharging pressure is changed (controlled). The turbine 44b of the supercharger 44 may include a “bypass passage of the turbine 44b and a bypass valve provided in the bypass passage” (not shown). The supercharging pressure may be changed by changing. That is, in this specification, “controlling the supercharger 44” means changing the supercharging pressure by changing the angle of the nozzle vane and / or the opening of the bypass valve.

The EGR system 60 includes an exhaust gas recirculation pipe 61, an EGR control valve 62, and an EGR cooler 63.
The exhaust gas recirculation pipe 61 communicates an exhaust passage (exhaust manifold 51) upstream of the turbine 44b and an intake passage (intake manifold 41) downstream of the throttle valve 46. The exhaust gas recirculation pipe 61 constitutes an EGR gas passage.
The EGR control valve 62 is disposed in the exhaust gas recirculation pipe 61. The EGR control valve 62 can change the exhaust gas amount (EGR gas amount) recirculated from the exhaust passage to the intake passage by changing the passage sectional area of the EGR gas passage in response to an instruction from the ECU 70. It has become.

  The EGR cooler 63 is interposed in the exhaust gas recirculation pipe 61 so that the temperature of the EGR gas passing through the exhaust gas recirculation pipe 61 is lowered. The EGR cooler 63 includes a bypass passage (not shown) and a bypass valve interposed in the bypass passage. Further, the EGR cooler 63 can adjust the amount of cooling water (refrigerant) that flows between the EGR cooler 63 and a cooler (not shown). Therefore, the EGR cooler 63 adjusts the bypass valve opening and / or the amount of cooling water in response to an instruction from the ECU 70 to thereby reduce the cooling efficiency of the cooler 63 (the temperature of the inflow gas of the cooler 63 and the outflow of the cooler 63). The efficiency expressed by the ratio to the gas temperature can be changed.

  The ECU 70 is an electronic circuit including a known microcomputer, and includes a CPU, a ROM, a RAM, a backup RAM, an interface, and the like. The ECU 70 is connected to sensors described below, and receives (inputs) signals from these sensors. Further, the ECU 70 sends instruction (drive) signals to various actuators.

  ECU 70 is connected to air flow meter 71, throttle valve opening sensor 72, intake pipe pressure sensor 73, fuel pressure sensor 74, in-cylinder pressure sensor 75, crank angle sensor 76, EGR control valve opening sensor 77, and water temperature sensor 78. Has been.

The air flow meter 71 measures the mass flow rate (intake air amount) of intake air (fresh air not including EGR gas) passing through the intake passage, and outputs a signal representing the intake air amount Ga. Further, the air flow meter 71 detects the temperature of the intake air (intake air temperature) and outputs a signal representing the intake air temperature THA.
The throttle valve opening sensor 72 detects the throttle valve opening and outputs a signal representing the throttle valve opening TA.
The intake pipe pressure sensor 73 outputs a signal representing the gas pressure (intake pipe pressure) Pim in the intake pipe in the intake passage and downstream of the throttle valve 46. It can also be said that the intake pipe pressure Pim is a supercharging pressure.

The fuel pressure sensor 74 detects the fuel pressure (fuel pressure, fuel injection pressure, common rail pressure) in the common rail (pressure accumulation chamber) 33 and outputs a signal representing the fuel injection pressure Fp.
The in-cylinder pressure sensor 75 is provided corresponding to only one cylinder (in this example, the first cylinder # 1) among the four cylinders (combustion chambers) # 1 to # 4. The in-cylinder pressure sensor 75 detects the pressure in the first cylinder # 1 (that is, the in-cylinder pressure) and outputs a signal representing the in-cylinder pressure Pc.
The crank angle sensor 76 outputs a signal corresponding to a rotational position (that is, crank angle) of a crankshaft (not shown) of the engine 10. The ECU 70 acquires the crank angle (absolute crank angle) θ of the engine 10 with reference to the compression top dead center of a predetermined cylinder based on signals from the crank angle sensor 76 and a cam position sensor (not shown). Further, the ECU 70 acquires the engine rotational speed Ne based on the signal from the crank angle sensor 76.

The EGR control valve opening sensor 77 detects the opening of the EGR control valve 62 and outputs a signal Vegr representing the opening.
The water temperature sensor 78 detects the cooling water temperature (cooling water temperature) of the engine 10 and outputs a signal representing the cooling water temperature THW.

In addition, the ECU 70 is connected to an accelerator opening sensor 81 and a vehicle speed sensor 82.
The accelerator opening sensor 81 detects the opening (accelerator pedal operation amount) of an accelerator pedal (not shown), and outputs a signal representing the accelerator pedal opening Accp.
The vehicle speed sensor 82 detects the traveling speed of the vehicle on which the engine 10 is mounted, and outputs a signal representing the traveling speed (vehicle speed) Spd.

(Overview of combustion control)
Next, an outline of the operation of the present control device will be described. The present control device determines that the heat release rate centroid position defined by the above-described definition is the predetermined target heat release rate centroid position for the cylinder (in this example, the first cylinder # 1) in which the in-cylinder pressure sensor 75 is disposed. Combustion control is performed so as to satisfy (that is, feedback control is performed on combustion parameters for controlling the combustion state of fuel in the first cylinder # 1). The target heat generation rate gravity center position is also referred to as target gravity center position, target heat generation rate gravity center angle, or target crank angle.

  Further, the present control device calculates the crankshaft angular velocity based on the output value of the crank angle sensor 76. The crankshaft angular velocity is an angle (crank angle) at which the crankshaft rotates per unit time. In addition, the present control device acquires the maximum value among the crankshaft angular velocities calculated during the combustion period of the first cylinder # 1 as the maximum crankshaft angular velocity ω1 of the first cylinder # 1. Further, the present control device similarly obtains the maximum crankshaft angular velocities ω2 to ω4 of the second cylinder # 2 to the fourth cylinder # 4 for the second cylinder # 2 to the fourth cylinder # 4. Hereinafter, the maximum crankshaft angular velocity is referred to as “maximum angular velocity”.

  Further, the present control device is configured such that “the cylinder in which the in-cylinder pressure sensor 75 is not disposed, that is, the maximum angular velocities ω2 to ω4 of the second cylinder # 2 to the fourth cylinder # 4” is “the in-cylinder pressure sensor 75 is disposed The combustion control is performed so as to coincide with the maximum cylinder angular velocity ω1 of the cylinder, that is, the first cylinder # 1 (that is, the combustion parameters of the cylinders # 2 to # 4 are feedback-controlled).

  More specifically, in the present control device, the combustion parameters for all cylinders # 1 to # 4 are such that the combustion parameters are in the engine operating state (engine load and engine rotation) so that the heat generation rate gravity center position matches the target gravity center position. The speed is determined in advance and stored in the ROM. This control device reads the combustion parameters from the ROM according to the actual operating state of the engine, and uses the combustion parameters to control the combustion states of the cylinders # 1 to # 4 to thereby control the cylinders # 1 to # 4. 4 feedforward control of the heat release rate center of gravity position.

  Further, the present control device estimates the actual heat generation rate gravity center position of the first cylinder # 1 based on the in-cylinder pressure Pc detected by the in-cylinder pressure sensor 75, and the estimated heat generation rate gravity center position is the target gravity center position. The combustion parameter of the cylinder # 1 is feedback-controlled so as to coincide with.

  In addition, the control device acquires the maximum angular velocities ω1 to ω4 of the cylinders # 1 to # 4 as described above. Further, the present control apparatus feedback-controls the combustion parameters of the second cylinder # 2 to the fourth cylinder # 4 for each cylinder so that the acquired maximum angular velocities ω2 to ω4 coincide with the acquired maximum angular velocities ω1. .

  More specifically, as shown in FIG. 4, as the maximum angular velocity ω increases, the heat generation rate gravity center position Gc is on the advance side. Accordingly, the maximum angular velocity ωn (n = 2 to 4) of any one of the second cylinder # 2 to the fourth cylinder # 4 (target cylinder #n (n = 2 to 4)) is the maximum of the first cylinder # 1. When it is higher than the angular velocity ω1, the heat generation rate gravity center position of the target cylinder #n is on the advance side with respect to the heat generation rate gravity center position (target gravity center position Gctgt) of the first cylinder # 1. In this case, the present control apparatus feedback-controls the combustion parameter of the cylinder of interest #n so that the maximum angular velocity ωn becomes smaller and matches the maximum angular velocity ω1.

  At this time, the “combustion parameter of the target cylinder #n” that is feedback-controlled is not a combustion parameter that affects the combustion state of the first cylinder # 1 (for example, supercharging pressure, fuel injection pressure, etc.), but the same cylinder # 1. Is a combustion parameter that does not affect the combustion state (for example, injection timing of main injection in the target cylinder #n).

  On the other hand, when the maximum angular velocity ωn is smaller than the maximum angular velocity ω1, the heat release rate gravity center position of the target cylinder #n is on the retard side with respect to the heat release rate gravity center position (target gravity center position Gctgt) of the first cylinder # 1. In this case, the present control device feedback-controls the combustion parameter of the cylinder of interest #n so that the maximum angular velocity ωn increases and matches the maximum angular velocity ω1.

  By such feedback control of the maximum angular velocity ωn (hereinafter also referred to as “maximum angular velocity feedback control”), when the maximum angular velocities ω2 to ω4 coincide with the maximum angular velocities ω1, the second cylinder # 2 to the fourth cylinder # 4 respectively. The heat release rate gravity center position of the first cylinder # 1 coincides with the heat release rate gravity center position of the first cylinder # 1, that is, the target gravity center position Gctgt.

  By the way, as shown in FIG. 2, the present control device does not depend on the engine load and the engine speed, at least when the engine load is within the “range from the first threshold value Pem1 to the second threshold value Pem2.” The target center-of-gravity position Gctgt is set to a constant crank angle θa (for example, ATDC 7 °). According to this, the fuel consumption of the engine 10 can be improved. The target center-of-gravity position Gctgt at this time is a constant crank angle θa ′ (crank angle within a predetermined range from θa) at which the running cost of the engine 10 determined by the relationship with the emission is minimized, and the engine load and It may be a crank angle at which the fuel consumption deterioration rate is constant near the minimum value regardless of the engine speed.

  On the other hand, when the load of the engine is in a range larger than the second threshold value Pem2, the present control device sets the target center-of-gravity position Gctgt to “from the constant crank angle θa as the load increases (as the fuel injection amount increases). Is set to a crank angle that gradually becomes retarded in the "retard angle range". According to this, it is avoided that the maximum value of the in-cylinder pressure exceeds the allowable pressure of the engine 10. Further, in the range where the engine load is larger than the second threshold value Pem2, the fuel injection amount can be increased although the fuel efficiency is somewhat deteriorated, so that the generated torque (and therefore the output) of the engine 10 can be increased.

  Since the exhaust loss increases as the heat generation rate gravity center position shifts to the retard side, the exhaust temperature rises. Then, when the engine 10 reaches an allowable exhaust temperature (allowable exhaust temperature), the present control device stops increasing the fuel injection amount.

  Further, the present control device sets the constant crank angle θa to the target center-of-gravity position Gctgt even when the engine load is equal to or less than the first threshold value Pem1. However, when the engine load is equal to or less than the first threshold value Pem1, the present control device may set a crank angle other than the constant crank angle θa as the target center-of-gravity position Gctgt based on other requirements. Further, as described above, when the load of the engine is in the “range from the first threshold value Pem1 to the second threshold value Pem2,” the control device “crank angle within a predetermined range from the constant crank angle θa (constant value). ) Θa ′ ”may be set as the target center-of-gravity position.

(Actual operation)
Next, processing for controlling the combustion state executed by the CPU of the ECU 70 (hereinafter simply referred to as “CPU”) will be described with reference to FIG. In the following description, the symbol MapX (P1, P2,...) Represents a lookup table (or function) that obtains a value X with arguments (parameters) P1, P2,. In addition, for simplicity of explanation, the CPU adopts the main injection timing, the supercharging pressure, and the fuel injection pressure as the above-described combustion parameters, and does not perform pilot injection and after injection.

<Feed forward control>
The CPU executes a “combustion state control routine” shown by a flowchart in FIG. 5 every time a predetermined time elapses. Accordingly, when the appropriate timing is reached, the CPU starts the process from step 500 in FIG. 5, sequentially performs the processes from step 505 to step 515 described below, and proceeds to step 520.

Step 505: The CPU acquires an accelerator pedal opening degree Accp and an engine speed Ne.
Step 510: The CPU determines a required injection amount (command injection amount) Qfin based on the accelerator pedal opening degree Accp and the engine rotational speed Ne (Qfin = MapQfin (Accp, Ne)). I can also say.
Step 515: The CPU acquires a maximum injection amount Qmax calculated separately. The maximum injection amount Qmax is “the maximum injection amount that can be injected within a range in which harmful substances such as smoke contained in the exhaust gas do not exceed a predetermined threshold” and “the torque of the engine 10 is the driving torque of the vehicle on which the engine 10 is mounted. The smaller injection amount of “the maximum injection amount that can be injected without exceeding the allowable limit torque of the transmission mechanism”.

  Next, the CPU proceeds to step 520 to determine whether or not the required injection amount Qfin is equal to or less than the maximum injection amount Qmax. If the required injection amount Qfin is equal to or less than the maximum injection amount Qmax, the CPU makes a “Yes” determination at step 520 to proceed to step 525, and sets the final fuel injection amount Qact to a value equal to the required injection amount Qfin. On the other hand, if the required injection amount Qfin is larger than the maximum injection amount Qmax, the CPU makes a “No” determination at step 520 to proceed to step 530 to set the final fuel injection amount Qact to a value equal to the maximum injection amount Qmax. . Note that if there is no restriction on emission and / or allowable limit torque, Steps 515 to 530 may be omitted. In this case, the final fuel injection amount Qact is always equal to the required injection amount Qfin.

  After performing the processing of step 525 or step 530, the CPU sequentially performs the processing of step 535 to step 545 described below, proceeds to step 595, and once ends this routine.

  Step 535: The CPU determines the fuel injection pressure Fp based on the final fuel injection amount Qact and the engine rotational speed Ne, and the lookup table MapFp (Qact, Ne). At this time, the fuel injection pressure Fp is set to a value substantially proportional to the required output Pr, as shown in block B1. However, as described above, in the region where the engine load (in this case, the required injection amount Qfin) is equal to or greater than a predetermined value and the maximum value of the in-cylinder pressure exceeds the allowable pressure, the fuel injection pressure Fp is the final fuel. It is set to a value that decreases as the injection amount Qact increases. The CPU controls the fuel pressurization pump 31 and the like by a drive routine (not shown) so that the actual fuel injection pressure becomes equal to the fuel injection pressure Fp determined in step 535.

  Step 540: The CPU determines the supercharging pressure Tp based on the final fuel injection amount Qact, the engine speed Ne, and the lookup table MapTp (Qact, Ne). At this time, the supercharging pressure Tp is set to a value substantially proportional to the required output Pr, as shown in block B2. However, as described above, in the region where the engine load (in this case, the required injection amount Qfin) exceeds a predetermined value and the maximum value of the in-cylinder pressure exceeds the allowable pressure, the supercharging pressure Tp is the final fuel. It is set to a value that decreases as the injection amount Qact increases. The CPU controls the supercharger 44 so that the actual supercharging pressure becomes equal to the supercharging pressure Tp determined in step 540 by a driving routine (not shown).

  Step 545: The CPU determines the fuel injection timing CMinj of the main injection based on the final fuel injection amount Qact and the engine rotational speed Ne, and the lookup table MapCMinj (Qact, Ne). This look-up table MapCMinj (Qact, Ne) is determined in advance by experiments so that the heat generation rate gravity center position matches the target gravity center position Gctgt shown in FIG. 2, and is stored in the ROM. Thereafter, the CPU proceeds to step 595 to end the present routine tentatively.

  When the crank angle of an arbitrary cylinder coincides with the fuel injection timing CMinj determined in step 545, the CPU injects fuel of the fuel injection amount Qact from the fuel injection valve 23 of that cylinder.

  As a result of the above processing, the heat release rate gravity center positions of the cylinders # 1 to # 4 are substantially matched with the target gravity center position Gctgt shown in FIG. The fuel injection timing CMinj of the main fuel is shown in FIGS. 6 and 7 so that the heat generation rate gravity center position Gc does not greatly deviate from the target gravity center position Gctgt due to individual differences and aging of the engine 10. Adjusted by feedback control.

<Feedback control>
The CPU executes the “heat generation rate gravity center position feedback control routine” shown in the flowchart of FIG. 6 for the first cylinder # 1 every time the crank angle of the first cylinder # 1 is 720 °. .

  By this routine, the injection timing CMinj of the main injection of the first cylinder # 1 is controlled by feedback control so that the actual heat generation rate gravity center position Gc1 of the first cylinder # 1 becomes equal to the target gravity center position Gctgt shown in FIG. Adjusted. The crank angle θ is represented by the crank angle (ATDC deg) after compression top dead center of the first cylinder # 1. Therefore, the crank angle θ on the advance side from the compression top dead center is a negative value.

  Specifically, when the crank angle of the first cylinder # 1 coincides with the intake top dead center of the cylinder # 1, the CPU starts the process from step 600 of FIG. 6 and proceeds to step 610, where the first cylinder # 1 The heat generation rate dQ (θ) [J / degATDC], which is the amount of heat generated per unit crank angle with respect to the crank angle θ [degATDC], is calculated based on the in-cylinder pressure Pc in the most recent cycle of (For example, see Patent Document 2 and Patent Document 3). The CPU acquires the in-cylinder pressure Pc of the first cylinder # 1 every time the unit crank angle elapses, and associates the in-cylinder pressure Pc with the crank angles of the first cylinder # 1 and the cylinder # 1. It is stored in the RAM.

Next, the CPU obtains / estimates the heat generation rate gravity center position Gc1 of the first cylinder # 1 by applying the heat generation rate dQ (θ) to the following equation (4). Actually, the heat release rate gravity center position Gc1 is calculated based on an expression obtained by converting the expression (4) into a digital operation expression. In the equation (4), CAs is a crank angle at which combustion starts in the first cylinder # 1 (combustion start crank angle), and CAe is a crank angle at which the combustion ends (combustion end crank angle). It should be noted that a crank angle sufficiently faster than the combustion start crank angle instead of CAs in the equation (4) is adopted in the calculation by the equation (4), and a crank angle sufficiently slower than the combustion end crank angle in place of the CAe. Can be employed in the calculation according to equation (4).

  Next, the CPU proceeds to step 615 and sets the target center-of-gravity position Gctgt based on the final fuel injection amount Qact (engine load) and the lookup table MapGctgt (Qact) equivalent to the lookup table shown in FIG. decide.

  Next, the CPU proceeds to step 620, and determines whether or not the heat generation rate gravity center position Gc1 of the first cylinder # 1 is retarded by a positive minute angle Δθs or more with respect to the target gravity center position Gctgt. If the center of gravity position Gc1 is on the retarded side by a positive minute angle Δθs or more with respect to the target center of gravity position Gctgt, the CPU makes a “Yes” determination at step 620 to proceed to step 625, where the main cylinder 1 The injection timing CMinj of the injection is advanced by a predetermined minute angle ΔCA. As a result, the gravity center position Gc1 slightly moves to the advance side, and thus approaches the target gravity center position Gctgt.

  Next, the CPU proceeds to step 630 and sets the value of the maximum angular velocity feedback permission flag F (hereinafter simply referred to as “permission flag”) to “0”. Thereafter, the CPU proceeds to step 695 to end the present routine tentatively.

  On the other hand, when the CPU executes the process of step 620, if the center of gravity position Gc1 is not retarded by a positive minute angle Δθs or more with respect to the target center of gravity position Gctgt, the CPU returns “No” in step 620. The process proceeds to step 635, where it is determined whether or not the gravity center position Gc1 is on the advance side with respect to the target gravity center position Gctgt by a positive minute angle Δθs or more. When the center of gravity position Gc1 is on the advance side with respect to the target center of gravity position Gctgt by a positive minute angle Δθs or more, the CPU makes a “Yes” determination at step 635 to proceed to step 640, where the main injection of the first cylinder # 1 is performed. The injection timing CMinj is retarded by a predetermined minute angle ΔCA. As a result, the gravity center position Gc1 slightly moves to the retarded angle side, and thus approaches the target gravity center position Gctgt.

  Next, the CPU proceeds to step 645 and sets the value of the permission flag F to “0”. Thereafter, the CPU proceeds to step 695 to end the present routine tentatively.

  Furthermore, at the time when the CPU executes the process of step 635, if the center of gravity position Gc1 is not an advance side of a positive minute angle Δθs or more with respect to the target center of gravity position Gctgt, the difference between the center of gravity position Gc1 and the target center of gravity position Gctgt The magnitude is less than a small angle Δθs. In this case, the CPU makes a “No” determination at step 635 to proceed to step 650 to set the value of the permission flag F to “1”. Thereafter, the CPU proceeds to step 695 to end the present routine tentatively. In this case, the injection timing CMinj of the main injection of the first cylinder # 1 is not corrected.

  Note that the CPU determines whether or not the current operating state defined by the accelerator pedal opening degree Accp and the engine rotational speed Ne is the same as the operating state before a predetermined time between Step 600 and Step 610. The “determining” step may be performed. Then, when it is determined that the current driving state is the same as the driving state before the predetermined time, the CPU proceeds to step 610 and thereafter, and the CPU determines that the current driving state is not the same as the driving state before the predetermined time. In that case, the process may proceed directly to step 695. At this time, the CPU sets the value of the permission flag F described above to “0”.

  According to this, feedback control of the heat release rate gravity center position Gc1 of the first cylinder # 1 is performed only when the operating state has not changed (when the operating state is steady), and when the operating state has changed. The feedback control of the gravity center position Gc1 can be performed after resetting the combustion parameter once by feedforward control.

  Further, the CPU executes the “maximum angular velocity feedback control routine” shown in the flowchart of FIG. 7 every time the crank angle of any cylinder of the second cylinder # 2 to the fourth cylinder # 4 has reached 720 °. It is like that. That is, the CPU executes the “maximum angular velocity feedback control routine” shown in the flowchart of FIG. 7 for each of the cylinders # 2 to # 4.

  By this routine, in each of the second cylinder # 2 to the fourth cylinder # 4, the actual heat generation rate gravity center positions Gc2 to Gc4 are equal to the target gravity center positions Gctgt shown in FIG. Each of the four main injection timings CMinj is adjusted by feedback control.

  Specifically, among the second cylinder # 2 to the fourth cylinder # 4, the crank angle of an arbitrary cylinder (target cylinder) #n (n = 2 to 4) is the intake top dead center of the cylinder #n. If they match, the CPU starts processing from step 700 in FIG. 7 and proceeds to step 705 to determine whether or not the value of the permission flag F is “1”. If the value of the permission flag F is not “1”, the CPU makes a “No” determination at step 705 to proceed to step 795 to end the present routine tentatively. On the other hand, if the value of the permission flag F is “1”, the CPU makes a “Yes” determination at step 705 to proceed to step 710.

  The CPU performs a crankshaft angular velocity calculation routine (not shown) from “the crank angle of the first cylinder # 1 is changed from 90 ° crank angle before compression top dead center (BTDC 90 ° CA) to 90 ° crank angle after compression top dead center (ATDC 90 ° CA). ) Is a specific period (combustion period) of the first cylinder # 1, and the crankshaft angular velocity is calculated at every predetermined crank angle interval (crank angle interval of 1 ° in this example). The CPU calculates the crankshaft angular velocity based on a signal (output value) from the crank angle sensor 76.

  Further, the CPU stores the crankshaft angular velocity calculated as described above in the RAM in association with “the crank angle of the first cylinder # 1 when the same angular velocity is calculated”.

  Similarly, the CPU determines the crankshafts at predetermined crank angle intervals in the specific period of each of the remaining cylinders # 2 to # 4 (the period until the crank angle of each cylinder advances from BTDC 90 ° CA to ATDC 90 ° CA). The angular velocity is calculated, and the calculated crankshaft angular velocity is stored in the RAM in association with “the crank angle of each cylinder # 2 to # 4 when the same angular velocity is calculated”.

  When the CPU makes a “Yes” determination at step 705 to proceed to step 710, the CPU determines the crankshaft angular velocity of the target cylinder #n (any one of the second cylinder # 2 to the fourth cylinder # 4) during the specific period. Of the angular velocities stored in the ROM, the maximum crankshaft angular velocity is acquired as the maximum angular velocity ωn.

  Next, the CPU proceeds to step 715, and acquires the maximum crankshaft angular speed as the maximum angular speed ω1 among the same angular speeds stored in the ROM as the crankshaft angular speed in the specific period of the first cylinder # 1.

  Next, the CPU proceeds to step 720 to determine whether or not the acquired maximum angular velocity ωn is greater than the acquired maximum angular velocity ω1. If the maximum angular velocity ωn is larger than the maximum angular velocity ω1, the CPU makes a “Yes” determination at step 720 to proceed to step 725 to delay the injection timing CMinj of the main injection of the cylinder of interest #n by a predetermined minute angle ΔCA. Horn. As a result, the heat release rate gravity center position Gcn of the cylinder #n of interest moves slightly to the retard side, so that the maximum angular velocity ωn approaches the maximum angular velocity ω1. As a result, the gravity center position Gcn approaches the target gravity center position Gctgt. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively.

  On the other hand, if the maximum angular velocity ωn is not larger than the maximum angular velocity ω1 at the time when the CPU executes the process of step 720, the CPU makes a “No” determination at step 720 to proceed to step 730, where the maximum angular velocity is reached. It is determined whether or not ωn is smaller than the maximum angular velocity ω1. If the maximum angular velocity ωn is smaller than the maximum angular velocity ω1, the CPU makes a “Yes” determination at step 730 to proceed to step 735 to advance the injection timing CMinj of the main injection of the target cylinder #n by a predetermined minute angle ΔCA. To do. As a result, the center-of-gravity position Gcn slightly moves toward the advance side, so that the maximum angular velocity ωn approaches the maximum angular velocity ω1. As a result, the gravity center position Gcn approaches the target gravity center position Gctgt. Thereafter, the CPU proceeds to step 795 to end the present routine tentatively.

  Furthermore, when the CPU executes the process of step 730, if the maximum angular velocity ωn is not smaller than the maximum angular velocity ω1, the maximum angular velocity ωn is equal to the maximum angular velocity ω1. In this case, the CPU makes a “No” determination at step 730 to directly proceed to step 795 to end the present routine tentatively. That is, in this case, the injection timing CMinj of the main injection of the target cylinder #n is not corrected.

  Note that the CPU determines whether or not the current operating state defined by the accelerator pedal opening Accp and the engine rotational speed Ne is the same as the operating state before a predetermined time between Step 700 and Step 705. The “determining” step may be performed. The CPU proceeds to step 705 and subsequent steps when it is determined that the current driving state is the same as the driving state before the predetermined time, and the CPU determines that the current driving state is not the same as the driving state before the predetermined time. If this is the case, the process may proceed directly to step 795.

  According to this, feedback control of the maximum angular velocity ωn of the cylinder of interest #n is performed only when the operating state has not changed (when the operating state is steady), and once the operating state has changed, feedforward is performed once. After resetting the combustion parameter by control, feedback control of the maximum angular velocity ωn can be performed.

  As described above, the control apparatus for an internal combustion engine according to the present embodiment has a heat generation rate when the load of at least the engine 10 is within the range (specific load range) from the first threshold value Pem1 to the second threshold value Pem2. The center-of-gravity position Gc becomes equal to a constant target center-of-gravity position (a constant crank angle θa or θa ′) regardless of the engine load (and / or the engine speed Ne), and the engine load is greater than the second threshold value Pem2. When the engine is in a large range, the larger the engine load, the more equal to the “target gravity center position on the more retarded angle side” in the retarded range than the certain target gravity center position (constant crank angle θa or θa ′). Thus, the combustion parameter of the first cylinder # 1 is feedback-controlled (see step 625 and step 640 in FIGS. 2 and 6).

  Further, the present control device feedback-controls the combustion parameters of the other cylinders # 2 to # 4 so that the maximum angular velocities ω2 to ω4 of the other cylinders # 2 to # 4 approach the maximum angular velocity ω1 of the first cylinder # 1. (See step 725 and step 735 in FIG. 7), thereby making the heat release rate gravity center positions of the cylinders # 2 to # 4 coincide with the target gravity center positions.

  Therefore, the present control device controls the heat generation rate gravity center position of each cylinder # 1 to # 4 to an appropriate crank angle (a constant crank angle θa or a crank angle θa ′ as close as possible to the crank angle θa), while operating at a high load. In the state, the maximum value of the in-cylinder pressure can be prevented from exceeding the allowable pressure. As a result, it is possible to improve the fuel efficiency of the engine and to prevent the torque generated by the engine at a high load from being lower than the required torque. In other words, the present control device can prevent the maximum torque that can be generated by the engine from being reduced.

  Further, the present control device controls the heat release rate centroid positions of all the cylinders # 1 to # 4 to the target centroid position even if the in-cylinder pressure sensor 75 is disposed only in one cylinder # 1. Can do.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, one or more of the values described below can be adopted as a combustion parameter for changing the combustion state of the first cylinder # 1.

(1) Timing of main injection (main injection) (2) Fuel injection pressure, which is the pressure when the fuel injection valve injects fuel (3) Pilot injection, which is fuel injection performed on the more advanced side than main injection (4) Number of pilot injections (5) Timing of pilot injection (6) Fuel injection amount of each pilot injection (7) After-injection, which is fuel injection performed on the retard side of the main injection Quantity (8) Supercharging pressure by supercharger 44 (9) Cooling efficiency of intercooler 45 (cooling capacity)
(10) EGR rate (or amount of EGR gas) that is the ratio of EGR gas to intake air
(11) Cooling efficiency (cooling capacity) of EGR cooler 63
(12) The intensity of the swirl flow in the cylinder (for example, the opening of the swirl control valve)

  Further, in the above embodiment, among the combustion parameter values (1) to (12) as the combustion parameters for changing the combustion states of the second cylinder # 2 to the fourth cylinder # 4, the cylinders # 2 to # 4 One or more of combustion parameter values (1) to (7) and (12) that can individually change the combustion state may be employed.

When the heat release rate center of gravity position Gc of the first cylinder # 1 is advanced and when the maximum angular velocities ω2 to ω4 of the second cylinder # 2 to the fourth cylinder # 4 are respectively increased, the control device May be performed. When retarding the heat generation rate gravity center position Gc, each combustion parameter may be changed to the opposite direction side of the following operation.
(1a) The control device moves the timing of main injection to the advance side.
(2a) The control device increases the fuel injection pressure.
(3a) The control device increases the fuel injection amount of pilot injection.
(4a) The control device changes the number of pilot injections so that the “heat generation rate gravity center angle of pilot injection” determined only for pilot injection moves to the advance side.
(5a) The control device changes the timing of pilot injection so that the heat generation rate gravity center angle of pilot injection moves to the advance side.
(6a) The control device changes the fuel injection amount of each pilot injection so that the heat generation rate gravity center angle of the pilot injection moves to the advance side.
(7a) The control device reduces the injection amount of after injection or does not perform after injection.
(8a) The control device increases the supercharging pressure.
(9a) The control device decreases the cooling efficiency of the intercooler 45 by increasing the bypass valve opening of the intercooler 45 or decreasing the amount of cooling water.
(10a) The control device reduces the EGR rate (decreases the EGR amount) by reducing the opening degree of the EGR control valve 62 (decreasing the passage cross-sectional area of the EGR gas passage).
(11a) The control device decreases the cooling efficiency of the EGR cooler 63 by increasing the bypass valve opening of the EGR cooler 63 or decreasing the amount of cooling water.
(12a) The control device increases the strength of the swirl flow.

  Further, in the above embodiment, the heat generation rate gravity center position (ie, the constant crank angle θa) as the control target when the load of the engine 10 is within the range from the first threshold value Pem1 to the second threshold value Pem2 is ATDC 7 °. However, this value is different for each institution.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 23 ... Fuel injection valve, 70 ... ECU, 75 ... In-cylinder pressure sensor, 76 ... Crank angle sensor, # 1 ... 1st cylinder, # 2 ... 2nd cylinder, # 3 ... 3rd cylinder, # 4 ... Cylinder 4

Claims (1)

Applied to an internal combustion engine having a plurality of cylinders, one in-cylinder pressure sensor disposed corresponding to only one of these cylinders, and one crank angle sensor, heat generation in each cylinder A control device for an internal combustion engine that controls the center of gravity position,
When at least the load of the engine is within the range from the first threshold value to the second threshold value that is larger than the first threshold value, the heat release rate gravity center position of each cylinder is a constant target gravity center position regardless of the load. When the load is in a range greater than the second threshold, the heat release rate centroid position of each cylinder is in a range that is retarded from the constant target centroid position as the load increases. In a control device that feedback controls a combustion parameter that changes the combustion state of each cylinder so as to be equal to the target center-of-gravity position on the more retarded side
A center-of-gravity position calculation unit that calculates the heat generation rate center-of-gravity position of a reference cylinder that is a cylinder in which the in-cylinder pressure sensor is disposed, based on an output value of the in-cylinder pressure sensor;
A first feedback control unit that feedback-controls the combustion parameter of the reference cylinder so that the heat generation rate gravity center position of the reference cylinder calculated by the gravity center position calculation unit is equal to the target gravity center position;
A maximum crankshaft angular velocity acquisition unit that acquires the maximum value of the crankshaft angular velocity during the combustion period of each cylinder calculated based on the output value of the crank angle sensor as the maximum crankshaft angular velocity of the cylinder;
A second feedback control unit that feedback-controls the combustion parameters of the remaining cylinders so that the maximum crankshaft angular velocity of the remaining cylinders not provided with the in-cylinder pressure sensor approaches the maximum crankshaft angular velocity of the reference cylinder When,
A control device comprising:

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