JP2017008786A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that can appropriately obtain fuel ignition timing even in a state where gas amount in a cylinder is deviated from gas amount during a steady operation.SOLUTION: Based on a ratio between reference gas amount and actual gas amount, a ratio between reference gas composition and an actual gas composition and a reference value of an inertia moment received by fuel spray from gas (reference inertia moment), a target inertia moment is calculated (ST4). Based on the target inertia moment, correction amount of injection control amount of main injection fuel is calculated (ST5). By using the correction amount, the injection control amount is corrected, and by using the corrected injection control amount, main injection from an injector is executed (ST7). Thus, even in a situation where an actual gas state in a cylinder is deviated from a gas state during a steady operation, fuel ignition timing can be obtained appropriately.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control device for an internal combustion engine. In particular, the present invention relates to improved fuel injection control.

  Conventionally, in a diesel engine mounted on a vehicle or the like, the fuel injection timing is controlled so that the ignition timing of the fuel injected from the injector into the cylinder is properly obtained.

  Patent Document 1 discloses that the pilot injection timing is set in consideration of the strength of the swirl flow in the cylinder, and thereby the ignition timing of the main injected fuel is appropriately obtained.

JP 2009-2177 A

  However, during transient operation of the engine, etc., the gas amount in the cylinder greatly deviates from the gas amount during steady operation (even if the engine speed and engine load are the same) Sometimes). In Patent Document 1, this divergence in gas amount is not taken into consideration. For this reason, the fuel injection timing at the time of transient operation or the like deviates from an appropriate time, and there is a possibility that the fuel ignition timing cannot be obtained properly. In this case, problems such as deterioration of exhaust emission and increase in combustion noise are caused.

  The present invention has been made in view of such a point, and the object of the present invention is to appropriately set the ignition timing of the fuel even in a situation where the gas amount in the cylinder deviates from the gas amount during steady operation. It is to provide a control device that can be obtained.

  The solution means of the present invention for achieving the above object is applied to an internal combustion engine having a fuel injection valve for injecting fuel into a cylinder, and presupposes a control device for performing fuel injection control of the fuel injection valve. . The control device includes a reference amount acquisition unit, an actual gas amount calculation unit, an actual gas composition calculation unit, a target moment of inertia calculation unit, a correction amount calculation unit, and a fuel injection command unit. The reference amount acquisition unit is defined in advance according to the engine operating state, the reference gas amount in the cylinder, the reference gas composition in the cylinder, the reference moment of inertia that the fuel spray receives from the gas flowing in the cylinder, and Each reference injection control amount of fuel injected from the fuel injection valve is acquired. The actual gas amount calculation unit calculates the actual gas amount in the cylinder as the actual gas amount. The actual gas composition calculation unit calculates the actual gas composition in the cylinder as the actual gas composition. The target moment of inertia calculation unit is configured to calculate from the gas flowing in the cylinder based on the ratio of the reference gas amount to the actual gas amount, the ratio of the reference gas composition to the actual gas composition, and the reference inertia moment. Calculate the target moment of inertia experienced by the fuel spray. The correction amount calculation unit calculates a correction amount of an injection control amount of fuel injected from the fuel injection valve based on the target moment of inertia. The fuel injection command unit corrects the reference injection control amount with the correction amount, and causes the fuel injection valve to execute fuel injection with the corrected injection control amount.

  By this specific matter, combustion injection can be performed with an injection control amount suitable for the actual gas amount and the actual gas composition in the cylinder. For this reason, even when the actual gas amount and the actual gas composition in the cylinder deviate from the gas amount and the gas composition in the steady operation state, it is possible to appropriately obtain the ignition timing of the fuel.

  In the present invention, the target moment of inertia (the target moment of inertia that the fuel spray receives from the gas flowing in the cylinder) is calculated based on the ratio between the reference gas amount and the actual gas amount and the ratio between the reference gas composition and the actual gas composition. The injection control amount is corrected based on this target moment of inertia. For this reason, even when the actual gas amount and the actual gas composition in the cylinder deviate from the gas amount and the gas composition in the steady operation state, it is possible to properly obtain the ignition timing of the fuel. It is possible to improve and reduce combustion noise.

It is a schematic block diagram of the diesel engine which concerns on embodiment, and its control system. It is sectional drawing which shows the combustion chamber of a diesel engine, and its peripheral part. It is a block diagram which shows the structure of control systems, such as ECU. It is a top view of the piston for demonstrating a moment of inertia. It is a flowchart figure which shows the procedure of main injection control. It is a figure which shows an example of a fuel injection pressure correction amount map. It is a figure which shows an example of a fuel injection amount correction amount map. It is a figure which shows an example of a fuel injection time correction amount map.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied to a common rail in-cylinder direct injection multi-cylinder (for example, in-line 4-cylinder) diesel engine (compression self-ignition internal combustion engine) mounted on an automobile will be described.

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

  As shown in FIG. 1, the engine 1 according to this embodiment includes a fuel supply system 2, a combustion chamber 3, an intake system 6, and an exhaust system 7.

  The fuel supply system 2 includes a supply pump 21, a common rail 22, an injector (fuel injection valve) 23, an engine fuel passage 24, and the like.

  The supply pump 21 supplies the fuel pumped up from the fuel tank to the common rail 22 through the engine fuel passage 24 after making the pressure high. The common rail 22 distributes high-pressure fuel to the injectors 23. The injector 23 is a piezo injector.

  The intake system 6 includes an intake manifold 61 connected to an intake port 15 a formed in a cylinder head 15 (see FIG. 2), and an intake pipe 62 is connected to the intake manifold 61. In this intake pipe 62, an air cleaner 63, an air flow meter 43, an intercooler 65, and an intake throttle valve (diesel throttle) 64 are arranged in this order from the upstream side.

  The exhaust system 7 includes an exhaust manifold 71 connected to an exhaust port 15 b formed in the cylinder head 15, and an exhaust pipe 72 is connected to the exhaust manifold 71. The exhaust pipe 72 is provided with an NSR (NOx Storage Reduction) catalyst 74 and a DPF (Diesel Particulate Filter) 75.

  As shown in FIG. 2, the cylinder block 11 is formed with a cylinder bore 12 for each cylinder (four cylinders). A piston 13 is accommodated in each cylinder bore 12. A cavity 13 b is recessed in the center of the top surface 13 a of the piston 13, and this cavity 13 b constitutes the combustion chamber 3. The fuel injected from the central portion of the combustion chamber 3 by the injector 23 burns by self-ignition, and the combustion pressure acts on the piston 13. The piston 13 is connected to a crankshaft (not shown) by a connecting rod 18, and engine power is taken out from the crankshaft.

  The cylinder head 15 is provided with an intake valve 16 that opens and closes an intake port 15a and an exhaust valve 17 that opens and closes an exhaust port 15b.

  Further, as shown in FIG. 1, the engine 1 is provided with a turbocharger (supercharger) 5. The turbocharger 5 includes a turbine wheel 52 and a compressor wheel 53 that are connected via a turbine shaft 51.

  Further, the engine 1 is provided with an EGR (Exhaust Gas Recirculation) passage 8 that connects the intake system 6 and the exhaust system 7. The EGR passage 8 is provided with an EGR valve 81 and an EGR cooler 82.

-ECU-
The ECU (Electronic Control Unit) 100 includes a microcomputer (not shown) such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output circuit. As shown in FIG. 3, the input circuit of the ECU 100 includes a crank position sensor 40, a rail pressure sensor 41, a throttle opening sensor 42, an air flow meter 43, exhaust temperature sensors 45a and 45b, a water temperature sensor 46, and an accelerator opening sensor 47. An intake pressure sensor 48, an intake temperature sensor 49, an in-cylinder pressure sensor 4A, a fuel temperature sensor 4B, and the like are connected. Since the functions of these sensors are well known, description thereof is omitted here.

  On the other hand, the supply pump 21, the injector 23, the intake throttle valve 64, the EGR valve 81, and the like are connected to the output circuit of the ECU 100.

  The ECU 100 executes various controls of the engine 1 based on outputs from the respective sensors, calculated values obtained by calculation formulas using the output values, or various maps stored in the ROM. For example, the ECU 100 executes fuel injection control such as pilot injection and main injection as fuel injection control of the injector 23.

  Pilot injection is an operation for injecting a small amount of fuel prior to main injection. This pilot injection has a preheating function for increasing the in-cylinder temperature. That is, the temperature in the cylinder is sufficiently increased until the main injection is started, thereby suppressing the ignition delay of the main injected fuel and ensuring the ignitability of the main injected fuel.

  The main injection is a fuel injection operation for generating torque of the engine 1. The fuel injection amount and the fuel injection timing in the main injection basically obtain the required torque according to the operating state quantity such as the engine speed, the accelerator operation amount (engine load), the coolant temperature, the intake air temperature, and the like. To be determined. For example, the fuel injection amount is set to be larger as the engine speed is higher and as the accelerator operation amount (accelerator opening) is larger.

  Further, the fuel injection pressure at the time of executing the fuel injection is determined by the internal pressure of the common rail 22 (common rail internal pressure). As the common rail internal pressure, generally, the target rail pressure, which is the target value of the fuel pressure supplied from the common rail 22 to the injector 23, basically becomes higher as the engine speed increases and the engine load increases. Is done. This target rail pressure is set according to a fuel pressure setting map stored in the ROM, for example.

  In the main injection control in the present embodiment, the fuel injection pressure determined in accordance with the engine rotational speed, the engine load, etc. (the reference fuel assigned to the operation grid point corresponding to the engine rotational speed and the engine load). The reference injection control amount such as injection pressure), fuel injection amount (reference fuel injection amount assigned to the operation grid point) and fuel injection timing (reference fuel injection timing assigned to the operation grid point) is set to the gas amount in the cylinder. The final injection control amount (corrected injection control amount) is determined by correcting according to the gas composition. The main injection from the injector 23 is executed with the determined injection control amount. The correction of the injection control amount will be described later.

  In addition to the pilot injection and main injection described above, after injection and post injection are performed as necessary. Since these injection functions are well known, description thereof is omitted here.

  Further, the ECU 100 controls the opening degree of the EGR valve 81 according to the operating state of the engine 1 and adjusts the exhaust gas recirculation amount (EGR gas amount) toward the intake manifold 61. The amount of EGR gas is set according to an EGR map that is created in advance by experiments, simulations, etc. and stored in the ROM. This EGR map is a map for determining the EGR rate using the engine speed and the engine load as parameters. The ECU 100 controls the opening degree of the EGR valve 81 so as to obtain an EGR gas amount corresponding to the intake air amount so that the EGR rate determined according to the EGR map is established.

-Main injection control-
Next, main injection control, which is a feature of this embodiment, will be described. In this main injection control, in consideration of the deviation of the actual gas state (actual gas state) from the gas state (reference gas state) in the steady operation state, the fuel injection is a target that the fuel spray receives from the gas flowing in the cylinder. A target inertia moment that is an inertia moment is obtained, and fuel injection control is performed based on the target inertia moment (at least one of the injection pressure, injection amount, and injection timing of the fuel injected from the injector 23 is corrected). For example, the injection control amount (at least one of the injection pressure, the injection amount, and the injection timing) of the injector 23 is corrected so that the moment of inertia that the fuel spray receives from the gas matches the target moment of inertia.

  This moment of inertia is a moment when the spray of fuel injected from the injector 23 receives the kinetic energy of gas flowing in the cylinder (mainly the kinetic energy of swirl flow). Becomes easier to diffuse in the cylinder.

  More specifically, the gas state (gas amount and gas composition) in the cylinder is different between the steady operation and the transient operation even at the same engine speed and the same engine load. An inertia moment (reference inertia moment) suitable for the engine rotation speed and the engine load in the steady operation state is assigned to the operation grid points corresponding to the engine rotation speed and the engine load by adaptation or the like. As fuel injection control during steady operation, the injection control amount (injection pressure, injection amount, and injection timing) of the injector 23 is controlled so that this reference moment of inertia is obtained. This reference moment of inertia is set in advance by experiments or the like as a value that can regulate exhaust emission and combustion noise within the regulation range when steady operation is performed at the engine rotation speed and engine load at the operation grid point. Is. In other words, during steady operation, the injection control amount is controlled so that the moment of inertia becomes the reference moment of inertia, so that it is possible to properly obtain the ignition timing of the fuel, and to improve exhaust emission and reduce combustion noise. be able to.

  However, as described above, the gas state (gas amount and gas composition) in the cylinder is different during transient operation and during steady operation. Therefore, if the injection control amount of the injector 23 is controlled so that the reference inertia moment assigned to the operation grid point is obtained during transient operation, the inertia moment suitable for the gas state (gas amount and gas composition) is obtained. Cannot be obtained.

  For example, when the amount of gas is small or the oxygen concentration is low as the gas composition, it is necessary to increase the volume of the fuel spray (increase the moment of inertia) to efficiently contribute oxygen in the cylinder to combustion. When the injection control amount of the injector 23 is controlled so that the reference moment of inertia can be obtained, oxygen in the cylinder cannot be sufficiently utilized, and the occurrence of smoke is a concern. In addition, when the amount of gas is large or the oxygen concentration is high as the gas composition, it is necessary to reduce the volume of the fuel spray (to reduce the moment of inertia) to optimize the air-fuel ratio of the fuel spray. When the injection control amount of the injector 23 is controlled so that the moment of inertia can be obtained, the pilot injection amount decreases, so that there is a possibility that the ignition delay occurs in the combustion of the main injected fuel and the combustion noise increases.

  As described above, if the ignition timing of the fuel is deviated from the appropriate timing, problems such as deterioration of exhaust emission and increase in combustion noise are caused.

  In view of this point, the present embodiment calculates a target inertia moment (target inertia moment) according to the actual gas state, and corrects the injection control amount of the injector 23 based on the target inertia moment. Yes.

  FIG. 4 is a plan view of the piston for explaining the moment of inertia. FIG. 4 shows the spray shape of fuel injected from one of the plurality of nozzle holes provided in the injector 23.

  A region M1 indicated by a broken line in FIG. 4 indicates the shape of the combustion field of the fuel spray in a steady operation state at a certain operation grid point. That is, at the time of steady operation, an appropriate moment of inertia (reference moment of inertia) is obtained by controlling the injection control amount of the injector 23 so that this combustion field M1 is formed, thereby improving exhaust emission and combustion noise. Can be planned.

  On the other hand, in the present embodiment, during the transient operation, for example, when the gas amount in the cylinder is small or the oxygen concentration is low as the gas composition, the combustion field of the fuel spray is in the region M2 indicated by the solid line in FIG. The injection control amount of the injector 23 is controlled so as to be formed. That is, the injector 23 is configured so that a moment of inertia (target moment of inertia) suitable for the gas state (gas amount and gas composition) during transient operation can be obtained, that is, a combustion field of fuel spray is formed in the region M2. The injection control amount is controlled. As a result, exhaust emission and combustion noise during transient operation can be improved.

  Hereinafter, an outline of the main injection control will be described.

  In this main injection control, (a) fuel from the reference gas amount Gcylb in the cylinder, the reference gas composition Cb in the cylinder, and the gas flowing in the cylinder, which is defined in advance according to the operating state (engine operating state) of the engine 1. (B) an operation for obtaining the reference inertia moment Ib received by the spray and a reference injection control amount of the fuel injected from the injector 23, (b) an operation for calculating the actual gas amount in the cylinder as the actual gas amount Gcyl, (c ) Operation for calculating the actual gas composition in the cylinder as the actual gas composition C, (d) the ratio between the reference gas amount Gcylb and the actual gas amount Gcyl, and the ratio between the reference gas composition Cb and the actual gas composition C And (e) calculating the target inertia moment It received by the fuel spray from the gas flowing in the cylinder based on the reference inertia moment Ib. An operation for calculating a correction amount of the injection control amount of the fuel injected from the injector 23 based on the current It, and (f) the reference injection control amount is corrected by the correction amount, and the injector 23 is corrected by the corrected injection control amount. The operation of executing the fuel injection from is sequentially performed. Details of the operations (a) to (f) will be described later.

  These operations are executed by the ECU 100. For this reason, in the ECU 100, a functional part that executes the operation (a) is configured as a reference amount acquisition unit referred to in the present invention. Further, in the ECU 100, a functional part that executes the operation (b) is configured as an actual gas amount calculation unit referred to in the present invention. Further, in the ECU 100, a functional part that executes the operation (c) is configured as an actual gas composition calculation unit in the present invention. Further, in the ECU 100, a functional part that executes the operation (d) is configured as a target moment of inertia calculation unit referred to in the present invention. Further, in the ECU 100, a functional part that executes the operation (e) is configured as a correction amount calculation unit in the present invention. Further, in the ECU 100, a functional portion that executes the operation (f) is configured as a fuel injection command section referred to in the present invention.

  These reference amount acquisition unit, actual gas amount calculation unit, actual gas composition calculation unit, target moment of inertia calculation unit, correction amount calculation unit, and fuel injection command unit constitute a control device according to the present invention.

  Hereinafter, a specific procedure of the main injection control will be described along the flowchart of FIG. This flowchart shows after every start of the engine 1 when the crankshaft rotates by a predetermined angle (more specifically, every time before main injection is started in any cylinder; for example, the piston 13 is compressed Every time when the predetermined crank angle position is reached before the dead center is reached: the engine 1 according to the present embodiment has four cylinders, so the ECU 100 is repeatedly executed at every 180 ° CA). In the following, a cylinder in which the main injection control amount is defined in the main injection control (a cylinder that has reached the timing before the main injection is started) is referred to as a control target cylinder.

  First, in step ST1, the reference gas amount Gcylb and reference gas composition in the cylinder (stored in the ROM) assigned to the operating grid point (current engine operating state) corresponding to the current engine speed and engine load are stored. Cb and reference moment of inertia Ib are acquired. That is, of the reference gas amount Gcylb, the reference gas composition Cb, and the reference moment of inertia Ib that are assigned in advance for each operation grid point, information assigned to the operation grid point corresponding to the current engine speed and engine load. Is read. The reference gas amount Gcylb is the mass of intake air in the cylinder to be controlled (the mass of intake air on the operating grid point). The reference gas composition Cb is the oxygen concentration in the gas in the cylinder to be controlled (oxygen concentration on the operating grid point).

  In step ST2, the reference injection control amount (stored in the ROM) assigned to the operation grid point corresponding to the current engine speed and engine load is acquired. Specifically, the reference injection pressure, the reference injection amount, and the reference injection timing assigned to the operation grid point are acquired.

  The operations of these steps ST1 and ST2 are “operations by the reference amount acquisition unit” according to the present invention, and are defined in advance according to the engine operating state, the reference gas amount in the cylinder, the reference gas composition in the cylinder, the cylinder This corresponds to an operation for acquiring a reference moment of inertia that the fuel spray receives from the gas flowing inside and a reference injection control amount of the fuel injected from the fuel injection valve.

  In step ST3, a gas amount (actual gas amount) Gcyl and a gas composition (actual gas composition) C in the current engine operating state are calculated.

  The actual gas amount Gcyl is the actual intake air mass introduced into the cylinder to be controlled, and is obtained based on output signals from the air flow meter 43 and the intake air temperature sensor 49. For example, the intake air amount (the integrated value of the intake air amount calculated based on the output signal from the air flow meter 43) during a predetermined period (for example, during the period from when the intake valve 16 of the cylinder to be controlled is opened to when it is closed) ) And a predetermined arithmetic expression or map using the intake air temperature (the intake air temperature detected by the output signal from the intake air temperature sensor 49) as a parameter, the actual gas amount Gcyl is obtained. The actual gas amount Gcyl is calculated as a larger value as the intake air amount is larger and the intake air temperature is lower. Further, the actual gas amount Gcyl is calculated by adding the EGR gas amount (EGR gas amount for achieving the EGR rate read from the EGR map) to the gas amount obtained based on the output signal from the air flow meter 43. You may make it do.

  This operation corresponds to the “operation by the actual gas amount calculation unit that calculates the actual gas amount in the cylinder as the actual gas amount” in the present invention.

  The actual gas composition C is an actual oxygen concentration in the gas introduced into the cylinder to be controlled, and is obtained from the EGR rate, the air-fuel ratio (A / F), and the like. The EGR rate is read from the EGR map as described above. The air-fuel ratio is obtained from an intake air amount and a fuel injection amount calculated based on an output signal from an air-fuel ratio sensor (not shown) or an output signal from the air flow meter 43. The actual gas composition C is obtained from a predetermined arithmetic expression or map using the EGR rate and the air-fuel ratio (A / F) as parameters. The actual gas composition C (oxygen concentration in the gas) is calculated as a higher value as the EGR rate is lower and as the air-fuel ratio (A / F) is larger.

  This operation corresponds to the “operation by the actual gas composition calculation unit, which calculates the actual gas composition in the cylinder as the actual gas composition” in the present invention.

  In step ST4, the target moment of inertia It is calculated. As described above, this target moment of inertia It is calculated as the moment of inertia capable of improving exhaust emission and combustion noise during transient operation.

  Specifically, the target moment of inertia It is determined by the ratio of the actual gas amount Gcyl to the reference gas amount Gcylb (Gcyl / Gcylb), the ratio of the actual gas composition C to the reference gas composition Cb (C / Cb), and , And a predetermined arithmetic expression or map using each of the reference moments of inertia Ib as parameters. The target inertia moment It is calculated as a larger value as the ratio of the actual gas amount Gcyl to the reference gas amount Gcylb is smaller and as the ratio of the actual gas composition C to the reference gas composition Cb is smaller.

  This operation is an operation by the “target inertia moment calculation unit” in the present invention, based on the ratio of the reference gas amount to the actual gas amount, the ratio of the reference gas composition to the actual gas composition, and the reference inertia moment. Corresponds to the operation of calculating the target moment of inertia that the fuel spray receives from the gas flowing in the cylinder.

  In step ST5, a correction amount of the control amount of the main injection (at least one of the fuel injection pressure, the fuel injection amount, and the fuel injection timing) is calculated. That is, a correction amount for the reference fuel injection pressure (fuel injection pressure correction amount), a correction amount for the reference fuel injection amount (fuel injection amount correction amount), and a correction amount for the reference fuel injection timing (fuel injection timing correction amount). At least one of them is calculated. Here, a case where one of the fuel injection pressure, the fuel injection amount, and the fuel injection timing is corrected will be described as an example.

  The correction amount is calculated by a predetermined arithmetic expression using the target moment of inertia It and the reference injection control amount as variables. Alternatively, a map for obtaining the correction amount using the target inertia moment It and the reference injection control amount as parameters is created by experiment and stored in the ROM of the ECU 100, and the correction amount is obtained by referring to this map. Also good.

  FIG. 6 is a diagram showing an example of a fuel injection pressure correction amount map used when correcting only the fuel injection pressure. In this fuel injection pressure correction amount map, the correction amount of the fuel injection pressure is obtained as a larger value as the target moment of inertia It is larger. In other words, the larger the target inertia moment It is, the higher the fuel injection pressure is set, thereby increasing the penetration force of the main injected fuel, thereby increasing the spray reach distance (expanding the fuel spray region to reduce the inertia moment to the target inertia To match the moment It). Specifically, in FIG. 6, when the correction amount of the fuel injection pressure is obtained as a positive value, the correction is made so that the fuel injection pressure becomes higher than the reference fuel injection pressure, and the moment of inertia is the reference. It becomes larger than the moment of inertia. On the other hand, when the correction amount of the fuel injection pressure is obtained as a negative value, the correction is made so that the fuel injection pressure becomes lower than the reference fuel injection pressure, and the inertia moment becomes smaller than the reference inertia moment.

  FIG. 7 is a diagram showing an example of a fuel injection amount correction amount map used when correcting only the fuel injection amount. In this fuel injection amount correction amount map, the fuel injection amount correction amount is obtained as a larger value as the target inertia moment It is larger. In other words, the larger the target inertia moment It is, the larger the fuel injection amount is set, thereby increasing the penetration force of the main injected fuel, thereby increasing the spray reach distance (expanding the fuel spray region to reduce the inertia moment to the target inertia To match the moment It). Specifically, in FIG. 7, when the correction amount of the fuel injection amount is obtained as a positive value, it is corrected so that the fuel injection amount becomes larger than the reference fuel injection amount (actually, the fuel injection amount The moment of inertia becomes larger than the reference moment of inertia). On the other hand, when the correction amount of the fuel injection amount is obtained as a negative value, it is corrected so that the fuel injection amount becomes smaller than the reference fuel injection amount (in practice, the fuel injection period becomes shorter). Corrected) and the moment of inertia becomes smaller than the reference moment of inertia.

  FIG. 8 is a diagram showing an example of a fuel injection timing correction amount map used when correcting only the fuel injection timing. In this fuel injection timing correction amount map, the correction amount is obtained as a value that increases the amount of shift of the fuel injection timing to the retard side as the target moment of inertia It increases. In other words, as the target inertia moment It is larger, the fuel injection timing is set to the retard side, thereby starting the main injection in a situation where the flow speed of the swirl becomes higher, thereby increasing the kinetic energy of the swirl flow (fuel spraying) The kinetic energy (moment of inertia) received by the. Specifically, in FIG. 8, when the fuel injection timing is obtained as a value on the retard side, the fuel injection timing is corrected to the retard side with respect to the reference fuel injection timing, and the movement received by the fuel spray Energy increases. That is, the moment of inertia increases. On the other hand, when the fuel injection timing is obtained as an advance value, the fuel injection timing is corrected to the advance side with respect to the reference fuel injection timing, and the kinetic energy received by the fuel spray is reduced. That is, the moment of inertia is reduced.

  Further, when correcting a plurality of injection control amounts among the fuel injection pressure, the fuel injection amount, and the fuel injection timing, the relationship between the correction amount of the plurality of injection control amounts and the spray arrival distance is verified by experiments, etc. A correction amount map is created based on the verification result, and each injection control amount is corrected according to the correction amount map.

  The operation of step ST5 is referred to in the present invention as "an operation by the correction amount calculation unit that calculates a correction amount of the injection control amount of the fuel injected from the fuel injection valve based on the target moment of inertia". Equivalent to.

  In step ST6, it is determined whether or not the main injection execution timing has come (the crank angle position has reached the main injection execution crank angle position). For example, when the correction amount of the fuel injection timing is calculated in step ST5, it is determined whether or not the fuel injection timing (main injection execution timing) corrected with this correction amount has come. If the fuel injection timing is not corrected, it is determined whether or not the fuel injection timing assigned to the current engine speed and engine load (operation grid point) has been reached.

  If the execution timing of the main injection has not yet been reached, a NO determination is made in step ST6 and the process waits for the execution timing to be reached.

  When the execution timing of the main injection is reached and YES is determined in step ST6, the process proceeds to step ST7 and main injection is executed.

  That is, when the correction amount of the fuel injection pressure is calculated in step ST5, the main injection is executed with the fuel injection pressure corrected with this correction amount. Specifically, the target rail pressure is changed, and the supply pump 21 is controlled accordingly.

  When the correction amount of the fuel injection amount is calculated in step ST5, the main injection is executed with the fuel injection amount corrected with this correction amount. Specifically, the valve opening period of the injector 23 is controlled according to the rail pressure so that the corrected fuel injection amount is obtained.

  The operation of step ST7 is “operation by the fuel injection command unit” in the present invention, wherein the reference injection control amount is corrected with the correction amount, and the fuel injection from the fuel injection valve is executed with the corrected injection control amount. Corresponds to “operation”.

  The above operation is repeated every time the crankshaft rotates by a predetermined angle (every time before the main injection is started in any cylinder).

  Since such main injection control is performed, the ECU 100 constitutes a control device for an internal combustion engine according to the present invention. This control device is configured to receive signals from the crank position sensor 40, the air flow meter 43, the accelerator opening sensor 47, the intake air temperature sensor 49, and the like as input signals. Further, this control device is configured to output a main injection command signal as an output signal to each injector 23.

  As described above, in this embodiment, the target moment of inertia It is based on the ratio of the actual gas amount Gcyl to the reference gas amount Gcylb (Gcyl / Gcylb) and the ratio of the actual gas composition C to the reference gas composition Cb (C / Cb). And the injection control amount is corrected based on this target moment of inertia It. Thereby, even if the actual gas state (actual gas amount Gcyl and actual gas composition C) in the cylinder is deviated from the gas state (reference gas amount Gcylb and reference gas composition Cb) during steady operation, It is possible to obtain an ideal fuel spray diffusion state corresponding to the actual gas state. In other words, the fuel ignition timing is obtained by appropriately obtaining the timing at which the air-fuel ratio in the fuel spray becomes the air-fuel ratio at which fuel ignition is possible (the timing at which exhaust emission can be improved and combustion noise can be reduced). Can be obtained appropriately. As a result, exhaust emission can be improved and combustion noise can be reduced.

  In this embodiment, the injection control amount is corrected by feedforward control according to the actual gas state. For this reason, the situation where the ignition timing of fuel deviates from an appropriate time can be prevented in advance. As a result, even in a situation where the operating state of the engine 1 fluctuates, it is possible to continuously maintain the effects of improving exhaust emission and reducing combustion noise (in the case of feedback control, exhaust emission is temporarily reduced). Worsening or increase in combustion noise).

-Other embodiments-
In the embodiment described above, the actual gas amount Gcyl and the actual gas composition C at the timing at which the piston 13 reaches the predetermined crank angle position before reaching the compression top dead center are calculated and obtained by using these calculated values. The injection control amount is corrected according to the target inertia moment It. The present invention is not limited to this, and estimates the actual gas amount Gcyl and the actual gas composition C at the reference main injection timing assigned to the operation grid points corresponding to the current engine speed and engine load, and these estimated values are calculated. The injection control amount may be corrected according to the target moment of inertia It obtained by use.

  In the above embodiment, the case where the fuel injection control according to the present invention is applied to the main injection control has been described. The present invention is not limited to this, and can also be applied to pilot injection control.

  Moreover, the said embodiment demonstrated the case where this invention was applied to the in-line 4 cylinder diesel engine 1 mounted in the motor vehicle. The present invention is applicable not only to automobiles but also to engines used for other purposes. Further, the number of cylinders and the engine type (separate type engine, V-type engine, horizontally opposed engine, etc.) are not particularly limited.

  Moreover, although the said embodiment demonstrated the case where this invention was applied to the engine 1 of a conventional vehicle (vehicle which mounted only an engine as a driving force source), the vehicle which mounts an engine and an electric motor as a driving force source. The present invention can also be applied to the engine.

  The present invention is applicable to fuel injection control in a diesel engine mounted on an automobile.

1 engine (internal combustion engine)
3 Combustion chamber 23 Injector (fuel injection valve)
100 ECU

Claims (1)

In a control device that is applied to an internal combustion engine having a fuel injection valve that injects fuel into a cylinder and performs fuel injection control of the fuel injection valve,
The reference gas amount in the cylinder, the reference gas composition in the cylinder, the reference moment of inertia that the fuel spray receives from the gas flowing in the cylinder, and the injection from the fuel injection valve, which are defined in advance according to the engine operating state A reference amount acquisition unit for acquiring each of the reference injection control amounts of the fuel to be
An actual gas amount calculation unit for calculating an actual gas amount in the cylinder as an actual gas amount;
An actual gas composition calculation unit for calculating an actual gas composition in the cylinder as an actual gas composition;
Based on the ratio between the reference gas amount and the actual gas amount, the ratio between the reference gas composition and the actual gas composition, and the reference inertia moment, the target inertia moment that the fuel spray receives from the gas flowing in the cylinder A target moment of inertia calculation unit for calculating
A correction amount calculation unit that calculates a correction amount of an injection control amount of fuel injected from the fuel injection valve based on the target moment of inertia;
A fuel injection command unit that corrects the reference injection control amount with the correction amount, and executes fuel injection from the fuel injection valve with the corrected injection control amount;
A control device for an internal combustion engine, comprising:

Images