JP2017020411A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device capable of obtaining controlled variable of after-injection to improve exhaust emission.SOLUTION: An air-fuel ratio in a combustion field of a fuel injected by main injection is calculated as local A/F (ST4). A remaining oxygen amount Or in a cylinder in a reference injection period of after-injection is calculated (ST5). A flow quantity in a cylinder necessary for introducing oxygen remaining in a region excluding the combustion field, to the combustion field of the fuel injected by main injection is calculated as a required cylinder flow quantity R on the basis of the local A/F and the remaining oxygen amount Or (ST6). Controlled variable of the after-injection to obtain the required cylinder flow quantity R is calculated (ST7). Thus oxygen deficiency in the combustion field of the main injection fuel can be solved even in a transient operation, generation of smoke in the combustion field of the main injection fuel can be suppressed, and exhaust emission can be improved.SELECTED DRAWING: Figure 4

Description

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

  Conventionally, in a diesel engine mounted on a vehicle or the like, after injection is performed after main injection that contributes to torque generation. The fuel injected in the after injection burns unburned components (smoke) in the main injection, thereby purifying the exhaust.

  Patent Document 1 discloses that the after injection amount is adjusted so that the ratio between the in-cylinder oxygen amount and the after injection amount during execution of the after injection becomes a preset target value.

JP 2012-145042 A

  By the way, in a transient operation or the like, if a delay occurs in the EGR gas reduction correction operation or a turbocharger delay occurs, the in-cylinder oxygen amount may be lower than that in the steady operation. There is. When such a situation occurs, in the case of Patent Document 1 (the one that adjusts the after-injection amount so that the ratio between the in-cylinder oxygen amount and the after-injection amount becomes the target value), the in-cylinder oxygen As the amount decreases, the after injection amount is corrected to decrease. As a result, the original function of after-injection, such as burning unburned components in main injection, cannot be fully exerted, and exhaust emission may be deteriorated.

  The inventor of the present invention indicates that the combustion region of the main injection fuel (combustion field where oxygen is consumed by the main injection fuel) is a partial region in the combustion chamber, and the oxygen concentration is high in the other regions. In addition, when after-injected fuel was executed, we focused on the flow of gas in the combustion chamber caused by it, and considered how to improve exhaust emissions using these.

  The present invention has been made in view of this point, and an object of the present invention is to provide a control device capable of obtaining a control amount of after-injection that can improve exhaust emission.

  The solution of the present invention for achieving the above object is applied to a compression self-ignition internal combustion engine that performs combustion by self-ignition of fuel injected into a cylinder from a fuel injection valve, A control device that executes main injection and after-injection as fuel injection is assumed. For this control device, an actual gas state amount calculation unit, a reference injection control amount acquisition unit, an injection pressure detection unit, a local air-fuel ratio calculation unit, a residual oxygen amount calculation unit, a required in-cylinder flow amount calculation unit, an after injection control amount calculation And an after-injection command unit. The actual gas state amount calculation unit calculates an actual gas amount and an actual gas composition in the cylinder. The reference injection control amount acquisition unit sets the current engine operation state among the reference injection amounts of the main injection and the after injection, and the reference injection control amounts of the reference injection timing, which are defined in advance according to the engine operation state. A corresponding reference injection control amount is acquired. The injection pressure detector detects the fuel injection pressure. The local air-fuel ratio calculating unit is configured to perform a reference injection of the after injection in the combustion field of the fuel injected in the main injection based on the gas amount, the gas composition, the reference injection control amount, and the injection pressure of the fuel. The air-fuel ratio at the time is calculated as the local air-fuel ratio. The residual oxygen amount calculation unit calculates the residual oxygen amount in the cylinder at the reference injection timing of the after injection based on the gas amount, the gas composition, the reference injection control amount, and the fuel injection pressure. The required in-cylinder flow amount calculation unit is provided in a combustion field of fuel injected in the main injection in a region other than the combustion field based on the local air-fuel ratio, the gas composition, and the residual oxygen amount in the cylinder. The flow amount in the cylinder necessary for introducing the oxygen that is being calculated is calculated as the required in-cylinder flow amount. The after injection control amount calculation unit calculates a control amount of the after injection for obtaining the required in-cylinder flow amount. The after injection command unit causes the fuel injection valve to execute after injection with the calculated after injection control amount.

  By this specific matter, oxygen remaining in the region other than the combustion field can be introduced into the combustion field of the main injection fuel by using the gas flow in the cylinder resulting from the after injection. Thereby, the oxygen shortage in the combustion field of the main injection fuel can be eliminated, and the generation of smoke in this combustion field can be suppressed.

  In the present invention, oxygen remaining in a region other than the combustion field is introduced into the combustion field of the main injection fuel based on the local air-fuel ratio in the combustion field of the main injection fuel, the amount of residual oxygen in the cylinder, and the like. The amount of flow in the cylinder necessary for this is obtained, and the control amount of the after injection is adjusted so that this amount of flow is obtained. For this reason, even during transient operation, it is possible to suppress the generation of smoke in the combustion field of the main injection fuel and improve exhaust emission.

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 flowchart figure which shows the procedure of after injection control. It is a figure which shows an example of the request | requirement in-cylinder flow amount calculation map. It is a figure which shows an example of an after injection frequency calculation map. It is a figure which shows an example of an after injection amount calculation map. It is a figure which shows an example of an after injection timing calculation 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 air temperature sensor 49, an in-cylinder pressure sensor 4A, an air-fuel ratio 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, main injection, and after 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 fuel injection timing in the main injection are determined so as to obtain the required torque according to the engine speed, the accelerator operation amount (engine load), and the like. 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.

  After-injection is an operation of injecting a small amount of fuel after main injection. By this after injection, the exhaust gas is purified by burning smoke, which is an unburned component generated in the cylinder by the main injection.

  The after-injection control in the present embodiment is a region where oxygen is not consumed due to the combustion of the main injected fuel, or a region where the amount of oxygen consumed due to this combustion is small and where there is a large amount of residual oxygen. Is sent to the combustion field of the main injection fuel by the flow in the combustion chamber 3 generated due to the after injection. As a result, the shortage of oxygen in this combustion field is resolved and the generation of smoke is suppressed. More specifically, before the combustion of the main injected fuel is completed, the residual oxygen is sent to the combustion field of the main injected fuel, and the oxygen shortage in the combustion field is resolved to suppress the generation of smoke. Yes. A specific procedure of this after injection control will be described later.

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

  The fuel injection pressure at the time of executing each fuel injection described above 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, becomes higher as the engine speed increases and the engine load increases. This target rail pressure is set according to a fuel pressure setting map stored in the ROM, for example.

  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.

-After injection control-
Next, after injection control, which is a feature of the present embodiment, will be described. As described above, this after-injection control is present in a region where oxygen is not consumed due to combustion of the main injected fuel, or a region where the amount of oxygen consumed by this combustion is small and the amount of residual oxygen is large. The oxygen that is present is sent to the combustion field of the main injection fuel by the flow in the combustion chamber 3 generated due to the after injection. This eliminates the oxygen shortage in the combustion field and suppresses the generation of smoke.

  Specifically, since the injection amount of the main injection is larger than the injection amount of the after injection, the penetration force of the main injection fuel is larger than the penetration force of the after injection fuel. The combustion field of the main injection fuel is formed in the outer peripheral portion of the combustion chamber 3. Therefore, in a situation where the main injection fuel is combusting (a situation where after-injection has not yet been executed), a large amount of oxygen remains around the injector 23 and in the central portion of the combustion chamber 3. . Generally, the pilot injection is executed at a stage before the main injection. Since the injection amount of the pilot injection is smaller than the injection amount of the main injection, the penetration force of the pilot injection fuel is small, and the pilot injection fuel burns in the central portion of the combustion chamber 3, as described above. Since the injection amount of the pilot injection is small, the oxygen consumption amount in the central portion of the combustion chamber 3 is small and the residual oxygen amount is large.

  In the present embodiment, oxygen remaining in the central portion of the combustion chamber 3 is sent to the combustion field of the main injection fuel by using the flow in the combustion chamber 3 that is generated as the after injection is performed (main injection fuel). During the combustion of the gas, oxygen is fed toward the combustion field), and the shortage of oxygen in the combustion field is resolved to suppress the generation of smoke. Further, since oxygen is required for the after-injected fuel to burn in the combustion chamber 3, the control amount of after-injection (the number of after-injections, At least one of the after injection amount and the after injection timing) is obtained, and the after injection is executed with this control amount.

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

  In this after-injection control, (a) an operation for calculating an actual gas amount and an actual gas composition in the cylinder, (b) a main injection defined in advance according to the operating state (engine operating state) of the engine 1 and Of the reference injection amount of each after injection and the reference injection control amount of the reference injection timing, the operation of obtaining the reference injection control amount corresponding to the current engine operating state, (c) detecting the fuel injection pressure (rail pressure) (D) based on the gas amount, the gas composition, the reference injection control amount, and the fuel injection pressure, and locally setting the air-fuel ratio at the reference injection timing of the after injection in the combustion field of the fuel injected in the main injection Calculate the residual oxygen amount in the cylinder at the reference injection timing of after injection based on the operation calculated as the air-fuel ratio, (e) gas amount, gas composition, reference injection control amount, and fuel injection pressure (F) Based on the local air-fuel ratio, gas composition, and residual oxygen amount in the cylinder, oxygen remaining in the region other than the combustion field is introduced into the combustion field of the fuel injected by the main injection. (G) an operation for calculating the control amount of the after injection for obtaining the required in-cylinder flow amount, and (h) the calculated after-injection. The operation of executing the after injection from the injector 23 with the controlled amount is sequentially performed. Details of the operations (a) to (h) 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 an actual gas state quantity calculation unit referred to in the present invention. In the ECU 100, a functional part that executes the operation (b) is configured as a reference injection control amount acquisition unit referred to in the present invention. In the ECU 100, a functional part that executes the operation (c) is configured as an injection pressure detection unit in the present invention. In the ECU 100, a functional part that executes the operation (d) is configured as a local air-fuel ratio calculating unit in the present invention. In the ECU 100, a functional part that executes the operation (e) is configured as a residual oxygen amount calculation unit in the present invention. The functional part that executes the operation (f) is configured as a required in-cylinder flow amount calculation unit in the present invention. The functional part that executes the operation (g) is configured as an after-injection control amount calculation unit in the present invention. The functional part that executes the operation (h) is configured as an after injection command unit in the present invention.

  These actual gas state amount calculation unit, reference injection control amount acquisition unit, injection pressure detection unit, local air-fuel ratio calculation unit, residual oxygen amount calculation unit, required in-cylinder flow amount calculation unit, after injection control amount calculation unit, and after A control device according to the present invention is constituted by the injection command section.

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

  First, in step ST1, 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, an actual gas amount gcyl is obtained by adding an EGR gas amount (an EGR gas amount for achieving an EGR rate read from the EGR map) to a gas amount obtained based on an output signal from the air flow meter 43 or the like. You may make it calculate.

  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 detected by an output signal from the air-fuel ratio sensor 4B. 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.

  These operations correspond to the “operations by the actual gas state quantity calculation unit, which calculate the actual gas amount and the actual gas composition in the cylinder” according to the present invention.

  In step ST2, the reference injection control amount (stored in the ROM) assigned to the operating grid point (current engine operating state) corresponding to the current engine speed and engine load is acquired. Specifically, the reference injection amounts q1 and q2 and the reference injection timings inj1 and inj2 for the main injection and the after injection assigned to the operation grid points in the current engine operating state are acquired.

  The operation of this step ST2 is the “operation by the reference injection control amount acquisition unit” according to the present invention, and the reference injection amount and the reference injection timing of each of the main injection and the after injection that are defined in advance according to the engine operating state. This corresponds to “operation for acquiring a reference injection control amount corresponding to the current engine operating state” among the respective reference injection control amounts.

  In step ST3, rail pressure (fuel injection pressure) pcr is detected. This rail pressure pcr is detected by an output signal from the rail pressure sensor 41.

  The operation in step ST3 corresponds to the “operation by the injection pressure detection unit, which detects the fuel injection pressure” in the present invention.

  In step ST4, a local A / F (local air-fuel ratio) is calculated. This local A / F is the air-fuel ratio at the reference injection timing inj2 of the after injection in the combustion field of the fuel injected by the main injection. That is, in the state where the main injection fuel is ignited and the combustion is continued while consuming oxygen in the combustion field, the combustion of the main injection fuel at the timing when the after injection is started (the reference injection timing inj2 of the after injection) The field air-fuel ratio is calculated in step ST4.

  This local A / F is a predetermined value using the actual gas amount gcyl, the actual gas composition C, the main injection reference injection amount q1, the main injection reference injection timing inj1, the after injection reference injection timing inj2, and the rail pressure pcr as parameters. It is obtained from an arithmetic expression or a map. The smaller the actual gas amount gcyl, the lower the actual gas composition C (oxygen concentration in the gas), the greater the reference injection amount q1 of the main injection, the closer the reference injection timing inj1 of the main injection is to the advance side. (The higher the in-cylinder pressure when the main injection is executed) and the more the reference injection timing inj2 of the after injection is on the advance side (the spread of the main injected fuel spray is smaller when the after injection is executed) The local A / F is calculated as a low value (rich side value).

  The operation of this step ST4 is “the operation by the local air-fuel ratio calculating section” in the present invention, which is injected in the main injection based on the gas amount, the gas composition, the reference injection control amount, and the fuel injection pressure. This corresponds to the operation of calculating the air-fuel ratio at the reference injection timing of after-injection in the fuel combustion field as the local air-fuel ratio.

  In step ST5, the residual oxygen amount Or in the cylinder at the reference injection timing inj2 of the after injection is calculated. As described above, at the time of combustion of the main injection fuel, a large amount of oxygen remains around the injector 23 and in the central portion of the combustion chamber 3. When the entire cylinder is considered, oxygen remains in the cylinder by an amount obtained by subtracting the amount of oxygen consumed by the combustion of the main injection fuel from the amount of oxygen before execution of the main injection. For this reason, the residual oxygen amount Or changes according to the combustion amount of the main injection fuel. In step ST5, the residual oxygen amount Or is calculated. The larger the residual oxygen amount Or, the larger the amount of oxygen that can be sent to the combustion field of the main injected fuel.

  This residual oxygen amount Or is a predetermined amount using the actual gas amount gcyl, the actual gas composition C, the main injection reference injection amount q1, the main injection reference injection timing inj1, the after injection reference injection timing inj2, and the rail pressure pcr as parameters. Calculated from an arithmetic expression or map The larger the actual gas amount gcyl, the higher the actual gas composition C (oxygen concentration in the gas), the smaller the reference injection amount q1 of the main injection, and the closer the reference injection timing inj1 of the main injection is to the retard side. (The lower the in-cylinder pressure when the main injection is executed and the more the combustion field of the main injected fuel is located on the outer peripheral side), and the more the reference injection timing inj2 of the after injection is on the advanced side (after injection is executed) The smaller the spread of the main injected fuel spray is, the more the remaining oxygen amount Or is calculated.

  The operation of this step ST5 is an operation by the “residual oxygen amount calculating section” in the present invention, and the reference injection timing of the after injection is based on the gas amount, the gas composition, the reference injection control amount, and the fuel injection pressure. Corresponds to the operation of calculating the residual oxygen amount in the cylinder.

  In step ST6, a required in-cylinder flow amount R is calculated. This required in-cylinder flow amount R is for introducing oxygen remaining in a region other than this combustion field (specifically, the central portion of the combustion chamber 3) into the combustion field of the fuel injected by the main injection. The amount of flow in the cylinder required for the above (the amount of gas movement in the cylinder). Specifically, the amount of flow in the cylinder necessary to send the amount of oxygen generated in the combustion field of the main injection fuel to the combustion field of the main injection fuel without excess or deficiency is sufficient for the amount of oxygen generated within the regulation range. Calculated.

  The required in-cylinder flow amount R is calculated by a predetermined arithmetic expression using the local A / F, the actual gas composition C, and the residual oxygen amount Or as variables. Alternatively, a map for determining the required in-cylinder flow amount R using the local A / F, the actual gas composition C, and the residual oxygen amount Or as parameters is created by experiment and stored in the ROM of the ECU 100. The required in-cylinder flow amount R may be obtained by referring to the amount calculation map.

  FIG. 5 is a diagram illustrating an example of a required in-cylinder flow amount calculation map at a certain oxygen concentration (actual gas composition C). In this required in-cylinder flow amount calculation map, the horizontal axis is the local A / F, and the vertical axis is the required in-cylinder flow amount R.

  In this required in-cylinder flow amount calculation map, the smaller the local A / F, the greater the required in-cylinder flow amount R that is required. This is because, as the local A / F (air-fuel ratio of the combustion field of the main injection fuel) is smaller, in order to suppress the amount of smoke generated, it is necessary to send a larger amount of oxygen to the combustion field of the main injection fuel. Considering that it is necessary to obtain a large in-cylinder flow rate.

  Further, in this required in-cylinder flow amount calculation map, the smaller the remaining oxygen amount Or, the greater the required in-cylinder flow amount R is required. This is because, when the residual oxygen amount Or is small, the amount of oxygen that can be sent to the combustion field of the main injected fuel decreases with the same in-cylinder flow amount, and the amount of smoke generated may increase. This is because it is necessary to obtain a large in-cylinder flow rate in order to secure a large amount of oxygen.

  A required in-cylinder flow amount calculation map for such a predetermined oxygen concentration (actual gas composition C) is stored in the ROM for each oxygen concentration. In each required in-cylinder flow amount calculation map, the lower the oxygen concentration, the larger the required in-cylinder flow amount R is obtained. This is because when the oxygen concentration is low, the amount of oxygen that can be sent to the combustion field of the main injected fuel decreases with the same in-cylinder flow amount, and the amount of smoke generated may increase. This is because it is necessary to obtain a large in-cylinder flow amount in order to secure a large amount.

  The operation of this step ST6 is an operation by the “required in-cylinder flow amount calculation unit” according to the present invention, which is based on the local air-fuel ratio, gas composition, and residual oxygen amount in the cylinder. This corresponds to the operation of calculating, as a required in-cylinder flow amount, a flow amount in the cylinder necessary for introducing oxygen remaining in a region other than the combustion field into the combustion field.

  In step ST7, the control amount of the after injection (the number of after injections, the after injection amount, and the after injection timing) is determined. That is, the after injection control amount for obtaining the required in-cylinder flow amount R calculated in step ST6 is calculated. The control amount of the after injection is obtained from a predetermined arithmetic expression or map using the required in-cylinder flow amount R and the actual gas amount gcyl as parameters.

  Here, a case where one of the number of after injections, the after injection amount, and the after injection timing is corrected will be described as an example.

  FIG. 6 is a diagram showing an example of an after injection number calculation map used when only the after injection number is corrected. In this after injection number calculation map, the horizontal axis is the required in-cylinder flow amount R, and the vertical axis is the number of after injections. The larger the required in-cylinder flow amount R, the greater the number of after injections. This is because as the number of after injections increases, the number of gas flows generated in the cylinder by the after-injected fuel increases, and the amount of gas movement can be increased. Further, the larger the actual gas amount gcyl, the greater the number of after injections. This is because as the actual gas amount gcyl increases, the penetration force of the after-injected fuel tends to decrease and the gas flow in the cylinder tends to decrease. Therefore, the number of after injections is increased in order to obtain a sufficient gas flow. is there.

  FIG. 7 is a diagram showing an example of an after injection amount calculation map used when correcting only the after injection amount. In this after injection amount calculation map, the horizontal axis is the required in-cylinder flow amount R, and the vertical axis is the after injection amount. The greater the required in-cylinder flow amount R, the greater the after-injection amount. This is because the penetration force of the after-injected fuel increases as the after-injection amount increases, and the amount of gas movement can be increased. Further, as the actual gas amount gcyl increases, the after injection amount increases. This is because as the actual gas amount gcyl increases, the penetration force of the after-injected fuel tends to decrease and the gas flow in the cylinder tends to decrease. Therefore, the after-injection amount is increased in order to obtain a sufficient gas flow. is there.

  FIG. 8 is a diagram illustrating an example of an after injection timing calculation map used when only the after injection timing is corrected. In this after injection timing calculation map, the horizontal axis represents the required in-cylinder flow amount R, and the vertical axis represents the after injection timing. Then, as the required in-cylinder flow amount R increases, the after injection timing is obtained as a retarded value. This is because the penetration force of the after-injected fuel increases as the after-injection timing is retarded (the side where the in-cylinder pressure decreases), and the amount of gas movement can be increased. Further, as the actual gas amount gcyl increases, the after injection timing is obtained as a retarded value. This is because as the actual gas amount gcyl increases, the penetration force of the after-injected fuel tends to decrease and the gas flow in the cylinder tends to decrease. Therefore, in order to obtain a sufficient gas flow, the after injection timing is set to the retarded side. To do.

  Also, when correcting multiple injection control amounts among the number of after injections, after injection amount, and after injection timing, the relationship between the multiple injection control amounts and the in-cylinder flow amount is verified through experiments, etc. A calculation map is created based on the result, and each injection control amount is corrected according to the calculation map.

  The operation of step ST7 corresponds to the “operation by the after-injection control amount calculation unit, which calculates the control amount of after-injection for obtaining the required in-cylinder flow amount” in the present invention.

  In step ST8, it is determined whether or not it is time to execute after injection (whether the crank angle position has become the execution crank angle position of after injection).

  If the after-injection execution timing has not yet been reached, a NO determination is made in step ST8 to wait until this execution timing is reached.

  When the after injection execution timing has been reached and YES is determined in step ST8, the process proceeds to step ST9, where after injection is executed.

  The operation of step ST9 corresponds to the “operation by the after-injection command unit, which executes after-injection from the fuel injection valve with the calculated control amount of after-injection” in the present invention.

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

  Since such after-injection control is performed, the ECU 100 (more specifically, each functional portion of the ECU 100 described above) constitutes a control device for an internal combustion engine according to the present invention. This control device receives each signal from the crank position sensor 40, rail pressure sensor 41, air flow meter 43, accelerator opening sensor 47, intake air temperature sensor 49, air-fuel ratio sensor 4B, etc. as an input signal. Yes. Further, this control device is configured to output an after injection command signal to each injector 23 as an output signal.

  As described above, in the present embodiment, the fuel remaining in the combustion field of the main injection fuel in the region other than the combustion field based on the local A / F in the combustion field of the main injection fuel and the residual oxygen amount Or in the cylinder. The flow amount in the cylinder (required in-cylinder flow amount Or) required to introduce the oxygen that is being supplied is obtained, and the control amount of the after injection is adjusted so that the required in-cylinder flow amount Or is obtained. For this reason, even during the transient operation, it is possible to solve the shortage of oxygen in the combustion field of the main injection fuel, suppress the generation of smoke in the combustion field of the main injection fuel, and improve exhaust emission. In the present embodiment, the control amount of after injection is determined by feedforward control. For this reason, it is possible to prevent the occurrence of smoke.

  Moreover, since oxygen can be introduced into the combustion field of the main injection fuel without excess or deficiency, it is possible to suppress the oxygen shortage in the combustion field of the after injection fuel, and the after injection function can be sufficiently exhibited.

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

  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 after-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)

A control device that is applied to a compression self-ignition internal combustion engine that performs combustion by self-ignition of fuel injected into a cylinder from a fuel injection valve, and that performs main injection and after injection as fuel injection from the fuel injection valve In
An actual gas state quantity calculating unit for calculating an actual gas amount and an actual gas composition in the cylinder;
The reference injection control amount corresponding to the current engine operating state is acquired from the reference injection amount of each of the main injection and the after injection and the reference injection control amount of the reference injection timing that are prescribed in advance according to the engine operating state. A reference injection control amount acquisition unit,
An injection pressure detector for detecting an injection pressure of the fuel;
Based on the gas amount, the gas composition, the reference injection control amount, and the injection pressure of the fuel, the air-fuel ratio at the reference injection timing of the after injection in the combustion field of the fuel injected by the main injection is locally determined. A local air-fuel ratio calculating unit that calculates the air-fuel ratio;
A residual oxygen amount calculation unit that calculates a residual oxygen amount in a cylinder at a reference injection timing of the after injection based on the gas amount, the gas composition, the reference injection control amount, and the injection pressure of the fuel;
In order to introduce oxygen remaining in a region other than the combustion field into the combustion field of the fuel injected by the main injection based on the local air-fuel ratio, the gas composition, and the residual oxygen amount in the cylinder A required in-cylinder flow amount calculation unit for calculating a required in-cylinder flow amount as a required in-cylinder flow amount;
An after injection control amount calculating unit for calculating a control amount of the after injection for obtaining the required in-cylinder flow amount;
An after-injection command section for executing after-injection from the fuel injection valve with the calculated control amount of after-injection;
A control device for an internal combustion engine, comprising:

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