JP2017008785A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that can appropriately obtain injection control amount during a transient operation.SOLUTION: Based on a ratio between reference gas flow velocity and actual gas flow velocity, a ratio between reference gas amount and actual gas amount and a ratio between a reference gas composition and an actual gas composition, cooling gas change amount that is a deviation of actual gas cooling loss amount from reference gas cooling loss amount is calculated. Based on the cooling loss change amount and a reference fuel spray reaching distance, a target fuel spray reaching distance of main injection fuel is calculated. Based on the target fuel spray reaching distance, correction amount of injection control amount of the main injection fuel is calculated. 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. Thus, the cooling loss amount as a whole of inside of cylinders (sum of cooling loss amount caused by gas flowing and cooling loss amount of spray) can be controlled to cooling loss amount that is appropriate in a current engine operating state, so as to improve a fuel consumption rate.SELECTED DRAWING: Figure 6

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 or the like mounted on a vehicle, control parameters for fuel injection (fuel injection pressure, fuel, etc.) are considered in consideration of a cooling loss (cooling loss) caused by cooling water taking heat in the cylinder. The injection amount and the fuel injection timing are corrected.

  In Patent Document 1, the cylinder inner surface temperature is estimated from the fuel integrated injection amount and the coolant temperature, the piston top surface temperature is estimated from the fuel integrated injection amount and the lubricating oil temperature, and the cooling loss index is calculated from these estimated temperatures. Is disclosed. The control parameters for fuel injection are corrected based on this cooling loss index.

JP2013-204521A

  However, during the transient operation of the engine, the gas state (gas amount and gas flow) in the cylinder greatly deviates from the gas state during steady operation, and accordingly, the cooling loss (cold loss due to gas flow) also increases. There is a possibility of divergence. In Patent Document 1, the divergence of the cooling loss due to the divergence of the gas state is not considered. For this reason, there is a possibility that the amount of cooling loss at the time of transient operation greatly deviates from the appropriate amount, leading to deterioration of the fuel consumption rate.

  This invention is made | formed in view of this point, The place made into the objective is to provide the control apparatus which can suppress the deterioration of the fuel consumption rate at the time of transient operation.

  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. . For this control device, a reference amount acquisition unit, an actual gas flow rate calculation unit, an actual gas amount calculation unit, an actual gas composition calculation unit, a cooling loss change amount calculation unit, a target spray reach distance calculation unit, a correction amount calculation unit, a fuel injection A command section is provided. The reference amount acquisition unit is defined in advance according to the engine operating state, and the reference gas flow velocity in the cylinder, the reference gas amount in the cylinder, the reference gas composition in the cylinder, and the fuel from the fuel injection valve Each reference spray reach distance of the spray is acquired. The actual gas flow rate calculation unit calculates the actual gas flow rate in the cylinder as the actual gas flow rate. 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 cooling loss change amount calculation unit is based on a ratio between the reference gas flow rate and the actual gas flow rate, a ratio between the reference gas amount and the actual gas amount, and a ratio between the reference gas composition and the actual gas composition. Thus, the deviation amount of the actual gas cooling loss amount with respect to the reference gas cooling loss amount specified in advance according to the engine operating state is calculated as the cooling loss change amount. The target spray reach distance calculation unit calculates a target spray reach distance of the fuel spray from the fuel injection valve based on the cooling loss change amount and the reference spray reach distance. The correction amount calculation unit calculates a correction amount for at least one injection control amount among the injection pressure, injection amount, and injection timing of the fuel injected from the fuel injection valve, based on the target spray reach distance. The fuel injection command unit corrects the 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, the fuel spray reach distance is adjusted according to the “gas cooling loss amount (cooling loss amount due to gas flow)” caused by the gas flowing in the cylinder, and by adjusting this spray reach distance, It is possible to adjust the “amount of spray cooling loss” resulting from the fuel spray being cooled by the inner wall surface of the combustion chamber. Therefore, it is possible to optimize the amount of cooling loss as a whole in the cylinder, which is the sum of the amount of cooling loss due to the gas flow and the amount of cooling loss of the spray. The consumption rate can be improved.

  In the present invention, the amount of change in cooling loss is calculated based on the ratio between the reference gas flow rate and the actual gas flow rate, 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. Using the amount of change, the injection control amount is corrected to adjust the spray reach distance. For this reason, it is possible to optimize the amount of cooling loss as a whole in the cylinder, and it is possible to improve the fuel consumption rate even during transient operation.

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 the spray arrival position of the main injection fuel adjusted when there is much cooling loss amount by a gas flow. It is a top view of the piston for demonstrating the spray arrival position of the main injection fuel adjusted when there is little cooling loss amount by a gas flow. It is a flowchart figure which shows the procedure of main injection control. It is a figure which shows an example of the target spray reach distance calculation map. 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, is basically 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 injection control amount, which is the injection pressure), the fuel injection amount (reference fuel injection amount assigned to the operation grid point), and the fuel injection timing (reference fuel injection timing assigned to the operation grid point). An injection control amount is determined, and main injection 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, fuel injection is controlled in consideration of the deviation of the actual gas cooling loss amount from the gas cooling loss amount during steady operation (the injection pressure, injection amount, and injection of fuel injected from the injector 23). This corrects at least one of the timings), so that the main injection to the position where the amount of cooling loss as a whole in the cylinder can be obtained properly (the position where the amount of cooling loss appropriate for the current engine operating state is obtained) can be obtained. The fuel spray position is adjusted.

  Specifically, the cooling loss includes a gas that is cooled by the inner wall surface of the cylinder and the top surface of the piston as the gas flows in the cylinder (hereinafter referred to as “cooling loss due to gas flow”), and a fuel spray. Some are cooled by the inner wall surface of the combustion chamber 3 (hereinafter referred to as “cold loss of spray”). In this embodiment, the amount of cooling loss of the spray is adjusted according to the amount of cooling loss due to gas flow (gas cooling loss amount), and the amount of cooling loss as a whole in the cylinder (cooling loss amount due to gas flow and cooling loss of spray) The injection control amount is corrected so that a cooling loss amount that is appropriate in the current engine operating state (a cooling loss amount that optimizes the fuel consumption rate) is obtained, and the spray of the main injected fuel is The position is adjusted. The amount of cooling loss that optimizes the fuel consumption rate is the amount of cooling loss assigned to each operating grid point corresponding to the engine speed and engine load (the amount of cooling loss as a whole in the cylinder), This value is set in advance by experiments or the like as a value that can optimize the fuel consumption rate at the engine rotation speed and the engine load at the operation grid point.

  4 and 5 are plan views of the piston 13 for explaining a region where the spray of the main injected fuel exists in the combustion chamber 3 (spray arrival position of the main injected fuel). In these drawings, the spray of the main injected fuel exists in the hatched region M, and the outer edge position thereof is the spray arrival position of the main injected fuel. Further, the distance between the outer edge position of the region M and the injector 23 is the spray reach distance.

  FIG. 4 is a plan view of the piston 13 for explaining the spray arrival position of the main injection fuel that is adjusted when the amount of cooling loss due to the gas flow is large. FIG. 5 is a plan view of the piston 13 for explaining the spray arrival position of the main injection fuel that is adjusted when the amount of cooling loss due to the gas flow is small.

  Thus, when the amount of cooling loss due to gas flow is large, as shown in FIG. 4, the spray reach distance of the main injection is shortened so that the fuel spray does not approach the inner wall surface 31 of the combustion chamber 3. To do. That is, the injection control amount is corrected so that the flight distance of the main injected fuel is shortened. Thereby, the amount of heat taken by the fuel spray from the inner wall surface 31 of the combustion chamber 3 is reduced, and the amount of cold loss of the spray is reduced. As a result, it is possible to optimize the amount of cooling loss as a whole in the cylinder (the sum of the amount of cooling loss due to gas flow and the amount of cooling loss of spray).

  Conversely, when the amount of cooling loss due to gas flow is small, as shown in FIG. 5, the spray reach distance of the main injection is lengthened so that the fuel spray approaches the inner wall surface 31 of the combustion chamber 3. That is, the injection control amount is corrected so that the flight distance of the main injected fuel becomes longer. Thereby, the amount of heat taken by the fuel spray from the inner wall surface 31 of the combustion chamber 3 increases, and the amount of cold loss of the spray increases. As a result, it is possible to optimize the amount of cooling loss as a whole in the cylinder. Further, in this case, since the main injection fuel can be burned by effectively using the oxygen present in the vicinity of the inner wall surface 31 of the combustion chamber 3, the occurrence of smoke can be suppressed.

  A plurality of injection holes are formed in the injector 23 along the circumferential direction. For this reason, the fuel spray injected from each nozzle hole is respectively injected toward a region having a predetermined interval in the circumferential direction, but a swirl flow is generated in the cylinder, and the nozzle hole Is set to a large number (for example, 10 injection holes are provided in the circumferential direction), and the combustion field M of the main injected fuel here is a uniform combustion over the entire circumferential direction. Suppose it is a place.

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

  In this main injection control, (a) the reference gas flow velocity Vb in the cylinder, the reference gas amount Gcylb in the cylinder, and the reference gas composition Cb in the cylinder, which are defined in advance according to the operating state (engine operating state) of the engine 1. , And an operation for obtaining the reference spray reach distance Pb of the fuel spray from the injector 23, (b) an operation for calculating the actual gas flow velocity in the cylinder as an actual gas flow velocity V, and (c) an actual gas in the cylinder. An operation for calculating the actual gas amount Gcyl, (d) an operation for calculating the actual gas composition in the cylinder as the actual gas composition C, (e) a ratio between the reference gas flow velocity Vb and the actual gas flow velocity V, Based on 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, the reference gas cooling that is defined in advance according to the operating state of the engine 1 is performed. (F) The operation of calculating the deviation amount of the actual gas cooling loss amount with respect to the amount as the cooling loss change amount ΔQc, (f) The fuel spray from the injector 23 based on the cooling loss change amount ΔQc and the reference spray reach distance Pb An operation for calculating the target spray reach distance Pt, (g) a correction amount of at least one injection control amount among the injection pressure, injection amount, and injection timing of the fuel injected from the injector 23 based on the target spray reach distance Pt (H) The operation of correcting the injection control amount with the correction amount and executing the fuel injection from the injector 23 with the corrected injection control 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 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 flow rate calculation unit in the present invention. Further, in the ECU 100, the functional part that executes the operation (c) is configured as an actual gas amount calculation unit in the present invention. Further, in the ECU 100, a functional part that executes the operation (d) is configured as an actual gas composition calculation unit in the present invention. Further, in the ECU 100, a functional portion that executes the operation (e) is configured as a cooling loss change amount calculation unit referred to in the present invention. Further, in the ECU 100, a functional part that executes the operation (f) is configured as a target spray reach distance calculation unit referred to in the present invention. Further, in the ECU 100, a functional part that executes the operation (g) is configured as a correction amount calculation unit referred to in the present invention. Further, in the ECU 100, a functional portion that executes the operation (h) is configured as a fuel injection command section referred to in the present invention.

  By these reference amount acquisition unit, actual gas flow rate calculation unit, actual gas amount calculation unit, actual gas composition calculation unit, cooling loss change amount calculation unit, target spray reach distance calculation unit, correction amount calculation unit, and fuel injection command unit A control device according to the present invention is configured.

  Hereinafter, a specific procedure of the main injection control will be described with reference to 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 flow velocity Vb and the reference gas amount 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. Gcylb and the reference gas composition Cb are acquired. In other words, among the reference gas flow velocity Vb, the reference gas amount Gcylb, and the reference gas composition Cb assigned in advance for each operation grid point, the operation grid point corresponding to the current engine speed and engine load is assigned. Information is read. The reference gas flow velocity Vb is a gas flow velocity (gas flow velocity on the operation grid point) in the cylinder to be controlled. 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 spray reach distance (stored in the ROM) assigned to the operation grid point corresponding to the current engine speed and engine load is acquired. Specifically, in this step ST2, the reference spray reach distance is divided by the representative length (distance from the injector 23 to the inner wall surface of the combustion chamber 3; the radial dimension of the combustion chamber 3 and the maximum spray reach distance). Thus, the ratio of the reference spray reach distance to the representative length is calculated (reference spray reach distance / representative length). Hereinafter, this value is simply referred to as a reference spray reach distance Pb (corresponding to a reference spray reach distance in the present invention).

  The operations of these steps ST1 and ST2 are “operations by the reference amount acquisition unit” according to the present invention, and the reference gas flow velocity in the cylinder, the reference gas amount in the cylinder, The operation of acquiring the reference gas composition and the reference spray reach distance of the fuel spray from the fuel injection valve ”.

  In step ST3, a gas flow rate (actual gas flow rate) V, 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 flow velocity V is an actual gas flow velocity in the cylinder to be controlled, and is calculated as a value corresponding to the engine rotation speed. That is, the flow rate of the intake air flowing into the cylinder from the intake pipe 62 through the intake manifold 61 changes depending on the engine rotation speed, and the flow rate of the swirl flow generated in the cylinder also changes depending on the engine rotation speed. . For this reason, the actual gas flow velocity V is obtained from an arithmetic expression or map using the engine speed as a parameter. The actual gas flow velocity V is calculated as a higher value as the engine speed is higher.

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

  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, a cooling loss change amount ΔQc is calculated. This cooling loss change amount ΔQc is a reference gas cooling loss amount (stored in the ROM) assigned to the operation grid point corresponding to the current engine speed and engine load (a reference value of the cooling loss amount due to the gas flow). ) Of the actual gas cooling loss amount (cooling loss amount due to actual gas flow). During transient operation, this difference (cooling loss change ΔQc) is the amount of gas cooling loss during steady operation (reference gas cooling loss) and the amount of gas cooling loss during transient operation (actual gas cooling loss). And the difference. Here, the cooling loss change amount ΔQc when the actual gas cooling loss amount is larger than the reference gas cooling loss amount is set to a positive value, and conversely, the actual gas cooling loss amount with respect to the reference gas cooling loss amount is The cooling loss change amount ΔQc when it is small is set to a negative value.

  Specifically, the amount of change in cooling loss ΔQc is determined by the ratio of the actual gas flow velocity V to the reference gas flow velocity Vb (V / Vb), the ratio of the actual gas amount Gcyl to the reference gas amount Gcylb (Gcyl / Gcylb), It is calculated | required by the arithmetic expression or map which uses each ratio (C / Cb) of the said actual gas composition C with respect to the said reference gas composition Cb as a parameter. As the ratio of the actual gas flow rate V to the reference gas flow rate Vb is larger, the ratio of the actual gas amount Gcyl to the reference gas amount Gcylb is smaller, and the ratio of the actual gas composition C to the reference gas composition Cb is smaller. The cooling loss change amount ΔQc is calculated as a large value.

  This operation is the operation by the “cooling loss change amount calculation unit” in the present invention, which is the ratio between the reference gas flow rate and the actual gas flow rate, the ratio between the reference gas amount and the actual gas amount, the reference gas composition and the actual gas composition. The operation of calculating the deviation amount of the actual gas cooling loss amount with respect to the reference gas cooling loss amount defined in advance according to the engine operating state as the cooling loss change amount ".

  In step ST5, the target spray reach distance is calculated. As described above, the target spray reach distance is a cooling amount in which the amount of cooling loss in the entire cylinder (the sum of the cooling loss amount due to gas flow and the cooling loss amount of the spray) is appropriate in the current engine operating state. It is calculated as defining the spray position of the main injection fuel obtained as a loss amount (cooling loss amount that optimizes the fuel consumption rate).

  Here, the ratio of the target spray reach distance to the representative length is calculated by dividing the target spray reach distance by the representative length (target spray reach distance / representative length). Hereinafter, this value is simply referred to as a target spray reach distance Pt (corresponding to a target spray reach distance in the present invention).

  The target spray reach distance Pt is calculated by an arithmetic expression using the cooling loss change amount ΔQc calculated in step ST4 and the reference spray reach distance Pb acquired in step ST2 as variables. Alternatively, a map for obtaining the target spray arrival distance Pt using each of the cooling loss change amount ΔQc and the reference spray arrival distance Pb as a parameter is created by experiment and stored in the ROM of the ECU 100, and this map (target spray arrival distance calculation map) is stored. You may make it obtain | require target spray arrival distance Pt by referring.

  FIG. 7 shows an example of the target spray reach distance calculation map. In this target spray reach distance calculation map, the horizontal axis is the cooling loss change amount ΔQc, and the vertical axis is the target spray reach distance Pt. And the target spray reach distance Pt is calculated | required as a small value, so that cooling loss variation | change_quantity (DELTA) Qc is large. That is, as the actual gas cooling loss amount is larger than the reference gas cooling loss amount, the target spray reach distance Pt is decreased, so that the fuel spray does not approach the inner wall surface of the combustion chamber 3, and the spray cooling loss amount is reduced. I try to reduce it. Conversely, as the actual gas cooling loss amount is smaller than the reference gas cooling loss amount, the target spray arrival distance Pt is increased so that the fuel spray approaches the inner wall surface of the combustion chamber 3. I try to make more. In addition, each straight line shown by the solid line, the broken line, and the alternate long and short dash line in FIG. 7 has different operation grid points, that is, has different reference spray reach distances Pb, and The relationship between the amount of change in cooling loss ΔQc and the target spray reach distance Pt in the operating state is shown.

  The operation of this step ST5 is an operation by the “target spray reach distance calculation unit” in the present invention, and the target spray reach distance of the fuel spray from the fuel injection valve based on the amount of change in cooling loss and the reference spray reach distance. Corresponds to “operation to calculate”.

  In step ST6, 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 an arithmetic expression using the target spray arrival distance Pt as a variable. Alternatively, a map for obtaining the correction amount using the target spray arrival distance Pt as a parameter may be created by experiment or the like and stored in the ROM of the ECU 100, and the correction amount may be obtained by referring to this map.

  FIG. 8 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 fuel injection pressure correction amount is obtained as a larger value as the target spray reach distance Pt is larger. In other words, the larger the target spray reach distance Pt, the higher the fuel injection pressure is set, thereby increasing the penetration force of the main injected fuel, thereby increasing the spray reach distance (spray to match the target spray reach distance Pt). To increase the reach distance). Specifically, in FIG. 8, 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. The spray reach distance is longer than the reference spray reach distance. 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 spray arrival distance of the main injection fuel is the reference spray arrival distance. It becomes shorter than the distance.

  FIG. 9 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 correction amount of the fuel injection amount is obtained as a larger value as the target spray reach distance Pt is larger. In other words, the larger the target spray reach distance Pt, the larger the fuel injection amount is set to increase the penetration force of the main injected fuel, thereby increasing the spray reach distance (spray to match the target spray reach distance Pt). To increase the reach distance). Specifically, in FIG. 9, when the correction amount of the fuel injection amount is obtained as a positive value, the correction is made so that the fuel injection amount becomes larger than the reference fuel injection amount, and the main injection fuel The spray reach distance is longer than the reference spray reach distance. 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, and the spray arrival distance of the main injection fuel is the reference spray arrival distance. It becomes shorter than the distance.

  FIG. 10 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 advance side as the target spray reach distance Pt increases. That is, when the main injection is started before the piston 13 reaches the compression top dead center (when the reference fuel injection timing is before the piston 13 reaches the compression top dead center), the target spray reach distance Pt. The larger the is, the more the fuel injection timing is set to the advance side, thereby starting the main injection in a situation where the in-cylinder pressure is low, thereby increasing the spray reach distance (spray to match the target spray reach distance Pt). To increase the reach distance). Specifically, in FIG. 10, when the fuel injection timing is obtained as a value on the advance side, the fuel injection timing is corrected to the advance side with respect to the reference fuel injection timing, and the spray of the main injection fuel The reach distance is longer than the reference spray reach distance. On the other hand, 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 spray arrival distance of the main injection fuel is the reference spray arrival distance Shorter than.

  When the main injection is started after the piston 13 reaches the compression top dead center (when the reference fuel injection timing is after the piston 13 reaches the compression top dead center), the target spray is performed. A fuel injection timing correction amount map (not shown) in which a correction amount is obtained as a value that increases the amount of shift of the fuel injection timing to the retard side as the reach distance Pt increases is used.

  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 this step ST6 is the operation by the “correction amount calculation unit” in the present invention, and at least of the injection pressure, the injection amount and the injection timing of the fuel injected from the fuel injection valve based on the target spray reach distance. This corresponds to “operation for calculating the correction amount of one injection control amount”.

  In step ST7, it is determined whether or not the execution timing of main injection has come (the crank angle position has become the execution crank angle position of main injection). For example, when the correction amount of the fuel injection timing is calculated in step ST6, 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, NO is determined in step ST7, and the process waits for the execution timing to be reached.

  When the execution timing of the main injection is reached and a YES determination is made in step ST7, the process proceeds to step ST8 and main injection is executed.

  That is, when the correction amount of the fuel injection pressure is calculated in step ST6, 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.

  Further, when the correction amount of the fuel injection amount is calculated in step ST6, 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 this step ST8 is the operation by the fuel injection command section referred to in the present invention, wherein the 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 the present embodiment, the ratio (V / Vb) of the actual gas flow rate V to the reference gas flow rate Vb, the ratio (Gcyl / Gcylb) of the actual gas amount Gcyl to the reference gas amount Gcylb, and the actual gas composition Cb. A cooling loss change amount ΔQc is calculated based on the ratio (C / Cb) of the gas composition C, and the injection control amount is corrected so that the target spray arrival distance Pt obtained from the cooling loss change amount ΔQc is obtained. Yes. As a result, it is possible to optimize the amount of cooling loss in the entire cylinder, which is the sum of the amount of cooling loss due to gas flow and the amount of cooling loss of spray, and the fuel consumption rate even during transient operation Can be improved.

-Other embodiments-
In the embodiment described above, the actual gas flow velocity V, the actual gas amount Gcyl, and the actual gas composition C at the timing when the piston 13 reaches the predetermined crank angle position before reaching the compression top dead center are calculated, and these calculated values are used. Then, the cooling loss change amount ΔQc is calculated, and the injection control amount is corrected according to the target spray reach distance Pt obtained from the cooling loss change amount ΔQc. The present invention is not limited to this, and estimates the actual gas flow velocity V, 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, respectively. The estimated value may be used to calculate the cooling loss change amount ΔQc, and the injection control amount may be corrected according to the target spray reach distance Pt obtained from the cooling loss change amount ΔQc.

  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 main 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,
Reference gas flow velocity in the cylinder, reference gas amount in the cylinder, reference gas composition in the cylinder, and reference spray reach distance of fuel spray from the fuel injection valve, which are defined in advance according to the engine operating state A reference amount acquisition unit for acquiring each;
An actual gas flow rate calculation unit for calculating an actual gas flow rate in the cylinder as an actual gas flow rate;
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 of the reference gas flow rate to the actual gas flow rate, the ratio of the reference gas amount to the actual gas amount, and the ratio of the reference gas composition to the actual gas composition, depending on the engine operating state A cooling loss change amount calculation unit for calculating a deviation amount of an actual gas cooling loss amount with respect to a predetermined reference gas cooling loss amount as a cooling loss change amount;
A target spray arrival distance calculating unit that calculates a target spray arrival distance of fuel spray from the fuel injection valve based on the cooling loss change amount and the reference spray arrival distance;
A correction amount calculation unit that calculates a correction amount of at least one injection control amount among injection pressure, injection amount, and injection timing of fuel injected from the fuel injection valve based on the target spray reach distance;
A fuel injection command unit that corrects the 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:

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