Control system for internal combustion engines

Abstract

To provide a control system for an internal combustion engine, which can properly detect a stoichiometric air-fuel ratio for current fuel according to a mixture ratio of diesel oil and biofuel to properly correct a control amount, without newly adding special sensors such as a fuel density sensor, a fuel oxygen concentration sensor, and a combustion pressure sensor to an existing internal combustion engine control system.SOLUTION: A control system for an internal combustion engine comprises: an inspection single-stage injection execution unit that can use light oil, biofuel, or a mixed fuel of light oil and biofuel, and performs an inspection single-stage injection of a predetermined amount of fuel during a deceleration fuel cut; a calculated air-fuel ratio acquisition unit for acquiring a calculated air-fuel ratio for a cylinder to which the inspection single-stage injection is executed; a λ acquisition unit for acquiring a value of λ during a fluctuation period due to the inspection single-stage injection; a stoichiometric air-fuel ratio acquisition unit for acquiring a stoichiometric air-fuel ratio of current fuel on the basis of the value of λ during the fluctuation period and the calculated air-fuel ratio; and a control correction unit for correcting a control amount for the internal combustion engine on the basis of the stoichiometric air-fuel ratio of current fuel.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to a control system for an internal combustion engine that can use diesel fuel, biofuel, or a mixture of diesel fuel and biofuel. [Background technology]

[0002] Vehicles equipped with diesel engines, which are compression-ignition internal combustion engines that use light oil as fuel, have been widely used for a long time. In recent years, some vehicles have also started using a mixed fuel, which is a mixture of light oil and so-called biofuels (renewable energy biofuels) such as fatty acid methyl esters, as fuel for these diesel engines.

[0003] Furthermore, compared to diesel fuel, biofuels have a higher oxygen content and a lower carbon-hydrogen ratio, resulting in a lower calorific value. For this reason, when using a mixed fuel with a relatively high biofuel ratio compared to 100% diesel fuel, the following (1) to (3) are known to occur. (1) Because biofuels have a high oxygen content, the oxygen concentration in EGR gas (recirculating gas that returns a portion of the exhaust gas to the intake) increases, leading to an increase in NOx emissions. (2) Because biofuels have a low calorific value, the torque generated by the internal combustion engine is reduced, and the power performance of the vehicle decreases. (3) Because biofuels have a low calorific value, the pilot injection, which is injected prior to the main injection, cannot raise the cylinder temperature to the target temperature, resulting in failure to achieve the desired combustion and the generation of combustion noise, etc.

[0004] To suppress the occurrences of (1) to (3) above, the fuel mixture ratio, which is the mixing ratio of diesel fuel and biofuel, should be detected and corrected accordingly. However, while it would be ideal if the fuel mixture ratio were known in advance, in situations where it is unknown whether the user will refuel with diesel fuel, biofuel, or a fuel mixture of a predetermined ratio, the current fuel mixture ratio in the fuel tank must be appropriately detected. For this reason, it is desirable to be able to appropriately detect the mixing ratio of diesel fuel and biofuel.

[0005] For example, Patent Document 1 discloses a biofuel identification device and control device that includes a fuel density sensor and a fuel oxygen concentration sensor in the fuel supply passage, and a combustion pressure sensor in at least one cylinder of an internal combustion engine. In Patent Document 1, the fuel density obtained by the fuel density sensor is used to convert the fuel mass, and the oxygen concentration in the fuel obtained by the fuel oxygen concentration sensor is used to calculate the mixing ratio of biofuel to diesel fuel. Furthermore, the calorific value per unit mass of fuel is estimated based on the output of the combustion pressure sensor and the output of the crankshaft rotation, and the type of biofuel is identified. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-149297 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The biofuel identification device and control device described in Patent Document 1 are undesirable because they require the addition of special sensors such as fuel density sensors, fuel oxygen concentration sensors, and combustion pressure sensors to existing internal combustion engine systems, and because the consideration of the mounting position and installation of these sensors is extremely time-consuming and laborious. In recent years, internal combustion engines in vehicles have a large number of parts and sensors arranged in close proximity to fit compactly inside the vehicle, leaving almost no space to install new sensors.

[0008] The present invention was conceived in view of these points, and aims to provide an internal combustion engine control system that can appropriately detect the current stoichiometric air-fuel ratio of the fuel according to the mixing ratio of diesel fuel and biofuel, and appropriately correct the control amount, without adding any special sensors such as fuel density sensors, fuel oxygen concentration sensors, or combustion pressure sensors to an existing internal combustion engine control system. [Means for solving the problem]

[0009] To solve the above problems, the first invention is a control system for an internal combustion engine that controls an internal combustion engine that can use any of the following fuels: diesel fuel, biofuel, or a mixed fuel of diesel fuel and biofuel. The biofuel is a fuel in which the oxygen content per unit amount is higher than that of diesel fuel. The control system includes an injector for injecting fuel into the internal combustion engine, an air flow rate detection device for detecting the amount of intake air into the internal combustion engine, and a λ detection device provided in the exhaust path of the internal combustion engine for detecting λ, which is the air-fuel ratio / stoichiometric air-fuel ratio, based on the oxygen concentration in the exhaust gas from the internal combustion engine. An EGR path that returns a portion of the exhaust gas to the intake path of the internal combustion engine, and an EGR valve provided in the EGR path that adjusts the opening degree of the EGR path, The system detects the operating state of the internal combustion engine and controls the injector based on the detected operating state. The EGR valve is controlled based on the target EGR rate determined based on the operating conditions. It has a control device, and in the normal operating state, the control device uses the injector to perform one combustion itinerary A multi-stage injection is performed, including a main injection which is the primary injection, and a pilot injection which is injected prior to the main injection, and a single-stage inspection injection is performed by an inspection unit that performs a single-stage inspection injection of a predetermined amount of fuel, during deceleration fuel cut, when the operating state is decelerating and fuel cut, and only the main injection is performed; a calculated air-fuel ratio acquisition unit acquires a calculated air-fuel ratio based on the mass of fresh air drawn in by the cylinder that performed the single-stage inspection injection, which is the fresh air mass detected using the air flow rate detection device, and the fuel mass based on the predetermined fuel amount; a λ acquisition unit acquires the value of λ from the λ detection device during the fluctuation period, which is the period during which λ fluctuates due to the single-stage inspection injection; a stoichiometric air-fuel ratio acquisition unit acquires the stoichiometric air-fuel ratio of the current fuel based on the value of λ acquired during the fluctuation period and the calculated air-fuel ratio; and the acquired stoichiometric air-fuel ratio of the current fuel And the relationship between the stoichiometric air-fuel ratio and the fuel mixture ratio. Based The fuel mixture ratio, which is the mixing ratio of the diesel fuel and the biofuel in the current fuel, is determined, and at least one of the following corrections is performed: an EGR correction that increases the target EGR rate as the mixing ratio of the biofuel increases, and a fuel injection amount correction that increases the amount injected from the injector as the mixing ratio of the biofuel increases. This is a control system for an internal combustion engine, comprising a control correction unit.

[0010] Next, the second invention is a control system for an internal combustion engine according to the first invention, wherein the control device performs a predetermined number of consecutive combustion operations in the single-stage injection execution unit for testing. itineraryThe single-stage test injections are performed continuously to cause combustion, the air-fuel ratio acquisition unit acquires the respective calculated air-fuel ratios corresponding to each of the single-stage test injections, and the λ acquisition unit acquires the continuous combustion itinerary This is a control system for an internal combustion engine that obtains the value of λ for a continuous period of variation, and uses the stoichiometric air-fuel ratio acquisition unit to obtain the current stoichiometric air-fuel ratio of the fuel based on the value of λ obtained during the variation period and the respective calculated air-fuel ratios.

[0011] Next, the third invention is a control system for an internal combustion engine according to the first or second invention, wherein at the time of shipment of the internal combustion engine, a controlled fuel is used, in which the fuel mixture ratio, which is the mixing ratio of the diesel fuel and the biofuel in the current fuel, and the stoichiometric air-fuel ratio are known in advance to be a predetermined fuel mixture ratio and a predetermined stoichiometric air-fuel ratio. The control device, after the internal combustion engine has warmed up and the amount of fluctuation in the operating state is less than or equal to a second predetermined fluctuation amount, continues for a second predetermined period, and obtains a shipment-calculated air-fuel ratio based on the mass of fresh air drawn into the cylinder during the second predetermined period, which is the fresh air mass detected using the air flow rate detection device, and the fuel mass, which is the mass of fuel injected using the injector during the second predetermined period, and calculates the shipment-estimated λ for the second predetermined period, which is the λ for the second predetermined period, from the obtained shipment-calculated air-fuel ratio and the predetermined stoichiometric air-fuel ratio, and the second A unit for acquiring actual λ at shipment, which is the λ detected using the λ detection device during a predetermined period; a unit for calculating the λ deviation ratio at shipment, which is the estimated λ at shipment and the actual λ at shipment, based on the estimated λ at shipment and the actual λ at shipment acquired during the second predetermined period; an air-fuel ratio correction rate update unit that updates and stores an air-fuel ratio correction rate to correct the calculated air-fuel ratio at shipment so that the λ deviation ratio at shipment approaches the second predetermined ratio range if the state in which the λ deviation ratio at shipment is outside the second predetermined ratio range continues during the second determination period; and when the λ deviation ratio at shipment falls within the second predetermined ratio range... The air-fuel ratio correction rate is updated and stored.When it is determined that the learning at the time of shipment has been completed, it has a shipment-time learning completion determination unit that stores the completion of the learning at the time of shipment. And when the learning at the time of shipment has not been completed at the time of shipment, the control device executes the processes of the shipment-time estimated λ calculation unit, the shipment-time actual λ acquisition unit, the shipment-time λ deviation ratio calculation unit, the air-fuel ratio correction rate update unit, and the shipment-time learning completion determination unit, and when obtaining the calculated air-fuel ratio at the time of shipment , the air-fuel ratio calculated at the time of shipment the air-fuel ratio correction rate Multiply obtains the calculated air-fuel ratio at the time of shipment corrected by the above, and when obtaining the calculated air-fuel ratio , the calculated air-fuel ratio the air-fuel ratio correction rate Multiply obtains the calculated air-fuel ratio corrected by the above. It is a control system for an internal combustion engine.

Advantages of the Invention

[0014] According to the first invention, by performing a single-stage injection for inspection of a predetermined fuel amount during fuel cut during deceleration, the air-fuel ratio of the result of the single-stage injection for inspection is obtained as the calculated air-fuel ratio, and using the calculated air-fuel ratio and the value of λ obtained using a λ detection device, the theoretical air-fuel ratio of the current fuel can be calculated. And appropriate correction according to the theoretical air-fuel ratio of the current fuel can be performed. Therefore, without newly adding special sensors such as a fuel density sensor, a fuel oxygen concentration sensor, or a combustion pressure sensor to an existing internal combustion engine control system, the theoretical air-fuel ratio of the current fuel according to the mixing ratio of light oil and biofuel can be appropriately detected and the control amount can be appropriately corrected.

[0015] According to the second invention, it becomes possible to make the period for detecting the value of λ using a λ detection device longer, and the theoretical air-fuel ratio of the current fuel can be calculated more accurately.

[0016] According to the third invention, at the time of shipment of the internal combustion engine (at the time of shipment from the manufacturing factory), using the control fuel for which it is known in advance that the fuel mixture ratio and the theoretical air-fuel ratio are the predetermined fuel mixture ratio and the predetermined theoretical air-fuel ratio, [fresh air mass / fuel mass] / predetermined theoretical air-fuel ratio (estimated λ at the time of shipment) is obtained, and based on the estimated λ at the time of shipment and the actual λ at the time of shipment detected using the λ detection device, the λ deviation ratio at the time of shipment (estimated λ at the time of shipment / actual λ at the time of shipment) is obtained. If [fresh air mass / fuel mass] is approximately the correct value, the λ deviation ratio at the time of shipment should be near approximately 1.0, but if it deviates to the larger or smaller side than 1.0, it is considered that [fresh air mass / fuel mass] is incorrect. Therefore, the air-fuel ratio correction rate for correcting [fresh air mass / fuel mass] so that the λ deviation ratio at the time of shipment approaches 1.0 is updated, and the air-fuel ratio correction rate is made to approach the correct value. That is, the error of the air flow rate detection device for detecting the fresh air mass and the error of the fuel injection amount from the injector can be appropriately corrected by the air-fuel ratio correction rate. As a result, the theoretical air-fuel ratio and the fuel mixture ratio can be obtained more accurately.

[0017] First invention According to this, according to the fuel mixture ratio, the control amount of the internal combustion engine can be appropriately corrected.

Brief Description of the Drawings

[0018] [Figure 1] It is a diagram for explaining an example of the overall configuration of the internal combustion engine system. [Figure 2] It is a flowchart for explaining the entire crank angle synchronization process among the processing procedures of the control device in the first embodiment. [Figure 3] It is a flowchart for explaining the details of [processing of the crank counter] in the flowchart shown in FIG. 2. [Figure 4] It is a flowchart for explaining the details of [normal fuel injection process] in the flowchart shown in FIG. 2. [Figure 5] It is a diagram for explaining an example of the operation waveform by the processing of the flowchart shown in FIG. 2. [Figure 6]This is a flowchart illustrating the entire time synchronization process among the processing procedures of the control device in the first embodiment. [Figure 7] This flowchart explains the details of the [supply detection process] in the flowchart shown in Figure 6. [Figure 8] This flowchart explains the details of the [fresh air intake volume delay time processing] in the flowchart shown in Figure 6. [Figure 9] This flowchart explains the details of the [λ detection process] in the flowchart shown in Figure 6. [Figure 10] This flowchart explains the details of the [Calculation of Stoichiometric Air-Fuel Ratio and Fuel Mixture Ratio] in the flowchart shown in Figure 6. [Figure 11] This flowchart explains the details of [EGR control] in the flowchart shown in Figure 6. [Figure 12] This diagram illustrates an example of the stoichiometric air-fuel ratio and fuel mixture ratio characteristics. [Figure 13] This diagram illustrates the outlines of the first to sixth embodiments. [Figure 14] This is a flowchart illustrating the entire [time synchronization (2) processing] of the control device processing procedure in the second embodiment. [Figure 15] This is a flowchart illustrating the entire process of the [crank angle synchronization (2) process] in the control device's processing procedure in the second embodiment. [Figure 16] This flowchart explains the details of the [Resupply Detection (2) Process] in the flowchart shown in Figure 14. [Figure 17] This flowchart, shown in Figure 14, details the [Air-fuel ratio correction rate learning process at the time of shipment]. [Figure 18] This flowchart, shown in Figure 14, details the [Stoichiometric Air-Fuel Ratio Learning Process during Normal Operation]. [Figure 19] This figure illustrates an example of an operating waveform in the second embodiment. [Figure 20]This is a flowchart illustrating the entire [time synchronization (4) process] of the processing procedure of the control device in the fourth embodiment. [Figure 21] This is a flowchart illustrating the entire process of the [crank angle synchronization (4) process] in the control device's processing procedure in the fourth embodiment. [Figure 22] This flowchart explains the details of the [Resupply Detection (4) Process] in the flowchart shown in Figure 20. [Modes for carrying out the invention]

[0019] ●[Overall configuration of internal combustion engine system 1 (Figure 1)] The internal combustion engine system 1, including the control system 2 of the present invention, will be described below with reference to the drawings. First, an example of the overall configuration of the internal combustion engine system 1 will be described using Figure 1. In the example of the internal combustion engine system 1 in Figure 1, the internal combustion engine 10 is a so-called diesel engine. The control system 2 includes a control device 50, an injector 21, and a λ detection device 92. The configuration of the internal combustion engine system 1 will be described below in order from the intake side to the exhaust side.

[0020] The intake manifold 11A is equipped with an airflow detection device 31. The airflow detection device 31 is, for example, an intake airflow sensor, and outputs a detection signal to the control device 50 corresponding to the airflow rate [g / sec] of the air inhaled by the internal combustion engine 10. The airflow detection device 31 is also equipped with an intake air temperature detection device 32A and an atmospheric pressure detection device 33A. The intake air temperature detection device 32A is, for example, an intake air temperature sensor, and outputs a detection signal to the control device 50 corresponding to the temperature of the intake air (in this case, outside air). The atmospheric pressure detection device 33A is, for example, a pressure sensor, and outputs a detection signal to the control device 50 corresponding to the atmospheric pressure. The intake manifold 11A is also connected to the compressor 82 of the supercharger 80.

[0021] An intake pipe 11A is connected to the inlet side of the compressor 82 of the supercharger 80, and an intake pipe 11C is connected to the discharge side of the compressor 82. The compressor 82 is rotationally driven by a turbine 81 which is rotated by the exhaust gas, and pressurizes the intake air that flows in from the intake pipe 11A and sends it to the intake pipe 11C. A pressure detection device 33B is also provided in the intake pipe 11A, which is upstream of the compressor 82. The pressure detection device 33B outputs a detection signal to the control device 50 corresponding to the pressure of the air before it is compressed by the compressor 82.

[0022] The downstream side of the intake manifold 11C is connected to the intake manifold 11D. The intake manifold 11C is equipped with a pressure detection device 33C, an intercooler 84, a throttle device 64, and an intake air temperature detection device 32B. The pressure detection device 33C is, for example, a pressure sensor, and outputs a detection signal to the control device 50 corresponding to the pressure of the intake air pumped by the compressor 82. The intercooler 84 lowers the temperature of the intake air pumped from the compressor 82, thereby increasing the oxygen density. The throttle device 64 adjusts the opening of the throttle valve to the target throttle opening based on the control signal from the control device 50. The intake air temperature detection device 32B is, for example, an intake air temperature sensor, and outputs a detection signal to the control device 50 corresponding to the temperature of the intake air that has been lowered by the intercooler 84.

[0023] The downstream side of the intake manifold 11D is connected to intake ports that guide intake air to each cylinder of the internal combustion engine 10. The intake air guided to the intake manifold 11D is drawn into each cylinder of the internal combustion engine 10 and used for combustion together with fuel injected from the injector 21. The intake manifold 11D is also equipped with a pressure detection device 33D. The pressure detection device 33D is, for example, a pressure sensor and outputs a detection signal to the control device 50 corresponding to the pressure of the intake air in the intake manifold 11D.

[0024] The internal combustion engine 10 is equipped with a rotation detection device 34A and a cylinder detection device 34B. The rotation detection device 34A is, for example, a crankshaft rotation sensor and outputs a detection signal (crank angle signal) to the control device 50 according to the rotation angle of the crankshaft of the internal combustion engine 10. The cylinder detection device 34B is, for example, a camshaft rotation sensor and outputs a detection signal (cylinder identification signal) to the control device 50 when, for example, the piston of cylinder 1 reaches top dead center of compression. The internal combustion engine 10 is also equipped with a load device 63 that can adjust the load on the internal combustion engine 10. The load device 63 is, for example, an alternator and changes the load on the internal combustion engine 10 based on a load control signal (power generation control signal) from the control device 50. The internal combustion engine 10 is also equipped with a coolant temperature detection device 32C. The coolant temperature detection device 32C is, for example, a water temperature sensor and outputs a detection signal to the control device 50 according to the temperature of the coolant (cooling water) that cools the internal combustion engine.

[0025] The accelerator pedal depression detection device 38 is, for example, an accelerator pedal depression sensor, which outputs a detection signal to the control device 50 according to the amount the driver depresses the accelerator pedal. The ignition switch 39 is an input device for the driver to start or stop the internal combustion engine, and the driver operates the ignition switch 39 to start the internal combustion engine when it is stopped or to stop the internal combustion engine when it is running.

[0026] The control device 50 calculates the required load based on the rotational speed of the internal combustion engine based on the detection signal from the rotational speed detection device 34A and the amount of accelerator pedal depression based on the detection signal from the accelerator pedal depression detection device 38, and calculates the amount of fuel corresponding to the required load. Then, based on the detection signals from the rotational speed detection device 34A and the cylinder detection device 34B, the control device 50 controls the injector 21 at a predetermined timing to inject the amount of fuel corresponding to the required load into each of the cylinders #1 to #4 of the internal combustion engine 10.

[0027] An exhaust manifold 12A is connected to the exhaust port of the internal combustion engine 10. The exhaust from the internal combustion engine 10 is guided through the exhaust manifold 12A, exhaust pipe 12B, and the turbine 81 of the supercharger 80, which rotates the turbine 81 and is then discharged into the exhaust pipe 12C. The exhaust from the internal combustion engine 10 contains carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), nitrogen oxides (NOx), and other substances.

[0028] The exhaust manifold 12A or exhaust pipe 12B is connected to the inlet side of the EGR pipe 13 (corresponding to the EGR path) which returns a portion of the exhaust gas to the intake. The outlet side of the EGR pipe 13 is connected to the intake pipe 11C or intake manifold 11D. The EGR pipe 13 is equipped with an EGR valve 13A for adjusting the opening degree of the EGR pipe. The control device 50 can adjust the flow rate of the EGR gas by adjusting the opening degree of the EGR valve 13A while the internal combustion engine 10 is in operation.

[0029] An exhaust pipe 12B is connected to the outlet side of the exhaust manifold 12A. The inlet side of the turbine 81 of the supercharger 80 is connected to the downstream side of the exhaust pipe 12B. An exhaust pipe 12C is connected to the outlet side of the turbine 81, and an exhaust gas purification device 40 is connected to the downstream side of the exhaust pipe 12C.

[0030] The exhaust gas purification device 40 is installed downstream of the connection point between the EGR piping 13 and the exhaust pipe 12B (or exhaust manifold 12A) (in this case, downstream of the exhaust pipe 12B). The exhaust gas purification device 40 consists of an upstream exhaust gas purification device 41 and a downstream exhaust gas purification device 45 located downstream of the upstream exhaust gas purification device 41. The upstream exhaust gas purification device 41 has, from upstream, a first oxidation catalyst 42 (DOC: Diesel Oxidation Catalyst) and a particulate matter collection filter 43 (DPF: Diesel Particulate Filter). The downstream exhaust gas purification device 45 has, from upstream, a urea SCR 46 (SCR: Selective Catalytic Reduction, SCR catalyst) and a second oxidation catalyst 47 (DOC: Diesel Oxidation Catalyst).

[0031] The first oxidation catalyst 42 purifies the exhaust by oxidizing carbon monoxide (CO), hydrocarbons (HC), etc. contained in the exhaust. The particulate matter collection filter 43 collects particulate matter (PM) contained in the exhaust and discharges only the exhaust downstream. The particulate matter collection filter 43 also has the function of purifying carbon monoxide and hydrocarbons by oxidizing them.

[0032] Upstream of the first oxidation catalyst 42 (upstream of the upstream exhaust gas purification device 41), the exhaust pipe 12C is equipped with a fuel additive valve 61A, an exhaust temperature detection device 36A (for example, an exhaust temperature sensor), and a λ detection device 92, etc. The λ detection device 92 may also be provided downstream of the first oxidation catalyst 42. The fuel additive valve 61A is capable of adding (injecting) fuel, and when regenerating the particulate matter collection filter 43 where collected particulate matter has accumulated (when burning and incinerating particulate matter), it injects fuel (corresponding to a reaction liquid) into the exhaust pipe 12C to cause an oxidation reaction in the first oxidation catalyst 42 and raise the temperature of the exhaust gas. A dispersion device 61B is also located in the exhaust pipe 12C to cause collision and disperse the fuel injected from the fuel additive valve 61A. Fuel is supplied to the fuel additive valve 61A from the fuel tank 90.

[0033] The λ detection device 92 is a so-called λ (lambda) sensor (also called an A / F sensor), and outputs a detection signal to the control device 50 according to the oxygen concentration in the exhaust gas (resulting in a detection signal corresponding to λ (= exhaust air-fuel ratio / stoichiometric air-fuel ratio)). (If the exhaust air-fuel ratio is equal to the stoichiometric air-fuel ratio, it outputs a detection signal corresponding to λ = 1.0). In addition, an exhaust temperature detection device 36B (for example, an exhaust temperature sensor) is provided downstream of the first oxidation catalyst 42 and upstream of the particulate matter collection filter 43. For example, the λ detection device 92 outputs a detection signal corresponding to a range of approximately λ = 0.9 to 3.0 (a detection signal corresponding to an air-fuel ratio range of approximately 12 to 50).

[0034] Downstream of the particulate matter collection filter 43, an exhaust temperature detection device 36C (e.g., an exhaust temperature sensor) is provided. In addition, a differential pressure detection device 35 (e.g., a differential pressure sensor) is provided within the upstream exhaust purification device 41 to detect the differential pressure (pressure difference) between the exhaust pressure downstream of the particulate matter collection filter 43 and the exhaust pressure downstream of the particulate matter collection filter 43. The exhaust temperature detection devices 36A, 36B, and 36C output a detection signal corresponding to the exhaust temperature to the control device 50.

[0035] The control device 50 detects the pressure difference between the upstream and downstream sides of the particulate matter collection filter 43 based on the detection signal from the differential pressure detection device 35, and can estimate the amount of particulate matter accumulated in the particulate matter collection filter 43 according to the detected pressure difference. When the estimated amount of accumulation exceeds a threshold, the control device 50 injects fuel (corresponding to the reaction liquid) from the fuel injection valve 61A to raise the exhaust temperature, thereby burning and incinerating the particulate matter accumulated in the particulate matter collection filter 43 and regenerating the particulate matter collection filter 43.

[0036] Furthermore, the downstream exhaust gas purification device 45 is equipped with a urea water injection valve 62A, a dispersion device 62B, a urea SCR 46, a second oxidation catalyst 47, etc., from the upstream side. The urea SCR 46 is connected to the downstream side of the particulate matter collection filter 43 via the exhaust pipe 12D. The urea water injection valve 62A is capable of adding (injecting) urea water and is positioned in the exhaust pipe 12D, which is downstream of the particulate matter collection filter 43 and upstream of the urea SCR 46, and injects urea water (corresponding to the reaction solution) into the exhaust gas at a predetermined timing. The injected urea water (liquid additive) collides with the dispersion device 62B, is scattered and atomized, and diffuses within the exhaust pipe 12D to reach the urea SCR 46. Urea water is supplied to the urea water injection valve 62A from a urea water tank (not shown). Urea SCR46 purifies exhaust gas by reducing nitrogen oxides (NOx) contained in it using ammonia gas generated from added urea solution.

[0037] Furthermore, a NOx detection device 37A (e.g., a NOx sensor) is provided in the exhaust pipe 12D upstream of the urea SCR46. Additionally, a NOx detection device 37B (e.g., a NOx sensor) and an exhaust temperature detection device 36D (e.g., an exhaust temperature sensor) are provided in the exhaust pipe 12E downstream of the urea SCR46. The NOx detection devices 37A and 37B output detection signals to the control device 50 according to the concentration of NOx in the exhaust, and the exhaust temperature detection device 36D outputs detection signals to the control device 50 according to the temperature of the exhaust. Based on the detection signals from the NOx detection devices 37A and 37B and the exhaust temperature detection device 36D, the control device 50 calculates the NOx purification rate of the urea SCR46 and controls the urea water injection valve 62A based on the calculated NOx purification rate.

[0038] The second oxidation catalyst 47 is connected downstream of the urea SCR 46 via the exhaust pipe 12E. The second oxidation catalyst 47 oxidizes and purifies residual ammonia gas in the exhaust. The second oxidation catalyst 47 also has the function of purifying carbon monoxide and hydrocarbons through oxidation reactions.

[0039] The fuel tank 90 stores fuel replenished by the user, etc. Users can replenish with any of the following fuels: diesel fuel, biofuel, or a mixture of diesel fuel and biofuel. Therefore, immediately after refueling, the control device 50 does not know the mixing ratio of diesel fuel and biofuel in the fuel tank 90, so it calculates the fuel mixing ratio using the processing procedure described below. The fuel tank 90 is also equipped with a fuel quantity detection device 91 (for example, a fuel quantity sensor, which corresponds to a fuel replenishment detection device). The fuel quantity detection device 91 outputs a detection signal to the control device 50 according to the amount of fuel in the fuel tank 90.

[0040] The control device 50 is a known device equipped with a CPU 51, RAM 52, ROM 53 (storage device), timer 54, non-volatile storage device 55 (e.g., EEPROM), etc. The CPU 51 performs various calculations based on various programs and maps stored in the ROM 53 (e.g., Flash-ROM). The RAM 52 temporarily stores the calculation results from the CPU and data input from various detection devices, and the non-volatile storage device 55 stores data that should be saved, for example, when the internal combustion engine 10 is stopped.

[0041] The control device 50 can detect the operating state of the internal combustion engine 10 based on the input detection signal. The control device 50 also outputs control signals to control various actuators such as the injector 21 that injects fuel into the cylinder, the fuel additive valve 61A, the urea water additive valve 62A, and the EGR valve 13A, in response to the detected operating state of the internal combustion engine 10 and requests from the driver based on the detection signal from the accelerator pedal depression amount detection device 38. The control device 50 (CPU 51) includes a single-stage injection execution unit for testing 51A, a calculated air-fuel ratio acquisition unit 51B, a λ acquisition unit 51C, a stoichiometric air-fuel ratio acquisition unit 51D, a fuel mixture ratio acquisition unit 51E, a control correction unit 51F, an estimated λ calculation unit, an actual λ acquisition unit, a λ deviation ratio calculation unit, a stoichiometric air-fuel ratio update unit, a factory estimated λ calculation unit, a factory actual λ acquisition unit, a factory λ deviation ratio calculation unit, an air-fuel ratio correction rate update unit, a factory learning completion determination unit, etc. Details of these will be described later.

[0042] As mentioned above, users can refuel with any of the following fuels: diesel fuel, biofuel, or a mixture of diesel fuel and biofuel (any of these fuels are usable). Therefore, the control device 50 does not know the fuel mixture ratio of the fuel immediately after refueling. Biofuel has a higher oxygen content per unit volume than diesel fuel, so the higher the biofuel mixture ratio, the higher the oxygen concentration in the EGR gas and the greater the NOx emissions. Also, compared to diesel fuel, biofuel has a lower carbon-hydrogen ratio and lower calorific value, so the higher the biofuel mixture ratio, the lower the torque generated by the internal combustion engine. Furthermore, the higher the biofuel mixture ratio, the less the in-cylinder temperature can be raised to the target temperature by the pilot injection injected prior to the main injection, which may result in combustion noise. However, if the control device 50 knows the fuel mixture ratio, it can appropriately suppress these issues by making corrections according to the fuel mixture ratio.

[0043] ●●[First Embodiment (Figures 2-12)] In the processing procedure of the control device 50 in the first embodiment described below, during deceleration fuel cut-off, only the main injection of a predetermined injection amount (test single-stage injection) is performed once or multiple times in succession, and the calculated air-fuel ratio is calculated based on the fresh intake mass of the cylinder on which the test single-stage injection was performed and the fuel mass of the test single-stage injection. Then, the value of λ is obtained based on the actual air-fuel ratio in the exhaust of the test single-stage injection. Since "λ = actual air-fuel ratio / stoichiometric air-fuel ratio of the current fuel", "stoichiometric air-fuel ratio of the current fuel = calculated air-fuel ratio / λ". Furthermore, using the fact that the stoichiometric air-fuel ratio of 100% diesel fuel is approximately 14.9 and the stoichiometric air-fuel ratio of 100% biofuel is approximately 12.5, the fuel mixture ratio (percentage of diesel fuel) is calculated from the stoichiometric air-fuel ratio of the current fuel. Note that in normal fuel injection, one combustion itinerary For this purpose, a multi-stage injection system is used, which includes a main injection and a pilot injection that precedes the main injection. However, for the single-stage injection used for testing to detect the fuel mixture ratio, only the main injection is used to avoid fuel pulsation and inject a more accurate amount of fuel.

[0044] ●[Processing procedure of control device 50] Next, an example of the processing procedure of the control device 50 will be explained using the flowcharts shown in Figure 2 and subsequent figures. The processing of the control device 50 includes processing synchronized with the crank angle (crank angle synchronized processing) and processing executed at predetermined time intervals (t1 [ms] intervals) (time synchronized processing). First, the crank angle synchronized processing will be explained using the flowcharts shown in Figures 2 to 5. Note that the internal combustion engine 10 is a 4-cylinder engine having cylinders #1 to #4, and combustion itinerary This will be explained using an example where the injection occurs in the order of cylinder #1 --> cylinder #3 --> cylinder #4 --> cylinder #2. In this embodiment, as shown in Figure 5, a crank angle signal is input every 30°CA (including the top dead center of each cylinder), and a cylinder identification signal is input immediately before the crank angle signal at the compression top dead center of cylinder #1. The time synchronization process will be explained using an example with a 4 ms interval (t1 ms = 4 ms). In this embodiment, an example will be described in which four (multiple) single-stage injections for inspection are performed consecutively in the order of cylinder #1, cylinder #3, cylinder #4, and cylinder #2.

[0045] ●[Execution of single-stage injection for testing and acquisition of calculated air-fuel ratio (crank angle synchronized processing) (Figures 2-5)] When the control device 50 (CPU 51) receives a crank angle signal (see Figure 5), it proceeds to step SK010 in Figure 2.

[0046] In step SK010, the control device 50 performs the [crank counter processing] and proceeds to step SK015. The "crank counter" is a counter that counts up by 1 each time a crank angle signal is input, as shown in Figure 5, and is reset to 0 (zero) each time a cylinder identification signal is input. Further details of the [crank counter processing] will be described later.

[0047] In step SK015, the control device 50 determines whether or not deceleration fuel cut-off is in progress. If deceleration fuel cut-off is in progress (Yes), the control device 50 proceeds to step SK020; otherwise, it proceeds to step SK210. As shown in Figure 5, during deceleration fuel cut-off, no fuel is injected, so the air-fuel ratio becomes theoretically infinite, and the value of λ from the λ detection device approaches the upper limit of λ.

[0048] If the process proceeds to step SK020, the control device 50 determines whether the refueling flag is ON or OFF. The "refueling flag" is a flag that is set to ON when it is detected that fuel has been refueled during the [refueling detection process] described later. If the refueling flag is ON (Yes), the control device 50 proceeds to step SK025, and if the refueling flag is OFF (No), it proceeds to step SK220.

[0049] If the process proceeds to step SK025, the control device 50 determines whether the mixture ratio detection execution flag is OFF or OFF. The "mixture ratio detection execution flag" is a flag that is set ON in step SK030 as shown in Figure 2, and is set ON during the execution of the single-stage injection for testing and the calculation of the fuel mixture ratio (see Figure 5). If the mixture ratio detection execution flag is OFF (Yes), the control device 50 proceeds to step SK030, and if the mixture ratio detection execution flag is ON (No), it proceeds to step SK035.

[0050] If the process proceeds to step SK030, the control device 50 starts up by initializing the standby timer to 0 (zero), initializing the injection counter to 0 (zero), initializing the exhaust counter to 0 (zero), setting the mixture ratio detection execution flag to ON, and proceeds to step SK035. The "standby timer" is a timer that measures a standby time set to be longer than the time from when the deceleration fuel cut occurs until the value of λ from the λ detection device reaches the upper limit of λ, as shown in Figure 5. The "injection counter" is a counter that counts in accordance with each single-stage injection for inspection, as shown in Figure 5, and the "exhaust counter" is an exhaust counter that counts in accordance with each single-stage injection for inspection, as shown in Figure 5. itinerary This is a counter that counts each time it reaches a certain point.

[0051] If the process proceeds to step SK035, the control device 50 determines whether the time measured by the standby timer is equal to or greater than the standby time. The standby time is determined to be an appropriate value through experiments and simulations using actual vehicles. If the time measured by the standby timer is equal to or greater than the standby time (Yes), the control device 50 proceeds to step SK100; otherwise, it terminates the process shown in Figure 2.

[0052] If the process proceeds to step SK100, the control device 50 determines whether the injection counter is 0 (zero). If the injection counter is 0, as shown in Figure 5, the control device 50 stores the fresh intake mass (#1) [g] of cylinder #1 as preparation for the first single-stage test injection (#1) (single-stage test injection to cylinder #1). If the injection counter is 0 (Yes), the control device 50 proceeds to step SK101, and if the injection counter is not 0 (No), it proceeds to step SK110.

[0053] If the process proceeds to step SK101, the control device 50 determines whether the crank counter is 18 or not. The timing of the crank counter being 18 is as shown in Figure 5, when the intake of cylinder #1 itineraryThis is the timing of the bottom dead center (the timing when intake (intake of fresh air) of cylinder #1 is almost complete). If the crank counter = 18 (Yes), the control device 50 proceeds to step SK104; otherwise, it terminates the process shown in Figure 2.

[0054] If the process proceeds to step SK104, the control device 50 stores the fresh intake mass (#1) [g] and proceeds to step SK109. As shown in Figure 1, taking into account the time delay due to the intake path from the air flow detection device 31 to the internal combustion engine 10, the control device 50 calculates the amount of fresh intake air [g / sec] from 12 [ms] ago, the rotational speed [rpm] at that time, and the number of cylinders of the internal combustion engine, and determines that cylinder #1 is the intake for the current intake. itinerary The mass of fresh air [g] drawn in (fresh air intake mass (#1)) is calculated and stored. Note that in the [fresh air intake amount delay time processing] (Figure 8) described later, the fresh air intake amount [g / sec] from t1*1 [ms] ago to t1*4 [ms] ago is stored, so the control device 50 reads out the appropriate intake amount. When the control device 50 calculates the fresh air intake mass, for example, if it uses the fresh air intake amount from 12 [ms] ago, and t1 [ms] = 4 [ms], it reads out and uses the "fresh air intake amount (t1*3 [ms] ago)".

[0055] If the process proceeds to step SK110, the control device 50 determines whether the injection counter is 1 or not. If the injection counter is 1, as shown in Figure 5, the control device 50 schedules (reserves) the first single-stage test injection (#1) (single-stage test injection to cylinder #1) and stores the fresh intake mass (#3) [g] of cylinder #3 as preparation for the second single-stage test injection (#3) (single-stage test injection to cylinder #3). If the injection counter is 1 (Yes), the control device 50 proceeds to step SK111, and if the injection counter is not 1 (No), it proceeds to step SK120.

[0056] If the process proceeds to step SK111, the control device 50 determines whether the crank counter is 0 or not. The timing of the crank counter being 0 is, as shown in Figure 5, the compression of cylinder #1. itinerary This is the timing of the top dead center, as well as the intake of cylinder #3. itinerary This is the timing of the bottom dead center (the timing when intake for cylinder #3 is almost complete). The control device 50 proceeds to step SK112 if the crank counter = 0 (Yes), and otherwise terminates the process shown in Figure 2 (No).

[0057] If the process proceeds to step SK112, the control device 50 schedules (reserves) a single-stage injection (#1) for inspection of cylinder #1 and proceeds to step SK113. The injection amount for the single-stage injection (#1) for inspection is a predetermined injection amount [mm 3 It is set to [ ] and only the main injection (no pilot injection) is used to suppress fuel pulsation and inject a more accurate amount of fuel. Also, the "predetermined injection amount" is the injection amount [mm] that is the value of λ that can be detected by the λ detection device. 3 It is set to ] (for example, an injection volume such that 1.0 < λ < 2.0). This schedule (reservation) executes "#1" of the "single-stage injection for inspection" shown in Figure 5.

[0058] In step SK113, the control device 50 stores the calculated air-fuel ratio (#1) and proceeds to step SK114. The control device 50 stores the fresh intake mass (#1) [g] of cylinder #1 [#1] stored in step SK104 and the predetermined injection amount [mm] of the single-stage injection for testing (#1). 3 ]*Fuel density[g / mm 3 Based on the above, the fuel mass [g] is calculated and stored, along with the calculated air-fuel ratio (#1) = "Fresh intake mass of cylinder #1 (#1) [g]" / "Fuel mass of single-stage injection for testing (#1) [g]". Note that the fuel density of 100% diesel fuel and the fuel density of 100% biofuel are not far apart and are close, so an appropriate value such as the fuel density of 100% diesel fuel or the fuel density of 80% diesel fuel (20% biofuel) is used as the fuel density.

[0059] In step SK114, the control device 50 stores the fresh intake mass (#3) [g], which is the mass of fresh intake air for cylinder #3, and proceeds to step SK118. The control device 50 calculates and stores the fresh intake mass (#3) [g] in the same manner as the fresh intake mass (#1) [g] in step SK104.

[0060] If the process proceeds to step SK120, the control device 50 determines whether the injection counter is 2 or not. If the injection counter is 2, as shown in Figure 5, the control device 50 schedules (reserves) the second single-stage test injection (#3) (single-stage test injection to cylinder #3) and stores the fresh intake mass (#4) [g] of cylinder #4 as preparation for the third single-stage test injection (#4) (single-stage test injection to cylinder #4). If the injection counter is 2 (Yes), the control device 50 proceeds to step SK121, and if the injection counter is not 2 (No), it proceeds to step SK130.

[0061] If the process proceeds to step SK121, the control device 50 determines whether the crank counter is 6 or not. The timing of the crank counter being 6 is, as shown in Figure 5, the compression of cylinder #3. itinerary This is the timing of the top dead center, as well as the intake of cylinder #4 itinerary This is the timing of the bottom dead center (the timing when intake for cylinder #4 is almost complete). If the crank counter is 6 (Yes), the control device 50 proceeds to step SK122; otherwise, it terminates the process shown in Figure 2.

[0062] If the process proceeds to step SK122, the control device 50 schedules (reserves) a single-stage injection for inspection of cylinder #3 (#3) and proceeds to step SK123. Also, similar to step SK112, the injection amount of the single-stage injection for inspection (#3) is a predetermined injection amount [mm 3 It is set to ] and only the main injection is used (no pilot injection). Also, similar to step SK112, the "predetermined injection amount" is the injection amount [mm] that is the value of λ that can be detected by the λ detection device. 3It is set to (for example, an injection volume where 1.0 < λ < 2.0). This schedule (reservation) executes "#3" of the "single-stage injection for inspection" shown in Figure 5.

[0063] In step SK123, the control device 50 stores the calculated air-fuel ratio (#3) and proceeds to step SK124. The control device 50 stores the fresh intake mass (#3) [g] of cylinder #3 [#3] stored in step SK114 and the predetermined injection amount [mm] of the single-stage injection for testing (#3). 3 ]*Fuel density[g / mm 3 Based on this, the fuel mass [g] and the calculated air-fuel ratio (#3) = "Fresh intake mass of cylinder #3 (#3) [g]" / "Fuel mass of single-stage injection for inspection (#3) [g]" are calculated and stored.

[0064] In step SK124, the control device 50 stores the fresh intake mass (#4) [g], which is the mass of fresh intake air for cylinder #4, and proceeds to step SK125. The control device 50 calculates and stores the fresh intake mass (#4) [g] in the same manner as the fresh intake mass (#1) [g] in step SK104.

[0065] In step SK125, the control device 50 increments the exhaust counter (+1) and proceeds to step SK118. As shown in Figure 5, when the crank counter is 6, the exhaust counter is set to 1, indicating the timing when the exhaust from the single-stage injection test of cylinder #1 (#1) ("Exhaust of #1" in Figure 5) is output to the exhaust path.

[0066] If the process proceeds to step SK130, the control device 50 determines whether the injection counter is 3 or not. If the injection counter is 3, as shown in Figure 5, the control device 50 schedules (reserves) the third single-stage test injection (#4) (single-stage test injection to cylinder #4) and stores the fresh intake mass (#2) [g] of cylinder #2 as preparation for the fourth single-stage test injection (#2) (single-stage test injection to cylinder #2). If the injection counter is 3 (Yes), the control device 50 proceeds to step SK131, and if the injection counter is not 3 (No), it proceeds to step SK140.

[0067] When the process proceeds to step SK131, the control device 50 determines whether the crank counter = 12. Note that the timing of the crank counter = 12 is the top dead center timing of the compression of cylinder #4 and the bottom dead center timing of the intake of cylinder #2 (the timing when the intake of cylinder #2 is almost completed) as shown in FIG. 5. When the crank counter = 12 (Yes), the control device 50 proceeds to step SK132; otherwise (No), the process shown in FIG. 2 ends. itinerary of the top dead center and the bottom dead center timing of the intake of cylinder #2 (the timing when the intake of cylinder #2 is almost completed). When the crank counter = 12 (Yes), the control device 50 proceeds to step SK132; otherwise (No), the process shown in FIG. 2 ends. itinerary of the bottom dead center (the timing when the intake of cylinder #2 is almost completed). When the control device 50 determines that the crank counter = 12 (Yes), it proceeds to step SK132; otherwise (No), it ends the process shown in FIG. 2.

[0068] When the process proceeds to step SK132, the control device 50 schedules (reserves) a single-stage injection for inspection (#4) of cylinder #4 and proceeds to step SK133. Also, similar to step SK112, the injection amount of the single-stage injection for inspection (#4) is set to a predetermined injection amount [mm 3 , and it is only the main injection (without pilot injection). Also, similar to step SK112, the "predetermined injection amount" is set to an injection amount [mm 3 (for example, an injection amount that makes 1.0 < λ < 2.0) that is a value of λ detectable by the λ detection device. By this schedule (reservation), the "#4" of the "single-stage injection for inspection" shown in FIG. 5 is executed.

[0069] In step SK133, the control device 50 stores the calculated air-fuel ratio (#4) and proceeds to step SK134. The control device 50 calculates the calculated air-fuel ratio (#4) = "fresh air intake mass (#4) [g] of cylinder #4" / "fuel mass [g]" based on the fresh air intake mass (#4) [g] of cylinder #4 stored in step SK124 and the fuel mass [g] based on the predetermined injection amount [mm 3 * fuel density [g / mm 3 of the single-stage injection for inspection (#4), and stores it.

[0070] In step SK134, the control device 50 stores the fresh intake mass (#2) [g], which is the mass of fresh intake air for cylinder #2, and proceeds to step SK135. The control device 50 calculates and stores the fresh intake mass (#2) [g] in the same manner as the fresh intake mass (#1) [g] in step SK104.

[0071] In step SK135, the control device 50 increments the exhaust counter (+1) and proceeds to step SK118. As shown in Figure 5, when the crank counter is 12, the exhaust counter is set to 2, indicating the timing when the exhaust from the single-stage injection test of cylinder #3 (#3) ("exhaust from #3" in Figure 5) is output to the exhaust path.

[0072] If the process proceeds to step SK140, the control device 50 determines whether the injection counter is 4 or not. If the injection counter is 4, the control device 50 schedules (reserves) the fourth single-stage test injection (#2) (single-stage test injection to cylinder #2), as shown in Figure 5. If the injection counter is 4 (Yes), the control device 50 proceeds to step SK141, and if the injection counter is not 4 (No), it proceeds to step SK150.

[0073] If the process proceeds to step SK141, the control device 50 determines whether the crank counter is 18 or not. The timing of the crank counter being 18 is, as shown in Figure 5, the compression of cylinder #2. itinerary This is the timing of the top dead center, as well as the intake of cylinder #1 itinerary This is the timing of the bottom dead center (the timing when intake for cylinder #1 is almost complete). If the crank counter is 18 (Yes), the control device 50 proceeds to step SK142; otherwise, it terminates the process shown in Figure 2.

[0074] If the process proceeds to step SK142, the control device 50 schedules (reserves) a single-stage injection for inspection of cylinder #2 (#2) and proceeds to step SK143. Also, similar to step SK112, the injection amount of the single-stage injection for inspection (#2) is a predetermined injection amount [mm3 It is set to ] and only the main injection is used (no pilot injection). Also, similar to step SK112, the "predetermined injection amount" is the injection amount [mm] that is the value of λ that can be detected by the λ detection device. 3 It is set to (for example, an injection volume where 1.0 < λ < 2.0). This schedule (reservation) executes "#2" of the "single-stage injection for inspection" shown in Figure 5.

[0075] In step SK143, the control device 50 stores the calculated air-fuel ratio (#2) and proceeds to step SK145. The control device 50 stores the fresh intake mass (#2) [g] of cylinder #2 [#2] stored in step SK134 and the predetermined injection amount [mm] of the single-stage injection for testing (#2). 3 ]*Fuel density[g / mm 3 Based on this, the fuel mass [g] and the calculated air-fuel ratio (#2) = "Fresh intake mass of cylinder #2 (#2) [g]" / "Fuel mass of single-stage injection for inspection (#2) [g]" are calculated and stored.

[0076] In step SK145, the control device 50 increments the exhaust counter (+1) and proceeds to step SK118. As shown in Figure 5, when the crank counter is 18, the exhaust counter is set to 3, indicating the timing when the exhaust from the single-stage injection test of cylinder #4 (#4) ("exhaust from #4" in Figure 5) is output to the exhaust path.

[0077] If the process proceeds to step SK150, the control device 50 determines whether the injection counter is 5 or not. If the injection counter is 5, the control device 50 does not schedule (reserve) the single-stage injection for testing, nor does it store the fresh air intake mass, as shown in Figure 5. If the injection counter is 5 (Yes), the control device 50 proceeds to step SK151, and if the injection counter is not 5 (No), it terminates the process shown in Figure 2.

[0078] If the process proceeds to step SK151, the control device 50 determines whether the crank counter is 0 or not. The timing of the crank counter being 0 is, as shown in Figure 5, the compression of cylinder #1. itineraryThis is the timing of the top dead center, as well as the intake of cylinder #3. itinerary This is the timing of the bottom dead center (the timing when intake for cylinder #3 is almost complete). The control device 50 proceeds to step SK155 if the crank counter = 0 (Yes), and otherwise terminates the process shown in Figure 2 (No).

[0079] In step SK155, the control device 50 increments the exhaust counter (+1) and proceeds to step SK156. As shown in Figure 5, when the crank counter is 0, the exhaust counter is set to 4, indicating the timing when the exhaust from the single-stage injection test of cylinder #2 (#2) ("exhaust from #2" in Figure 5) is output to the exhaust path.

[0080] In step SK156, the control device 50 sets the supply flag to OFF and proceeds to step SK118.

[0081] If the process proceeds to step SK118, the control device 50 sets the λ detection request flag to ON and proceeds to step SK109.

[0082] If the process proceeds to step SK109, the control device 50 counts up the injection counter by +1 and terminates the process shown in Figure 2.

[0083] If the process proceeds to step SK210, the control device 50 performs the [normal fuel injection process] and proceeds to step SK220. Details of the [normal fuel injection process] will be described later.

[0084] If the process proceeds to step SK220, the control device 50 sets the mixing ratio detection execution flag to OFF and terminates the process shown in Figure 2.

[0085] ●[Crank counter processing (Figure 3)] When the control device 50 executes the [crank counter processing] in step SK010 shown in Figure 2, it proceeds to step SA010 of the [crank counter processing] shown in Figure 3. In the process shown in Figure 3, the counting operation of the "crank counter" from 0 to 23 shown in Figure 5 is performed.

[0086] If the process proceeds to step SA010, the control device 50 determines whether or not a cylinder identification signal has been input. If a cylinder identification signal has been input (Yes), the control device 50 proceeds to step SA015; if no cylinder identification signal has been input (No), it proceeds to step SA020.

[0087] If the process proceeds to step SA015, the control device 50 initializes the crank counter to 0 (zero), terminates the process shown in Figure 3, and returns the process to step SK015 shown in Figure 2.

[0088] If the process proceeds to step SA020, the control device 50 increments the crank counter (+1), terminates the process shown in Figure 3, and returns to step SK015 shown in Figure 2.

[0089] ●[Normal fuel injection process (Figure 4)] When the control device 50 executes the [normal fuel injection process] in step SK210 shown in Figure 2, it proceeds to step SB010 of the [normal fuel injection process] shown in Figure 4. In the process shown in Figure 4, a normal fuel injection process is performed, which is not during fuel cut-off.

[0090] If the process proceeds to step SB010, the control device 50 determines whether or not it is the injection schedule timing. Step SB010 is an existing process. If it is the injection schedule timing (Yes), the control device 50 proceeds to step SB015; otherwise (No), it terminates the process shown in Figure 4 and returns to step SK220 shown in Figure 2.

[0091] If the process proceeds to step SB015, the control device 50 calculates the required injection amount (for 100% diesel fuel) based on the operating conditions of the internal combustion engine (e.g., rotational speed and accelerator pedal depression amount), and proceeds to step SB020. Since the process in step SB015 is an existing process, a detailed explanation is omitted.

[0092] In step SB020, the control device 50 calculates the provisional pilot injection amount, provisional main injection amount, provisional pilot injection timing, and provisional main injection timing based on the requested injection amount (in the case of 100% diesel fuel), and proceeds to step SB025. Since the processing in step SB020 is an existing process, a detailed explanation is omitted.

[0093] In step SB025, the control device 50 calculates the pilot injection correction amount, main injection correction amount, pilot injection timing correction amount, and main injection timing correction amount based on the fuel mixture ratio obtained in the process described later, and proceeds to step SB030. The control device 50 increases the pilot injection correction amount and main injection correction amount as the proportion of biofuel in the fuel mixture ratio increases. The process in step SB025 is almost the same as the existing process.

[0094] In step SB030, the control device 50 calculates the pilot injection amount by adding the pilot injection correction amount to the provisional pilot injection amount, and calculates the main injection amount by adding the main injection correction amount to the provisional main injection amount. The control device 50 also calculates the pilot injection timing by adding the pilot injection timing correction amount (positive or negative) to the provisional pilot injection timing, and calculates the main injection timing by adding the main injection timing correction amount (positive or negative) to the provisional main injection timing. The processing in step SB030 is almost the same as the existing processing. Then the control device 50 proceeds to step SB035.

[0095] In step SB035, the control device 50 schedules (reserves) a multi-stage injection including pilot injection and main injection based on the calculated pilot injection amount and main injection amount, pilot injection timing and main injection timing, and then finishes the process shown in Figure 4, returning to step SK220 shown in Figure 2. Since the process in step SB035 is an existing process, a detailed explanation is omitted.

[0096] ●[Overall processing for determining the fuel mixture ratio (time-synchronized processing ( / t1[ms] interval)) (Figures 6-12)] Next, the time synchronization process will be explained using flowcharts and the like shown in Figures 6 to 12. The control device 50 (CPU 51) starts the process shown in Figure 6 at predetermined time intervals of several ms (in this embodiment, "t1 [ms] interval" = 4 [ms] intervals) and proceeds to step ST010.

[0097] In step ST010, the control device 50 executes the [supply detection process] and proceeds to step ST015. Details of the [supply detection process] will be described later.

[0098] In step ST015, the control device 50 performs the [fresh air intake volume delay processing] and proceeds to step ST020. Details of the [fresh air intake volume delay processing] will be described later.

[0099] In step ST020, the control device 50 determines whether the λ detection request flag (see Figure 5) is ON or OFF. If the λ detection request flag is ON (Yes), the control device 50 proceeds to step ST025; otherwise, it proceeds to step ST050.

[0100] If the process proceeds to step ST025, the control device 50 executes the [λ detection process] and proceeds to step ST030. Details of the [λ detection process] will be described later.

[0101] In step ST030, the control device 50 determines whether the stoichiometric air-fuel ratio calculation request flag (a flag set to ON in the [λ detection process]) is ON or not. If the stoichiometric air-fuel ratio calculation request flag is ON (Yes), the control device 50 proceeds to step ST035; otherwise, it proceeds to step ST060.

[0102] If the process proceeds to step ST035, the control device 50 performs the [calculation of stoichiometric air-fuel ratio and fuel mixture ratio] and proceeds to step ST060. Details of the [calculation of stoichiometric air-fuel ratio and fuel mixture ratio] process will be described later.

[0103] If the process proceeds to step ST050, the control device 50 resets the [calculated air-fuel ratio / λ] integrated value to 0 (zero), resets the number of integrations to 0 (zero), and proceeds to step ST060.

[0104] If the process proceeds to step ST060, the control device 50 executes [EGR control] and terminates the process shown in Figure 6. Details of the [EGR control] process will be described later.

[0105] ●[Resupply detection process (Figure 7)] When the control device 50 executes the [refueling detection process] in step ST010 shown in Figure 6, it proceeds to step SU010 of the [refueling detection process] shown in Figure 7. In the process shown in Figure 7, the control device 50 determines whether or not fuel has been refueled (replenished), and if it determines that fuel has been refueled (replenished), it sets the refueling flag (stored in the non-volatile memory device) to ON.

[0106] If the process proceeds to step SU010, the control device 50 determines whether the ignition switch has been operated from ON to OFF. If the control device 50 determines that the ignition switch has been operated from ON to OFF (Yes), it proceeds to step SU030; otherwise, it proceeds to step SU015.

[0107] If the process proceeds to step SU030, the control device 50 stores the fuel amount detected by the fuel amount detection device 91 in the IG_OFF fuel amount (stored in the non-volatile memory device), terminates the process shown in Figure 7, and returns to step ST015 of the flowchart shown in Figure 6.

[0108] If the process proceeds to step SU015, the control device 50 determines whether the ignition switch has been operated from OFF to ON. If the ignition switch has been operated from OFF to ON (Yes), the control device 50 proceeds to step SU020; otherwise (No), it terminates the process shown in Figure 7 and returns to step ST015 of the flowchart shown in Figure 6.

[0109] If the process proceeds to step SU020, the control device 50 determines whether the amount of fuel obtained by subtracting the amount of fuel at IG_OFF from the current amount of fuel detected using the fuel amount detection device 91 is equal to or greater than the refueling determination fuel amount. The refueling determination fuel amount is a pre-set amount of fuel, and an appropriate value for determining refueling is set. If "current amount of fuel - amount of fuel at IG_OFF" is equal to or greater than the refueling determination fuel amount (Yes), the control device 50 proceeds to step SU025; otherwise (No), it terminates the process shown in Figure 7 and returns to step ST015 of the flowchart shown in Figure 6.

[0110] If the process proceeds to step SU025, the control device 50 sets the replenishment flag (stored in the non-volatile memory device) to ON, terminates the process shown in Figure 7, and returns to step ST015 of the flowchart shown in Figure 6.

[0111] ●[Delayed fresh air intake volume processing (Figure 8)] When the control device 50 executes the [fresh air intake volume delay time processing] of step ST015 shown in Figure 6, it proceeds to step SV010 of the [fresh air intake volume delay time processing] shown in Figure 8. In the process shown in Figure 8, the control device 50 stores the fresh air intake volume (Ga [g / sec]) from a predetermined time prior, which is used when calculating the fresh air intake mass (#n) to be stored in steps SK104, SK114, SK124, and SK134 of the flowchart in Figure 2 described above.

[0112] Step SV010 If the process proceeds as described, the control device 50 copies the fresh air intake amount (t1*3 [ms] ago) to the fresh air intake amount (t1*4 [ms] ago), the fresh air intake amount (t1*2 [ms] ago) to the fresh air intake amount (t1*3 [ms] ago), the fresh air intake amount (t1*1 [ms] ago) to the fresh air intake amount (t1*2 [ms] ago), and the fresh air intake amount (current) to the fresh air intake amount (t1*1 [ms] ago). Then the control device 50 copies the current fresh air intake amount (Ga [g / sec]) to the fresh air intake amount (current). As a result of this process, when t1[ms]=4[ms], the current fresh air intake amount (Ga) is stored in the fresh air intake amount (present), the fresh air intake amount (t1*1[ms] ago) is stored in the fresh air intake amount (Ga) from 4[ms] ago, the fresh air intake amount (Ga) from 8[ms] ago is stored in the fresh air intake amount (t1*2[ms] ago), the fresh air intake amount (Ga) from 12[ms] ago is stored in the fresh air intake amount (Ga) from 12[ms] ago, and the fresh air intake amount (Ga) from 16[ms] ago is stored in the fresh air intake amount (Ga) from 16[ms] ago. The control device 50 then completes the process shown in Figure 8 and returns to step ST020 of the flowchart shown in Figure 6.

[0113] ●[λ detection process (Figure 9)] When the control device 50 executes the [λ detection process] of step ST025 shown in Figure 6, it proceeds to step SW010 of the [λ detection process] shown in Figure 9. In the process shown in Figure 9, the control device 50 detects the value of λ in the "exhaust of #1" to "exhaust of #2" corresponding to the single-stage test injections (#1) to (#2) shown in Figure 5, and calculates the stoichiometric air-fuel ratio of the current fuel by calculating the calculated air-fuel ratio (#n) / λ. The period from "exhaust of #1" to "exhaust of #2" in Figure 5 corresponds to the period of variation in λ caused by the single-stage test injections #1 to #2. Note that "λ = current actual air-fuel ratio / current stoichiometric air-fuel ratio of the fuel", so current actual air-fuel ratio / λ = current stoichiometric air-fuel ratio of the fuel. Note that the [λ detection process] shown in Figure 9 is executed only when the λ detection request flag is ON, as shown in Figure 6. Furthermore, the λ detection request flag is set to ON when a single-stage injection for inspection is scheduled (reserved), as shown in step SK118 in Figure 2 and in Figure 5.

[0114] If the process proceeds to step SW010, the control device 50 obtains the value of λ using the λ detection device 92 and proceeds to step SW015.

[0115] As shown in Figure 5, after the deceleration fuel cut flag changes from 0 to 1 (OFF to ON), fuel injection is stopped, so the air-fuel ratio (intake mass / fuel mass) becomes infinite, and the value of λ detected by the λ detection device fluctuates towards the upper limit of λ, eventually reaching the upper limit of λ. Subsequently, when the single-stage test injection (#1) is executed with the value of λ at the upper limit of λ, the value of λ changes in the direction from the upper limit of λ towards 1.0 in the exhaust of the single-stage test injection (#1) ("Exhaust of #1" in Figure 5). This value of λ that has changed from the upper limit of λ is obtained in the following process and used to calculate the stoichiometric air-fuel ratio.

[0116] In step SW015, the control device 50 determines whether the value of λ is below the fluctuation threshold. The fluctuation threshold is a value slightly smaller than the upper limit of λ and is set to an appropriate value through experiments and simulations using actual vehicles. If the value of λ is below the fluctuation threshold (Yes), the control device 50 proceeds to step SW020; otherwise, it proceeds to step SW070.

[0117] If the process proceeds to step SW020, the control device 50 determines whether the exhaust counter is 1 or less. As shown in Figure 5, if the exhaust counter is 1 or less, it means that the value of λ for the exhaust of #1 has been detected. If the exhaust counter is 1 or less (Yes), the control device 50 proceeds to step SW025; otherwise, it proceeds to step SW030.

[0118] If the process proceeds to step SW025, the control device 50 adds [calculated air-fuel ratio (#1) / current value of λ] to the [calculated air-fuel ratio / λ] integrated value and stores the added value in the [calculated air-fuel ratio / λ] integrated value. In other words, it integrates [calculated air-fuel ratio (#1) / current value of λ]. The calculated air-fuel ratio (#1) is stored in step SK113 in Figure 2 and is the air-fuel ratio calculated as "new intake air volume mass of cylinder #1 (#1) [g] stored in step SK104 / fuel mass of single-stage injection for inspection (#1) [g]". The control device 50 then counts up the number of integrations (+1), sets the integration execution flag to ON, terminates the process shown in Figure 9, and returns the process to step ST030 shown in Figure 6.

[0119] If the process proceeds to step SW030, the control device 50 determines whether the exhaust counter is 2 or not. As shown in Figure 5, if the exhaust counter is 2, it means that the value of λ for the exhaust of #3 has been detected. If the exhaust counter is 2 (Yes), the control device 50 proceeds to step SW035; otherwise, it proceeds to step SW040.

[0120] If the process proceeds to step SW035, the control device 50 adds [calculated air-fuel ratio (#3) / current value of λ] to the [calculated air-fuel ratio / λ] integrated value and stores the added value in the [calculated air-fuel ratio / λ] integrated value. In other words, it integrates [calculated air-fuel ratio (#3) / current value of λ]. The calculated air-fuel ratio (#3) is stored in step SK123 in Figure 2 and is the air-fuel ratio calculated as "new intake air volume mass of cylinder #3 (#3) [g] stored in step SK114 / fuel mass of single-stage injection for inspection (#3) [g]". The control device 50 then counts up the number of integrations (+1), sets the integration execution flag to ON, terminates the process shown in Figure 9, and returns the process to step ST030 shown in Figure 6.

[0121] If the process proceeds to step SW040, the control device 50 determines whether the exhaust counter is 3 or not. As shown in Figure 5, if the exhaust counter is 3, it means that the value of λ for the exhaust of #4 has been detected. If the exhaust counter is 3 (Yes), the control device 50 proceeds to step SW045; otherwise, it proceeds to step SW055.

[0122] If the process proceeds to step SW045, the control device 50 adds [calculated air-fuel ratio (#4) / current value of λ] to the [calculated air-fuel ratio / λ] integrated value and stores the added value in the [calculated air-fuel ratio / λ] integrated value. In other words, it integrates [calculated air-fuel ratio (#4) / current value of λ]. The calculated air-fuel ratio (#4) is stored in step SK133 in Figure 2 and is the air-fuel ratio calculated as "new intake air volume mass of cylinder #4 (#4) [g] stored in step SK124 / fuel mass of single-stage injection for inspection (#4) [g]". The control device 50 then counts up the number of integrations (+1), sets the integration execution flag to ON, terminates the process shown in Figure 9, and returns the process to step ST030 shown in Figure 6.

[0123] If the process proceeds to step SW055, the control device 50 adds [calculated air-fuel ratio (#2) / current value of λ] to the [calculated air-fuel ratio / λ] integrated value and stores the added value in the [calculated air-fuel ratio / λ] integrated value. In other words, it integrates [calculated air-fuel ratio (#2) / current value of λ]. The calculated air-fuel ratio (#2) is stored in step SK143 in Figure 2 and is the air-fuel ratio calculated as "new intake air volume mass of cylinder #2 (#2) [g] stored in step SK134 / fuel mass of single-stage injection for inspection (#2) [g]". The control device 50 then counts up the number of integrations (+1), sets the integration execution flag to ON, terminates the process shown in Figure 9, and returns to step ST030 shown in Figure 6.

[0124] If the process proceeds to step SW070, the control device 50 determines whether the cumulative execution flag is ON or OFF. If the cumulative execution flag is ON (Yes), the control device 50 proceeds to step SW075; otherwise (No), it terminates the process shown in Figure 9 and returns to step ST030 shown in Figure 6.

[0125] If the process proceeds to step SW075, the control device 50 determines whether the exhaust counter is 4 or not. If the exhaust counter is 4 (Yes), the control device 50 determines that it is the time when the variation of λ has ended (the exhaust of #2 in Figure 5 has ended) and proceeds to step SW080 to end the detection of λ as a result of the single-stage injection for testing. Otherwise (No), the process shown in Figure 9 is terminated and the process returns to step ST030 shown in Figure 6.

[0126] If the process proceeds to step SW080, the control device 50 determines that the fluctuation of λ has ended, sets the λ detection request flag to OFF, sets the integration execution flag to OFF, sets the stoichiometric air-fuel ratio calculation request flag to ON, terminates the process shown in Figure 9, and returns to step ST030 shown in Figure 6. The stoichiometric air-fuel ratio calculation request flag, as used in step ST030 in Figure 6, is used to terminate the detection of λ which has fluctuated due to the single-stage test injection and to start the execution of calculating the stoichiometric air-fuel ratio and fuel mixture ratio.

[0127] ●[Calculate the stoichiometric air-fuel ratio and fuel mixture ratio (Figure 10)] When the control device 50 executes step ST035 [Calculate stoichiometric air-fuel ratio and fuel mixture ratio] shown in Figure 6, it proceeds to step SX010 [Calculate stoichiometric air-fuel ratio and fuel mixture ratio] shown in Figure 10. In the process shown in Figure 10, the control device 50 calculates the stoichiometric air-fuel ratio of the current fuel using the [Calculated air-fuel ratio / λ] integrated value obtained in Figure 9 and the number of integrations, and then calculates the fuel mixture ratio based on the calculated stoichiometric air-fuel ratio. Note that the [Calculation of stoichiometric air-fuel ratio and fuel mixture ratio] shown in Figure 10 is executed only when the stoichiometric air-fuel ratio detection request flag is ON, as shown in Figure 6. The stoichiometric air-fuel ratio detection request flag is a flag that is set to ON in step SW080 in Figure 9.

[0128] If the process proceeds to step SX010, the control device 50 calculates the stoichiometric air-fuel ratio of the current fuel based on the [calculated air-fuel ratio / λ] cumulative value and the number of cumulative calculations, and proceeds to step SX015. Since "the stoichiometric air-fuel ratio of the current fuel = the current actual air-fuel ratio / λ", the control device 50 calculates "[calculated air-fuel ratio / λ] cumulative value" / "number of cumulative calculations", finds the average value of "[calculated air-fuel ratio / λ] cumulative value", calculates the stoichiometric air-fuel ratio of the current fuel, and stores it in the non-volatile memory device.

[0129] In step SX015, the control device 50 calculates the current fuel mixture ratio (percentage of diesel fuel) based on the current stoichiometric air-fuel ratio of the fuel and the [stoichiometric air-fuel ratio / fuel mixture ratio characteristics] shown in Figure 12, stores it in the non-volatile memory device, and proceeds to step SX020. In Figure 12, the [stoichiometric air-fuel ratio / fuel mixture ratio characteristics] shows the fuel-air-fuel ratio on the horizontal axis and the fuel mixture ratio (percentage of diesel fuel) on the vertical axis. In Figure 12, "AF1" is the stoichiometric air-fuel ratio when using 100% biofuel, for example, 12.5. Also in Figure 12, "AF2" is the stoichiometric air-fuel ratio when using 100% diesel fuel, for example, 14.9. For example, if the stoichiometric air-fuel ratio calculated in step SX010 was AFx, the control device 50 can use the [stoichiometric air-fuel ratio / fuel mixture ratio characteristics] shown in Figure 12 to calculate that the fuel mixture ratio (percentage of diesel fuel) relative to the stoichiometric air-fuel ratio = AFx is Yx%.

[0130] In step SX020, the control device 50 sets the stoichiometric air-fuel ratio calculation request flag to OFF and the mixture ratio detection execution flag to OFF, ending the process shown in Figure 10, and returning to step ST060 in the flowchart of Figure 6.

[0131] ●[EGR control (Figure 11)] When the control device 50 executes the [EGR control] step ST060 shown in Figure 6, it proceeds to step SY010 of the [EGR control] shown in Figure 11. The control device 50 adjusts the opening degree of the EGR valve 13A in the process shown in Figure 11.

[0132] If the process proceeds to step SY010, the control device 50 calculates the provisional target EGR rate and proceeds to step SY015. Since step SY010 is an existing process, details are omitted.

[0133] In step SY015, the control device 50 calculates the EGR rate correction amount based on the fuel mixture ratio and proceeds to step SY020. The control device 50 increases the EGR rate correction amount as the proportion of biofuel in the fuel mixture ratio increases. The process in step SY015 is almost the same as the existing process.

[0134] In step SY020, the control device 50 calculates the target EGR rate by adding the EGR rate correction amount to the provisional target EGR rate, and proceeds to step SY025. The processing in step SY020 is almost the same as the existing processing.

[0135] In step SY025, the control device 50 controls the opening degree of the EGR valve 13A so that the actual EGR rate approaches the target EGR rate. Since the process in step SY025 is an existing process, a detailed explanation is omitted. The control device 50 then completes the process shown in Figure 11, returns to the step below step ST060 in the flowchart of Figure 6, and completes the process shown in Figure 6.

[0136] Furthermore, the control device 50 (CPU 51) that executes steps SK112, SK122, SK132, and SK142 in the flowchart shown in Figure 2 corresponds to the single-stage test injection execution unit 51A (see Figure 1), which performs single-stage test injections #1 to #2, consisting of only a predetermined amount of main injection, during deceleration fuel cut-off when the internal combustion engine is operating in a deceleration and fuel cut-off state.

[0137] Furthermore, the control device 50 (CPU 51) that executes steps SK113, SK123, SK133, and SK143 in the flowchart shown in Figure 2 corresponds to the calculated air-fuel ratio acquisition unit 51B (see Figure 1), which acquires the calculated air-fuel ratio based on the fresh air mass, which is the mass of fresh air drawn in by the cylinder that performed the single-stage inspection injection #1 to the single-stage inspection injection #2, and the fuel mass, which is based on the predetermined fuel amount for the single-stage inspection injection.

[0138] Furthermore, the control device 50 (CPU 51) that performs the [λ detection process] shown in Figure 9 corresponds to the λ acquisition unit 51C (see Figure 1), which acquires the value of λ from the λ detection device during the variation period, which is the period during which λ fluctuates due to the single-stage injection for inspection.

[0139] Furthermore, the control device 50 (CPU 51) that performs the [λ detection process] shown in Figure 9 and step SX010 of the flowchart shown in Figure 10 corresponds to the stoichiometric air-fuel ratio acquisition unit 51D (see Figure 1), which acquires the current stoichiometric air-fuel ratio of the fuel based on the λ value acquired during the fluctuation period and the calculated air-fuel ratio.

[0140] Furthermore, the control device 50 (CPU 51) executing step SX015 in the flowchart of Figure 10 corresponds to a fuel mixture ratio acquisition unit 51E (see Figure 1) that acquires the fuel mixture ratio, which is the mixture ratio of diesel and biofuel in the current fuel, based on the acquired stoichiometric air-fuel ratio of the current fuel, the stoichiometric air-fuel ratio of a fuel with a diesel mixture ratio of 100%, and the stoichiometric air-fuel ratio of a fuel with a biofuel mixture ratio of 100%.

[0141] Furthermore, the control device 50 (CPU 51) that performs the [normal fuel injection process] in Figure 4 and the [EGR control] in Figure 11 corresponds to a control correction unit 51F (see Figure 1) that corrects the control amount of the internal combustion engine based on the acquired fuel mixture ratio.

[0142] ●●[Second Embodiment to Sixth Embodiment (Figure 13)] In the first embodiment described above, the process of determining the stoichiometric air-fuel ratio and fuel mixture ratio during deceleration fuel cut-off was explained. Hereafter, the second to sixth embodiments will be described depending on the presence or absence of each of (A) to (C), including (B) the process of learning the stoichiometric air-fuel ratio and determining the fuel mixture ratio during normal operation, and (C) the process of learning the air-fuel ratio correction rate at the time of shipment in order to improve the accuracy of the stoichiometric air-fuel ratio and fuel mixture ratio. Figure 13 shows the relationship between the presence or absence of each of the above processes (A), (B), and (C) and the first to sixth embodiments. When process (C) is included, at the time of shipment from the manufacturing plant of the internal combustion engine, only "managed fuel" is placed in the fuel tank, which is known in advance to have (a predetermined fuel mixture ratio, a predetermined stoichiometric air-fuel ratio, and a predetermined fuel density) (fuel mixture ratio, stoichiometric air-fuel ratio, and fuel density). For example, as "managed fuel," fuel such as 100% diesel fuel or fuel that is 93% diesel fuel and 7% biofuel may be used.

[0143] ●●[Second Embodiment (Figures 14-19)] Next, the second embodiment will be described using Figures 14 to 19. As shown in Figure 13, the second embodiment does not include process (A), but does include processes (B) and (C). In the second embodiment, the time synchronization process shown in Figure 6 is replaced with the time synchronization process shown in Figure 14 [time synchronization (2) process]. Also, the crank angle synchronization process shown in Figure 2 is replaced with the crank angle synchronization process shown in Figure 15 [crank angle synchronization (2) process]. The differences from the first embodiment will be mainly explained below.

[0144] ●[Time synchronization (2) processing ( / t1[ms] interval) (Figure 14)] First, the [time synchronization (2) processing] in the second embodiment will be explained using Figure 14. The control device 50 (CPU 51) starts the processing shown in Figure 14 at predetermined time intervals of several [ms] (in this embodiment, "t1 [ms] interval" = approximately 4 [ms] intervals) and proceeds to step ST110.

[0145] In step ST110, the control device 50 executes the [supply detection (2) process] and proceeds to step ST115. Details of the [supply detection (2) process] will be described later.

[0146] In step ST115, the control device 50 determines whether the factory learning completion flag is OFF or OFF. If the factory learning completion flag is OFF (Yes), the control device 50 proceeds to step ST120; otherwise, it proceeds to step ST220. The factory learning completion flag is a flag that is set to ON when the above-mentioned "(C) process of learning the air-fuel ratio correction rate at the time of shipment" is completed at the time of shipment from the manufacturing plant of the internal combustion engine.

[0147] If the process proceeds to step ST120, the control device 50 determines whether the initialization completion flag is OFF or OFF. If the initialization completion flag is OFF (Yes), the control device proceeds to step ST125; if the initialization completion flag is ON (No), it proceeds to step ST130. The initialization completion flag is used to initialize the stored fuel mixture ratio, stoichiometric air-fuel ratio, and air-fuel ratio correction rate to a predetermined fuel mixture ratio, a predetermined stoichiometric air-fuel ratio, and an initial value (1.0) after the fuel tank has been filled with only the management fuel at the time of shipment.

[0148] If the process proceeds to step ST125, the control device 50 substitutes a predetermined fuel mixture ratio into the fuel mixture ratio, a predetermined stoichiometric air-fuel ratio into the stoichiometric air-fuel ratio, an initial value (1,0) into the air-fuel ratio correction rate, sets the initialization completion flag to ON, and proceeds to step ST130. The fuel mixture ratio, stoichiometric air-fuel ratio, air-fuel ratio correction rate, and initialization completion flag are stored in the non-volatile memory device.

[0149] If the process proceeds to step ST130, the control device 50 executes the [Air-fuel ratio correction rate learning process at the time of shipment] and proceeds to step ST235. The [Air-fuel ratio correction rate learning process at the time of shipment] corresponds to the "(C) Process to learn the air-fuel ratio correction rate at the time of shipment" described above, and details will be described later.

[0150] If the process proceeds to step ST220, the control device 50 determines whether the refueling flag is ON or OFF. If the refueling flag is ON (Yes), the control device 50 proceeds to step ST225; otherwise, it proceeds to step ST235. The refueling flag is a flag that is set to ON when refueling is detected in the [Refueling Detection (2) Process] described later.

[0151] If the process proceeds to step ST225, the control device 50 determines whether the stoichiometric air-fuel ratio learning completion flag is OFF or OFF. If the stoichiometric air-fuel ratio learning completion flag is OFF (Yes), the control device 50 proceeds to step ST230; otherwise, it proceeds to step ST235. The stoichiometric air-fuel ratio learning completion flag is a flag that is set to ON when the above-mentioned "(B) process of learning the stoichiometric air-fuel ratio and determining the fuel mixture ratio during normal operation" is completed.

[0152] If the process proceeds to step ST230, the control device 50 executes the [Stoichiometric Air-Fuel Ratio Learning Process during Normal Operation] and proceeds to step ST235. The [Stoichiometric Air-Fuel Ratio Learning Process during Normal Operation] corresponds to the "(B) Process to learn the stoichiometric air-fuel ratio during normal operation and determine the fuel mixture ratio" described above, and details will be described later.

[0153] If the process proceeds to step ST235, the control device 50 obtains the fuel mixture ratio based on the stoichiometric air-fuel ratio and proceeds to step ST240. Similar to the first embodiment, the control device 50 calculates the fuel mixture ratio (percentage of diesel fuel) = Yx[%] corresponding to the stoichiometric air-fuel ratio = AFx based on the value of the stoichiometric air-fuel ratio and the [stoichiometric air-fuel ratio / fuel mixture ratio characteristics] shown in Figure 12.

[0154] In step ST240, the control device 50 executes [EGR control] and terminates the process shown in Figure 14. Note that the [EGR control] is the same as in the first embodiment shown in Figure 11, so its explanation is omitted.

[0155] ●[Crank angle synchronization (2) process (Figure 15)] Next, the [crank angle synchronization (2) processing] in the second embodiment will be explained using Figure 15. When the control device 50 (CPU 51) receives a crank angle signal (see Figure 5), it proceeds to step SK310 in Figure 15.

[0156] In step SK310, the control device 50 performs the [crank counter processing] and proceeds to step SK315. Note that the [crank counter processing] is the same as in the first embodiment shown in Figure 3, so its explanation is omitted.

[0157] In step SK315, the control device 50 determines whether or not deceleration fuel cut-off is in progress. If deceleration fuel cut-off is in progress (Yes), the control device 50 terminates the process shown in Figure 15; otherwise, it proceeds to step SK320.

[0158] If the process proceeds to step SK320, the control device 50 performs the [normal fuel injection process] and proceeds to step SK325. Note that the [normal fuel injection process] is the same as that of the first embodiment shown in Figure 4, so its explanation is omitted.

[0159] In step SK325, the control device 50 determines whether or not the pilot injection and main injection schedules (reservations) in step SK320's [normal fuel injection process] have been executed. If the schedules (reservations) have been executed (Yes), the control device 50 proceeds to step SK330; otherwise, it terminates the process shown in Figure 15.

[0160] If the process proceeds to step SK330, the control device 50 determines the fresh intake mass of the cylinder for which the fuel injection schedule was performed, and stores the value obtained by adding the determined fresh intake mass to the integrated fresh mass value as a new integrated fresh mass value. The fresh intake mass can be determined in the same manner as in steps SK104, SK114, SK124, and SK134 of the first embodiment shown in Figure 2. The control device 50 also determines the fuel injection amount [mm²] scheduled for this operation. 3 The value obtained by adding ] to the integrated fuel injection amount is stored as the new integrated fuel injection amount. Then the control device 50 terminates the process shown in Figure 15.

[0161] ●[Resupply detection (2) process (Figure 16)] When the control device 50 executes the [Fueling Detection (2) Process] in step ST110 shown in Figure 14, it proceeds to step SU010 of the [Fueling Detection (2) Process] shown in Figure 16. In the process shown in Figure 16, if the control device 50 determines that fuel has been refueled (replenished), it sets the refueling flag (stored in the non-volatile memory device) to ON and the stoichiometric air-fuel ratio learning completion flag (stored in the non-volatile memory device) to OFF. Note that the [Fueling Detection (2) Process] shown in Figure 16 is the same as the [Fueling Detection Process] of the first embodiment shown in Figure 7, except that step SU025 has been changed to step SU025B. The changes will be explained below in detail.

[0162] If the process proceeds to step SU025B, the control device 50 sets the refueling flag (stored in the non-volatile memory) to ON, sets the stoichiometric air-fuel ratio learning completion flag (stored in the non-volatile memory) to OFF, terminates the process shown in Figure 16, and returns to step ST115 of the flowchart shown in Figure 14. If fuel has been refueled (replenished), the above "(B) Process to learn the stoichiometric air-fuel ratio and determine the fuel mixture ratio during normal operation" should be executed, so the stoichiometric air-fuel ratio learning completion flag is set to OFF.

[0163] ●[Air-fuel ratio correction rate learning process at the time of shipment (Figure 17)] When the control device 50 executes the [Factory Air-Fuel Ratio Correction Rate Learning Process] of step ST130 shown in Figure 14, it performs the [Factory Air-Fuel Ratio Correction Rate Learning Process] shown in Figure 17. Correction factor The process proceeds to step SL010 of the learning process (corresponding to "(C) Process to learn the air-fuel ratio correction rate at the time of shipment" above). As mentioned above, at the time of shipment, only "managed fuel" whose (fuel mixture ratio, stoichiometric air-fuel ratio, fuel density) is known in advance to be (predetermined fuel mixture ratio, predetermined stoichiometric air-fuel ratio, predetermined fuel density) is placed in the fuel tank. In the example of the operation waveform in Figure 19, the process in Figure 17 is executed between time Ta and time Td, which is the time of shipment (time Ta to time Td corresponds to "time of shipment").

[0164] In step SL010, the control device 50 determines whether the internal combustion engine has warmed up or not. If the control device 50 determines that the engine has warmed up (Yes), it proceeds to step SL015; otherwise, it proceeds to step SL080. Whether the engine has warmed up or not is determined, for example, by the coolant temperature detected by the coolant temperature detection device 32C.

[0165] If the process proceeds to step SL015, the control device 50 determines whether the fluctuation amount of the operating state of the internal combustion engine is in a stable steady state of less than or equal to the second predetermined fluctuation amount. If the fluctuation amount of the operating state is less than or equal to the second predetermined fluctuation amount (Yes), the control device 50 proceeds to step SL020; otherwise, if it is in a transient state (No), it proceeds to step SL080. For example, during the second predetermined period (step SL025) in which the fluctuation amount is measured, the control device 50 appropriately updates and stores the maximum and minimum values ​​of the rotational speed, intake air volume, and fuel injection volume of the internal combustion engine. Then, if the following conditions are met, the control device 50 determines that the fluctuation amount of the operating state ≤ the second predetermined fluctuation amount is met: |Fluctuation amount of rotational speed| = Maximum value of rotational speed - Minimum value of rotational speed ≤ Second rotational speed fluctuation amount, |Fluctuation amount of intake air volume| = Maximum value of intake air volume - Minimum value of intake air volume ≤ Second intake air volume fluctuation amount, and |Fluctuation amount of fuel injection volume| = Maximum value of fuel injection volume - Minimum value of fuel injection volume ≤ Second fuel injection volume fluctuation amount. In the example of the operating waveform in Figure 19, the fluctuation amount of the operating state of the internal combustion engine is less than or equal to the second predetermined fluctuation amount during the time interval Tb to Tc, indicating a stable steady state. The second rotational speed fluctuation amount, second intake volume fluctuation amount, and second fuel injection volume fluctuation amount are set to appropriate values ​​obtained through experiments and simulations using actual vehicles.

[0166] If the process proceeds to step SL080, the control device 50 initializes the integrated value of fresh gas mass, the integrated value of fuel injection amount, the integrated value of actual λ, and the number of λ integrations to (zero), terminates the process shown in Figure 17, and returns to step ST235 of the flowchart shown in Figure 14.

[0167] If the process proceeds to step SL020, the control device 50 updates the actual λ integrated value and the number of λ integrations and proceeds to step SL025. The control device 50 adds the value of λ detected by the λ detection device 92 to the actual λ integrated value and stores it as the new actual λ integrated value, and adds "1" to the number of λ integrations and stores it as the new number of λ integrations.

[0168] In step SL025, the control device 50 determines whether the state in which the operating state fluctuation amount ≤ the second predetermined fluctuation amount has continued for the second predetermined period. If the control device 50 determines that it has continued for the second predetermined period (Yes), it proceeds to step SL030. If it has not yet continued for the second predetermined period (No), it terminates the process shown in Figure 17 and returns to step ST235 of the flowchart shown in Figure 14. The second predetermined period is set to, for example, a few seconds to several tens of seconds.

[0169] If the process proceeds to step SL030, the control device 50 calculates the total fuel injection amount and the predetermined fuel density [g / mm³]. 3 The fuel mass integrated value is obtained and stored by multiplying by ]. The predetermined fuel density is the fuel density of the "managed fuel," and its exact value is known in advance. The control device 50 also obtains (calculates) the estimated λ at the time of shipment based on the fresh air mass integrated value, the fuel mass integrated value, the air-fuel ratio correction rate, and the stoichiometric air-fuel ratio (in this case, the predetermined stoichiometric air-fuel ratio). The control device 50 calculates the estimated λ at the time of shipment using the formula: Estimated λ at shipment = [Fresh air mass integrated value / Fuel mass integrated value] * Air-fuel ratio correction rate / Stoichiometric air-fuel ratio. Note that [Fresh air mass integrated value / Fuel mass integrated value] corresponds to the air-fuel ratio calculated at the time of shipment. The air-fuel ratio correction rate is initially set to 1.0 in step ST125 in Figure 14, and then updated in step SL050 in Figure 17. The "estimated λ at shipment" for time Tb to time Tc in "Value of λ" in Figure 19 is the estimated λ at shipment calculated in step SL030.

[0170] The control device 50 also obtains the actual λ at the time of shipment based on the actual λ integrated value and the number of λ integrations. The control device 50 calculates the actual λ at the time of shipment (the average value of the actual λ) using the formula: Actual λ at shipment = Actual λ integrated value / Number of λ integrations. Then, the control device 50 initializes the new air mass integrated value, fuel injection amount integrated value, actual λ integrated value, and number of λ integrations (to zero), starts remeasurement for the second predetermined period, and proceeds to step SL035.

[0171] In step SL035, the control device 50 calculates the shipment λ deviation ratio and proceeds to step SL040. The control device 50 calculates the shipment λ deviation ratio using the formula: Shipment λ Deviation Ratio = Shipment Estimated λ / Shipment Actual λ. As shown in the time Tb to time Tc of the "Shipment λ Deviation Ratio" in Figure 19, the shipment λ deviation ratio is updated at the second predetermined period.

[0172] In step SL040, the control device 50 determines whether the factory-set λ deviation ratio is within the second predetermined ratio range (for example, within the range of 0.99 to 1.01). At the time of shipment, a "managed fuel" is used, which is known to have (fuel mixture ratio, stoichiometric air-fuel ratio, fuel density) as (predetermined fuel mixture ratio, predetermined stoichiometric air-fuel ratio, predetermined fuel density). Therefore, the estimated λ at shipment and the actual λ at shipment should be approximately equal, and the factory-set λ deviation ratio should be approximately 1.0. However, in reality, errors occur in the integrated fresh air mass value due to the intake air volume detection error of the air flow detection device 31, and errors occur in the integrated fuel injection amount value due to the injection amount error from the injector, resulting in an error in [integrated fresh air mass value / integrated fuel mass value] (air-fuel ratio calculated at shipment). In order to correct this error with the air-fuel ratio correction rate, it is first determined whether the factory-set λ deviation ratio is within the second predetermined ratio range. The control device 50 proceeds to step SL055 if the λ deviation ratio at the time of shipment is within the second predetermined ratio range (Yes), and proceeds to step SL045 if it is not within the second predetermined ratio range (No).

[0173] If the process proceeds to step SL045, the control device 50 determines whether the second judgment period continues (the state in which the initial λ deviation ratio is outside the second predetermined ratio range). If the control device 50 determines that the second judgment period is continuing (Yes), it proceeds to step SL050. If the second judgment period is not yet continuing (No), it terminates the process shown in Figure 17 and returns to step ST235 of the flowchart shown in Figure 14. The second judgment period is set to be longer than the second predetermined period; for example, the second judgment period is set to several tens of seconds.

[0174] If the process proceeds to step SL050, the control device 50 updates the air-fuel ratio correction rate and stores it in the non-volatile memory device, starts remeasurement for the second judgment period, finishes the process shown in Figure 17, and returns to step ST235 of the flowchart shown in Figure 14. An example of updating the air-fuel ratio correction rate is shown in the "air-fuel ratio correction rate" at time Tb to time Tc of the operation waveform in Figure 19, and is updated every second judgment period. In order to avoid mislearning, the air-fuel ratio correction rate is updated, for example, by a predetermined amount so that the "factory λ deviation ratio" gradually approaches the second predetermined ratio range (e.g., 0.99 to 1.01).

[0175] If the process proceeds to step SL055, the control device 50 sets the factory learning completion flag to ON, stores it in the non-volatile memory, terminates the process shown in Figure 17, and returns to step ST235 of the flowchart shown in Figure 14. In the example of the operation waveform in Figure 19, at time Tc, it is determined that the factory λ deviation ratio has fallen within the second predetermined ratio range, and the "factory learning completion flag" is set from OFF to ON.

[0176] In Figure 19, under "Value of λ," "Actual λ at Shipment" and "Actual λ" are the values ​​of λ detected using a λ detection device, while "Estimated λ at Shipment" and "Estimated λ" are the values ​​of λ calculated from [fresh air mass / fuel mass]*air-fuel ratio correction rate / stoichiometric air-fuel ratio. In the example shown in Figure 19, at "Shipment" from time Ta to time Td, the air-fuel ratio correction rate learning is not yet complete in the initial time from Ta to time Tb, so as shown in "Value of λ," there is a difference between "Actual λ at Shipment" and "Estimated λ at Shipment." Consequently, there is a difference between "Actual O2 concentration" and "Target O2 concentration" in the "Intake Manifold O2 Concentration," and there is also a difference between "Actual NOx Amount" and "Target NOx Amount." However, the air-fuel ratio correction rate is learned between time Tb and time Tc (factory learning is performed), and after time Tc, when factory learning is completed, the "factory value of λ" matches between the "factory actual λ" and the "factory estimated λ". Consequently, after time Tc, the "actual O2 concentration" and the "target O2 concentration" of the "intake manifold O2 concentration" match, and the "actual NOx amount" and the "target NOx amount" of the "NOx amount" match. Note that the example in Figure 19 shows a case where, for example, 100% diesel fuel is used as the "managed fuel" at "factory," and 80% diesel fuel and 20% biofuel is refueled between time Td and time Te.

[0177] ●[Stoichiometric air-fuel ratio learning process during normal operation (Figure 18)] When the control device 50 executes the [Stoichiometric Air-Fuel Ratio Learning Process during Normal Operation] in step ST230 shown in Figure 14, it proceeds to step SN010 of the [Stoichiometric Air-Fuel Ratio Learning Process during Normal Operation] shown in Figure 18 (corresponding to the above "(B) Process to learn the stoichiometric air-fuel ratio during normal operation and determine the fuel mixture ratio"). In the example of the operation waveform in Figure 19, the process in Figure 18 is executed after time Te following refueling.

[0178] In step SN010, the control device 50 determines whether the internal combustion engine has warmed up or not. If the control device 50 determines that the engine has warmed up (Yes), it proceeds to step SN015; otherwise, it proceeds to step SN080. Whether the engine has warmed up or not is determined, for example, by the coolant temperature detected by the coolant temperature detection device 32C.

[0179] If the process proceeds to step SN015, the control device 50 determines whether the fluctuation amount of the operating state of the internal combustion engine is in a stable steady state of less than or equal to a first predetermined fluctuation amount. If the fluctuation amount of the operating state is less than or equal to the first predetermined fluctuation amount (Yes), the control device 50 proceeds to step SN020; otherwise, if it is in a transient state (No), it proceeds to step SN080. For example, during the first predetermined period (step SN025) in which the fluctuation amount is measured, the control device 50 appropriately updates and stores the maximum and minimum values ​​of the rotational speed, intake air volume, and fuel injection volume of the internal combustion engine. Then, if the following conditions are met, the control device 50 determines that the fluctuation amount of the operating state ≤ the first predetermined fluctuation amount is met: |Fluctuation amount of rotational speed| = Maximum value of rotational speed - Minimum value of rotational speed ≤ First rotational speed fluctuation amount, |Fluctuation amount of intake air volume| = Maximum value of intake air volume - Minimum value of intake air volume ≤ First intake air volume fluctuation amount, and |Fluctuation amount of fuel injection volume| = Maximum value of fuel injection volume - Minimum value of fuel injection volume ≤ First fuel injection volume fluctuation amount. In the example of the operating waveform in Figure 19, the fluctuation amount of the operating state of the internal combustion engine is less than or equal to the first predetermined fluctuation amount during the time interval Tf to Tg, indicating a stable steady state. The first rotational speed fluctuation amount, the first intake air volume fluctuation amount, and the first fuel injection volume fluctuation amount are set to appropriate values ​​obtained through experiments and simulations using actual vehicles.

[0180] If the process proceeds to step SN080, the control device 50 initializes the integrated value of fresh gas mass, the integrated value of fuel injection amount, the integrated value of actual λ, and the number of λ integrations to (zero), terminates the process shown in Figure 18, and returns to step ST235 of the flowchart shown in Figure 14.

[0181] If the process proceeds to step SN020, the control device 50 updates the actual λ integrated value and the number of λ integrations and proceeds to step SN025. The control device 50 adds the value of λ detected by the λ detection device 92 to the actual λ integrated value and stores it as the new actual λ integrated value, and adds "1" to the number of λ integrations and stores it as the new number of λ integrations.

[0182] In step SN025, the control device 50 determines whether the state in which the operating state fluctuation amount ≤ the first predetermined fluctuation amount has continued for the first predetermined period. If the control device 50 determines that it has continued for the first predetermined period (Yes), it proceeds to step SN030. If it has not yet continued for the first predetermined period (No), it terminates the process shown in Figure 18 and returns to step ST235 of the flowchart shown in Figure 14. The first predetermined period is set to, for example, a few seconds to tens of seconds.

[0183] If the process proceeds to step SN030, the control device 50 determines the fuel density [g / mm³] based on the "stoichiometric air-fuel ratio fuel density characteristic" (not shown) which has a fuel density corresponding to the stoichiometric air-fuel ratio set, and the stored stoichiometric air-fuel ratio. 3 The control device 50 then calculates the fuel density [g / mm³] into the integrated fuel injection amount. 3 The integrated fuel mass value is obtained and stored by multiplying by ]. The control device 50 also obtains estimated λ based on the integrated fresh air mass value, integrated fuel mass value, air-fuel ratio correction rate, and stoichiometric air-fuel ratio. The control device 50 calculates estimated λ using the formula: estimated λ = [integrated fresh air mass value / integrated fuel mass value] * air-fuel ratio correction rate / stoichiometric air-fuel ratio. Note that [integrated fresh air mass value / integrated fuel mass value] corresponds to the calculated air-fuel ratio. The air-fuel ratio correction rate is an updated value in step SL050 of Figure 17, after an initial value (1.0) is set in step ST125 of Figure 14. The "estimated λ" in the "value of λ" from time Tf to time Tg in Figure 19 is the estimated λ calculated in step SN030.

[0184] The control device 50 also acquires the actual λ based on the actual λ integrated value and the number of λ integrations. The control device 50 calculates the actual λ (the average value of the actual λ) using the formula: actual λ = actual λ integrated value / number of λ integrations. Then, the control device 50 initializes the new air mass integrated value, fuel injection amount integrated value, actual λ integrated value, and number of λ integrations (to zero), starts remeasurement for the first predetermined period, and proceeds to step SN035.

[0185] In step SN035, the control device 50 calculates the λ deviation ratio and proceeds to step SN040. The control device 50 calculates the λ deviation ratio using the formula: λ deviation ratio = estimated λ / actual λ. As shown in the time Tf to time Tg of the "λ deviation ratio" in Figure 19, the λ deviation ratio is updated at the first predetermined period.

[0186] In step SN040, the control device 50 determines whether the λ deviation ratio is within a first predetermined ratio range (for example, within the range of 0.99 to 1.01). If the stored stoichiometric air-fuel ratio is the correct stoichiometric air-fuel ratio corresponding to the current fuel mixture ratio, the estimated λ and the actual λ should be approximately equal, and the λ deviation ratio should be approximately 1.0. However, if the stored stoichiometric air-fuel ratio is not the correct stoichiometric air-fuel ratio for the current fuel, the λ deviation ratio will fall outside the first predetermined ratio range. To detect this state and obtain the correct stoichiometric air-fuel ratio, the control device 50 determines whether the λ deviation ratio is within the first predetermined ratio range. If the λ deviation ratio is within the first predetermined ratio range (Yes), the control device 50 proceeds to step SN055; otherwise, it proceeds to step SN045.

[0187] If the process proceeds to step SN045, the control device 50 determines whether the state in which the λ deviation ratio is outside the first predetermined ratio range continues for the first determination period. If the control device 50 determines that the first determination period is continuing (Yes), it proceeds to step SN050. If the first determination period is not yet continuing (No), it terminates the process shown in Figure 18 and returns to step ST235 of the flowchart shown in Figure 14. The first determination period is set to a length greater than or equal to the first predetermined period; for example, the first determination period is set to several tens of seconds.

[0188] If the process proceeds to step SN050, the control device 50 updates the stoichiometric air-fuel ratio and stores it in the non-volatile memory device, starts remeasurement for the first judgment period, terminates the process shown in Figure 18, and returns to step ST235 of the flowchart shown in Figure 14. An example of updating the stoichiometric air-fuel ratio is shown in the "stoichiometric air-fuel ratio" at time Tf to time Tg of the operation waveform in Figure 19, and is updated every first judgment period. Note that, in order to avoid mislearning, the stoichiometric air-fuel ratio is updated, for example, by a predetermined amount, so that the "λ deviation ratio" gradually approaches a first predetermined ratio range (e.g., 0.99 to 1.01).

[0189] If the process proceeds to step SN055, the control device 50 sets the stoichiometric air-fuel ratio learning completion flag to ON and stores it in the non-volatile memory, sets the refueling flag to OFF and stores it in the non-volatile memory, terminates the process shown in Figure 18, and returns to step ST235 of the flowchart shown in Figure 14. In the example of the operation waveform in Figure 19, at time Tg, it is determined that the λ deviation ratio has fallen within the first predetermined ratio range, and the "stoichiometric air-fuel ratio learning completion flag" is set from OFF to ON.

[0190] The example in Figure 19 shows a scenario where, for example, 100% diesel fuel is used as the "managed fuel" at the time of "shipment," and 80% diesel fuel and 20% biofuel is refueled between time Td and time Te. Therefore, in the example shown in Figure 19, after time Te, when the fuel is refueled, the learning of the stoichiometric air-fuel ratio has not yet been completed, so as shown in the "value of λ," there is a difference between the "actual λ" and the "estimated λ." Consequently, between time Te and time Tf, there is a difference between the "actual O2 concentration" and the "target O2 concentration" in the "intake manifold O2 concentration," and there is also a difference between the "actual NOx amount" and the "target NOx amount." However, between time Tf and time Tg, the stoichiometric air-fuel ratio is learned, and after time Tg, when the learning of the stoichiometric air-fuel ratio is completed, the "actual λ" and the "estimated λ" match in the "value of λ." Consequently, from time Tg onward, the "actual O2 concentration" and the "target O2 concentration" of the "intake manifold O2 concentration" coincide, and the "actual NOx amount" and the "target NOx amount" of the "NOx amount" also coincide.

[0191] ●●[Third Embodiment] In the third embodiment, as shown in Figure 13, process (C) is omitted from the second embodiment. Specifically, steps ST115 to ST130 are omitted from the flowchart shown in Figure 14, and the process shown in Figure 17 is omitted. Also, the air-fuel ratio correction rate used in step SN030 in Figure 18 is set to 1.0 (no correction of the calculated air-fuel ratio).

[0192] ●●[Fourth Embodiment (Figures 20-22)] Next, the fourth embodiment will be described using Figures 20 to 22. The fourth embodiment has processes (A), (B), and (C) as shown in Figure 13. Therefore, the fourth embodiment is the second embodiment shown in Figures 14 to 19 with the addition of process (A) of the first embodiment, and the [time synchronization (4) process] shown in Figure 20 is executed instead of the [time synchronization (2) process] shown in Figure 14. Also, the [crank angle synchronization (4) process] shown in Figure 21 is executed instead of the [crank angle synchronization (2) process] shown in Figure 15. The differences from the second embodiment will be mainly explained below.

[0193] ●[Time synchronization (4) processing ( / t1[ms] interval) (Figure 20)] First, the [Time Synchronization (4) Processing] in the fourth embodiment will be explained using Figure 20. The [Time Synchronization (4) Processing] shown in Figure 20 is the same as the [Time Synchronization (2) Processing] in the second embodiment shown in Figure 14, except that the [Supply Detection (2) Processing] in step ST110 is changed to [Supply Detection (4) Processing], and steps ST210D and ST015 to ST050 are added.

[0194] In step ST110D, the control device 50 executes the [supply detection (4) process] and proceeds to step ST115. Details of the [supply detection (4) process] will be described later.

[0195] If the process proceeds to step ST210D, the control device 50 determines whether the supply flag is ON or OFF. If the supply flag is ON (Yes), the control device 50 proceeds to step ST015; otherwise, it proceeds to step ST220.

[0196] Steps ST015 to ST050 are the same as steps ST015 to ST050 of the [Time Synchronization Processing] in the first embodiment shown in Figure 6, so their explanation will be omitted.

[0197] In the above [Time Synchronization (4) Processing], processing (C) (steps ST120 to ST130) is executed at the time of shipment, and during normal operation after refueling, processing (A) (steps ST015 to ST050) is executed first, and after processing (A) is completed, processing (B) (step ST230) is executed.

[0198] ●[Crank angle synchronization (4) process (Figure 21)] Next, the [crank angle synchronization (4) processing] in the fourth embodiment will be explained using Figure 21. When the control device 50 receives a crank angle signal (see Figure 5), it proceeds to step SK410 in Figure 21.

[0199] In step SK410, the control device 50 determines whether the refueling flag is ON or OFF. If the refueling flag (a flag that is ON when refueling is performed and OFF after the process in (A) is executed) is ON (Yes), the control device 50 proceeds to step SK420; otherwise, the control device 50 proceeds to step SK430.

[0200] If the process proceeds to step SK420, the control device 50 executes the [crank angle synchronization process] and terminates the process shown in Figure 21. Note that the [crank angle synchronization process] is the same as the [crank angle synchronization process] in the first embodiment shown in Figure 2, so its explanation is omitted. Note that in steps SK113, SK123, SK133, and SK143 shown in Figure 2, when storing the calculated air-fuel ratio, the value corrected using the air-fuel ratio correction rate may be stored.

[0201] If the process proceeds to step SK430, the control device 50 executes the [crank angle synchronization (2) process] and terminates the process shown in Figure 21. Note that the [crank angle synchronization (2) process] is the same as the [crank angle synchronization (2) process] in the second embodiment shown in Figure 15, so its explanation is omitted.

[0202] ●[Resupply detection (4) process (Figure 22)] When the control device 50 executes the [Resupply Detection (4) Process] of step ST110D shown in Figure 20, it proceeds to step SU010 of the [Resupply Detection (4) Process] shown in Figure 22. Note that the [Resupply Detection (4) Process] shown in Figure 22 is the same as the [Resupply Detection (2) Process] of the second embodiment shown in Figure 16, except that step SU025B has been changed to step SU025D. The changes will be explained below in detail.

[0203] If the process proceeds to step SU025D, the control device 50 sets the replenishment flag (stored in the non-volatile memory) to ON, sets the refueling flag (stored in the non-volatile memory) to ON, sets the stoichiometric air-fuel ratio learning completion flag (stored in the non-volatile memory) to OFF, terminates the process shown in Figure 22, and returns to step ST115 of the flowchart shown in Figure 20. If fuel has been replenished, the "replenishment flag" used in process (A) is set to ON, and the "refueling flag" and "stoichiometric air-fuel ratio learning completion flag" used in process (B) are set to ON and OFF, respectively.

[0204] In the fourth embodiment described above, first, process (C) is executed at the time of shipment, and after shipment, if fuel is refueled, process (A) is executed, followed by process (B). Therefore, when fuel is refueled and the refueling flag is set to ON, the [crank angle synchronization process] of process (A) is executed first, and after process (A) is completed and the refueling flag is set to OFF, the [crank angle synchronization (2) process] of process (B) is executed.

[0205] ●●[Fifth Embodiment] In the fifth embodiment, as shown in Figure 13, process (C) is omitted from the fourth embodiment. Specifically, steps ST115 to ST130 are omitted from the flowchart shown in Figure 20, and the process shown in Figure 17 is omitted. Also, the air-fuel ratio correction rate used in step SN030 in Figure 18 is set to 1.0, and in steps SK113, SK123, SK133, and SK143 shown in Figure 2, when the calculated air-fuel ratio is stored, the air-fuel ratio correction rate is also set to 1.0 when correction is made using the air-fuel ratio correction rate (no correction of the calculated air-fuel ratio).

[0206] ●●[Sixth Embodiment] In the sixth embodiment, as shown in Figure 13, the process (B) from the fourth embodiment is omitted. That is, steps ST220 to ST230 are omitted from the flowchart shown in Figure 20, and the process shown in Figure 18 is omitted.

[0207] The control device 50, which performs steps SN010 to SN030 in Figure 18 as described above, corresponds to an estimated λ calculation unit (not shown) that, when the internal combustion engine has warmed up and the amount of fluctuation in the operating state is less than or equal to a first predetermined fluctuation amount, maintains this state for a first predetermined period, acquires a calculated air-fuel ratio based on the mass of fresh air drawn into the cylinder during the first predetermined period, which is the fresh air mass detected using an air flow rate detection device, and the mass of fuel injected using an injector during the first predetermined period, and calculates an estimated λ, which is the λ of the first predetermined period, based on the acquired calculated air-fuel ratio and the stored stoichiometric air-fuel ratio.

[0208] Furthermore, the control device 50 that executes steps SN010 to SN030 in Figure 18, as described above, corresponds to a real λ acquisition unit (not shown) that acquires the actual λ, which is the λ detected using the λ detection device during the first predetermined period.

[0209] Furthermore, the control device 50 that performs step SN035 in Figure 18, as described above, corresponds to a λ deviation ratio calculation unit (not shown) that calculates the λ deviation ratio based on the estimated λ and actual λ acquired during the first predetermined period.

[0210] Furthermore, the control device 50 that executes steps SN040 to SN050 in Figure 18, as described above, corresponds to a stoichiometric air-fuel ratio update unit (not shown) that updates and stores the stoichiometric air-fuel ratio so that the λ deviation ratio approaches the first predetermined ratio range if the state in which the λ deviation ratio is outside the first predetermined ratio range continues for the first determination period.

[0211] Furthermore, the control device 50 that performs step ST235 in Figure 14 and step ST235 in Figure 20, as described above, corresponds to a fuel mixture ratio acquisition unit 51E (see Figure 1) that acquires the fuel mixture ratio, which is the mixture ratio of diesel fuel and biofuel, based on the stoichiometric air-fuel ratio, the stoichiometric air-fuel ratio of a fuel with a diesel fuel mixture ratio of 100%, and the stoichiometric air-fuel ratio of a fuel with a biofuel mixture ratio of 100%.

[0212] Furthermore, the control device 50 that performs step ST240 in Figure 14 and step ST240 in Figure 20, as described above, and the control device 50 that performs steps SB025 and SB030 in Figure 4 and steps SY015 and SY020 in Figure 11, correspond to a control correction unit 51F (see Figure 1) that corrects the control amount of the internal combustion engine based on the acquired fuel mixture ratio.

[0213] Furthermore, the control device 50 that executes steps SL010 to SL030 in Figure 17 as described above corresponds to a unit that calculates the estimated λ at shipment (not shown) when the internal combustion engine has warmed up and the amount of fluctuation in the operating state is less than or equal to a second predetermined fluctuation amount and this state continues for a second predetermined period, and it obtains the air-fuel ratio calculated at shipment, which is the air-fuel ratio based on the mass of fresh air drawn into the cylinder during the second predetermined period, detected using an air flow rate detection device, and the fuel mass, which is the mass of fuel injected using an injector during the second predetermined period, and calculates the estimated λ at shipment, which is the λ of the second predetermined period, based on the obtained estimated air-fuel ratio at shipment and a predetermined stoichiometric air-fuel ratio.

[0214] Furthermore, the control device 50 that executes steps SL010 to SL030 in Figure 17, as described above, corresponds to a shipment-time actual λ acquisition unit (not shown) that acquires the shipment-time actual λ, which is the λ detected using the λ detection device during the second predetermined period.

[0215] Furthermore, the control device 50 that performs step SL035 in Figure 17 described above corresponds to a shipment time λ deviation ratio calculation unit (not shown) that calculates the shipment time λ deviation ratio based on the shipment time estimated λ and the shipment time actual λ acquired during the second predetermined period.

[0216] Furthermore, the control device 50 that executes steps SL040 to SL050 in Figure 17, as described above, corresponds to an air-fuel ratio correction rate update unit (not shown) that updates and stores an air-fuel ratio correction rate to correct the air-fuel ratio calculated at the time of shipment so that the air-fuel ratio at the time of shipment approaches the second predetermined ratio range if the state in which the λ deviation ratio at the time of shipment is outside the second predetermined ratio range continues for the second determination period.

[0217] Furthermore, the control device 50 that executes steps SL040 and SL055 in Figure 17, as described above, corresponds to a factory learning completion determination unit (not shown) that determines that factory learning is complete when the factory λ deviation ratio falls within a second predetermined ratio range, and stores the completion of factory learning.

[0218] As described above, the control system of this embodiment can appropriately detect the fuel mixture ratio, which is the mixing ratio of diesel fuel and biofuel, and appropriately correct the control amount without adding any special sensors such as fuel density sensors, fuel oxygen concentration sensors, or combustion pressure sensors to an existing internal combustion engine control system.

[0219] ●[Other] The control system 2 for the internal combustion engine of the present invention is not limited to the configuration, appearance, structure, processing procedures, etc., described in this embodiment, and various modifications, additions, and deletions are possible without altering the essence of the present invention.

[0220] In this embodiment, a predetermined number of consecutive combustions occur during deceleration fuel cut-off. itinerary In the example described, four consecutive single-stage test injections are performed to generate combustion, but the test injection may be performed only once, or two or more times consecutively.

[0221] The internal combustion engine control system 2 of the present invention is not limited to vehicles equipped with diesel engines, but can be applied to various devices equipped with diesel engines.

[0222] In the first embodiment, the stoichiometric air-fuel ratio of the current fuel can be obtained in a manner that also accommodates changes in the amount of oxygen per unit volume due to the degradation of the (mixed) biofuel over time. In the first embodiment, step SX015 of the flowchart shown in Figure 10 may be omitted, and the EGR rate correction amount may be calculated in step SY015 of the flowchart shown in Figure 11 according to the current stoichiometric air-fuel ratio of the fuel. Alternatively, the pilot injection correction amount, main injection correction amount, pilot injection timing correction amount, and main injection timing correction amount may be calculated in step SB025 of the flowchart shown in Figure 4 according to the current stoichiometric air-fuel ratio of the fuel.

[0223] Furthermore, while this embodiment describes an example of correcting the pilot injection amount, main injection amount, and target EGR rate according to the fuel mixture ratio, the control amount is not limited to these amounts, and other control amounts may be corrected according to the fuel mixture ratio. In addition, at least one of the following corrections may be performed: fuel injection amount correction (correction of pilot injection amount and main injection amount) and EGR correction (correction of target EGR rate).

[0224] Furthermore, although the fuel mixture ratio calculation was described in an example where it is performed only once after refueling, it may be performed multiple times after refueling, or it may be performed a predetermined number of times each time the ignition switch is detected as OFF->ON, regardless of refueling.

[0225] Furthermore, in this embodiment, an example was given in which the stoichiometric air-fuel ratio of 100% diesel fuel was set to, for example, 14.9. However, the description is not limited to this value, and the stoichiometric air-fuel ratio of 100% diesel fuel may be set to, for example, 14.6.

[0226] Furthermore, when terms such as greater than or equal to (≧), less than or equal to (≦), greater than (>), less than (<), etc. are used, the equals sign may or may not be included. Also, the numerical values ​​used in the description of this embodiment are examples only and are not limited to these values. [Explanation of symbols]

[0227] 1. Internal Combustion Engine System 2. Control System 10 Internal combustion engine 11A, 11C intake pipe 11D Intake Manifold 12A Exhaust Manifold 12B, 12C, 12D, 12E exhaust pipes 13 EGR piping 13A EGR valve 21 Injectors 31 Air flow detection device 32A, 32B Intake Air Temperature Detection Device 32C Coolant Temperature Detection Device 33A Atmospheric pressure detection device 33B, 33C, 33D Pressure detection device 34A Rotation detection device 34B Cylinder detection device 35 Differential pressure detection device 36A~36D Exhaust Temperature Detection Device 37A, 37B NOx Detector 38. Accelerator pedal depression detection device 39 Ignition Switch 40 Exhaust purifying device 41 Upstream exhaust gas purification system 42 First Oxidation Catalyst 43. Particulate matter collection filter 45 Downstream exhaust gas purification device 46 Urea SCR 47 Second Oxidation Catalyst 50 Control device 51 CPU 51A Single-stage injection unit for inspection 51B Calculated air-fuel ratio acquisition section 51C λ acquisition section 51D Theoretical air-fuel ratio acquisition section 51E Fuel mixture ratio acquisition part 51F Control Correction Unit 55 Non-volatile memory devices 61A Fuel Addition Valve 61B Dispersion device 62A Urea solution injection valve 62B Dispersion device 63. Load device (alternator) 80 Supercharger 81 Turbine 82 Compressor 84 Intercooler 90 Fuel Tank 91 Fuel level detection device (fuel replenishment detection device) 92 λ detection device

Claims

1. An internal combustion engine control system for controlling an internal combustion engine that can use any of the following fuels: diesel fuel, biofuel, or a mixed fuel obtained by mixing the diesel fuel and the biofuel, The biofuel is a fuel in which the amount of oxygen per unit volume is greater than that of the diesel fuel. The control system is An injector for injecting fuel into the internal combustion engine, An airflow detection device for detecting the amount of air intake to the internal combustion engine, A λ detection device is provided in the exhaust path of the internal combustion engine and detects λ, which is the air-fuel ratio / stoichiometric air-fuel ratio, based on the oxygen concentration in the exhaust gas from the internal combustion engine. An EGR path that returns a portion of the exhaust gas to the intake path of the internal combustion engine, An EGR valve provided in the EGR path for adjusting the opening degree of the EGR path, A control device that detects the operating state of the internal combustion engine, controls the injector based on the detected operating state, and controls the EGR valve based on the target EGR rate determined based on the operating state, It has, The control device is In the normal operating conditions, the injector performs multi-stage injection, which includes a main injection that is the primary injection for one combustion stroke, and a pilot injection that is injected prior to the main injection. During deceleration fuel cut-off, when the aforementioned operating state is deceleration and fuel cut-off, a single-stage test injection unit performs a single-stage test injection of a predetermined amount of fuel, consisting only of the main injection. A calculated air-fuel ratio acquisition unit acquires a calculated air-fuel ratio based on the mass of fresh air drawn in by the cylinder that performed the aforementioned single-stage injection for testing, which is the mass of fresh air detected using the air flow rate detection device, and the fuel mass based on the predetermined fuel amount. A λ acquisition unit that acquires the value of λ from the λ detection device during the variation period, which is the period during which λ fluctuates due to the single-stage injection for inspection, A stoichiometric air-fuel ratio acquisition unit acquires the current stoichiometric air-fuel ratio of the fuel based on the value of λ acquired during the aforementioned variation period and the calculated air-fuel ratio. A control correction unit that obtains the stoichiometric air-fuel ratio of the current fuel, determines the fuel mixture ratio which is the mixing ratio of the diesel fuel and the biofuel in the current fuel based on the relationship between the stoichiometric air-fuel ratio and the fuel mixture ratio, and performs at least one of the following corrections: EGR correction which increases the target EGR rate as the mixing ratio of the biofuel increases, and fuel injection amount correction which increases the amount injected from the injector as the mixing ratio of the biofuel increases. Having, Control system for internal combustion engines.

2. A control system for an internal combustion engine according to claim 1, The control device is In the inspection single-stage injection execution unit, the inspection single-stage injection is performed continuously so that combustion occurs in a predetermined number of consecutive combustion strokes. The air-fuel ratio acquisition unit acquires the respective air-fuel ratios corresponding to each of the single-stage injections for testing. The λ acquisition unit acquires the value of λ for the continuous variation period by a continuous combustion process. The stoichiometric air-fuel ratio acquisition unit acquires the current stoichiometric air-fuel ratio of the fuel based on the value of λ acquired during the fluctuation period and the respective calculated air-fuel ratios. Control system for internal combustion engines.

3. A control system for an internal combustion engine according to claim 1 or 2, At the time of shipment of the internal combustion engine, a controlled fuel is used in which the fuel mixture ratio, which is the mixing ratio of the diesel fuel and the biofuel in the current fuel, and the stoichiometric air-fuel ratio are known in advance to be a predetermined fuel mixture ratio and a predetermined stoichiometric air-fuel ratio. The control device is After the internal combustion engine has warmed up and the amount of fluctuation in the operating state is less than or equal to a second predetermined fluctuation, the following is maintained for a second predetermined period: The air-fuel ratio calculated at the time of shipment is obtained based on the mass of fresh air drawn into the cylinder during the second predetermined period, which is the fresh air mass detected using the air flow rate detection device, and the fuel mass, which is the mass of fuel injected using the injector during the second predetermined period. The estimated λ at the time of shipment is calculated based on the obtained air-fuel ratio calculated at the time of shipment and the predetermined stoichiometric air-fuel ratio. A shipment-time actual λ acquisition unit acquires the shipment-time actual λ, which is the λ detected using the λ detection device during the second predetermined period. A unit for calculating the deviation ratio of the shipment time λ, which calculates the deviation ratio of the shipment time λ based on the estimated λ at shipment time and the actual λ at shipment time obtained during the second predetermined period, An air-fuel ratio correction rate update unit updates and stores an air-fuel ratio correction rate for correcting the air-fuel ratio calculated at the time of shipment so that the λ deviation ratio at the time of shipment approaches the second predetermined ratio range if the state in which the λ deviation ratio at the time of shipment is outside the second predetermined ratio range continues for the second determination period. A factory learning completion determination unit determines that the factory learning process, which updates and stores the air-fuel ratio correction rate, is complete when the factory λ deviation ratio falls within the second predetermined ratio range, and stores the completion of the factory learning process. It has, The control device is If the factory learning is not completed at the time of shipment, the following processes are executed: the factory estimated λ calculation unit, the factory actual λ acquisition unit, the factory λ deviation ratio calculation unit, the air-fuel ratio correction rate update unit, and the factory learning completion determination unit. When obtaining the air-fuel ratio calculated at the time of shipment, the air-fuel ratio calculated at the time of shipment is multiplied by the air-fuel ratio correction rate to obtain the corrected air-fuel ratio calculated at the time of shipment, and when obtaining the calculated air-fuel ratio, the calculated air-fuel ratio is multiplied by the air-fuel ratio correction rate to obtain the corrected air-fuel ratio. Control system for internal combustion engines.

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