CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

Abstract

Control device (20) for an internal combustion engine (100) which controls an internal combustion engine (100) which includes an intercooler (7) which cools the intake air and an EGR flow path pipe (40) which returns a portion of the exhaust gas in an exhaust path to an upstream side of the intercooler (7) as EGR gas, wherein the control device (20) for the internal combustion engine (100) comprises: a moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D) configured to calculate a total moisture quantity contained in a mixed gas obtained by mixing fresh air flowing into the charge air cooler (7) and the EGR gas; a dew condensation calculation unit (303) configured to calculate a dew condensation generation quantity (WQcon) in the charge air cooler (7) based on the total moisture quantity calculated by the moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D); a dew condensation determination unit (303) configured to set an end dew condensation generation quantity (WQcon2) to 0 if the calculated dew condensation generation quantity (WQcon) does not exceed a predetermined threshold (SL), and to set the end dew condensation generation quantity (WQcon2) to the calculated dew condensation generation quantity (WQcon) if the calculated dew condensation generation quantity (WQcon) exceeds the predetermined threshold (SL); an EGR correction unit (304) configured to correct a flow rate of the returned EGR gas based on the final dew condensation generation quantity (WQcon2) set by the dew condensation determination unit (303); a first moisture quantity calculation unit (301, 301B) configured to calculate a first moisture quantity (WQair) which is a moisture quantity contained in the fresh air; and a second moisture quantity calculation unit (302, 302B, 302C, 302D) configured to calculate a second moisture quantity (WQegr) which is a moisture quantity contained in the EGR gas, wherein the total moisture quantity is a sum of the first moisture quantity (WQair) and the second moisture quantity (WQegr), wherein the second moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D) is designed to calculate the second moisture quantity (WQegr) based on a fuel property, a target EGR rate (TEGR) of the EGR gas before correction by the EGR correction unit (304) and an intake air quantity (Qair), and wherein the EGR correction unit (304) contains an EGR gas correction table in which EGR gas correction amounts (HOSegr) for correcting the EGR gas according to the final dew condensation generation amount (WQcon2) are set such that as the final dew condensation generation amount (WQcon2) increases the EGR gas correction amount (HOSegr).

Description

Technical field

[0001] The present invention relates to a control device for an internal combustion engine. State of the art

[0002] In recent years, technical developments have been implemented to improve the thermal efficiency of internal combustion engines used to power vehicles or to drive the generator of hybrid vehicles, through the regulation of fuel consumption or exhaust emissions. One such technology is exhaust gas recirculation (EGR), which recirculates a portion of the exhaust gas back into the intake system via a dedicated channel.

[0003] By introducing EGR, the difference between cylinder pressure and atmospheric pressure during the intake stroke can be reduced, and pumping losses can be lowered under conditions where the internal combustion engine's power output is low. When the engine's power output is relatively high, abnormal combustion (knocking) can also be suppressed, and exhaust losses reduced. Furthermore, in recent years, due to the increasing demand for fuel-efficient vehicles, efforts have been made to increase the amount of EGR injected into the intake manifold.

[0004] One technique for estimating the EGR flow rate for the recirculation from the exhaust manifold to the intake manifold is, for example, the technique described in PTL 1. PTL 1 describes a technique for estimating the EGR flow rate based on the opening degree of the EGR valve and a differential pressure across the EGR valve. Citation list of patent literature

[0005] PTL 1: JP 2001-280202 A

[0006] US 8286616 B2 describes a condensation control system in which two EGR valves are each controlled by a control module.

[0007] EP 2199585 A1 describes an EGR device for a turbocharger in which relatively hot exhaust gas is recirculated from the outlet to the inlet of the compressor to prevent condensation.

[0008] DE 102014215194 A1 describes a turbocharging method for an engine in which the amount of recirculated air is controlled according to a temperature at the compressor inlet. TECHNICAL PROBLEM

[0009] The intake manifold is equipped with an intercooler that cools the intake gas. The EGR gas also mixes with the fresh air drawn in through the intake manifold and flows through the intercooler. Additionally, when dew condenses in the intercooler, water vapor exceeding the saturated amount turns into water, while other components such as oxygen, carbon dioxide, and nitrogen remain as gases, thus altering the composition of the EGR gas. The amount of EGR gas flowing into the combustion chamber is then reduced by the amount of water vapor removed.

[0010] Furthermore, in the technique described in PTL 1, the actual EGR flow rate into the combustion chamber is lower than the estimated EGR flow rate because the occurrence of dew condensation in the charge air cooler is not taken into account. Consequently, abnormal combustion, such as knocking, can occur with the technique described in PTL 1. Summary of the invention

[0011] It is an object of the present invention to provide a control device for an internal combustion engine which is able to adequately control the flow of the EGR gas taking into account possible condensation phenomena. Solution to the problem

[0012] The above problem is solved by the features of claim 1. A control device is provided for an internal combustion engine that includes an intercooler, which cools the intake air, and an EGR flow path pipe, which returns a portion of the exhaust gas in an exhaust path to an upstream side of the intercooler as EGR gas. The control device for the internal combustion engine comprises a unit for calculating the amount of moisture, a unit for calculating dew condensation, and an EGR correction unit. The moisture calculation unit calculates a total amount of moisture contained in the mixed gas in which the fresh air flowing into the intercooler and the EGR gas are mixed. Based on the total amount of moisture calculated by the moisture calculation unit, the dew condensation calculation unit calculates a dew condensation generation quantity in the intercooler.The EGR correction unit corrects the flow rate of the recirculated EGR gas based on the amount of dew condensation generated calculated by the dew condensation calculation unit. Claim 1 specifies further features. Advantageous effects of the invention

[0013] The control device for an internal combustion engine with the configuration described above can be used to appropriately correct the flow of the EGR gas. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. Figure 1 is a schematic configuration diagram illustrating a system configuration of an internal combustion engine on which a control device of the internal combustion engine is mounted according to an embodiment. [ Fig. 2] Fig. Figure 2 is a block diagram showing a configuration of the control device of the internal combustion engine according to the embodiment. [ Fig. 3] Fig. Figure 3 is a block diagram showing a configuration of an EGR gas correction process in the control device for an internal combustion engine according to the embodiment. [ Fig. 4] Fig. Figure 4 is a block diagram showing a configuration around a first moisture quantity calculation unit according to a first embodiment. [ Fig. 5] Fig. Figure 5 is a flowchart showing a process for calculating an initial quantity of moisture according to the first embodiment. [ Fig. 6] Fig. Figure 6 is a block diagram showing a configuration of a first moisture quantity calculation unit according to a second embodiment. [ Fig. 7] Fig. Figure 7 is a block diagram showing a configuration of a first moisture quantity calculation unit according to a second embodiment. [ Fig. 8] Fig. Figure 8 is a block diagram showing a configuration around a second moisture quantity calculation unit according to the first embodiment. [ Fig. 9] Fig. Figure 9 is a diagram illustrating a relationship between an octane rating and a CH ratio. [ Fig. 10] Fig. Figure 10 is a flowchart showing a process for calculating a second quantity of moisture according to the first embodiment. [ Fig. 11] Fig. Figure 11 is a block diagram showing a configuration around a second moisture quantity calculation unit according to the second embodiment. [ Fig. 12] Fig. Figure 12 is a diagram that illustrates a relationship between pressure, absolute humidity, and condensation limit temperature. [ Fig. 13] Fig. Figure 13 is a flowchart showing a process for calculating a second quantity of moisture according to the second embodiment. [ Fig. 14] Fig. Figure 14 is a block diagram showing a configuration around a second moisture quantity calculation unit according to a third embodiment. [ Fig. 15] Fig. Figure 15 is a flowchart showing a process for calculating a second quantity of moisture according to the third embodiment. [ Fig. 16] Fig. Figure 16 is a block diagram showing a configuration around a second moisture quantity calculation unit according to a fourth embodiment. [ Fig. 17] Fig. Figure 17 is a flowchart showing a process for calculating a second quantity of moisture according to the fourth embodiment. [ Fig. 18] Fig. Figure 18 is a block diagram showing a configuration around a unit for calculating the amount of saturated moisture in the charge air cooler in the embodiment. [ Fig. 19] Fig. Figure 19 is a flowchart showing a process for calculating a saturated moisture quantity in the charge air cooler according to the fourth embodiment. [ Fig. 20] Fig. Figure 20 is a flowchart illustrating a process for calculating a dew condensation generation quantity in a dew condensation calculation unit according to the embodiment. [ Fig. 21] Fig. Figure 21 is a block diagram showing a configuration of an EGR correction unit according to the embodiment. [ Fig. 22] Fig. Figure 22 is a flowchart showing an operating example of the EGR correction unit according to the embodiment. [ Fig. 23] Fig. Figure 23 is a diagram that shows a relationship between an EGR gas correction quantity and a dew condensation generation quantity. [ Fig. 24] Fig. Figure 24 is a diagram showing an EGR gas correction table stored in an EGR gas correction calculation unit according to the embodiment. [ Fig. 25] Fig. Figure 25 is a diagram that illustrates a relationship between a combustion rate and a target EGR rate. [ Fig. 26] Fig. Figure 26 illustrates a relationship between a combustion rate and a target EGR rate and is a diagram illustrating a change in combustion rate when dew condensation occurs. [ Fig. 27] Fig. Figure 27 illustrates a relationship between a combustion rate and a target EGR rate and is a diagram illustrating a change in combustion rate when dew condensation occurs. [ Fig. 28] Fig. Figure 28 illustrates a relationship between a combustion rate and a target EGR rate and is a diagram illustrating a concept of an EGR correction quantity when dew condensation occurs. [ Fig. 29] Fig. Figure 29 is a flowchart illustrating a process for calculating the EGR gas correction quantity in an EGR gas correction quantity calculation unit according to the embodiment. [ Fig. 30] Fig. Figure 30 is a time diagram that illustrates an example of the execution of an EGR gas correction process. Description of embodiments 1. Embodiments

[0014] An internal combustion engine control device according to one embodiment (hereinafter referred to as the "present example") is described below with reference to the Fig. Figures 1 to 30 are described. The common elements in each drawing are designated with the same reference symbols. 1-1. Configuration example of an internal combustion engine

[0015] First, a configuration example for an internal combustion engine is described.

[0016] Fig. Figure 1 is a schematic configuration diagram showing a system configuration of an internal combustion engine of the present example.

[0017] At the in Fig. The combustion engine 100 shown in Figure 1 is a direct-injection engine in which fuel, consisting of gasoline, is injected directly into a cylinder. The combustion engine 100 is a four-stroke engine, repeating four strokes consisting of an intake stroke, a compression stroke, a combustion (expansion) stroke, and an exhaust stroke. Furthermore, the combustion engine 100 is, for example, a multi-cylinder engine with four cylinders. It should be noted that the number of cylinders in the combustion engine 100 is not limited to four, but can also include six, eight, or more cylinders. The number of strokes in the combustion engine 100 is not limited to four.

[0018] As in Fig. As shown in Figure 1, the internal combustion engine 100 comprises a first humidity sensor 1, an airflow sensor 2, an electronically controlled throttle valve 3, a pressure sensor 4, a compressor 5a, an intercooler 7, an intake air temperature sensor 17, a cylinder 14, and a return valve 18. The first humidity sensor 1, the airflow sensor 2, the electronically controlled throttle valve 3, the pressure sensor 4, the compressor 5a, the intercooler 7, the intake air temperature sensor 17, and the return valve 18 are arranged in positions up to the cylinder 14 in an intake manifold.

[0019] The first humidity sensor 1 detects the humidity of the intake fresh air. The first humidity sensor 1 is arranged on the upstream side of a connection to an EGR flow path pipe 40, which will be described later. The airflow sensor 2 measures the intake air volume and temperature. The present example describes an example in which the first humidity sensor 1 and the airflow sensor 2 are provided separately, but the present invention is not limited to this, and the humidity of the intake air can be detected by the airflow sensor 2.

[0020] The electronically controlled throttle valve 3 is driven by a drive motor (not shown) to open and close it. The degree of opening of the electronically controlled throttle valve 3 is then adjusted depending on the driver's accelerator pedal input. This adjusts the amount of air entering the charge air cooler 7 and the cylinder 14.

[0021] Compressor 5a is a supercharger that charges the intake air. The rotational force is transmitted to compressor 5a via a turbine 5b, which will be described later. A charge pressure sensor 22, which detects the pressure of the charged intake air, is located on the downstream side of compressor 5a. The intake air temperature sensor 17 detects the temperature of the intake air charged by compressor 5a. The return valve 18 regulates the amount of air flowing from the downstream side of compressor 5a to the upstream side of compressor 5a.

[0022] The charge air cooler 7 is located on the upstream side of cylinder 14 and on the downstream side of the electronically controlled throttle valve 3, the first humidity sensor 1, the airflow sensor 2, and the intake air temperature sensor 17. The charge air cooler 7 cools the intake air. The charge air cooler 7 is equipped with a coolant temperature sensor 48 for the charge air cooler, which measures the temperature of the coolant.

[0023] Cylinder 14 is equipped with a piston 26, an intake valve 25, an exhaust valve, an injector 13, a spark plug 16, and a variable valve 6. The piston 26 is slidably mounted within cylinder 14. The piston 26 compresses a gas mixture of fuel and gas that flows into cylinder 14. The piston 26 then moves back and forth within cylinder 14 due to the combustion pressure generated there.

[0024] The intake valve 25 is arranged to open and close in an intake port of cylinder 14, and the exhaust valve is arranged to open and close in an exhaust port of cylinder 14. The opening / closing amounts of the intake valve 25 and the exhaust valve are adjusted by the variable valve 6. The intake quantity and the internal EGR quantity of all cylinders are adjusted by adjusting the variable valve 6.

[0025] Injector 13, controlled by an internal combustion engine control unit (ECU) 20 (described later), injects fuel into cylinder 14. As a result, a mixture of fuel and air is generated in cylinder 14. A high-pressure fuel pump (not shown) is connected to injector 13. The fuel, whose pressure is increased by the high-pressure fuel pump, is supplied to injector 13. A fuel pressure sensor for measuring the injection pressure is also provided in a fuel line connecting injector 13 and the high-pressure fuel pump.

[0026] An ignition coil (not shown) is connected to the spark plug 16. The ignition coil, controlled by the control unit 20 for an internal combustion engine, generates a high voltage and applies this voltage to the spark plug 16. This generates sparks in the spark plug 16. The gas mixture in the cylinder then combusts and explodes due to the sparks generated in the spark plug 16. The piston 26 is forced downwards by the exploded gas mixture. This downward movement of the piston 26 is converted into a rotary motion of the crankshaft and becomes the driving force for the vehicle or similar device.

[0027] An exhaust pipe 15 is connected to an exhaust port of cylinder 14. The exhaust pipe 15 is equipped with the turbine 5b, an electronically controlled boost pressure control valve 11, a three-way catalytic converter 10, and an air-fuel ratio sensor 9. The turbine 5b is set in rotation by the exhaust gas flowing through the exhaust pipe 15 and transmits the rotational force to the compressor 5a. The electronically controlled boost pressure control valve 11 regulates the exhaust gas flow to the turbine 5b.

[0028] The three-way catalytic converter 10 cleans the pollutants contained in the exhaust gas through an oxidation / reduction reaction. The air-fuel ratio sensor 9 is located on the upstream side of the three-way catalytic converter 10. The air-fuel ratio sensor 9 then detects the air-fuel ratio of the exhaust gas flowing through the exhaust pipe 15.

[0029] Furthermore, the combustion engine 100 includes an EGR flow path pipe 40, which recirculates exhaust gas (EGR gas) from a position downstream of the three-way catalyst 10 to a position upstream of the compressor 5a and downstream of the airflow sensor 2. The EGR flow path pipe 40 is equipped with an EGR cooler 42, an EGR valve 41, a differential pressure sensor 43, and a second humidity sensor 46.

[0030] The EGR cooler 42 cools the EGR gas. The EGR cooler 42 is equipped with a water temperature sensor 47 for the EGR cooler, which detects the temperature of the cooling water. The EGR valve 41 controls an EGR flow to adjust the flow rate of the EGR gas flowing through the EGR flow path pipe 40. The differential pressure sensor 43, which detects a differential pressure before and after the EGR valve 41, is located near the EGR valve 41. The differential pressure before and after the EGR valve 41 is the difference between the pressure on the upstream side of the EGR valve 41 and the pressure on the downstream side in the EGR flow path pipe 40.

[0031] An EGR temperature sensor 44 is located downstream of the EGR valve 41. The EGR temperature sensor 44 detects the temperature of the EGR gas flowing through the EGR flow path pipe 40. The second humidity sensor 46 is located downstream of the EGR valve 41 and detects the humidity of the EGR gas flowing through the EGR flow path pipe 40. The second humidity sensor 46 is located between the EGR valve 41 and a connection point where the EGR gas is recirculated into the intake air.

[0032] A portion of the exhaust gas cleaned by the three-way catalytic converter 10 flows into the EGR flow path pipe 40 without being discharged to the outside and is used as EGR gas. After passing through the EGR cooler 42 and the EGR valve 41, the EGR gas flows upstream of the compressor 5a, where it mixes with the intake fresh air. The resulting mixture of EGR gas and fresh air then flows into cylinder 14 after passing through the charge air cooler 7 and the electronically controlled throttle valve 3.

[0033] The signals detected by the respective sensors, such as the first humidity sensor 1, the airflow sensor 2, the pressure sensor 4, the intake air temperature sensor 17, and the boost pressure sensor 22, are sent to the control unit 20 for an internal combustion engine, which is an engine control unit (ECU). In addition, a signal detected by an accelerator pedal opening sensor 12, which detects the amount of accelerator pedal depressed, i.e., the accelerator pedal opening degree, is also sent to the control unit 20 for an internal combustion engine. Furthermore, a signal detected by a brake switch 19, which detects that the brake is being applied, is also sent to the control unit 20 for an internal combustion engine.

[0034] The control device 20 for an internal combustion engine calculates the required torque based on the main signal from the accelerator pedal opening sensor 12. That is, the accelerator pedal opening sensor 12 is used as a sensor to detect the required torque for the internal combustion engine 100. Furthermore, the control device 20 calculates the rotational speed of the internal combustion engine 100 based on an output signal from a crankshaft angle sensor (not shown). Then, the control device 20 optimally calculates the main operating parameters of the internal combustion engine 100, such as airflow, fuel injection quantity, ignition timing, and fuel pressure, based on the operating state of the internal combustion engine 100, which is obtained from outputs from various sensors.

[0035] The fuel injection quantity calculated by the control unit 20 for an internal combustion engine is converted into a valve opening pulse signal and output to the injector 13. The ignition timing calculated by the control unit 20 for an internal combustion engine is also output as an ignition signal to the spark plug 16. Additionally, a throttle opening degree calculated by the control unit 20 for an internal combustion engine is output as a throttle control signal to the electronically controlled throttle valve 3. An EGR valve opening degree calculated by the control unit 20 for an internal combustion engine is output to the EGR valve 41 as an EGR valve opening drive signal. 1-2. Configuration example for a control device 20 for an internal combustion engine

[0036] The following is a configuration example of the control device 20 for an internal combustion engine with reference to Fig. 2 described.

[0037] Fig. Figure 2 is a block diagram showing a configuration of the control device 20 for an internal combustion engine.

[0038] As in Fig. As shown in Figure 2, the control device 20 for an internal combustion engine, which is an engine control unit (ECU), comprises a microcomputer 121 with a central processing unit (CPU), which is an example of a control unit, and a power source IC 120 that controls the power supplied to the microcomputer 121. Furthermore, the control device 20 for an internal combustion engine performs calculations by digitally converting an output value from each sensor using an analog-to-digital converter (ADC) or a timer integrated into the microcomputer 121, which detects one cycle of a periodic signal. The control device 20 then controls each actuator by outputting a calculation result as a control signal.

[0039] Examples of signal input to the control device 20 for an internal combustion engine are the output signals of the humidity sensors 1 and 46, the airflow sensor (intake air temperature sensor) 2, the pressure sensor 4, the intake air temperature sensor 17, the accelerator pedal opening sensor 12, the brake switch 19, the EGR temperature sensor 44, and the like. Examples of signal input to the control device 20 for an internal combustion engine include output signals of the water temperature sensor 47 for the EGR cooler 42, the water temperature sensor 48 for the charge air cooler 7, the boost pressure sensor 22, and the like.

[0040] Furthermore, the signal calculated by the control device 20 for an internal combustion engine is output, for example, to the electronically controlled charge pressure control valve 11, the recirculation valve 18, the electronically controlled throttle valve 3, the variable valve 6, the EGR valve 41, the injector 13, the spark plug 16 and the like.

[0041] Furthermore, the control device 20 for an internal combustion engine calculates the amount of moisture contained in the EGR gas based on the output signals of the various sensors and calculates the EGR gas correction quantity. Subsequently, the control device 20 for an internal combustion engine controls the actuation of the EGR valve 41 based on the calculated EGR gas correction quantity. 1-3. Configuration example of an EGR gas correction process in the control device 20 for an internal combustion engine

[0042] The following is a configuration example of an EGR gas correction process in the control device 20 for an internal combustion engine with reference to Fig. 3 described. Fig. Figure 3 is a block diagram showing a configuration of an EGR gas correction process in the control device 20 for an internal combustion engine.

[0043] As in Fig. As shown in Figure 3, the control device 20 for an internal combustion engine comprises a first moisture quantity calculation unit 301, a second moisture quantity calculation unit 302, a dew condensation calculation unit 303, an EGR correction unit 304 and a calculation unit 312 for a quantity of saturated moisture for the charge air cooler.

[0044] The first humidity calculation unit 301 calculates the amount of moisture contained in the intake fresh air at the location of the first humidity sensor 1, based on the humidity information detected by the first humidity sensor 1, the air volume detected by the airflow sensor 2, the intake air temperature information, the pressure information detected by the pressure sensor 4, and the like. Hereinafter, the amount of moisture calculated by the first humidity calculation unit 301 is referred to as the first moisture amount. A method for calculating the first moisture amount in the first humidity calculation unit 301 is described later. The first humidity calculation unit 301 outputs the calculated first moisture amount to the dew condensation calculation unit 303.

[0045] The amount of moisture calculated by the control device 20 for an internal combustion engine of the present example is a mass flow rate of water vapor flowing per unit of time.

[0046] The second moisture calculation unit 302 calculates the amount of moisture contained in the EGR gas that has passed through the EGR cooler 42. Hereinafter, the moisture amount calculated by the second moisture calculation unit 302 is referred to as the second moisture amount. A procedure for calculating the second moisture amount in the second moisture calculation unit 302 is described later. The second moisture calculation unit 302 outputs the calculated second moisture amount to the dew condensation calculation unit 303.

[0047] The calculation unit 312 for the amount of saturated moisture in the charge air cooler calculates a saturated absolute humidity, which is the absolute humidity when dew condensation occurs in the charge air cooler 7, and a saturated humidity amount, which is the humidity amount when dew condensation occurs. A procedure for calculating the saturated absolute humidity and the amount of saturated moisture in the calculation unit 312 for the amount of saturated moisture in the charge air cooler is described later. The calculation unit 312 for the amount of saturated moisture in the charge air cooler outputs the calculated amount of saturated moisture to the dew condensation calculation unit 303.

[0048] After the EGR gas is recirculated into the intake air, the EGR gas, mixed with the fresh air, is charged by the compressor 5a, has a high temperature and high pressure, and is then cooled by the charge air cooler 7. Due to the relationship between the state of the gas before passing through the charge air cooler 7 (temperature, pressure, moisture content) and the temperature of the coolant flowing through the charge air cooler 7, condensation can occur. The condensation calculation unit 303 then calculates the amount of condensation in the charge air cooler 7.

[0049] The dew condensation calculation unit 303 calculates the amount of dew condensation generated in the charge air cooler 7 from the relationship between the first amount of moisture, the second amount of moisture and the amount of saturated moisture in the charge air cooler 7. The dew condensation calculation unit 303 then outputs the calculated amount of dew condensation generated to the EGR correction unit 304.

[0050] The EGR correction unit 304 determines, based on the amount of dew condensation obtained from the dew condensation calculation unit 303, whether dew condensation is occurring in the charge air cooler 7. Furthermore, the EGR correction unit 304 calculates the amount of EGR gas correction based on the determination result, the amount of dew condensate formed, and the target EGR rate. The EGR correction unit 304 calculates an EGR valve opening command value to implement the calculated EGR correction amount. The EGR correction unit 304 outputs the calculated command value for the EGR valve opening to the EGR valve 41. A procedure for calculating the amount of EGR gas correction in the EGR correction unit 304 is described later.

[0051] The target EGR rate is an EGR rate before correction by the EGR correction unit 304. 2. Configuration example for the process of calculating the first moisture quantity 2-1. First embodiment

[0052] Next, a first embodiment of the method for calculating the first quantity of moisture is described with reference to the Fig. 4 and Fig. 5 described.

[0053] Fig. Figure 4 is a block diagram showing a configuration around a first moisture quantity calculation unit 301 according to a first embodiment. Fig. Figure 5 is a flowchart showing a process for calculating the first quantity of moisture according to the first embodiment.

[0054] As in Fig. As shown in Figure 4, the first humidity quantity calculation unit 301 is connected to the airflow sensor 2 and a first calculation unit 305 for absolute humidity. The first calculation unit 305 for absolute humidity is connected to the airflow sensor 2, the first humidity sensor 1, and the pressure sensor 4. The first humidity sensor 1 in the Fig. In the example shown, relative humidity RHair is recorded as humidity information. The first humidity sensor 1 then outputs the relative humidity RHair to the first processing unit 305 for the absolute humidity. Relative humidity indicates the ratio to the pressure of saturated water vapor, which defines the limit at which water can exist as a gas (water vapor). It should be noted that the mass that can exist as water vapor varies considerably depending on temperature and pressure conditions and therefore must be converted to absolute humidity.

[0055] An intake air temperature Tair, measured by airflow sensor 2, and an intake air pressure Pair, measured by pressure sensor 4, are output to the first calculation unit 305 for absolute humidity. The first calculation unit 305 then calculates the saturated water vapor pressure Psair and the absolute humidity SHair in the fresh air based on the relative humidity RHair, the intake air temperature Tair, and the intake air pressure Pair.

[0056] The pressure Psair of saturated water vapor is calculated using the Tetens equation with the following expression 1. The unit for the pressure Psair of saturated water vapor and the intake air pressure Pair is hPa, and the unit for the intake air temperature Tair is degC. Psair=6.1078×107.5×Tair237.3+Tair×1013Pair

[0057] The absolute humidity SHair in the fresh air is calculated from the pressure Psair for saturated water vapor, the relative humidity RHair, and the intake air temperature Tair using the following expression 1. The unit of absolute humidity SHair is g / m³. 3 , and the unit of relative humidity RHair is dimensionless. SHair=217×Psair×RHairTair+273.15

[0058] The first absolute humidity calculation unit 305 then outputs the calculated absolute humidity SHair to the first humidity quantity calculation unit 301. The first humidity quantity calculation unit 301 calculates the amount of moisture in the fresh air, i.e., a first humidity quantity WQair, based on an air volume Qair, which is the measured value of the airflow sensor 2, the absolute humidity SHair in the fresh air calculated by the first absolute humidity calculation unit 305, and an air density Dair. The first humidity quantity WQair is calculated using the following expression 3. The unit of the first humidity quantity WQair and the air volume Qair is g / s, and the unit of the air density Dair is kg / m³. 3 . WQair=Qair1000×SHairDair

[0059] Next is a process for calculating the first moisture quantity WQegr with reference to Fig. 5 described.

[0060] As in Fig. As shown in Figure 5, the first absolute humidity calculation unit 305 of the control device 20 for an internal combustion engine reads the signals from the first humidity sensor 1 and the pressure sensor 4 (step S501). That is, the first absolute humidity calculation unit 305 acquires the relative humidity RHair, which is detected by the first humidity sensor 1, and the intake air pressure Pair, which is detected by the pressure sensor 4. In the process of step S501, the first absolute humidity calculation unit 305 acquires the intake air temperature Tair from the airflow sensor 2.

[0061] Next, the first absolute humidity calculation unit 305 calculates the absolute humidity SHair of the fresh air based on the signal (S502) acquired in step S501. In step S502, the first absolute humidity calculation unit 305 calculates the pressure Psair for saturated water vapor in the fresh air using expression 1 above. Then, the first absolute humidity calculation unit 305 calculates the absolute humidity SHair in the fresh air using the calculated pressure Psair of saturated water vapor and expression 2 above. The first absolute humidity calculation unit 305 outputs the calculated absolute humidity SHair to the first humidity quantity calculation unit 301.

[0062] Next, the first humidity calculation unit 301 calculates the first humidity quantity WQair in the fresh air using the absolute humidity SHair and the expression 3 above (step S503). In the process of step S503, the first humidity calculation unit 301 detects the air quantity Qair from the airflow sensor 2. This completes the process of calculating the first humidity quantity WQair. As in Fig. As shown in Figure 3, the first moisture quantity calculation unit 301 outputs the calculated first moisture quantity WOair to the dew condensation calculation unit 303. 2-2. Second embodiment

[0063] Next, a second embodiment of the process for calculating the first quantity of moisture is described with reference to the Fig. 6 and Fig. 7 described.

[0064] Fig. Figure 6 is a block diagram showing a configuration around a first moisture quantity calculation unit 301B according to the second embodiment. Fig. Figure 7 is a flowchart showing a process for calculating a first quantity of moisture according to the second embodiment.

[0065] In the second embodiment, the first humidity sensor 1 detects the absolute humidity SHair as humidity information. As in Fig. As shown in Figure 6, the air volume Qair detected by the airflow sensor 2 and the absolute humidity SHair detected by the first humidity sensor 1 are output to the first humidity quantity calculation unit 301B.

[0066] Next is a process for calculating the first moisture quantity WQegr with reference to Fig. 7 described.

[0067] As in Fig. As shown in Figure 7, the first humidity calculation unit 301B of the control device 20 for an internal combustion engine reads the signals from the first humidity sensor 1 and the pressure sensor 2 (step S701). That is, the first humidity calculation unit 301B detects the absolute humidity SHair detected by the first humidity sensor 1 and the air volume Qair detected by the airflow sensor 2.

[0068] Next, the first humidity calculation unit 301B calculates the first humidity quantity WQair in the fresh air using the absolute humidity SHair, the air quantity Qair, and expression 3 above (step S702). This completes the process of calculating the first humidity quantity WQair. The first humidity calculation unit 301B outputs the calculated first humidity quantity WQair to the dew condensation calculation unit 303. 3. Configuration example for the process of calculating the second moisture quantity 3-1. First embodiment

[0069] Next, a first embodiment of the process for calculating the second quantity of moisture is described with reference to the Fig. 8 and Fig. 10 described.

[0070] Fig. Figure 8 is a block diagram showing a configuration around the second moisture quantity calculation unit according to a first embodiment.

[0071] As in Fig. As shown in Figure 8, an EGR flow calculation unit 306 is connected to the second moisture quantity calculation unit 302. The EGR flow calculation unit 306 calculates the flow rate of the EGR gas (EGR flow rate Qegr). The airflow sensor 2 is connected to the EGR flow calculation unit 306, and the air quantity Qair, which is a measured value from the airflow sensor 2, is output. The EGR flow calculation unit 306 also outputs the target EGR rate TEGR calculated by the control device 20 for an internal combustion engine.

[0072] Since the EGR rate is the ratio of the recirculated exhaust gas to the intake air, the EGR rate is defined by the following expression 4 from the ratio of the exhaust gas flow Qair + the EGR flow Qegr and the EGR flow Qegr. TEGR=QegrQair+Qegr

[0073] By transforming expression 4 into an equation to determine the EGR gas flow rate Qegr, the following expression 5 is obtained. Qegr=TEGR1−TEGR×Qair

[0074] Here, as described above, the target EGR rate is the EGR rate before the correction in the EGR correction unit 304 is taken into account. The unit of air volume Qair and EGR flow rate Qegr is g / s, and the unit of the target EGR rate TEGR is dimensionless.

[0075] The EGR flow calculation unit 306 then outputs the calculated EGR flow Qegr to the second moisture quantity calculation unit 302.

[0076] The EGR flow rate Qegr calculated by the EGR flow calculation unit 306 and the fuel property are output to the second moisture quantity calculation unit 302. The fuel property is a characteristic of the currently supplied fuel and is determined by the control device 20 for an internal combustion engine. The fuel property can be the result of determining normal or high octane or be specified as RON (octane number).

[0077] Fig. Figure 9 is a diagram illustrating the relationship between an octane rating and a CH ratio A. The CH ratio A indicates the ratio of H₂ to the saturated hydrocarbon C as a fuel component. As shown in Fig. As shown in Figure 9, the CH ratio A tends to decrease as the octane rating increases. When comparing regular and high-octane fuels, the high-octane fuel generally has a higher octane rating.

[0078] If the fuel property is determined using the octane rating, the control device 20 for an internal combustion engine therefore stores the information in Fig. The diagram shown in 9 is stored in memory. The control device 20 for an internal combustion engine then determines the CH ratio A from the data in Fig. 9 shown in the diagram.

[0079] When the fuel properties are determined by identifying the characteristics of regular and high-octane fuels, the CH ratio A between the regular and high-octane fuels is pre-stored in the memory of the control device 20 for an internal combustion engine. This allows the CH ratio A to be determined by ascertaining whether the current fuel is regular or high-octane.

[0080] Once the CH ratio A is determined, the ratio of the gas composition produced by the combustion of the fuel can be calculated. That is, the amount of moisture WQegr contained in the EGR gas can be determined.

[0081] Firstly, if the volume ratio of nitrogen and oxygen in the air is 79 to 21, then the chemical formula for the combustion of the fuel CnHm is the following expression 6. CnHm+(n+m4)(O2+7921N2)→nCO2+m2H2O+(n+m4)×7921N2

[0082] Here, if the CH ratio is A, then A is the following expression 7. A=HC=mn

[0083] Substituting expression 7 into expression 6 yields the following expression 8. CnHn4+(4+A4×n)(O2+7921N2)→nCO2+nA2H2O+(4+A4×n)×7921N2

[0084] According to expression 8, the volume fraction of CO2, H2O and N2 in the exhaust gas is the following expression 9. CO2:H2O:N2=n:nA2:4+A4×n×7921=1:A2:4+A4×7921

[0085] The mass ratio RATEw of water vapor in the exhaust gas produced by combustion is therefore given by the following expression 10. Here, [CO2] represents a molecular weight of carbon dioxide of 44 g / mol, [H2O] a molecular weight of water of 18 g / mol and [N2] a molecular weight of nitrogen of 28 g / mol. RATEw=A2×[H2O]1×[CO2]+A2×[H2O]+4+A4×7921×[N2] =27×A448+106×A

[0086] As shown in Expression 10, the mass ratio of water vapor in the exhaust gas is determined solely by the CH ratio A. Therefore, the second moisture quantity calculation unit 302 can calculate the moisture quantity in the EGR gas, i.e., the second moisture quantity WQegr, using Expression 11. The unit of the second moisture quantity WQegr in the EGR gas is g / s. The second moisture quantity calculation unit 302 also outputs the calculated second moisture quantity WQegr to the dew condensation calculation unit 303. WQegr=Qegr×RATEw

[0087] Next is a process for calculating the second moisture quantity WQegr with reference to Fig. 10 described. Fig. Figure 10 is a flowchart illustrating the process of calculating the second moisture quantity WQegr in the first embodiment.

[0088] As in Fig. As shown in Figure 10, the EGR flow calculation unit 306 detects the air quantity Qair from the airflow sensor 2 and reads the target EGR rate TEGR from the control device 20 for an internal combustion engine (step S1001). Next, the EGR flow calculation unit 306 calculates the EGR flow rate Qegr using the air quantity Qair, the target EGR rate TEGR, and the expression 5 above (step S1002). The EGR flow calculation unit 306 then outputs the calculated EGR flow rate Qegr to the second moisture quantity calculation unit 302.

[0089] Next, the second moisture quantity calculation unit 302 reads the fuel property determination result from the control device 20 for an internal combustion engine. Then, the second moisture quantity calculation unit 302 calculates the mass ratio RATEw of water vapor in the exhaust gas by expression 10 (step S1003). As described above, if the fuel property determination is performed from the determination of regular and high-octane fuel, the CH ratio A can be obtained in advance by storing the CH ratio A corresponding to the determination result in memory. If the fuel property is determined by the octane number, the CH ratio A can be obtained from the in Fig. The result can be read from the diagram shown in Figure 9. Although the example of determining the fuel property has been described, the present invention is not limited to this, and, for example, the CH ratio A can be stored as a fixed value in a memory under the assumption of a general fuel property, without determining the fuel property.

[0090] Next, the second moisture quantity calculation unit 302 calculates the second moisture quantity WQegr based on the EGR flow rate Qegr obtained from the EGR flow rate calculation unit 306, the mass ratio RATEw of water vapor in the exhaust gas calculated in step S1003, and expression 11 (S1004). This completes the process of calculating the second moisture quantity WQegr. The second moisture quantity calculation unit 302 outputs the calculated second moisture quantity WQegr to the dew condensation calculation unit 303.

[0091] As described above, according to the process of calculating the second moisture quantity WQegr of the first embodiment, it is not necessary to provide the second moisture sensor 46, and the number of parts can be reduced, since the second moisture quantity WQegr can be obtained from the fuel property (CH ratio A). 3-2. Second embodiment

[0092] Next, a second embodiment of the process for calculating the second quantity of moisture is described with reference to the Fig. 11 and Fig. 13 described.

[0093] Fig. Figure 11 is a block diagram showing a configuration around a second moisture quantity calculation unit 302B in the fourth embodiment.

[0094] The calculation process according to the second embodiment takes into account the dew condensation of the EGR cooler 42. As in Fig. Figure 11 shows that an EGR flow calculation unit 306 and a calculation unit 308B for saturated moisture content are connected to the second moisture content calculation unit 302B. A calculation unit 307 for saturated absolute humidity and the calculation unit 306 for EGR flow are connected to the calculation unit 308B for saturated moisture content.

[0095] The saturated absolute humidity calculation unit 307 calculates the saturated absolute humidity SHsegr in the EGR cooler 42. The saturated absolute humidity calculation unit 307 outputs a cooling water temperature Tegrc, which is detected by the water temperature sensor 47, which detects the temperature of the cooling water in the EGR cooler 42. The saturated absolute humidity calculation unit 307 then calculates the saturated absolute humidity SHsegr in the EGR cooler 42 based on the exhaust gas pressure Pexh and the cooling water temperature Tegrc.

[0096] The saturated absolute humidity (SHsegr) is the absolute limiting humidity at which no dew formation occurs in the EGR cooler 42. The unit of saturated absolute humidity (SHsegr) is g / m³. 3The exhaust pressure Pexh can be estimated based on an operating condition or measured directly by installing a sensor. If the exhaust pressure Pexh is estimated based on the operating condition, a map can be created in advance that includes the crankshaft speed and the load as axes, and the exhaust pressure Pexh can then be estimated based on this map.

[0097] Fig. Figure 12 is a diagram illustrating the relationship between pressure, absolute humidity, and condensation limit temperature. The horizontal axis represents pressure, and the vertical axis represents absolute humidity. From the in Fig. The diagram shown in Figure 12 illustrates whether dew condensation occurs when the pressure and absolute humidity are determined under a specific temperature condition. If the pressure and temperature are known, the absolute humidity at that temperature can also be obtained. Then, the calculation unit 307 calculates the saturated absolute humidity SHsegr in the EGR cooler 42 from the value in Fig. 12 shown diagram and outputs the calculated saturated absolute humidity SHsegr to the calculation unit 308B for saturated moisture quantity.

[0098] Unit 308B, used to calculate the amount of saturated moisture, calculates a quantity of saturated moisture WQsegr in the EGR cooler 42 based on the saturated absolute humidity SHsegr and the EGR flow rate Qegr, which is output by unit 306 for calculating the EGR flow rate. The quantity WQsegr of saturated moisture indicates the maximum mass flow rate of water vapor that can be present in the EGR gas if condensation occurs in the EGR cooler 42. The quantity of saturated moisture WQsegr is calculated using the following expression 12, where Degr is the density of the exhaust gas and the unit is kg / m³. 3 The unit of saturated moisture WQsegr is g / s. WQsegr=Qegr1000×SHsegrDegr

[0099] The calculation unit 308B outputs the calculated amount of saturated moisture WQsegr to the second moisture calculation unit 302B. The second moisture calculation unit 302B compares the moisture amount in the EGR gas calculated by expression 11 with the saturated moisture amount WQsegr calculated by expression 12 and selects a smaller value. This selected value is the second moisture amount WQegr output by the second moisture calculation unit 302B.

[0100] Fig. Figure 13 is a flowchart illustrating the process of calculating the second moisture quantity WQegr in the second embodiment.

[0101] As in Fig. As shown in Figure 13, the control device 20 for an internal combustion engine first calculates the exhaust pressure Pexh from the crankshaft speed and the load (step S1301). The calculated exhaust pressure Pexh is then output to the calculation unit 307 for saturated absolute humidity.

[0102] Next, the saturated absolute humidity calculation unit 307 acquires the coolant temperature Tegrc of the EGR cooler 42 from the water temperature sensor 47 (step S1302). Then, the saturated absolute humidity calculation unit 307 calculates the saturated absolute humidity SHsegr in the EGR cooler 42 from the exhaust pressure Pexh, the coolant temperature Tegrc, and the Fig. 12. Graphic shown (step S1303). In addition, the calculation unit 307 for saturated absolute humidity outputs the calculated saturated absolute humidity SHsegr to the calculation unit 308B for the amount of saturated humidity.

[0103] Furthermore, the EGR flow calculation unit 306 detects the air quantity Qair from the airflow sensor 2 and reads the target EGR rate TEGR from the control device 20 for an internal combustion engine (step S1304). Next, the EGR flow calculation unit 306 calculates the EGR flow rate Qegr using the air quantity Qair, the target EGR rate TEGR, and the expression 5 above (step S1305). Then, the EGR flow calculation unit 306 outputs the calculated EGR flow rate Qegr to the second moisture quantity calculation unit 302 and the saturated moisture quantity calculation unit 308B.

[0104] It should be noted that the processing of steps S1301 to S1303, performed by calculation unit 307 for saturated absolute humidity, and the processing of steps S1304 to S1305, performed by calculation unit 306 for EGR flow, can be carried out simultaneously. Alternatively, the processing of steps S1301 to S1303 can be carried out after the processing of steps S1304 to S1305.

[0105] Next, unit 308B calculates the amount of saturated moisture WQsegr in the EGR cooler 42 based on the saturated absolute humidity SHsegr, the EGR flow rate Qegr output by unit 306 for calculating the EGR flow rate, and expression 12 (step S1306). Then, unit 308B outputs the calculated amount of saturated moisture WQsegr to the second moisture quantity calculation unit 302B.

[0106] Next, the second moisture quantity calculation unit 302 reads the fuel property determination result from the control device 20 for an internal combustion engine. Then, the second moisture quantity calculation unit 302 calculates the mass ratio RATEw of water vapor in the exhaust gas according to expression 10 (step S1307). Next, the second moisture quantity calculation unit 302B calculates the moisture content in the EGR gas based on the EGR flow rate Qegr obtained from the EGR flow calculation unit 306, the mass ratio RATEw of water vapor in the exhaust gas calculated in step S1307, and expression 11 (S1308).

[0107] Next, the second moisture quantity calculation unit 302B compares the saturated moisture quantity WQsegr obtained from the moisture quantity calculation unit 308B with the moisture quantity calculated in step S1308 and selects a smaller value. The second moisture quantity calculation unit 302B then calculates the selected moisture quantity as the second moisture quantity WQegr (step S1309). This allows the moisture quantity in the EGR gas, taking into account dew condensation in the EGR cooler 42, to be calculated as the second moisture quantity WQegr. The second moisture quantity calculation unit 302B outputs the calculated second moisture quantity WQegr to the dew condensation calculation unit 303.

[0108] According to the procedure for calculating the second moisture quantity WQegr of the second embodiment, the second moisture quantity WQegr can be calculated more accurately than in the procedure for calculating the second moisture quantity WQegr of the first embodiment by taking into account the dew condensation in the EGR cooler 42. Furthermore, in the procedure for calculating the second moisture quantity WQegr of the second embodiment, it is not necessary to provide the second moisture sensor 46, and the number of parts can be reduced. 3-3. Third embodiment

[0109] Next, a third embodiment of the process for calculating the second quantity of moisture is described with reference to the Fig. 14 and Fig. 15 described.

[0110] Fig. Figure 14 is a block diagram showing a configuration around a second moisture quantity calculation unit 302C in the third embodiment.

[0111] The calculation process according to the third embodiment uses the humidity information from the second humidity sensor 46. In the calculation process according to the third embodiment, the second humidity sensor 46 detects a relative humidity RHegr as the humidity information.

[0112] As in Fig. As shown in Figure 14, an EGR flow calculation unit 306 and a second calculation unit 309 for saturated absolute humidity are connected to the second humidity quantity calculation unit 302C. The second humidity sensor 46 outputs the relative humidity RHegr as humidity information to the second calculation unit 309 for absolute humidity. The intake air pressure Pair, detected by the pressure sensor 4, and the coolant temperature Tegrc of the EGR cooler 42, detected by the water temperature sensor 47, are output to the second calculation unit 309 for absolute humidity. The second unit 309 then calculates a saturated water vapor pressure Psegr and an absolute humidity SHegr in the EGR gas passing through the second humidity sensor 46, using the relative humidity RHegr, the intake air pressure Pair, and the coolant temperature Tegrc.

[0113] The pressure Psegr of saturated water vapor is calculated from the following expression 13. Psegr=6.1078×107.5×Tegrc237.3+Tegrc×1013Pair

[0114] The unit of saturated water vapor pressure Psegr is hPa, and the unit of cooling water temperature Tegrc is degC.

[0115] Here, the EGR gas is cooled to the temperature of the cooling water flowing through the EGR cooler 42 as it passes through it. Therefore, the cooling water temperature Tegrc, measured by the water temperature sensor 47, is used as the temperature of the EGR gas flowing through the second humidity sensor 46. As in Fig. As shown in Figure 1, the second humidity sensor 46 is located on the inlet side of the EGR valve 41. Therefore, the inlet air pressure Tegrc detected by the pressure sensor 4 is used as the pressure of the EGR gas flowing through the second humidity sensor 46.

[0116] The temperature and pressure of the EGR gas are not limited to the examples described above. For instance, sensors that detect the temperature and pressure of the EGR gas, and the values ​​detected by these sensors, can be used as the temperature and pressure of the EGR gas. However, by using the values ​​detected by the water temperature sensor 47 and the pressure sensor 4, it is not necessary to provide a new sensor, and the number of components can be reduced.

[0117] The absolute humidity SHegr is calculated using the following expression 14. Here, the unit of absolute humidity SHegr is g / m³. 3 , and the unit of relative humidity RHegr is dimensionless. SHegr=217×Psair×RHegrTegrc+273.15

[0118] Furthermore, the second absolute humidity calculation unit 309 outputs the calculated absolute humidity SHegr to the second moisture quantity calculation unit 302C. The second moisture quantity calculation unit 302C calculates the moisture content in the EGR gas, i.e., the second moisture content WQegr, based on the EGR flow rate Qegr calculated by the EGR flow rate calculation unit 306, the absolute humidity SHegr detected by the second humidity sensor 309, and expression 15. WQegr=Qegr1000×SHegrDegr

[0119] Next is a process for calculating the second moisture quantity WQegr with reference to Fig. 15 described.

[0120] Fig. Figure 15 is a flowchart illustrating the process of calculating the second moisture quantity WQegr in the third embodiment.

[0121] As in Fig. As shown in Figure 15, the second unit 309 for calculating absolute humidity reads the signals from the second humidity sensor 46, the pressure sensor 4, and the water temperature sensor 47 (step S1501). That is, the first calculation unit 305 for absolute humidity acquires the relative humidity RHegr, which is acquired by the second humidity sensor 46, the intake air pressure Pair, which is acquired by the pressure sensor 4, and the coolant temperature Tegrc of the EGR cooler 42, which is acquired by the water temperature sensor 47.

[0122] Next, the second unit 309 calculates the absolute humidity using the saturated water vapor pressure Psegr from the acquired signal and expression 13. Furthermore, the second unit 309 calculates the absolute humidity SHegr from the calculated saturated water vapor pressure Psegr, the acquired information, and expression 14 (step S1502). Finally, the second unit 309 outputs the calculated absolute humidity SHegr to the second humidity quantity calculation unit 302C.

[0123] The EGR flow calculation unit 306 detects the air volume Qair from the airflow sensor 2 and reads the target EGR rate TEGR from the control device 20 for an internal combustion engine (step S1503). Next, the EGR flow calculation unit 306 calculates the EGR flow rate Qegr using the air volume Qair, the target EGR rate TEGR, and the expression 5 above (step S1504). The EGR flow calculation unit 306 then outputs the calculated EGR flow rate Qegr to the second moisture quantity calculation unit 302C.

[0124] It should be noted that the processing of steps S1501 to S1502, performed by the second calculation unit 309 for absolute humidity, and the processing of steps S1503 to S1504, performed by calculation unit 306 for EGR flow, can be carried out simultaneously. Alternatively, the processing of steps S1501 to S1502 can be carried out after the processing of steps S1503 to S1504.

[0125] Next, the second moisture quantity calculation unit 302C calculates the second moisture quantity WQegr based on the EGR flow rate Qegr, which is recorded by the EGR flow rate calculation unit 306, the absolute humidity SHegr, which is recorded by the second absolute humidity calculation unit 309, and expression 15 (S1505). This completes the process of calculating the second moisture quantity WQegr. The second moisture quantity calculation unit 302C outputs the calculated second moisture quantity WQegr to the dew condensation calculation unit 303.

[0126] According to the procedure for calculating the second moisture quantity WQegr of the third embodiment, the second moisture quantity WQegr can be calculated more accurately by using the actual measured value recorded by the second moisture sensor 46 as moisture information. 3-4. Fourth embodiment

[0127] Next, a fourth embodiment of the process for calculating the second quantity of moisture is described with reference to the Fig. 16 and Fig. 17 described.

[0128] Fig. Figure 16 is a block diagram showing a configuration around a second moisture quantity calculation unit 302D in the fourth embodiment.

[0129] The calculation process according to the fourth embodiment uses the humidity information from the second humidity sensor 46 similarly to the calculation process according to the third embodiment. In addition, the second humidity sensor 46 also records the absolute humidity SHegr as humidity information in the calculation process according to the fourth embodiment.

[0130] As in Fig. As shown in Figure 16, the absolute humidity SHegr detected by the second humidity sensor 46 and the EGR flow rate Qegr calculated by the EGR flow calculation unit 306 are output to the second moisture quantity calculation unit 302D. The second moisture quantity calculation unit 302D calculates the moisture quantity in the EGR gas, i.e., the second moisture quantity WQegr, based on the EGR flow rate Qegr calculated by the EGR flow calculation unit 306, the absolute humidity SHegr detected by the second humidity sensor 46, and the expression shown in Figure 15.

[0131] Next is a process for calculating the second moisture quantity WQegr with reference to Fig. 17 described.

[0132] Fig. Figure 17 is a flowchart illustrating the process of calculating the second moisture quantity WQegr in the fourth embodiment.

[0133] As in Fig. As shown in Figure 17, the second humidity calculation unit 302D reads the absolute humidity SHegr detected by the second humidity sensor 46 (step S1701). Next, the EGR flow calculation unit 306 detects the air quantity Qair from the airflow sensor 2 and reads the target EGR rate TEGR from the control device 20 for an internal combustion engine (step S1702). The EGR flow calculation unit 306 then calculates the EGR flow rate Qegr using the air quantity Qair, the target EGR rate TEGR, and expression 5 above (step S1703). Finally, the EGR flow calculation unit 306 outputs the calculated EGR flow rate Qegr to the second humidity calculation unit 302D.

[0134] It should be noted that the processing of step S1701, performed by the second moisture quantity calculation unit 302D, and the processing of steps S1702 to S1503, performed by the EGR flow calculation unit 306, can be carried out simultaneously. Alternatively, the processing of step S1701 can be carried out after the processing of steps S1702 to S1703.

[0135] Next, the second moisture quantity calculation unit 302D calculates the second moisture quantity WQegr based on the EGR flow rate Qegr, which is detected by the EGR flow rate calculation unit 306, the absolute humidity SHegr, which is detected by the second humidity sensor 46, and expression 15 (S1704). This completes the process of calculating the second moisture quantity WQegr. The second moisture quantity calculation unit 302D outputs the calculated second moisture quantity WQegr to the dew condensation calculation unit 303.

[0136] According to the process of calculating the second moisture quantity WQegr of the fourth embodiment, the second moisture quantity WQegr can be calculated more accurately, similar to the process of calculating the second moisture quantity WQegr of the third embodiment, by using the actual measured value recorded by the second moisture sensor 46 as moisture information. 4. Operational example for calculating the amount of saturated moisture in the charge air cooler

[0137] Next, an example of calculating the amount of saturated moisture in the charge air cooler 7 will be given with reference to the Fig. 18 and Fig. 19 described.

[0138] Fig. Figure 18 is a block diagram showing a configuration around unit 312 for calculating the amount of saturated moisture in the charge air cooler.

[0139] As in Fig. Figure 18 shows that a calculation unit 310 for the saturated absolute humidity in the charge air cooler and a calculation unit 311 for the total gas flow are connected to the calculation unit 312 for the amount of saturated humidity in the charge air cooler. The calculation unit 310 for the saturated absolute humidity of the charge air cooler outputs the saturated absolute humidity SHsat of the charge air cooler 7 from the calculation unit 312 for the amount of saturated humidity in the charge air cooler. Additionally, a total gas flow Qtotal is output from the calculation unit 311 for the total gas flow to the calculation unit 312 for the saturated humidity in the charge air cooler.

[0140] A coolant temperature Tic of the charge air cooler 7, measured by water temperature sensor 48, and a boost pressure Pchg, measured by boost pressure sensor 22 (which is the pressure after charging), are output to the calculation unit 310 for the saturated absolute humidity of the charge air cooler. The calculation unit 310 then calculates the absolute saturation humidity SHsat from the coolant temperature Tic and the boost pressure Pchg, assuming that dew condensation occurs in the charge air cooler 7. If dew condensation occurs in the charge air cooler 7, as in Fig. As shown in Figure 12, the saturated absolute humidity SHsat can be determined from the ratio between pressure and temperature.

[0141] The air volume Qair detected by airflow sensor 2 and the EGR flow rate Qegr calculated by the EGR flow calculation unit 306 are output to the total gas flow calculation unit 311. The total gas volume flowing through the charge air cooler 7 is the sum of the air volume Qair detected by airflow sensor 2 and the EGR flow rate Qegr calculated by the EGR flow calculation unit 306. Therefore, to calculate the total gas flow rate, unit 311 calculates the total gas flow rate Qtotal from the air volume Qair, the EGR flow rate Qegr, and the following expression 16. Qtotal = Qair + Qegr

[0142] The calculation unit 312 for saturated humidity in the charge air cooler calculates a quantity WQsat of saturated humidity in the charge air cooler 7 from the saturated absolute humidity SHsat and the total gas flow rate Qtotal. The quantity WQsat of saturated humidity is calculated from the saturated absolute humidity SHsat, the total gas flow rate Qtotal, and the following expression 17. The unit of the total gas flow rate Qtotal and the quantity WQsat of saturated humidity is g / s. Dtotal is the density of a gas mixture of fresh air and EGR gas, and one unit of this is g / m³. 3 . WQsat=Qtotal1000×SHsatDtotal

[0143] Next, a process for calculating the amount WQsat of saturated moisture in the charge air cooler is described, with reference to Fig. 19 described. Fig. Figure 19 is a flowchart that illustrates a process for calculating the amount of saturated moisture WQsat in the charge air cooler.

[0144] As in Fig. As shown in Figure 19, the calculation unit 310 for the saturated absolute humidity of the charge air cooler first reads the coolant temperature Tic of the charge air cooler 7, measured by the water temperature sensor 48, and the boost pressure Pchg, measured by the boost pressure sensor 22 (step S1901). Next, the calculation unit 310 for saturated absolute humidity in the charge air cooler calculates a saturated water vapor pressure Psat and the saturated absolute humidity SHsat in the charge air cooler 7 from the relationship between the coolant temperature Tic, the boost pressure Pchg, and the pressure and temperature measured in Fig. Figure 12 is shown (step S1902). The calculation unit 310 for the saturated absolute humidity in the charge air cooler then outputs the calculated saturated absolute humidity SHsat to the calculation unit for the amount WQsat of saturated humidity in the charge air cooler.

[0145] Next, the EGR flow calculation unit 306 acquires the air quantity Qair from the airflow sensor 2 and reads the target EGR rate TEGR from the control device 20 for an internal combustion engine (step S1903). The EGR flow calculation unit 306 then calculates the EGR flow rate Qegr using the air quantity Qair, the target EGR rate TEGR, and expression 5 above (step S1903). Finally, the EGR flow calculation unit 306 outputs the calculated EGR flow rate Qegr to the total gas flow calculation unit 311.

[0146] Next, the total gas flow calculation unit 311 calculates the total gas flow Qtotal from the air volume Qair detected by the airflow sensor 2 and the EGR flow Qegr calculated by the EGR flow calculation unit 306 (step S1905). Then, the total gas flow calculation unit 311 outputs the calculated total gas flow Qtotal to the unit 312 for calculating the amount of saturated moisture in the charge air cooler.

[0147] Next, the calculation unit 312 for the amount of saturated moisture in the charge air cooler calculates the amount WQsat of saturated moisture in the charge air cooler 7 based on the saturated absolute humidity SHsat, the total gas flow rate Qtotal, the density Dtotal of the mixed gas, and expression 17 (step S1906). This completes the process of calculating the amount WQsat of saturated moisture in the charge air cooler. The calculation unit 312 for the amount of saturated moisture in the charge air cooler outputs the calculated amount WQsat of saturated moisture in the charge air cooler to the dew condensation calculation unit 303. 5. Operational example for calculating the amount of dew condensation produced

[0148] Next, a process for calculating a dew condensation production quantity in the dew condensation calculation unit 303 is described with reference to Fig. 20 described.

[0149] Fig. Figure 20 is a flowchart that represents a process for calculating a dew condensation production quantity.

[0150] As in Fig. As shown in Figure 20, the dew condensation calculation unit 303 reads the first moisture quantity WQair, calculated by the first moisture quantity calculation unit 301, and the second moisture quantity WQegr, calculated by the second moisture quantity calculation unit 302. The dew condensation calculation unit 303 then reads the quantity WQsat of saturated moisture in the charge air cooler 7, calculated by the calculation unit 312 for saturated moisture in the charge air cooler (step S2001).

[0151] Next, the dew condensation calculation unit 303 calculates a dew condensation generation quantity WQcon from the first moisture quantity WQair, the second moisture quantity WQegr, the quantity WQsat of saturated moisture and the following expression 18 (step S2002). WQcon=(WQair+WQegr)−WQsat

[0152] The unit of WQcon here is g / s.

[0153] The sum (WQair + WQegr) of the first moisture quantity WQair and the second moisture quantity WQegr in expression 18 is the total moisture quantity in the gas mixture before it passes through the charge air cooler 7. The dew condensation generation quantity WQcon can then be calculated by determining the difference between the quantity WQsat of saturated moisture in the charge air cooler 7 and the total moisture quantity in the mixed gas. The dew condensation calculation unit 303 then outputs the calculated dew condensation generation quantity WQcon to the EGR correction unit 304. 6. EGR Correction Unit 6-1. Configuration Example of the EGR Correction Unit

[0154] Next, a configuration example of the EGR correction unit 304 will be given with reference to Fig. 21 described.

[0155] Fig. Figure 21 is a block diagram showing the EGR correction unit 304.

[0156] As in Fig. As shown in Figure 21, the EGR correction unit 304 comprises a unit 313 for determining dew condensation, a unit 314 for calculating the EGR gas correction quantity, and a unit 315 for controlling the opening degree of the EGR valve. The dew condensation generation quantity WQcon calculated by the dew condensation calculation unit 303 is output to the dew condensation determination unit 313. The dew condensation determination unit 313 then calculates a final dew condensation generation quantity WQcon2 based on the dew condensation generation quantity WQcon.

[0157] Here, during dew condensation in the charge air cooler 7, moisture condenses that exceeds the amount of saturated moisture WQsat. Therefore, the amount of dew condensation generated WQcon, calculated using expression 18, is a positive value. Conversely, if no dew condensation occurs in the charge air cooler 7, the total moisture content of the mixed gas before it flows through the charge air cooler 7 is less than the amount of saturated moisture WQsat. Therefore, the amount of dew condensation generated WQcon, calculated using expression 18, is a negative value.

[0158] Since each sensor has a detection error, it cannot be determined that dew condensation occurs on the charge air cooler 7, even if the dew condensation generation quantity WQcon calculated by the dew condensation calculation unit 303 has a positive value. Therefore, in the dew condensation determination unit 313 of this example, the dew condensation determination is carried out taking into account the detection error, which is pre-inferred from the sensor specifications of the first humidity sensor 1, the airflow sensor 2, and the like. Then, in the dew condensation determination unit 313, a threshold value SL is pre-defined from the detection error assumed from the sensor specification of each sensor.

[0159] If the relationship between the dew condensation generation quantity WQcon and the threshold SL is found to satisfy expression 19 below, the dew condensation determination unit 313 determines that dew condensation has occurred in the charge air cooler 7. At this point, the dew condensation determination unit 313 receives the final dew condensation generation quantity WQcon2 from the following expression 20. As shown in expression 20, the final dew condensation generation quantity WQcon2 is the dew condensation quantity WQcon calculated by the dew condensation calculation unit 303. Qcon≥SL WQcon2=WQcon

[0160] On the other hand, if the dew condensation determination unit 313 determines that the relationship between the dew condensation production quantity WQcon and the threshold SL does not correspond to expression 19, the dew condensation determination unit 313 determines that no dew condensation has occurred in the charge air cooler 7. Therefore, the dew condensation determination unit 313 calculates the final dew condensation production quantity WQcon2 as “0”, as shown in expression 21. WQcon2=0

[0161] Subsequently, the dew condensation determination unit 313 outputs the calculated final dew condensation production quantity WQcon2 to the EGR gas correction quantity calculation unit 314.

[0162] The EGR gas correction quantity calculation unit 314 then calculates the EGR gas correction quantity HOSegr from the final dew condensation generation quantity WQcon2 and the target EGR rate TEGR. A procedure for calculating the EGR gas correction quantity HOSegr is described later. Subsequently, the EGR gas correction quantity calculation unit 314 outputs the calculated EGR gas correction quantity HOSegr to the EGR valve opening degree command unit 315.

[0163] The EGR valve opening degree control unit 315 corrects the target EGR rate TEGR based on the EGR gas correction quantity HOSegr and calculates a corrected EGR rate HEGR. The corrected EGR rate HEGR is calculated using the following expression 22. Here, the units of the corrected EGR rate HEGR, the target EGR rate TEGR, and the EGR gas correction quantity HOSegr are all dimensionless. HEGR=TEGR+HOSegr

[0164] In addition, the EGR valve opening degree command unit 315 sends an opening degree command signal to the EGR valve 41, so that the EGR rate (EGR quantity) becomes the calculated corrected EGR rate HEGR. 6-2. Operating example of the EGR correction unit 304

[0165] Next, an operational example of the EGR correction unit 304 will be presented with reference to Fig. 22 described.

[0166] Fig. Figure 22 is a flowchart showing an operating example of the EGR correction unit 304.

[0167] As in Fig. As shown in Figure 22, the dew condensation determination unit 313 of the EGR correction unit 304 first reads the dew condensation generation quantity WQcon calculated by the dew condensation calculation unit 303 (step S2201). Next, the dew condensation determination unit 313 determines whether the dew condensation generation quantity WQcon is equal to or greater than a predetermined threshold value SL (step S2202).

[0168] In step S2202, if the dew condensation determination unit 313 determines that the dew condensation production quantity WQcon is equal to or greater than the threshold SL (YES in S2202), the dew condensation determination unit determines that the final dew condensation production quantity WQcon2 is the dew condensation production quantity WQcon (step S2203).

[0169] In step S2202, if the dew condensation determination unit 313 determines that the dew condensation production quantity WQcon has not reached the threshold SL (NO determination in S2202), the dew condensation determination unit 313 determines the final dew condensation production quantity WQcon2 as “0” (step S2204).

[0170] After completion of processing in step S2203 or step S2204, the dew point determination unit 313 outputs the determined final dew point generation quantity WQcon2 to the EGR gas correction quantity calculation unit 314. Next, the EGR gas correction quantity calculation unit 314 reads a target EGR rate TEGR, which is an EGR rate before correction (step S2205). Then, the EGR gas correction quantity calculation unit 314 calculates the EGR gas correction quantity HOSegr from the final dew point generation quantity WQcon2 and the target EGR rate TEGR (step S2206). A procedure for calculating the EGR gas correction quantity HOSegr is described later.

[0171] The EGR gas correction quantity calculation unit 314 then outputs the calculated EGR gas correction quantity HOSegr to the EGR valve opening degree command unit 315. The EGR valve opening degree command unit 315 then calculates a corrected EGR rate HEGR based on the EGR gas correction quantity HOSegr, the target EGR rate TEGR, and expression 22. Next, the EGR valve opening degree command unit 315 calculates an EGR valve opening degree command value to implement the calculated corrected EGR rate HEGR and transmits the EGR valve opening degree command value to the EGR valve 41 (step S2207). This completes the correction process of the EGR rate and the EGR gas flow rate by the EGR correction unit 304. 6-3. Operational example for calculating the EGR gas correction quantity

[0172] Next, a process for calculating the EGR gas correction quantity in the EGR gas correction quantity calculation unit 314 is described with reference to the Fig. described in sections 23 to 29.

[0173] Fig. Figure 23 is a diagram illustrating the relationship between an EGR gas correction quantity and a dew condensation generation quantity. When dew condensation occurs in the charge air cooler 7, the water vapor content of a mixed gas component of fresh air and EGR gas decreases. That is, the larger the final dew condensation generation quantity WQcon2, the greater the decrease in the water vapor content. Therefore, as shown in Fig. Figure 23 shows that the EGR gas correction quantity HOSegr is increased when the final dew condensation generation quantity WQcon2 is greater.

[0174] Fig. Figure 24 is a diagram showing an EGR gas correction table stored in the EGR gas correction quantity calculation unit 314. As in Fig. As shown in Figure 24, the value of the EGR gas correction quantity HOSegr is set to "0" if no dew condensation occurs in the charge air cooler 7, i.e., if the value of the final dew condensation generation quantity WQcon2 is equal to "0". Then the value of the in Fig. The table shown in 24 is set so that the value of the EGR gas correction quantity HOSegr also increases when the final dew condensation generation quantity WQcon2 increases.

[0175] The EGR gas correction quantity HOSegr with respect to the final dew condensation generation quantity WQcon2 can be calculated using a combustion rate to be described later or determined experimentally. If the EGR gas correction quantity HOSegr is determined experimentally, an initial ignition timing ADV1, i.e., the ignition timing at which the target EGR rate is set, is first stored under the condition that no dew condensation occurs in the charge air cooler 7. Next, a condition is created in which dew condensation occurs in the charge air cooler 7 while the target EGR rate is maintained by a method such as intentionally lowering the temperature of the cooling water flowing through the charge air cooler 7, and the final dew condensation generation quantity WQcon2 in this state is stored.

[0176] As described above, during dew condensation, the flow rate of the EGR gas decreases, which can lead to knocking. Therefore, the optimal ignition timing is a second ignition point, ADV2, on the retarded side of the first ignition point, ADV1; that is, the ignition point before the onset of dew condensation. The EGR rate is increased until the optimal ignition point, in the dew condensation state, reaches the first ignition point, ADV1, from the second ignition point, ADV2. The EGR rate at which the optimal ignition point reaches the first ignition point, ADV1, is defined as the corrected EGR rate. Consequently, the relationship between the EGR gas correction quantity, HOSegr, and the final dew condensation generation quantity, WQcon2, can be obtained from the final dew condensation generation quantity, WQcon2, and the difference between the corrected EGR rate and the target EGR rate, and the value of the... Fig. The values ​​shown in the table 24 can be determined through an experiment.

[0177] Next, a method for calculating the EGR correction amount HOSegr from a combustion rate VL with reference to the Fig. Described in sections 25 to 28.

[0178] The Fig. Figures 25 to 28 are diagrams illustrating the relationship between the combustion rate VL and the target EGR rate TEGR.

[0179] Here, the flame is an oxidation reaction of the unmixed gas, and the combustion propagates in the direction of the upstream unmixed gas. This combustion propagation speed is the combustion velocity. The combustion velocity is broadly divided into laminar flow combustion velocity, which is the rate at which the flame propagates, and turbulent flow combustion velocity, which is the rate at which the flame is accelerated due to turbulence. The combustion velocity described in this example is a laminar flow combustion velocity. The combustion velocity decreases because the mixed gas contains more components that inhibit combustion. Since the EGR gas is exhaust gas after combustion, it also consists of components that inhibit combustion, such as carbon dioxide and water vapor.

[0180] Therefore, as in Fig. Figure 25 shows that with increasing EGR rate, the effect of combustion inhibition decreases, and the combustion velocity VL decreases. This means that the EGR rate and the combustion velocity VL have a negative correlation.

[0181] Fig. Figure 26 is a diagram illustrating the relationship between the target EGR rate TEGR and the combustion velocity VL in the presence or absence of dew condensation in the charge air cooler 7. A solid line in Fig. Figure 26 indicates a state in which no dew condensation occurs in the charge air cooler 7, and a dashed line indicates a state in which dew condensation occurs in the charge air cooler 7. Furthermore, the target EGR rate in the first state a, when no dew condensation occurs, is set as the first EGR rate TEGRa, and the combustion velocity is set as the first combustion velocity VLa.

[0182] As in Fig. As shown in Figure 26, the water vapor, which inhibits combustion, decreases when dew condensation occurs in the first state a, thus increasing the combustion rate VL. Therefore, the first state a transitions into a second state b, indicated by a dashed line, in which dew condensation has taken place, and the combustion rate VL transitions into a second combustion rate VLb, which is higher than the first combustion rate VLa.

[0183] Fig. Figure 27 is a diagram in which a third state c is added, in which the amount of dew condensation produced is greater than in the second state b. As in Fig. As shown in Figure 27, in the third state c the amount of dew condensation increases and the amount of water vapor decreases further compared to the second state b, so that the combustion rate VL changes to the third combustion rate VLc faster than the second combustion rate VLb.

[0184] As in Fig. 26 and Fig. As shown in Figure 27, the combustion rate VL increases when the amount of dew condensation increases, thus increasing the possibility of abnormal combustion such as knocking. This results in the ignition timing being retarded, preventing the desired ignition timing from being achieved, leading to increased fuel consumption and reduced torque. To avoid this increase in fuel consumption and torque, combustion must occur at the desired ignition timing.

[0185] Fig. Figure 28 is a diagram illustrating a calculation state of the EGR gas correction quantity when the state is shifted from the first state a to the second state b due to the generation of dew condensation at the target EGR rate of the first EGR rate TEGRa.

[0186] As in Fig. As shown in Figure 28, the combustion speed VL increases from the first combustion speed VLa to the second combustion speed VLb when the state shifts from the first state a to the second state b. If the EGR rate is not corrected, the ignition timing is retarded by the increased combustion speed VL.

[0187] Conversely, to achieve a desired ignition timing, the EGR rate is increased until the second combustion rate VLb in the second state b equals the first combustion rate VLa in the first state a, i.e., until the second state b becomes a fourth state d. The EGR rate in the fourth state d is referred to as the second EGR rate TEGRb. The EGR gas correction quantity HOSegr, calculated by the EGR gas correction quantity calculation unit 314, is a difference between the second EGR rate TEGRb and the first EGR rate TEGRa (HOSegr = TEGRb - TEGRa).

[0188] A method for calculating the actual combustion rate is then described.

[0189] The equation for determining the combustion rate is calculated using the following expressions 23 and 24, based on the well-known Metghalchi & Keck equation. Although the case described here uses gasoline as fuel, the coefficient is modified for other fuels. VL represents a desired combustion rate, φf an equivalence ratio, T a cylinder internal temperature at the ignition time, P a cylinder internal pressure at the ignition time, Y an EGR rate, and Vcon a combustion rate that increases when dew condensation occurs.

[0190] Furthermore, the units of VL, VL, ref, Vcon, and e(φ) are m / s, the unit of T is K, the unit of P is hPa, and the unit of the EGR rate is dimensionless. Additionally, the cylinder internal temperature T and the cylinder internal pressure P at the ignition point are geometrically determined from the specifications of internal combustion engine 100. The combustion velocity Vcon, which increases when dew condensation occurs, is a difference between the second combustion velocity VLb and the first combustion velocity VLa, for example, in Fig. 28 and is in a proportional relationship to the final dew condensation production quantity WQcon2. VL=VL,ref−e(φ)+Vcon VL,ref=0.305×(T298)1.87×(P1013)−0.12×(1−2.06×Y0.77)e(φ)=0.549×(φ−1.21)

[0191] Fig. Figure 29 is a flowchart illustrating a process for calculating the EGR gas correction quantity in an EGR gas correction quantity calculation unit 314. In the Fig. The processing shown in section 29 involves a calculation of the EGR gas correction quantity HOSegr of the Fig. 22 shown step S2206.

[0192] As in Fig. As shown in Figure 29, the EGR gas correction quantity calculation unit 314 reads the target EGR rate TEGR and the final dew condensation generation quantity WQcon2 (step S2901). Next, the EGR gas correction quantity calculation unit 314 calculates an EGR gas correction quantity HOSegr (step S2902). During the processing of step S2902, for example, if the EGR gas correction quantity HOSegr is obtained from the EGR gas correction table, which is shown in Figure 29, the EGR gas correction quantity HOSegr is calculated as follows: Fig. The table shown in section 24 is used. Then the EGR gas correction quantity calculation unit 314 is searched in the table shown. Fig. 24 shown in the table according to the value of the EGR gas correction quantity HOSegr from the final dew condensation generation quantity WQcon2 to obtain the EGR gas correction quantity HOSegr.

[0193] When the EGR gas correction quantity HOSegr is determined using the combustion rate, the EGR gas correction quantity calculation unit 314 determines the EGR gas correction quantity HOSegr according to expressions 23 and 24. Furthermore, the cylinder internal temperature T and the cylinder internal pressure P at the ignition time are determined geometrically from the specifications of the internal combustion engine 100. The equivalence ratio φ receives information from the control device 20 of the internal combustion engine.

[0194] Consequently, the corrected EGR rate HEGR can be calculated from the EGR gas correction amount HOSegr obtained from the EGR gas correction table, the combustion rate, and expression 22. The EGR valve opening control unit 315 then calculates an EGR valve opening command value to implement the calculated corrected EGR rate HEGR and transmits this command value to the EGR valve 41. This allows for appropriate correction of the flow of EGR gas recirculated into the intake air and enables ignition to be performed at a desired ignition timing without retarding it, even in the presence of dew condensation. This ensures good combustion without any deterioration in fuel consumption or reduction in torque. 7. Example of a time diagram of EGR gas correction

[0195] Next, an example of a time diagram is given when the EGR gas correction process described above is carried out, with reference to Fig. 30 described.

[0196] Fig. Figure 30 is a time diagram showing an example of the EGR gas correction process.

[0197] As in Fig.As shown in Figure 30, at time t = t0, when the combustion engine 100 is stopped, the temperature Tic of the coolant in the charge air cooler 7 is low, and dew condensation occurs. When the combustion engine 100 is running, the temperature Tic of the coolant in the charge air cooler 7 rises over time. At time t = t1, the amount WQsat of saturated moisture in the charge air cooler 7 is greater than the sum of the first moisture amount WQair, which is the moisture amount in the fresh air, and the second moisture amount WQegr, which is the moisture amount in the EGR gas. After time t1, no further dew condensation occurs in the charge air cooler 7.

[0198] Since dew condensation occurs in the charge air cooler 7 from time t0 to time t1, the EGR gas correction quantity HOSegr is added to the target EGR rate TEGR. If the temperature Tic of the coolant increases, the amount of saturated moisture WQsat increases, so the final dew condensation production quantity WQcon2 decreases. Therefore, the EGR gas correction quantity HOSegr also decreases. After time t = t1, the values ​​for the final dew condensation production quantity WQcon2 and the EGR gas correction quantity HOSegr become "0".

[0199] The invention is not limited to the embodiments described above and illustrated in the drawings, and various modifications can be made without deviating from the core of the invention described in the claims.

[0200] In the embodiment described above, an example was described in which the first moisture quantity WQair is calculated as the moisture quantity in the fresh air, the second moisture quantity WQegr is calculated as the moisture quantity of the EGR gas, and the total moisture quantity in the mixed gas is calculated. However, the present invention is not limited to this. For example, a sensor for detecting the moisture information in the mixed gas, in which the fresh air and the EGR gas are mixed, can be provided on the upstream side of the charge air cooler 7, and the moisture quantity contained in the mixed gas can be calculated from the moisture information detected by the sensor immediately before it enters the charge air cooler 7. This simplifies the process for calculating the moisture quantity. Reference symbol list 1 first humidity sensor 2 airflow sensors 3 Electronically controlled throttle valve 4 pressure sensor 5a Compressor 5b Turbine 6 variable valve 7 Intercoolers 9 Air-fuel ratio sensor 10 Three-way catalytic converter 11 Electronically controlled boost pressure control valve 12 Sensor for the degree of opening of the accelerator pedal 13 Injector 14 cylinders 15 Exhaust pipe 16 Spark plug 17 Intake air temperature sensor 18 Return valve 19 brake switches 20 Control device for internal combustion engine 22 Boost pressure sensor 25 Inlet valve 26 pistons 40 EGR flow path tube 41 EGR valve 42 EGR coolers 43 Differential pressure sensor 44 EGR temperature sensor 46 second humidity sensor 47, 48 Water temperature sensor 100 internal combustion engine 121 Microcomputer (control unit) 301, 301B first unit for calculating the amount of moisture 302, 302B, 302C, 302D second unit for calculating the amount of moisture 303 Dew condensation calculation unit 304 EGR correction unit 305 First unit for calculating absolute humidity 306 EGR flow calculation unit 307 Unit for calculating saturated absolute humidity 308B Unit for calculating the amount of saturated moisture 309 second unit for calculating absolute humidity 310 Unit for calculating saturated absolute humidity in the charge air cooler 311 Unit for calculating the total gas flow 312 Unit for calculating the amount of saturated moisture in the charge air cooler 313 Dew condensation determination unit 314 Calculation unit of the EGR gas correction quantity 315 EGR valve opening degree control unit WQair first moisture amount WQegr second moisture quantity WQsat amount of saturated moisture WQcon2 final dew condensation generation amount HOSegr EGR gas correction quantity

Claims

[1] Control device (20) for an internal combustion engine (100) which controls an internal combustion engine (100) which includes an intercooler (7) which cools the intake air and an EGR flow path pipe (40) which returns a portion of the exhaust gas in an exhaust path to an upstream side of the intercooler (7) as EGR gas, wherein the control device (20) for the internal combustion engine (100) comprises: a moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D) configured to calculate a total moisture quantity contained in a mixed gas obtained by mixing fresh air flowing into the charge air cooler (7) and the EGR gas; a dew condensation calculation unit (303) configured to calculate a dew condensation generation quantity (WQcon) in the charge air cooler (7) based on the total moisture quantity calculated by the moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D); a dew condensation determination unit (303) configured to set an end dew condensation generation quantity (WQcon2) to 0 if the calculated dew condensation generation quantity (WQcon) does not exceed a predetermined threshold (SL), and to set the end dew condensation generation quantity (WQcon2) to the calculated dew condensation generation quantity (WQcon) if the calculated dew condensation generation quantity (WQcon) exceeds the predetermined threshold (SL); an EGR correction unit (304) configured to correct a flow rate of the returned EGR gas based on the final dew condensation generation quantity (WQcon2) set by the dew condensation determination unit (303); a first moisture quantity calculation unit (301, 301B) configured to calculate a first moisture quantity (WQair) which is a moisture quantity contained in the fresh air; and a second moisture quantity calculation unit (302, 302B, 302C, 302D) configured to calculate a second moisture quantity (WQegr) which is a moisture quantity contained in the EGR gas, wherein the total moisture quantity is a sum of the first moisture quantity (WQair) and the second moisture quantity (WQegr), wherein the second moisture quantity calculation unit (301, 301B, 302, 302B, 302C, 302D) is designed to calculate the second moisture quantity (WQegr) based on a fuel property, a target EGR rate (TEGR) of the EGR gas before correction by the EGR correction unit (304) and an intake air quantity (Qair), and wherein the EGR correction unit (304) contains an EGR gas correction table in which EGR gas correction amounts (HOSegr) for correcting the EGR gas according to the final dew condensation generation amount (WQcon2) are set such that as the final dew condensation generation amount (WQcon2) increases the EGR gas correction amount (HOSegr). [2] Control device (20) for an internal combustion engine (100) according to claim 1, wherein the first moisture quantity calculation unit (301, 301B) calculates the first moisture content on the basis of moisture information from a first moisture sensor (1) which is arranged on an upstream side of a connection with the EGR flow path tube (40) and detects moisture in the fresh air. [3] Control device (20) for an internal combustion engine (100) according to claim 1, comprising: a unit (308B) for calculating the amount of saturated moisture, configured to calculate the amount of saturated moisture of an EGR cooler that cools the EGR gas before it is recirculated, wherein the second moisture quantity calculation unit (302, 302B, 302C, 302D) calculates the second moisture quantity based on the amount of saturated moisture of the EGR cooler calculated by the amount of saturated moisture calculation unit (308B), the fuel property, the target EGR rate and the intake air quantity. [4] Control device (20) for an internal combustion engine (100) according to claim 1, wherein the second moisture quantity calculation unit (302, 302B, 302C, 302D) calculates the second moisture quantity based on moisture information from a second moisture sensor (46) that detects moisture of the EGR gas flowing through the EGR flow path tube (40). [5] Control device (20) for an internal combustion engine (100) according to claim 1, comprising: a unit for calculating an amount of saturated moisture in the charge air cooler (7) which is configured to calculate an amount of saturated moisture in the charge air cooler (7), wherein the dew condensation calculation unit (303) calculates the dew condensation generation quantity on the basis of the total moisture quantity and the quantity of saturated moisture in the charge air cooler (7) calculated by the calculation unit of the quantity of saturated moisture in the charge air cooler (7). [6] Control device (20) for an internal combustion engine (100) according to claim 5, wherein the EGR correction unit (304) corrects a flow of the EGR gas on the basis of a target EGR rate of the EGR gas before correction and a dew condensation generation quantity calculated by the dew condensation calculation unit (303). [7] Control device (20) for an internal combustion engine (100) according to claim 6, wherein the EGR correction unit (304) calculates an EGR valve opening degree command value based on the target EGR rate and an EGR gas correction quantity to correct the EGR gas and outputs a calculated EGR valve opening degree command value to an EGR valve that controls a flow of the EGR gas. [8] Control device (20) for an internal combustion engine (100) according to claim 1, wherein the EGR correction unit (304) corrects the flow of the EGR gas such that the combustion rate when dew condensation occurs in the charge air cooler (7) is the same as the combustion rate when no dew condensation occurs. [9] Control device (20) for an internal combustion engine (100) according to claim 8, wherein the EGR correction unit (304) calculates the combustion speed on the basis of a cylinder internal pressure of a cylinder forming the internal combustion engine (100), a cylinder internal temperature of the cylinder, an equivalence ratio and an EGR rate. [10] Control device (20) for an internal combustion engine (100) according to claim 1, comprising: a dew condensation determination unit configured to calculate a final dew condensation production quantity based on the dew condensation production quantity calculated by the dew condensation calculation unit (303) and a preset threshold, wherein the EGR correction unit (304) corrects the flow rate of the EGR gas on the basis of the final dew condensation generation quantity calculated by the dew condensation determination unit.

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