Control device for internal combustion engine and control method for internal combustion engine

Abstract

To improve reliability and certainty of an estimation result when estimating a combustion chamber wall temperature from a change of a combustion chamber wall surface temperature.SOLUTION: A control device for an internal combustion engine is provided with an in-cylinder air amount calculation section that calculates an air amount flowing into a cylinder of the internal combustion engine on the basis of an air flow rate sensor. The control device for the internal combustion engine includes a calculation section that calculates an intermediate parameter indicating intake efficiency for calculating an in-cylinder inflow air amount on the basis of intake pipe pressure. The intermediate parameter is corrected on the basis of one or both of an estimation value or a measurement value of physical quantity that changes along with a change of a combustion chamber wall surface temperature in the cylinder of the internal combustion engine.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine and a control method for an internal combustion engine.

Background Art

[0002] Reduction of harmful components emitted from automobiles is essential. Usually, in order to reduce harmful components, a three-way catalyst for purifying harmful components is installed in the exhaust pipe of an automobile engine. In order to purify harmful components with the three-way catalyst, it is necessary to keep the ratio of air to fuel (air-fuel ratio) burned in the engine cylinder within a predetermined range. For the control used to keep the air-fuel ratio within a predetermined range, an air flow sensor installed in the intake duct of the engine or an intake pipe pressure sensor installed in the intake manifold is used. Then, using these sensors, the air flow rate inhaled into the engine cylinder is estimated, and control is performed to determine the fuel injection amount based on the estimated value.

[0003] For example, in a system using an air flow sensor, a difference occurs between the air flow rate measured by the air flow sensor and the air flow rate inhaled into the engine cylinder under conditions where the operating state of the engine changes transiently. Therefore, when determining the fuel injection amount based on the air flow rate measured by the air flow sensor, the air-fuel ratio may deviate from the predetermined range depending on the conditions. Therefore, control is performed to estimate the air flow rate inhaled into the engine cylinder under conditions where the operating state of the engine changes transiently. In the following description, this control is referred to as intake air metering control.

[0004] The intake air metering control for an engine equipped with an air flow sensor estimates the air flow rate inhaled into the engine cylinder by, for example, the following process. That is, the intake air metering control estimates the pressure in the intake manifold (intake pipe pressure) based on the air flow rate measured by the air flow sensor, and estimates the air flow rate inhaled into the engine cylinder based on the estimated intake pipe pressure and an intermediate parameter determined in advance by experiment or the like. This process of estimating the air flow rate inhaled into the engine cylinder is repeatedly executed.

[0005] Now, regarding the state related to the performance of an internal combustion engine, for example, there is the temperature of the wall of the combustion chamber of the internal combustion engine (hereinafter referred to as the wall surface temperature). Assume a state where the operating state of the engine switches from a low-output state to a high-output state and then operates to maintain a constant output. At this time, the temperatures of the walls constituting the combustion chamber of the internal combustion engine, specifically the piston crown surface, the cylinder liner wall surface, and the head wall surface (combustion chamber wall surface temperature), transiently increase and eventually reach a certain temperature (steady temperature).

[0006] Conversely, when the operating state of the engine switches from a high-output state to a low-output state and then operates to maintain a constant output, the combustion chamber wall surface temperature transiently decreases and eventually reaches the steady temperature. Under such conditions, an error is likely to occur in the estimated value of the intake pipe pressure estimated by intake air metering control. This is because while the relationship between the air flow rate and the intake pipe pressure realized by the combustion chamber wall surface temperature changes, normal intake air metering control cannot reproduce such changes.

[0007] As such a conventional technique related to the control of an internal combustion engine, for example, the control device described in Patent Document 1 is known. That is, Patent Document 1 discloses a control device for an internal combustion engine that includes means for correcting the air flow rate inhaled into the engine based on an estimated value of the combustion chamber wall surface temperature of the internal combustion engine.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] By the way, in the prior art as described in Patent Document 1, when correcting the air flow rate inhaled into the engine based on the estimated value of the combustion chamber wall temperature of the internal combustion engine, it is necessary to grasp in advance the relationship between the combustion chamber wall temperature of the internal combustion engine and the intermediate parameter (intake efficiency), and many experiments are required to investigate this relationship. In addition, the adaptation itself when estimating the temperature of the combustion chamber wall is also necessary. Further, in the prior art, even if the combustion chamber wall temperature is estimated, it is necessary to confirm the reliability of the correction.

[0010] The present invention has been made in view of the above, and an object of the present invention is to provide a control device for an internal combustion engine and a control method for an internal combustion engine that can improve the reliability and certainty of an estimation result when estimating a combustion chamber wall temperature based on a change in the combustion chamber wall temperature.

Means for Solving the Problems

[0011] In order to solve the above problems, for example, the configuration described in the claims is adopted. This application includes a plurality of means for solving the above problems. For example, as a control device for an internal combustion engine, it includes a cylinder internal air amount calculation unit that calculates the amount of air entering the cylinder of the internal combustion engine based on an air flow rate sensor. And the control device for the internal combustion engine includes a calculation unit that calculates an intermediate parameter indicating an intake efficiency for calculating an in-cylinder inflow air amount based on an intake pipe pressure, and the intermediate parameter is corrected based on one or both of an estimated value or a measured value of a physical quantity that changes as the combustion chamber wall temperature in the cylinder of the internal combustion engine changes.

Effects of the Invention

[0012] According to the present invention, in a state where the wall temperature of the combustion chamber transiently changes, the intermediate parameter used in the intake air metering control for calculating the air flow rate flowing into the engine based on the measured value of the air flow sensor can be simply and appropriately corrected. Therefore, according to the present invention, the estimation error of the intake pipe pressure estimated value can be reduced. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Mode for Carrying Out the Invention

[0014] Hereinafter, a control device for an internal combustion engine and a control method for an internal combustion engine according to each embodiment example of the present invention will be described with reference to the accompanying drawings. In the following embodiment examples, an internal combustion engine mounted on an automobile or the like and using gasoline as fuel will be exemplified and described, but the present invention can also be applied to other internal combustion engines having different fuel types, specifications, and uses.

[0015] <First Embodiment> The first embodiment of the present invention will be described with reference to FIGS. 1 to 11. FIG. 1 is a diagram schematically showing an example of the system configuration of an internal combustion engine mounted on an automobile, extracted together with related configurations. The internal combustion engine (Internal Combustion Engine ENG) illustrated in FIG. 1 is an in-cylinder injection type internal combustion engine for automobiles that is driven by spark ignition combustion. That is, the internal combustion engine shown in FIG. 1 includes an in-cylinder fuel injection mechanism that directly injects gasoline fuel into a plurality of cylinders, and an intake mechanism that supplies air into the cylinders. Further, the internal combustion engine shown in FIG. 1 includes an ignition mechanism that ignites the air-fuel mixture of the gasoline fuel and air injected into the cylinder, an exhaust mechanism that exhausts the air after combustion in the cylinder, and the like. In FIG. 1, only one of the plurality of cylinders is shown together with the related configuration.

[0016] The internal combustion engine ENG is provided with an air flow sensor 1 that measures the intake air amount (air flow rate) and the intake air temperature, an intake air pressure sensor 3 that measures the intake air pipe pressure (intake air pressure), an electronic control throttle 2 that adjusts the intake air pipe pressure, and an ECU 100 that is a control device for controlling the overall operation of the internal combustion engine ENG. The intake air pipe pressure adjusted by the electronic control throttle 2 can be referred to as the air flow rate. The air flow sensor 1 is referred to as an AFS (Air Flow Sensor). The intake air pressure sensor 3 is referred to as a MAP (Manifold Absolute Pressure sensor). The ECU is an abbreviation for Electronic Control Unit.

[0017] The detection results (output information) of various sensors such as the air flow sensor 1 and the intake air pressure sensor 3 are transmitted to the ECU 100. Further, the internal combustion engine ENG includes a fuel injection device 13 (hereinafter also referred to as an injector 13) that injects fuel into the cylinder 14 of each cylinder, and an ignition coil 16 and an ignition plug 17. In addition, the internal combustion engine ENG is provided with an ignition device for each cylinder that supplies ignition energy to the fuel injected into the cylinder 14.

[0018] The cylinder head is provided with a variable valve 5 that adjusts the air-fuel mixture flowing into the cylinder or the exhaust gas discharged from the cylinder for each cylinder. Then, by adjusting the variable valve 5, the intake air amount and the internal EGR amount of all the cylinders of the cylinder head are adjusted. An oil jet system 20 for lowering the piston temperature is provided on the back of the piston of each cylinder. The oil jet system 20 is connected to a variable displacement (hydraulically variable) oil pump 20a, and by adjusting the output (flow rate, oil pressure) of the oil pump, the amount of oil injected from the oil jet system 20 toward the piston is adjusted.

[0019] A high-pressure fuel pump (not shown) for supplying high-pressure fuel to the fuel injection device 13 is connected to the fuel injection device 13 by a fuel pipe. Further, the fuel injection device 13 is provided with a fuel pressure sensor for measuring the fuel injection pressure. The detection result (output information) of the fuel pressure sensor is transmitted to the ECU 100. An internal combustion engine ENG is equipped with a crank angle sensor 19 for detecting the piston position. The detection result (output information) of the crank angle sensor 19 is transmitted to the ECU 100.

[0020] The exhaust pipe 15 is provided with a three-way catalyst 10 for purifying the exhaust gas and an air-fuel ratio sensor 9 for detecting the air-fuel ratio of the exhaust gas on the upstream side of the three-way catalyst 10. Further, the internal combustion engine ENG is provided with a temperature sensor 18 for measuring the temperature of the cooling water circulating around the internal combustion engine ENG. The detection results (output information) of the air-fuel ratio sensor 9 and the temperature sensor 18 are transmitted to the ECU 100. The accelerator pedal is provided with an accelerator opening sensor 12. The accelerator opening sensor 12 detects the amount of depression of the accelerator pedal, that is, the accelerator opening. The detection result (output information) of the accelerator opening sensor 12 is transmitted to the ECU 100.

[0021] The ECU 100 calculates the required torque based on the output information from the accelerator opening sensor 12. That is to say, the accelerator opening sensor 12 can also be regarded as a required torque detection sensor that detects the required torque for the internal combustion engine. Further, the ECU 100 calculates the rotational speed of the internal combustion engine based on the output information of the crank angle sensor 19. The ECU 100 appropriately calculates the main operating amounts of the internal combustion engine, such as the air flow rate, fuel injection amount, ignition timing, and fuel pressure, based on the operating state of the internal combustion engine obtained from the output information of various sensors.

[0022] The fuel injection amount calculated by the ECU 100 is converted into an opening valve pulse signal and sent to the injector 13. Also, an ignition signal is sent to the ignition coil 16 so as to be ignited at the ignition timing calculated by the ECU 100. Further, the throttle opening calculated by the ECU 100 is sent to the electronic control throttle 2 as a throttle drive signal.

[0023] Fuel is injected from the injector 13 into the air flowing into the cylinder 14 from the intake pipe through the intake valve, thereby forming an air-fuel mixture. The air-fuel mixture is ignited (exploded) by the spark generated by the spark plug 17 at a predetermined ignition timing. Due to the combustion pressure caused by this ignition, the piston is pushed down, and the rotating shaft (crankshaft) connected to the piston via the connecting rod is rotationally driven, generating a driving force as the internal combustion engine ENG. Further, the exhaust gas after explosion is sent into the three-way catalyst 10 through the exhaust pipe 15, the exhaust components are purified in the three-way catalyst 10, and then discharged to the outside. Note that, in the internal combustion engine ENG in this embodiment example, a case where variable valve timing control (VTC: Variable Timing Control) that continuously adjusts the opening and closing timing of the intake valve according to the engine speed and load is adopted is exemplified.

[0024] Figure 2 is a diagram schematically showing the hardware configuration of the ECU 100, which is a control device for an internal combustion engine. In FIG. 2, the following output information and the like are input to the input circuit 21 of the ECU 100. That is, the air flow rate (intake air amount) from the air flow sensor 1 and the intake pipe pressure (intake pressure) from the intake pressure sensor 3 are input to the input circuit 21. Although not shown in FIG. 2, the primary coil voltage or secondary coil voltage from the voltage sensor of the ignition coil 16 is input to the input circuit 21.

[0025] Further, the fuel injection pressure from the fuel pressure sensor of the fuel injection device 13, the crank angle from the crank angle sensor 19, the air-fuel ratio of the exhaust gas (exhaust air-fuel ratio) from the air-fuel ratio sensor 9, and the temperature of the cooling water from the temperature sensor 18 are input to the input circuit 21 of the ECU 100. Furthermore, the accelerator opening (throttle opening) from the accelerator opening sensor 12, the rotational speed of the rotating shaft (crankshaft), and various setting values of the VTC (VTC setting) are input to the input circuit 21. The output information from these various sensors and the like becomes the input information of the ECU 100. Note that the input information input to the ECU 100 is not limited to these.

[0026] The input information input to the input circuit 21 of the ECU 100 is sent to the input port side within the input / output port 22. The input information sent to the input / output port 22 is temporarily stored in the RAM (Random Access Memory) 23c and is processed by arithmetic operations in accordance with a predetermined control program by the CPU 23a. The CPU 23a is an arithmetic processing unit called the Central Processing Unit. The control program describing the content of the arithmetic processing executed by the CPU 23a is pre-written in the ROM (read-only memory) 23b.

[0027] The output information indicating the operation amount to the fuel injection valve and ignition coil for controlling the internal combustion engine, which is calculated in accordance with the control program, is temporarily stored in the RAM 23c and then sent to the output port side within the input / output port 22 and sent to the ignition control unit 24, the fuel injection control unit 25, and the like. Note that actuators other than the actuators described so far are also used for the internal combustion engine ENG, but the description thereof is omitted here.

[0028] In this embodiment example, the ECU 100 has an ignition control unit 24 and a fuel injection control unit 25 as drive circuits. The ignition control unit 24 acquires information regarding the energization timing and energization time to the ignition coil 16 as the operation amount of an associated actuator, and controls the energization timing and energization time to the ignition coil 16 based on the acquired operation amount.

[0029] The fuel injection control unit 25 acquires information regarding the valve opening timing and valve opening period of the fuel injection device 13 as the operation amount of an associated actuator, and controls the valve opening timing and valve opening period of the fuel injection device 13 and the opening and closing of a valve for pressure adjustment provided in the fuel pressure pump based on the acquired operation amount. Note that, in this embodiment example, the ECU 100 is configured to include an ignition control unit 24 for controlling the energization time and discharge energy amount to the ignition coil, and a fuel injection control unit 25 for controlling the injection timing and injection period of the fuel injection device. However, this is just an example. That is, a part of each of the ignition control unit 24 and the fuel injection control unit 25 may be implemented in a device separate from the ECU 100.

[0030] FIG. 3 is a functional block diagram schematically showing intake air metering control in the ECU 100 of this embodiment example. The intake air metering control shown in FIG. 3 is a program executed by the CPU 23a in the ECU 100. In this intake air metering control, the air flow sensor measurement value, engine speed, and coolant temperature are input, and the cylinder inflow air flow rate is calculated. The intake pipe pressure estimation unit 301 calculates the pressure of the intake pipe based on the conservation equations of mass and energy and the gas state equation for the mass and energy within the volume from the throttle to the engine. Note that the mass conservation equation, the energy conservation equation, and the gas state equation can be described as follows.

[0031]

Equation

[0032]

Equation

[0033] [Number]

[0034] [Number]

[0035] Here, Equation [Number 1] is the mass conservation equation, Equation [Number 2] is the energy conservation equation, and Equation [Number 3] is the gas state equation. In these equations, t is time [s], m in is the gas mass in the intake pipe [kg], m atm is the air flow sensor measurement value (air flow rate) [kg / s], m egr is the EGR flow rate [kg / s], m cyl is the gas flow rate flowing into the cylinder (cylinder inlet gas flow rate) [kg / s]. Also, in these equations, e in is the specific internal energy of the gas in the intake pipe [J / kg], γ atm is the specific heat ratio of the atmosphere [-], γ egr is the specific heat ratio of the EGR gas [-], γ in is the specific heat ratio of the gas in the intake pipe [-], R atm is the gas constant of the atmosphere [J / kg / K], R egr is the gas constant of the EGR gas [J / kg / K].

[0036] Furthermore, in these equations, R in is the gas constant of the gas in the intake pipe "J / kg / K", T atm is the atmospheric temperature [K], T egr is the EGR gas temperature [K], T in is the gas temperature in the intake pipe (intake pipe temperature), V in is the intake pipe volume [m 3 , α in is the heat transfer coefficient [W / m2 / K], S in is the area of contact between the intake pipe and the gas [m 2 , Twall is the temperature of the intake pipe wall surface [K], P inis the intake pipe pressure. Note that m atm and m egr and m cyl As shown in each formula, the actual notation is [·] added above m. In the notation in the following specification, [·] above m is similarly omitted.

[0037] The specific heat ratio and gas constant are physical quantities that change depending on the gas composition. Each gas composition can be assumed and determined with reference to experimental results, literature values, etc. The heat transfer coefficient can also be determined by fitting it to the previously conducted experiments. The EGR flow rate estimation unit 306 calculates the EGR flow rate, and the cylinder inflow gas flow rate calculation unit 303 calculates the cylinder inflow gas flow rate. The EGR gas temperature can be approximated by the cooling water temperature passing through the EGR cooler, or obtained by referring to a map experimentally fitted in advance with the operating conditions and the cooling water temperature as axes.

[0038] [Equation 1] and [Equation 2] are equations for numerically integrating to calculate the gas mass m in in the intake pipe and the specific internal energy e in in the intake pipe after the values of the variables on the right side are given. Furthermore, by substituting the gas mass m in in the intake pipe obtained by [Equation 1] and the specific internal energy e in in the intake pipe obtained by [Equation 2] into [Equation 3], the gas temperature T in is calculated, and by substituting these into [Equation 4], the intake pipe pressure P in is calculated.

[0039] The intake efficiency calculation unit 302 calculates the intake efficiency, which is an intermediate parameter of the intake metering control. The calculation method of the intake efficiency will be described in detail using FIG. 4 and the like. The cylinder inflow gas flow rate calculation unit 303 calculates the gas flow rate flowing into the engine cylinder based on the estimated intake pipe pressure and the intake efficiency. Note that the cylinder gas flow rate is calculated by the following [Equation 5].

[0040]

Equation

[0041] Here, η is the intake efficiency [-], N e is the rotational speed [rpm], V D is the displacement per cylinder [m3], n cyl is the number of cylinders [-]. The cylinder inflow air flow rate calculation unit 304 calculates the cylinder inflow gas flow rate based on the cylinder gas flow rate and the EGR rate. That is, the cylinder inflow air flow rate calculation unit 304 calculates the air flow rate (cylinder inflow air flow rate) flowing into the cylinder using the gas flow rate calculated by the cylinder gas flow rate calculation unit 303 and the EGR rate calculated by the EGR distribution estimation unit 307 described later. Specifically, the cylinder inflow air flow rate is calculated by the following Equation 6.

[0042]

Equation

[0043] Here, m air is the cylinder inflow air flow rate [kg / s], y EGR is the EGR rate [-] calculated by the EGR distribution estimation unit 307. The exhaust pressure estimation unit 305 estimates the exhaust pressure based on the cylinder inflow gas flow rate and the rotational speed. For example, the exhaust pressure estimation unit 305 creates a map of the exhaust pressure with the cylinder inflow gas flow rate and the rotational speed as axes in advance based on experiments and simulations, and estimates the exhaust pressure using the map.

[0044] The EGR flow rate estimation unit 306 calculates the estimated intake pipe pressure value, the estimated exhaust pressure value, and the EGR gas flow rate flowing into the intake pipe. For example, the EGR flow rate estimation unit 306 creates a map with the differential pressure between the estimated exhaust pressure value and the estimated intake pipe pressure value and the EGR valve opening as axes in advance based on experiments and simulations, and estimates the EGR flow rate using the map. The EGR distribution estimation unit 307 estimates the distribution of the EGR gas in the intake pipe based on the EGR gas flow rate, and calculates the EGR rate of the gas flowing into the cylinder. First, the EGR rate is calculated by the following [Equation 7].[[]END]]

[0045]

Number

[0046] Furthermore, as a means for estimating the distribution of the EGR gas and calculating the EGR rate of the gas flowing into the cylinder, the EGR distribution estimation unit 307 calculates it by applying a first-order lag filter. For example, when calculating the EGR rate of the gas flowing into the cylinder, the EGR distribution estimation unit 307 can be calculated using the following [Equation 8].

[0047]

Number

[0048] Here, y EGR,d is the EGR rate [―] of the gas flowing into the cylinder calculated by applying a first-order lag filter, Δt is the calculation period [s], and τ EGR is the delay time [s]. In [Equation 8], the EGR rate y EGR,d of the gas flowing into the cylinder calculated by applying a first-order lag filter is expressed as a function of time, and the value at time t + Δt (y EGR,d (t + Δt)) is calculated from the value at time t (y EGR,d (t)) and the EGR rate obtained by [Equation 7]. Note that the delay time τ EGR depends on the pipe length from the part where the EGR gas and air merge to the engine cylinder, etc., and needs to be determined according to the operating conditions by engine tests and simulations. Through the processing described above, the calculation of the air flow rate flowing into the cylinder is performed.

[0049] FIG. 4 is a functional block diagram showing the processing contents of the intake efficiency calculation unit 302 in FIG. 3. The basic intake efficiency calculation unit 401 calculates a reference intake efficiency based on the rotational speed and the estimated intake pipe pressure value. In this embodiment, the intake efficiency is defined by the following [Equation 9].

[0050]

Number

[0051] [Number 9] The intake efficiency η shown in the formula is adapted by conducting experiments and simulations under the conditions (steady conditions) where the engine reaches a steady state. For example, when operating under steady conditions with the EGR flow rate set to 0, the time-averaged value of the cylinder inlet gas flow rate m cyl is consistent with the time-averaged value of the air flow rate m AFM measured by the air flow sensor. Utilizing this, the time-averaged value of the air flow rate measured by the air flow sensor obtained from the test under steady conditions can be substituted into the cylinder inlet gas flow rate m cyl to calculate the reference intake efficiency (basic intake efficiency).

[0052] The basic intake efficiency calculation unit 401 creates a map with the rotational speed and intake pipe pressure as axes from the basic intake efficiency calculated in this way. During engine operation, the intake efficiency is calculated by searching this map based on the rotational speed and the estimated intake pipe pressure. Note that since this map is created based on the experimental results obtained under steady conditions, it is created based on the data measured when the combustion chamber wall temperature reaches a steady state.

[0053] Therefore, if the wall temperature is in a state different from the steady state (transient state) during engine operation, the intake efficiency calculated by referring to the map does not match the intake efficiency during operation, and there is an error in the calculated value of the intake efficiency, resulting in an error in the estimated value of the intake pipe pressure. In this exemplary embodiment, a wall temperature correction unit 402 is provided to correct the error in the calculated value of the intake efficiency when the engine state during operation is in a transient state.

[0054] The wall temperature correction unit 402 calculates a correction value for the intake efficiency, which is an intermediate parameter, based on a wall temperature correlation physical quantity that is a physical quantity that changes with the change in the combustion chamber wall temperature, and determines whether the wall temperature is in a transient state and performs correction. The change in the combustion chamber wall temperature is either one or both of the estimated value and the measured value. The intake efficiency correction value K calculation unit 403 calculates the correction value of the intake efficiency, and the wall surface temperature transient determination unit 404 sets a flag indicating whether the wall surface temperature is in a transient state. Next, the switch unit 405 selects a process according to the flag.

[0055] FIG. 5 is a flowchart showing the processing content of the wall surface temperature correction unit 402 of the intake efficiency calculation unit 302. First, the intake efficiency correction value K calculation unit 403 of the wall surface temperature correction unit 402 estimates the steady value of the wall temperature correlation parameter in step S501. For example, when using the intake pipe pressure as the wall temperature correlation parameter, the engine continues to operate under the operating conditions (torque, rotational speed, etc.) during operation. Therefore, the wall surface temperature correction unit 402 can consider the intake pipe pressure when the wall surface temperature reaches a steady state as the steady value. Subsequently, the intake efficiency correction value K calculation unit 403 of the wall surface temperature correction unit 402 calculates the intake efficiency correction value K based on the following equation (10) in step S502.

[0056]

Equation

[0057] Here, C is a coefficient, F m is the measured or estimated value of the wall temperature correlation parameter during operation, F st is the steady value of the wall surface correlation parameter. The coefficient C is a numerical value whose sign changes according to the correlation with the wall temperature correlation parameter. If a physical quantity having a positive correlation with the wall temperature (a physical quantity that increases as the wall temperature increases) is used as the wall temperature correlation parameter, C becomes a negative value. Also, if a physical quantity having a negative correlation with the wall surface temperature (a physical quantity that decreases as the wall temperature increases) is used as the wall temperature correlation parameter, C becomes a positive value. Subsequently, the wall surface temperature transient determination unit 404 of the wall surface temperature correction unit 402 determines whether the wall surface temperature is in a transient state, that is, whether the wall surface temperature deviates from the steady temperature, based on the following equation (11) in step S503.

[0058]

Equation

[0059] Here, e is a coefficient provided for transient determination and is ideally 0. However, due to signal noise, vibration, etc., an appropriate numerical value e is selected. When it is determined to be True (= transient) in step S503, the wall surface temperature correction unit 402 proceeds to step S504, determines that the wall surface temperature is in a transient state and the intake efficiency correction value K does not need to be changed, and ends the process.

[0060] When it is determined to be False (= steady state) in step S503, the wall surface temperature correction unit 402 proceeds to step S505, changes the intake efficiency correction value K to 1, and ends the process. Note that steps S501 and S502 are processes performed by the intake efficiency correction value K calculation unit 403. Also, step S503 is a process performed by the wall temperature transient determination unit 404, and steps S504 and S505 are processes performed by the switch unit 405.

[0061] Next, the case of using the intake pipe pressure as the wall temperature correlation parameter will be described. Since the intake pipe pressure is a physical quantity that increases as the wall surface temperature increases, C in Equation [3] is set to a negative value. For example, when the value of C is set to -1, the correction formula becomes as shown in the following Equation

[12] .

[0062]

Equation

[0063] Here, p in,m is the measured value of the intake pipe pressure, and p in,s is the intake pipe pressure (intake pipe pressure steady value) when the combustion chamber wall surface temperature reaches a steady value.

[0064] Figure 6 is a schematic diagram of a map for calculating the intake pipe pressure steady value p_(in,st). For example, as shown in FIG. 6A, a map having the rotation speed and the gas flow rate (air flow rate or the sum of the air flow rate and the EGR flow rate) as axes may be used. Alternatively, as shown in FIG. 6B, a map having the rotation speed, the throttle opening, and the EGR opening as axes may be used. Also, the gas temperature in the intake pipe may be provided on the axes of each map. Further, maps using different axes may be switched and used according to conditions. These maps are maps created based on data acquired when the engine is in a steady state.

[0065] FIG. 7 is a diagram showing the time change of the estimated intake pipe pressure when the intermediate parameter (intake efficiency) is corrected based on the measured intake pipe pressure. From the top of FIG. 7, the throttle opening, the wall temperature, the intake efficiency correction value, the intake pipe pressure, and the air flow rate are shown respectively. The horizontal axis represents time. The diagram of the wall temperature shows the steady state value of the wall temperature by a dotted line and the measured value by a solid line. The diagram of the intake pipe pressure shows the measured value by a solid line, the estimated value according to the present application by a broken line, the estimated value in the case without correction (correction coefficient K is 1) by a one-dot chain line, and the steady state value by a dotted line. The diagram of the air flow rate shows the steady state value by a dotted line and the measured value by a solid line. The diagram of the throttle opening shows that it starts to open from time t0 and the throttle opening becomes constant after time t1. After the throttle opening becomes constant, at time t s the wall temperature reaches the steady state value. Between time t1 and t s the wall temperature gradually increases due to the change in the engine output accompanying the change in the throttle opening.

[0066] At this time, the measured value (solid line) of the intake pipe pressure gradually increases, and the measured value (solid line) of the air flow rate gradually decreases. A difference occurs between the measured value of the intake pipe pressure and the steady state value (dotted line) of the intake pipe pressure. This difference is the correlation between the difference between the steady state value (dotted line) and the measured value (solid line) of the wall temperature. When the intake efficiency is corrected using Equation

[12] , the intake efficiency correction value is calculated as a value greater than 0. As shown in the diagram of the intake pipe pressure, the estimated intake pipe pressure (broken line) in the present embodiment (with correction) shows a good agreement with the measured value. On the other hand, when the intake efficiency is not corrected (when the present embodiment is not applied), the estimated value (without correction) is the estimated result of the intake pipe pressure as shown by the dashed-dotted line, and the error from the measured value becomes large.

[0067] Here, as a supplement, the derivation process of Equation

[12] will be described, and it will be explained that the difference between the measured value of the intake pipe pressure and the steady value of the intake pipe pressure becomes apparent under the influence of the wall temperature. The intake efficiency is a function of the intake pipe pressure, engine speed, and cylinder wall temperature.

[0068]

Equation

[0069] Here, η is the intake efficiency, p in is the intake pipe pressure, N e is the engine speed, T w is the combustion chamber wall temperature. Assuming that the combustion chamber wall temperature is close to the steady temperature, the right side is Taylor-expanded.

[0070]

Equation

[0071]

Equation

[0072] Here, T w,st is the wall temperature steady value. Since the change in the in-cylinder gas temperature accompanying the change in the wall temperature changes the intake efficiency, the intake efficiency can be considered as a function of the in-cylinder gas temperature, and thus the equation is further transformed.

[0073]

Equation

[0074] Here, T cylis the gas temperature [K] inside the engine cylinder. Further, transform Equation

[16] to make it a function of the gas temperature inside the engine cylinder.

[0075]

Number

[0076] Here, derive the equation for the partial derivative of the intake efficiency with respect to the gas temperature inside the cylinder. Equation

[17] is derived by expressing the amount of gas inhaled into the cylinder in two types of equations. Calculate the amount of gas inhaled in one combustion cycle by multiplying Equation [1] by the time of one combustion cycle (two engine rotations).

[0077]

Number

[0078] Here, M 1cyc is the amount of gas inhaled in one combustion cycle [kg], R is the gas constant [J / kg / K], T in is the gas temperature [K] in the intake pipe, V D is the displacement volume [m3] per cylinder, n cyl is the number of cylinders [-]. Also, assuming that the pressure inside the cylinder at the intake valve closing time (IVC: Intake Valve Close) is equal to the intake pipe pressure and the temperature inside the cylinder is equal to the gas temperature in the intake pipe, the amount of gas entering one cylinder at the timing when the intake valve is closed can be calculated by the following Equation

[19] .

[0079]

Number

[0080] Here, M cyl,gas is the amount of gas [kg] inside the cylinder at the intake valve closing time, V IVC is the cylinder volume at the intake valve closing time. The value obtained by summing M cyl,air for the number of cylinders is the amount of gas inhaled in one combustion cycle, and M1cyc It is equal to this. From this, by setting the product of the formula [Equation 18] and the number of cylinders of the engine equal to the formula [Equation 19] and arranging it as a formula for the intake efficiency, the following formula [Equation 20] is obtained.

[0081]

Number

[0082] By differentiating both sides of the [Equation 20] with respect to the gas temperature in the cylinder, a partial differential formula [Equation 21] of the intake efficiency with respect to the gas temperature in the cylinder is obtained.

[0083]

Number

[0084] The intake efficiency correction formula of the [Equation 22] is obtained from the [Equation 17] and the [Equation 21].

[0085]

Number

[0086]

Number

[0087] Here, T cyl,st is the gas temperature [K] in the cylinder under the steady cylinder wall temperature condition. Next, when differentiating the [Equation 19] under the condition that the mass in the cylinder is constant, the relationship of the [Equation 24] between the gas temperature in the cylinder and the intake pipe pressure is obtained.

[0088]

Number

[0089] Furthermore, as in the following [Equation 25], the fluctuation component δ pin of the intake pipe pressure is determined.

[0090]

Number

[0091] If determined in this way, the [Equation 23] can be transformed into the [Equation 26], and it can be seen that the intake efficiency correction amount has a relationship with the intake pipe pressure change.

[0092]

Number

[0093] In this way, the intake efficiency correction formula is not derived from just the correlation of phenomena. Although some approximations are needed, it is a relationship derived based on physical formulas and is not equivalent to just a fitting. Subsequently, the case of using the air flow rate as the wall temperature correlation parameter will be described. Since the air flow rate is a physical quantity that decreases as the wall surface temperature increases, set C in the [Equation 3] to a positive value. For example, if set to 1, the correction formula becomes as follows in the [Equation 27].

[0094]

Number

[0095] Here, m m is the measured value of the air flow rate, and m st is the steady value of the air flow rate. Figure 8 is a schematic diagram of a map for calculating the steady value m st of the air flow rate. For example, as shown in Figure 8A, use a map with the rotational speed and throttle opening as axes. In addition to this, as shown in Figure 8B, it may also be a map with the rotational speed and intake pipe pressure as axes. Also, the gas temperature in the intake pipe may be provided on the axes of each map. Furthermore, maps using different axes may be switched and used according to the conditions. These maps are maps created based on data obtained when the engine is in a steady state. When referring to the map in Figure 8B, the measured value of the intake pipe pressure is used.

[0096] FIG. 9 is a diagram showing the time change of the estimated intake pipe pressure when the intermediate parameter (intake efficiency) is corrected based on the measured air flow rate. Similar to FIG. 7, the throttle opening, wall temperature, intake efficiency correction value, intake pipe pressure, and air flow rate are shown in order from the top. The horizontal axis represents time. In the diagram of the wall temperature, the steady-state value of the wall temperature is shown by a dotted line, and the measured value is shown by a solid line. In the diagram of the intake pipe pressure, the measured value is shown by a solid line, the estimated value according to the present application is shown by a broken line, and the estimated value in the case without correction (correction coefficient K is 1) is shown by a one-dot chain line.

[0097] In the diagram of the air flow rate, the steady-state value is shown by a dotted line, and the measured value is shown by a solid line. In the diagram of the throttle opening, it shows that the throttle opening starts to open from time t0 and becomes constant after time t1. After the throttle opening becomes constant, the wall temperature reaches the steady-state value at time ts. Between time t1 and t s Until, due to the change in the engine output accompanying the change in the throttle opening, the wall temperature gradually increases. At this time, a difference occurs between the measured value (solid line) of the air flow rate and the steady-state value (dotted line) of the air flow rate. This difference is the correlation between the difference between the steady-state value (dotted line) and the measured value (solid line) of the wall temperature.

[0098] By calculating the intake efficiency correction value using Equation

[27] , it can be seen that the estimated intake pipe pressure (broken line) in the embodiment of the present example (with correction) shows a good agreement with the measured value. On the other hand, when the intake efficiency is not corrected, the estimated value of the intake pipe pressure (without correction) becomes the estimated result of the intake pipe pressure as shown by the one-dot chain line, and the error from the measured value is large.

[0099] Next, the case of using the gas flow rate as the wall temperature correlation parameter will be described. Since the gas flow rate is a physical quantity that decreases as the wall temperature increases, C in Equation [3] is set to a positive value. For example, it can be set to 1, and the correction formula becomes as follows in Equation

[28] .

[0100]

Equation

[0101] Here, m g,m is the gas flow rate during operation, and m g,st is the steady-state value of the gas flow rate. The gas flow rate is the flow rates of air and EGR gas. In a system equipped with a flow meter for measuring the EGR gas flow rate, it can be given by the measured value. Also, when not equipped with a flow meter for measuring the EGR gas flow rate, it is necessary to estimate based on the intake pipe pressure, exhaust pressure, and EGR valve opening degree. For example, by creating in advance a matching map of the steady-state EGR gas flow rate with the difference between the intake pipe pressure and the exhaust pressure and the EGR valve opening degree as axes, during operation, it can be estimated based on the same map.

[0102] Figure 10 is a schematic diagram of a map for calculating the steady-state value m g,st of the gas flow rate. For example, as shown in Figure 10A, the map can have the engine speed, throttle opening degree, and EGR valve opening degree as axes. Additionally, as shown in Figure 10B, the map can also have the engine speed and intake pipe pressure as axes. Also, the gas temperature in the intake pipe can be provided on the axes of each map. Furthermore, the map can be switched and used according to conditions with different axes. These maps are maps created based on data obtained when the engine is in a steady state. When referring to Figure 10B, the measured value of the intake pipe pressure is used.

[0103] Figure 11 is a diagram showing the time change of the estimated intake pipe pressure when correcting the intermediate parameter (intake efficiency) based on the estimated gas flow rate. Similar to Figures 7 and 9, Figure 11 shows, from top to bottom in order, the throttle opening degree, wall temperature, intake efficiency correction value, intake pipe pressure, and gas flow rate. The diagram of the wall temperature shows the steady-state value of the wall temperature with a dotted line and the measured value with a solid line. The diagram of the intake pipe pressure shows the measured value with a solid line, the estimated value according to the present application with a dashed line, and the estimated value in the case without correction (with the correction coefficient K being 1) with a one-dot chain line. The diagram of the gas flow rate shows the steady-state value with a dotted line and the measured value or estimated value with a solid line. The diagram of the throttle opening degree shows that it starts to open from time t0 and the throttle opening degree becomes constant after time t1.

[0104] After the throttle opening becomes constant, the wall surface temperature reaches a steady state value at time ts. From time t1 to t s Until then, due to the change in the engine output accompanying the change in the throttle opening, the wall surface temperature gradually increases. At this time, there is a difference between the measured or estimated value of the gas flow rate and the steady-state value of the gas flow rate (dotted line). This difference is the correlation between the difference between the steady-state value of the wall surface temperature (dotted line) and the measured value (solid line). As described above, by calculating the intake efficiency correction value using Equation

[28] , the estimated value of the intake pipe pressure (broken line) in the embodiment of the present example (with correction) shows a good agreement with the measured value. On the other hand, when the intake efficiency is not corrected, that is, when there is no correction, the estimated result of the intake pipe pressure as shown by the dashed-dotted line is obtained, and the error from the measured value shown by the solid line becomes large.

[0105] As described above, by correcting using the estimated or measured value of the physical quantity that changes with the change in the combustion chamber wall surface temperature, it becomes possible to correct the intake efficiency with the data obtained in the steady state and a simple correction formula. As a result, it is possible to suppress the man-hours for adaptation and realize the correction.

[0106] <Second Embodiment Example> Next, a second embodiment of the present invention will be described with reference to FIGS. 12 to 15. In this embodiment, the system configuration of the internal combustion engine, the hardware configuration of the ECU, and the intake air metering control processing example are the configurations described with reference to FIGS. 1 to 3 in the first embodiment, respectively, and redundant descriptions are omitted.

[0107] FIG. 12 is a functional block diagram showing the processing content of the intake efficiency calculation unit 302. The basic intake efficiency calculation unit 1201 is a processing unit that calculates a reference intake efficiency based on the rotational speed and the estimated value of the intake pipe pressure. The reference intake efficiency is mapped with the rotational speed and the intake pipe pressure as axes, and during operation, a value is retrieved and calculated based on the rotational speed and the estimated value of the intake pipe pressure. Note that the same map conforms to the data measured when the combustion chamber wall surface temperature reaches a steady state.

[0108] The wall temperature correction unit 1202 calculates a correction value for the intake efficiency, which is an intermediate parameter, based on the difference between the steady-state value of the wall temperature, which is a physical quantity that changes with the change in the combustion chamber wall temperature, and the wall temperature during operation. Then, the wall temperature correction unit 1202 determines whether the wall temperature is in a transient state and performs the correction. The wall temperature difference calculation unit 1203 calculates the difference between the steady-state value of the wall temperature and the wall temperature during operation (the difference from the steady temperature).

[0109] The intake efficiency correction value K calculation unit 1204 calculates a correction value for the intake efficiency based on the difference from the steady temperature. The wall temperature transient determination unit 1205 sets a flag indicating whether the wall temperature is in a transient state. The switch unit 1206 performs a selection process based on the flag set by the wall temperature transient determination unit 1205.

[0110] FIG. 13 is a flowchart showing the processing contents of the wall temperature correction unit 1202 of the intake efficiency calculation unit 302. First, the wall temperature correction unit 1202 estimates the wall temperature steady-state value in step S1301. Subsequently, the wall temperature difference calculation unit 1203 calculates the difference from the wall temperature steady-state value as shown in Equation

[29] in step S1302.

[0111]

Equation

[0112] Here, the correction T w is the measured or estimated value of the wall temperature, and T w,st is the wall temperature steady-state value. Subsequently, the intake efficiency correction value K calculation unit 1204 calculates the intake efficiency correction value K as shown in Equation

[30] in step S1303.

[0113]

Equation

[0114] Here, T inis the gas temperature in the intake pipe, and measured or estimated values may be used. Note that Equation

[30] can also be derived by the following procedure. When the temperature of the air inhaled into the engine cylinder changes due to heat transfer on the surface of the cylinder wall, the energy conservation equation is given by the following equation.

[0115]

Equation

[0116] Here, c p is the specific heat at constant pressure [J / kg / K], h tr is the heat transfer coefficient [W / m2 / K], S cyl is the cylinder wall area [m 2 . Integrating Equation

[31] with constants other than the gas temperature in the cylinder, and setting the initial value as the gas temperature T in the intake pipe in yields the equation for the gas temperature in the cylinder shown in Equation

[32] .

[0117]

Equation

[0118]

Equation

[0119] Here, α may be calculated according to the operating conditions and various detected values, or may be calculated with an approximate value given. For example, a trial calculation shows that it becomes a value of about 0.5 to 1. Next, differentiating Equation

[32] gives Equation

[34] for the partial derivative of the gas temperature in the cylinder with respect to the cylinder wall temperature.

[0120]

Equation

[0121] From the expressions [Equation 16], [Equation 33], and [Equation 34], the following [Equation 35] is obtained.

[0122]

Equation

[0123] Therefore, the intake efficiency correction amount K is given by the following [Equation 36].

[0124]

Equation

[0125] Thus, the intake efficiency correction amount K is not derived merely for adjustment but is calculated based on the equation that governs the physical phenomenon. In step S1304, the wall temperature transition determination unit 1205 determines whether the wall surface temperature is in a transient state based on the following [Equation 37].

[0126]

Equation

[0127] Here, e is a coefficient provided for transient determination and is ideally 0. However, due to signal noise, vibration, etc., it is necessary to select an appropriate value for e. Next, if it is determined as True (= transient) in step S1304, the process proceeds to step S1305, and the switch unit 1206 determines that the wall surface temperature is in a transient state and the correction value K does not need to be changed, and ends the process. If it is determined as False (= steady state) in step S1304, the process proceeds to step S1306, and the switch unit 1206 changes the correction value K to 1 and ends the process.

[0128] FIG. 14 is a schematic diagram of a map for calculating the steady wall temperature value. For example, the map may have the rotational speed and the gas flow rate as axes. This map is created based on the data acquired when the engine is in a steady state.

[0129] FIG. 15 is a diagram showing the time change of the intake pipe pressure estimated value when the intermediate parameter (intake efficiency) is corrected based on the difference between the estimated wall temperature and the steady wall temperature (the difference from the steady temperature). FIG. 15 shows, in order from the top, the throttle opening, the wall surface temperature, the corrected intake efficiency value, the intake pipe pressure, and the gas flow rate. The horizontal axis represents time. In the diagram of the wall surface temperature, the steady wall temperature value is shown by a dotted line and the measured value is shown by a solid line. In the diagram of the intake pipe pressure, the measured value is shown by a solid line, the estimated value according to the present application is shown by a broken line, and the estimated value in the case of no correction (correction coefficient K is 1) is shown by a one-dot chain line.

[0130] In the diagram of the gas flow rate, the measured value or the estimated value is shown by a solid line. The diagram of the throttle opening shows that the throttle starts to open from time t0 and the throttle opening becomes constant after time t1. After the throttle opening becomes constant, at time t s the wall surface temperature reaches the steady value. From time t1 to t s until, due to the change in the engine output accompanying the change in the throttle opening, the wall surface temperature gradually increases. Naturally, during this period, the wall surface temperature has a difference from the steady wall temperature value. Focusing on this difference, it has been found that the equation that can be easily corrected using the model equation is Equation

[36] .

[0131] According to the present embodiment, the corrected intake efficiency value is appropriately calculated using Equation

[36] , and the estimated intake pipe pressure value (broken line) shows a good agreement with the measured value. On the other hand, when the intake efficiency is not corrected, that is, in the case of no correction, the estimated result of the intake pipe pressure as shown by the one-dot chain line is obtained, and it can be seen that the error from the measured value becomes large. As described above, according to the second embodiment, by using the difference from the steady value of the wall surface temperature, it becomes possible to correct the intake efficiency without having a map of the intermediate parameter (intake efficiency) with respect to the wall surface temperature.

[0132] <The Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. 16 to 17. In this embodiment, the system configuration of the internal combustion engine, the hardware configuration of the ECU, and the intake air metering control processing example are the configurations described with reference to FIGS. 1 to 3 in the first embodiment, respectively. Also, the processing configuration of the intake air efficiency calculation unit is the configuration described with reference to FIG. 4 in the first embodiment, and the map for calculating the steady-state value of the intake pipe pressure is the one described with reference to FIG. 6 in the first embodiment and is applied. Duplicate descriptions of these configurations and processes in the first embodiment are omitted.

[0133] FIG. 16 is a flowchart showing the processing content of the wall surface temperature correction unit 402 of the intake air efficiency calculation unit 302 in FIG. 4. First, the intake air efficiency correction value K calculation unit 403 of the wall surface temperature correction unit 402 estimates the steady-state value of the intake pipe pressure in step S1601. This can be estimated using the relationship shown in FIG. 6. Subsequently, in step S1602, the intake air efficiency correction value K calculation unit 403 calculates the intake air efficiency correction value K based on the following formula.

[0134]

Equation

[0135] Here, C is a coefficient, and p in,e is the estimated value of the intake pipe pressure. The coefficients C and D are negative real numbers. For example, C can be set to -1 and D to -2, etc. The coefficients C and D can be set otherwise. Note that the second term on the right side of Equation

[38] is a term that corrects the difference between the wall surface temperature of the engine during actual operation and the steady state, and the third term on the right side of Equation

[38] is a term that corrects the difference between the wall surface temperature of the engine that is not explicitly represented in the intake air metering control but is implicitly recognized in the calculation and the steady state. Subsequently, the wall temperature transient determination unit 404 determines in step S1603 whether the wall surface temperature is in a transient state based on the following formula, that is, whether the wall surface temperature is away from the steady-state temperature.

[0136]

Equation

[0137] Here, e is a coefficient provided for transient determination, and ideally it is 0. However, due to signal noise, vibration, etc., it is necessary to select an appropriate value for e. If it is determined to be True (= transient) in step S1603, the process proceeds to step S1604, and the switch unit 405 determines that the wall surface temperature is in a transient state and the correction value K does not need to be changed, and ends the process.

[0138] If it is determined to be False (= steady state) in step S1603, the process proceeds to step S1605, and the switch unit 405 changes the correction value K to 1 and ends the process. Note that steps S1601 and S1602 are processes implemented by the intake efficiency correction value calculation unit 403 in FIG. 4, step S1603 is the process of the wall temperature transient determination unit 404 in FIG. 4, and steps S1604 and S1605 are the processes of the switch unit 405 in FIG. 4.

[0139] FIG. 17 is a diagram showing the time change of the intake pipe pressure estimated value when the intermediate parameter (intake efficiency) is corrected based on the measured intake pipe pressure value and the estimated intake pipe pressure value. FIG. 17 shows, in order from the top, the throttle opening, the wall surface temperature, the intake efficiency correction value, the intake pipe pressure, and the air flow rate. The horizontal axis represents time. In the diagram of the wall surface temperature, the dotted line indicates the steady state value of the wall surface temperature, and the solid line indicates the measured value. In the diagram of the intake pipe pressure, the solid line indicates the measured value, the broken line indicates the estimated value according to the present application, the one-dot chain line indicates the estimated value in the case without correction (the correction coefficient K is 1), and the dotted line indicates the steady state value. In the diagram of the air flow rate, the dotted line indicates the steady state value, and the solid line indicates the measured value.

[0140] The example in FIG. 17 shows the case where the throttle opening starts to open from time t0 and becomes constant after time t1. After the throttle opening becomes constant, at time t s the wall surface temperature reaches the steady state value. From time t1 to t sUntil then, due to the change in the engine output accompanying the change in the throttle opening, the wall surface temperature gradually increases. At this time, the measured value (solid line) of the intake pipe pressure gradually increases, and the measured value (solid line) of the air flow rate gradually decreases. A difference occurs between the measured value of the intake pipe pressure and the steady-state value of the intake pipe pressure (dotted line). This difference is the correlation between the steady-state value of the wall surface temperature (dotted line) and the measured value (solid line).

[0141] By using Equation

[38] , the intake efficiency correction value is calculated as a value greater than 0, and the estimated value (broken line) of the intake pipe pressure in this embodiment example (with correction) shows a good agreement with the measured value. Also, around time t1, a difference occurs between the estimated value and the measured value. However, according to Equation

[38] , since the error between the wall surface temperature that the intake air metering control implicitly recognizes and the wall surface temperature during operation is corrected, the time change of the estimated value progresses in the direction of matching the measured value. On the other hand, when the correction of the intake efficiency is not performed, the estimated result of the intake pipe pressure as shown by the dashed-dotted line is obtained, showing an error.

[0142] Thereby, also according to the third embodiment example, it is possible to correct the intake efficiency by using the data acquired in the steady state and a simple correction formula. As a result, it is possible to suppress the man-hours for adaptation and realize the correction.

[0143] <Modification Example> Note that each of the embodiment examples described so far has been described in detail for the purpose of easily explaining the present invention, and is not necessarily limited to those having all the configurations described. Also, part or all of the configurations and processes described in one embodiment example may be combined with other embodiment examples.

[0144] Also, in each block diagram, only the control lines and information lines considered necessary for explanation are shown, and not all control lines and information lines are necessarily shown on the product. In reality, it may be considered that almost all configurations are interconnected. Also, the flow of the processes shown in each flowchart is also an example, and if the processing results are the same, the order of some processes may be changed, or a plurality of processes may be executed simultaneously.

[0145] Also, in each embodiment example, when obtaining a physical quantity during the calculation for the wall surface temperature correction unit to obtain a correction value, an estimated value or a measured value of the physical quantity was obtained. In contrast, both the estimated value and the measured value of the physical quantity may be obtained, and correction may be performed based on both values. For example, as a physical quantity that changes with the change in the combustion chamber wall surface temperature in the internal combustion engine cylinder, correction may be performed based on one or both of the estimated value or the measured value. Also, for example, the steady-state intake pipe pressure value may be calculated based on one or both of the throttle opening degree, the EGR valve opening degree, the measured value by the air flow rate sensor, the measured value or the estimated value of the EGR flow rate, the engine speed, and the measured value or the estimated value of the intake pipe temperature.

[0146] Also, the physical quantity that changes with the change in the combustion chamber wall surface temperature may be calculated based on one or both of the measured value by the air flow rate sensor, the measured value or the estimated value of the gas flow rate, or the measured value or the estimated value of the gas temperature in the intake pipe. Furthermore, the correction value of the intermediate parameter may be calculated based on one or both of the reference value of the gas temperature in the intake pipe and the measured value or the estimated value of the gas temperature in the intake pipe.

[0147] Furthermore, as described with reference to FIG. 2, the control device 100 is configured as a computer including a CPU and a memory, and implements a program for executing the processes described in each embodiment example so as to function as a control device. Configuring it as such a computer is an example, and part or all of the functions performed by the control device 100 may be realized by hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0148] Also, regarding the program to be installed in the computer when the control device 100 is configured by a computer, in addition to being prepared in the memory within the control device 100, it may be placed on a recording medium such as an external memory, an IC card, an SD card, or an optical disk and transferred.

Description of Symbols

[0149] 1…Air flow sensor, 2…Electronic control throttle, 3…Intake pressure sensor, 5…Variable valve, 9…Air-fuel ratio sensor, 10…Three-way catalyst, 12…Accelerator opening sensor, 13…Fuel injection device (injector), 14…Cylinder, 15…Exhaust pipe, 16…Ignition coil, 17…Spark plug, 18…Temperature sensor, 19…Crank angle sensor, 20…Oil jet system, 20a…Oil pump, 21…Input circuit, 22…Input / output port, 23a…CPU, 23b…ROM, 23c…RAM, 24…Ignition control unit, 25…Fuel injection control unit, 100…ECU, 301…Intake pipe pressure estimation unit, 302…Intake efficiency calculation unit, 303…Cylinder inflow gas flow rate calculation unit, 304…Cylinder flow air flow rate calculation unit, 305…Exhaust pressure estimation unit, 306…EGR flow rate estimation unit, 307…EGR distribution estimation unit, 401…Basic intake efficiency calculation unit, 402…Wall temperature correction unit, 403…Intake efficiency correction value K calculation unit, 404…Wall temperature transient determination unit, 405…Switch unit, 1201…Basic intake efficiency calculation unit, 1202…Wall temperature correction unit, 1203…Wall temperature difference calculation unit, 1204…Intake efficiency correction value K calculation unit, 1205…Wall temperature transient determination unit, 1206…Switch unit, ENG…Internal combustion engine (engine)

Claims

1. In a control device for an internal combustion engine including an in-cylinder air amount calculation unit that calculates the amount of air entering the cylinder of the internal combustion engine based on an air flow rate sensor, a calculation unit is provided that calculates an intermediate parameter indicating an intake efficiency for calculating an in-cylinder inflow air amount based on an intake pipe pressure, the intermediate parameter is corrected based on one or both of an estimated value or a measured value of a physical quantity that changes with a change in the combustion chamber wall temperature in the cylinder of the internal combustion engine A control device for an internal combustion engine.

2. The physical quantity that changes with the change in the combustion chamber wall temperature is the intake pipe pressure The control device for an internal combustion engine according to claim 1.

3. The calculation unit that calculates the intermediate parameter includes an estimation unit for an intake pipe pressure steady value that is the intake pipe pressure when the combustion chamber wall temperature reaches a steady state, the intake pipe pressure steady value estimation unit calculates a correction value for the intermediate parameter based on the intake pipe pressure steady value and the estimated value or measured value of the intake pipe pressure The control device for an internal combustion engine according to claim 2.

4. The calculation unit that calculates the intermediate parameter calculates a correction value for the intermediate parameter based on the measured value of the intake pipe pressure and the estimated value of the intake pipe pressure The control device for an internal combustion engine according to claim 2.

5. The intake pipe pressure steady value is calculated based on the throttle opening degree, the EGR valve opening degree, the measured value by the air flow rate sensor, the measured value or estimated value of the EGR flow rate, the engine speed, and the measured value or estimated value of the intake pipe temperature The control device for an internal combustion engine according to claim 3.

6. The physical quantity that changes with the change in the combustion chamber wall temperature is the measured value by the air flow rate sensor, or the measured value or estimated value of the gas flow rate The control device for an internal combustion engine according to claim 1.

7. The calculation unit that calculates the correction value for the intermediate parameter includes an estimation unit for an air flow rate steady value that is the air flow rate when the combustion chamber wall temperature reaches a steady state, or a gas flow rate steady value that is the gas flow rate when the combustion chamber wall temperature reaches a steady state, the gas flow rate steady value estimation unit calculates a correction value for the intermediate parameter based on the air flow rate steady value or the gas flow rate steady value and the measured value of the air flow rate The control device for an internal combustion engine according to claim 6.

8. The air flow rate steady value or the gas flow rate steady value is calculated based on the throttle opening degree and the engine speed The control device for an internal combustion engine according to claim 7.

9. The physical quantity that changes with the change in the combustion chamber wall temperature is the measured value or estimated value of the gas temperature in the intake pipe. The control device for an internal combustion engine according to claim 1.

10. The correction value of the intermediate parameter is calculated based on the reference value of the gas temperature in the intake pipe and the measured value or estimated value of the gas temperature in the intake pipe. The control device for an internal combustion engine according to claim 7.

11. The reference value of the gas temperature in the intake pipe is calculated based on the throttle opening, the EGR valve opening, and the engine speed. The control device for an internal combustion engine according to claim 10.

12. It includes a calculation unit that calculates the difference from the cylinder wall temperature in the reference state based on the throttle opening and the engine speed. The physical quantity that changes with the change in the combustion chamber wall temperature is the difference from the cylinder wall temperature in the reference state. The control device for an internal combustion engine according to claim 1.

13. The calculation unit that calculates the correction value of the intermediate parameter includes an estimation unit for the wall temperature steady value, which is the wall temperature when the combustion chamber wall temperature reaches a steady state. The wall temperature steady value estimation unit calculates the correction value of the intermediate parameter based on the difference from the combustion chamber wall temperature. The control device for an internal combustion engine according to claim 1.

14. In a control method for an internal combustion engine that performs an in-cylinder air amount calculation process for calculating the amount of air entering the internal combustion engine cylinder based on an air flow sensor, A calculation process is performed to calculate an intermediate parameter indicating the intake efficiency for calculating the in-cylinder inflow air amount based on the intake pipe pressure. The intermediate parameter is corrected based on one or both of the estimated value or measured value of the physical quantity that changes with the change in the combustion chamber wall temperature in the internal combustion engine cylinder. Control method for an internal combustion engine.

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