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

Abstract

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

Description

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

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

[0002] It is essential to reduce harmful components emitted from automobiles. To reduce harmful components, a three-way catalyst is usually installed in the exhaust pipe of an automobile engine to purify the harmful components. In order to purify the harmful components with a three-way catalyst, the ratio of air to fuel (air-fuel ratio) burned in the engine cylinders must be kept within a specified range. Controls used to keep the air-fuel ratio within the specified range include an air flow sensor installed in the engine's intake duct and an intake manifold pressure sensor installed in the intake manifold. These sensors are used to estimate the air flow rate taken into the engine cylinders, and the fuel injection amount is determined based on the estimated value.

[0003] For example, in a system using an airflow sensor, a difference occurs between the airflow measured by the airflow sensor and the airflow taken into the engine cylinders when the engine's operating state changes transiently. Therefore, if the fuel injection amount is determined based on the airflow measured by the airflow sensor, the air-fuel ratio may fall outside the predetermined range under certain conditions. For this reason, control is performed to estimate the airflow taken into the engine cylinders when the engine's operating state changes transiently. In the following description, this control is referred to as intake metering control.

[0004] Intake metering control for an engine equipped with an airflow sensor estimates the amount of air taken into the engine cylinders, for example, by the following process. That is, intake metering control estimates the intake manifold pressure (intake pipe pressure) based on the airflow measured by the airflow sensor, and estimates the amount of air taken into the engine cylinders based on the estimated intake pipe pressure and intermediate parameters that are determined in advance through experiments or the like. This process of estimating the amount of air taken into the engine cylinders is repeatedly executed.

[0005] An example of a condition related to the performance of an internal combustion engine is the temperature of the combustion chamber wall (hereinafter referred to as the wall temperature). Assume that the engine's operating state switches from a low-output state to a high-output state, and then the engine operates to maintain a constant output. At this time, the temperatures of the walls that make up the combustion chamber of the internal combustion engine, specifically the piston crown, cylinder liner, and head walls (combustion chamber wall temperature) transiently increase and eventually reach a constant temperature (steady-state temperature).

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

[0007] A known example of conventional technology relating to such control of an internal combustion engine is the control device described in Patent Document 1. Patent Document 1 discloses a control device for an internal combustion engine that includes a means for correcting the flow rate of air taken into the engine based on an estimated value of the wall temperature of the combustion chamber of the internal combustion engine.

[0008] Patent No. 7269104

[0009] In the prior art disclosed in Patent Document 1, when correcting the air flow rate into an internal combustion engine based on an estimated value of the combustion chamber wall temperature, it is necessary to understand the relationship between the combustion chamber wall temperature and an intermediate parameter (intake efficiency) in advance, and investigating this relationship requires numerous experiments. Furthermore, the estimation of the combustion chamber wall temperature itself must be adapted. Furthermore, even if the combustion chamber wall temperature is estimated in the prior art, it is necessary to confirm the accuracy of the correction.

[0010] The present invention has been made in consideration of the above, and aims 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 accuracy of the estimation results when estimating the combustion chamber wall temperature based on changes in the combustion chamber wall surface temperature.

[0011] To solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above problems, and one example thereof is a control device for an internal combustion engine that includes an in-cylinder air amount calculation unit that calculates the amount of air entering a cylinder of the internal combustion engine based on an air flow sensor. The control device for the internal combustion engine also includes a calculation unit that calculates an intermediate parameter indicating intake efficiency for calculating the amount of air flowing into the cylinder based on an intake manifold pressure, and the intermediate parameter is corrected based on one or both of an estimated value and a measured value of a physical quantity that changes with a change in the temperature of the combustion chamber wall surface in the cylinder of the internal combustion engine.

[0012] According to the present invention, when the wall temperature of the combustion chamber is transiently changing, it is possible to simply and appropriately correct an intermediate parameter used in intake metering control, which calculates the air flow rate flowing into the engine based on the measurement value of the air flow sensor. Therefore, according to the present invention, it is possible to reduce the estimation error of the intake manifold pressure estimation value. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0013] FIG. 1 is a configuration diagram showing an example of a system configuration of an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an example of a hardware configuration of an ECU according to the first embodiment of the present invention. FIG. 3 is a functional block diagram showing an example of an intake metering control process according to the first embodiment of the present invention. FIG. 4 is a functional block diagram showing an example of a process of an intake efficiency calculation unit according to the first embodiment of the present invention. FIG. 5 is a flowchart showing an example of a process of a wall surface temperature correction unit of the intake efficiency calculation unit according to the first embodiment of the present invention. FIG. 6 is a schematic diagram of a map for calculating an intake manifold pressure steady-state value according to the first embodiment of the present invention. FIG. 7 is a characteristic diagram showing an example of a time change of an intake manifold pressure estimated value when an intermediate parameter (intake efficiency) is corrected based on an intake manifold pressure measured value according to the first embodiment of the present invention. FIG. 8 is a characteristic diagram showing an example of a time change of an intake manifold pressure estimated value when an intermediate parameter (intake efficiency) is corrected based on an air flow rate measured value according to the first embodiment of the present invention. FIG. 9 is a schematic diagram showing an example of a map for calculating a gas flow rate steady-state value according to the first embodiment of the present invention. 1 is a characteristic diagram showing an example of time change of an intake manifold pressure estimated value when an intermediate parameter (intake efficiency) is corrected based on a gas flow rate estimated value according to a first embodiment of the present invention. FIG. 2 is a functional block diagram showing an example of processing by an intake efficiency calculation unit according to a second embodiment of the present invention. FIG. 3 is a flowchart showing an example of processing by a wall surface temperature correction unit of the intake efficiency calculation unit according to a second embodiment of the present invention. FIG. 4 is a schematic diagram showing an example of a map for calculating a wall temperature steady-state value according to a second embodiment of the present invention. FIG. 5 is a characteristic diagram showing an example of time change of an intake manifold pressure estimated value when an intermediate parameter (intake efficiency) is corrected based on a difference (difference from steady temperature) between a wall temperature estimated value and a wall temperature steady-state value according to a second embodiment of the present invention. FIG. 6 is a flowchart showing an example of processing by a wall surface temperature correction unit of an intake efficiency calculation unit according to a third embodiment of the present invention. FIG. 7 is a characteristic diagram showing an example of time change of an intake manifold pressure estimated value when an intermediate parameter (intake efficiency) is corrected based on an intake manifold pressure measurement value and an intake manifold pressure estimated value according to a third embodiment of the present invention.

[0014] Hereinafter, an internal combustion engine control device and an internal combustion engine control method according to embodiments of the present invention will be described with reference to the accompanying drawings. Note that in the following embodiments, an internal combustion engine that is mounted on an automobile or the like and uses gasoline as fuel will be described as an example, but the present invention can also be applied to other internal combustion engines that use different types of fuel, specifications, or uses.

[0015] First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 to 11. FIG. 1 is a schematic diagram illustrating an example of the system configuration of an internal combustion engine mounted on an automobile, along with related components. The internal combustion engine (internal combustion engine ENG) illustrated in FIG. 1 is a direct-injection internal combustion engine for an automobile that is driven by spark ignition combustion. That is, the internal combustion engine illustrated in FIG. 1 includes an in-cylinder fuel injection mechanism that directly injects gasoline fuel into each of multiple cylinders, and an intake mechanism that supplies air into the cylinders. The internal combustion engine illustrated in FIG. 1 also includes an ignition mechanism that ignites a mixture of gasoline fuel and air injected into the cylinder, an exhaust mechanism that exhausts the air after combustion in the cylinder, and the like. Note that FIG. 1 illustrates only one of the multiple cylinders, along with related components.

[0016] The internal combustion engine ENG is equipped with an air flow sensor 1 that measures the intake air amount (air flow rate) and intake air temperature, an intake pressure sensor 3 that measures the intake pipe pressure (intake air pressure), an electronically controlled throttle 2 that adjusts the intake pipe pressure, and an ECU 100 that is a control device that controls the overall operation of the internal combustion engine ENG. The intake pipe pressure adjusted by the electronically controlled throttle 2 can be rephrased as air flow rate. The air flow sensor 1 is called an AFS (Air Flow Sensor). The intake pressure sensor 3 is called a MAP (Manifold Absolute Pressure sensor). 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 pressure sensor 3 are sent to the ECU 100. The internal combustion engine ENG is made up of a fuel injection device 13 (hereinafter also referred to as an injector 13) that injects fuel into a cylinder 14 of each cylinder, an ignition coil 16, and an ignition plug 17. The internal combustion engine ENG is also 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 equipped with a variable valve 5 for each cylinder that adjusts the air-fuel mixture flowing into the cylinder or the exhaust gas discharged from the cylinder. Adjusting the variable valve 5 adjusts the intake air volume and internal EGR volume for all cylinders in the cylinder head. An oil jet system 20 is provided behind the piston of each cylinder to lower the piston temperature. The oil jet system 20 is connected to a variable displacement (variable oil pressure) oil pump 20a, and the amount of oil sprayed from the oil jet system 20 toward the piston is adjusted by adjusting the output (flow rate, oil pressure) of the oil pump.

[0019] A high-pressure fuel pump (not shown) is connected to the fuel injection device 13 via a fuel pipe for supplying high-pressure fuel to the fuel injection device 13. The fuel injection device 13 is also 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. The 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 that purifies the exhaust gas, and an air-fuel ratio sensor 9 that detects the air-fuel ratio of the exhaust gas upstream of the three-way catalyst 10. The internal combustion engine ENG is also provided with a temperature sensor 18 that measures the temperature of the coolant 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 sent to the ECU 100. The accelerator pedal is provided with an accelerator position sensor 12. The accelerator position sensor 12 detects the amount of depression of the accelerator pedal, i.e., the accelerator position. The detection result (output information) of the accelerator position sensor 12 is sent to the ECU 100.

[0021] The ECU 100 calculates the required torque based on the output information from the accelerator position sensor 12. In other words, the accelerator position sensor 12 can also be considered a required torque detection sensor that detects the torque required for the internal combustion engine. The ECU 100 also calculates the rotation speed of the internal combustion engine based on the output information from the crank angle sensor 19. The ECU 100 appropriately calculates the main operating variables 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 a valve-opening pulse signal and sent to the injector 13. An ignition signal is also sent to the ignition coil 16 so that ignition occurs at the ignition timing calculated by the ECU 100. The throttle opening calculated by the ECU 100 is also sent to the electronically controlled throttle 2 as a throttle drive signal.

[0023] An injector 13 injects fuel into air that flows from an intake pipe through an intake valve into a cylinder 14 to form an air-fuel mixture. The air-fuel mixture is ignited (exploded) by a spark generated by a spark plug 17 at a predetermined ignition timing. The combustion pressure caused by this ignition pushes a piston downward, rotating a rotating shaft (crankshaft) connected to the piston via a connecting rod, generating driving force for the internal combustion engine ENG. Exhaust gases generated after the explosion are sent through an exhaust pipe 15 to a three-way catalyst 10, where exhaust components are purified and then discharged to the outside. The internal combustion engine ENG in this embodiment employs variable valve timing control (VTC), which continuously adjusts the opening and closing timing of the intake valve according to the engine speed and load.

[0024] Figure 2 is a diagram that schematically shows the hardware configuration of ECU 100, which is a control device for an internal combustion engine. In Figure 2, the following output information and the like are input to an input circuit 21 of ECU 100. That is, the input circuit 21 receives 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. In addition, although not shown in Figure 2, the input circuit 21 also receives the coil primary voltage or secondary voltage from a voltage sensor of the ignition coil 16.

[0025] Furthermore, the input circuit 21 of the ECU 100 receives as input the fuel injection pressure from the fuel pressure sensor of the fuel injector 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 coolant from the temperature sensor 18. Furthermore, the input circuit 21 receives as input the accelerator opening (throttle opening) from the accelerator opening sensor 12, the rotation speed of the rotating shaft (crankshaft), and various VTC setting values ​​(VTC settings). The output information from these sensors and the like becomes input information to the ECU 100. However, the input information input to the ECU 100 is not limited to these.

[0026] Input information input to the input circuit 21 of the ECU 100 is sent to the input port side of the input / output port 22. The input information sent to the input / output port 22 is temporarily stored in a random access memory (RAM) 23c and is then processed by a CPU 23a in accordance with a predetermined control program. The CPU 23a is a processing unit known as a central processing unit. A control program describing the content of the processing to be executed by the CPU 23a is written in advance in a read-only memory (ROM) 23b.

[0027] Output information indicating the amounts of operation of the fuel injection valves and ignition coils that control the internal combustion engine, calculated according to the control program, is temporarily stored in RAM 23c and then sent to the output port side of input / output port 22, and then sent to ignition control unit 24, fuel injection control unit 25, etc. Note that the internal combustion engine ENG also uses actuators other than those described above, but their description will be omitted here.

[0028] In this embodiment, the ECU 100 has, as drive circuits, an ignition control unit 24 and a fuel injection control unit 25. The ignition control unit 24 acquires information relating to the timing and duration of energization of the ignition coil 16 as the operation amount of the associated actuator, and controls the timing and duration of energization of 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 duration of the fuel injection device 13 as the operation amount of the associated actuator, and controls the valve opening timing and valve opening duration of the fuel injection device 13 and the opening and closing of a valve for adjusting pressure in the fuel pressure pump based on the acquired operation amount. Note that in this embodiment, the ECU 100 is configured to include the ignition control unit 24 for controlling the energization time and discharge energy amount of the ignition coil, and the fuel injection control unit 25 for controlling the injection timing and injection duration of the fuel injection device, but this is just an example. In other words, part of each control unit 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 illustrating the intake metering control in the ECU 100 of this embodiment. The intake metering control shown in FIG. 3 is a program executed by the CPU 23a in the ECU 100. In this intake metering control, the airflow sensor measurement value, engine speed, and coolant temperature are input, and the cylinder inflow air flow rate is calculated. An intake pipe pressure estimation unit 301 calculates the intake pipe pressure based on the mass within the volume from the throttle to the engine, the energy conservation equation, and the gas state equation. The mass conservation equation, energy conservation equation, and gas state equation can be written as follows:

[0031]

[0032]

[0033]

[0034]

[0035] Here, [Equation 1] is the mass conservation equation, [Equation 2] is the energy conservation equation, and [Equation 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 into the cylinder (cylinder inflow 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 EGR gas [-], γ in is the specific heat ratio of the gas in the intake pipe [-], R atm is the atmospheric gas constant [J / kg / K], R egr is the gas constant of the EGR gas [J / kg / K].

[0036] Furthermore, in these formulas, 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], Tin 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 / m ２ / K], S in is the contact area between the intake pipe and the gas [m ２ ], Twall is the temperature of the intake pipe wall [K], P in is the intake pipe pressure. atm , m egr , m cyl As shown in each formula, the actual notation is one in which [·] is added above m. In the notation in the following specification, the [·] above m will be similarly omitted.

[0037] The specific heat ratio and gas constant are physical quantities that change depending on the gas composition. They can be determined by assuming each gas composition and referring to experimental results, literature values, etc. The heat transfer coefficient can also be determined by fitting it to a previously conducted experiment. 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 coolant temperature passing through the EGR cooler, or can be determined by referring to a map previously experimentally fitted based on the operating conditions and coolant temperature.

[0038] The formulas [1] and [2] are given the values ​​of the variables on the right-hand side, and by integrating them numerically, the gas mass m in the intake pipe can be calculated. in and the specific internal energy e in the intake pipe in Furthermore, the gas mass m in the intake pipe calculated by [Equation 1] is calculated as follows. in and the specific internal energy e in the intake pipe calculated by [Equation 2] in By substituting into the formula (3), the gas temperature T in are calculated, and by substituting these into the formula (4), the intake pipe pressure P in is calculated.

[0039] An intake efficiency calculation unit 302 calculates the intake efficiency, which is an intermediate parameter of intake metering control. The method of calculating the intake efficiency will be described in detail using FIG. 4, etc. A cylinder inflow gas flow rate calculation unit 303 calculates the gas flow rate flowing into the engine cylinder based on the estimated intake manifold pressure value and the intake efficiency. The cylinder gas flow rate is calculated using the following equation (5).

[0040]

[0041] where η is the intake efficiency [-], N e is the rotation speed [rpm], V D is the displacement per cylinder [m 3 ], n cyl is the number of cylinders [-]. A 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 flowing into the cylinder (cylinder inflow air flow rate) using the gas flow rate calculated by the cylinder gas flow rate calculation unit 303 and the EGR rate calculated by an EGR distribution estimation unit 307 (described later). Specifically, the cylinder inflow air flow rate is calculated by the following equation (6).

[0042]

[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 engine speed. For example, the exhaust pressure estimation unit 305 creates in advance a compatibility map of exhaust pressure based on the cylinder inflow gas flow rate and the engine speed based on experiments and simulations, and estimates the exhaust pressure using this map.

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

[0045]

[0046] Furthermore, the EGR distribution estimation unit 307 estimates the distribution of EGR gas and calculates the EGR rate of the gas flowing into the cylinder 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 use the following equation (8):

[0047]

[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], τ EGR is the delay time [s]. In the formula (8), the EGR rate y of the gas flowing into the cylinder calculated by applying a first-order delay filter is EGR,d is specified as a function of time, and the value (y EGR,d (t+Δt)) is the value of time t (y EGR,d (t)) and the EGR rate calculated by the formula [7]. EGR The flow rate of air entering the cylinder depends on factors such as the length of the piping from the point where the EGR gas and air meet to the engine cylinder, and must be determined for each operating condition through engine tests and simulations. The flow rate of air entering the cylinder is calculated through the process described above.

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

[0050]

[0051] The intake efficiency η shown in Equation 9 is calculated by performing experiments and simulations under conditions where the engine reaches a steady state (steady state). For example, when the engine is operated under steady state conditions with the EGR flow rate set to 0, the cylinder inflow gas flow rate m cyl The time average value of the air flow rate m measured by the air flow sensor AFM Using this, the time average value of the air flow measured by the air flow sensor obtained in the steady-state test is calculated as the cylinder inflow gas flow rate m cyl The reference intake efficiency (basic intake efficiency) can be calculated by substituting

[0052] The basic intake efficiency calculation unit 401 creates a map based on the rotation speed and intake manifold pressure from the basic intake efficiency calculated in this way. While the engine is running, the intake efficiency is calculated by searching the map based on the rotation speed and the estimated intake manifold pressure. Note that the map is created based on experimental results obtained under steady conditions, and therefore is created based on data measured when the combustion chamber wall temperature has reached a steady state.

[0053] Therefore, if the wall surface temperature is in a state (transient state) different from the steady state during engine operation, the intake efficiency calculated by referring to the map will not match the intake efficiency during operation, and the calculated value of the intake efficiency will have an error, resulting in an error in the estimated value of the intake pipe pressure. In this embodiment, a wall surface 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] A wall surface temperature correction unit 402 calculates a correction value for intake efficiency, which is an intermediate parameter, based on a wall surface temperature-correlated physical quantity, which is a physical quantity that changes with changes in the combustion chamber wall surface temperature, and determines whether the wall surface temperature is in a transient state and performs correction. The change in combustion chamber wall surface temperature is either an estimated value or a measured value, or both. An intake efficiency correction value K calculation unit 403 calculates the correction value for intake efficiency, and a wall surface temperature transient determination unit 404 sets a flag indicating whether the wall surface temperature is in a transient state. Next, a switch unit 405 selects processing according to the flag.

[0055] 5 is a flowchart showing the processing contents of the wall surface temperature correction unit 402 of the intake efficiency calculation unit 302. First, in step S501, the intake efficiency correction value K calculation unit 403 of the wall surface temperature correction unit 402 estimates a steady-state value of the wall temperature correlation parameter. For example, if the intake pipe pressure is used as the wall temperature correlation parameter, the engine continues to operate under the operating conditions (torque, rotation 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-state value. Next, in step S502, 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).

[0056]

[0057] where C is a coefficient and F ｍ is the measured or estimated value of the wall temperature correlation parameter during operation, F ｓｔ is the steady-state value of the wall surface correlation parameter. The coefficient C is a numerical value whose sign changes depending on 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 will be 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 will be a positive value. Next, in step S503, the wall temperature transient determination unit 404 of the wall surface temperature correction unit 402 determines whether the wall surface temperature is in a transient state, i.e., whether the wall surface temperature is deviating from the steady-state temperature of the wall surface, based on the following equation (11).

[0058]

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

[0060] If step S503 determines that the result is False (=steady), the wall surface temperature correction unit 402 proceeds to step S505, changes the intake efficiency correction value K to 1, and ends the process. Steps S501 and S502 are processes performed by the intake efficiency correction value K calculation unit 403. 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, a case where intake pipe pressure is used as the wall temperature correlation parameter will be described. Since intake pipe pressure is a physical quantity that increases with an increase in wall surface temperature, C in equation (3) is set to a negative value. For example, if the value of C is set to -1, the correction formula becomes equation (12) below.

[0062]

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

[0064] 6 is a schematic diagram of a map for calculating the intake pipe pressure steady-state value p_(in, st). For example, as shown in FIG. 6A, a map may be used with the rotation speed and gas flow rate (air flow rate or the sum of the air flow rate and EGR flow rate) as axes. Alternatively, as shown in FIG. 6B, a map may be used with the rotation speed, throttle opening, and EGR opening as axes. Furthermore, the gas temperature in the intake pipe may be set as the axis of each map. Furthermore, maps using different axes may be used by switching depending on the conditions. These maps are created from data acquired when the engine is in a steady state.

[0065] FIG. 7 is a diagram showing the change over time in the estimated intake pipe pressure value when the intermediate parameter (intake efficiency) is corrected based on the measured intake pipe pressure. From the top of FIG. 7, the graphs show the throttle opening, wall temperature, intake efficiency correction value, intake pipe pressure, and air flow rate. The horizontal axis shows time. In the graph of wall temperature, the dotted line shows the steady-state value of the wall temperature, and the solid line shows the measured value. In the graph of intake pipe pressure, the solid line shows the measured value, the dashed line shows the estimated value according to the present application, the dashed line shows the estimated value without correction (correction coefficient K is 1), and the dotted line shows the steady-state value. In the graph of air flow rate, the dotted line shows the steady-state value, and the solid line shows the measured value. In the graph of throttle opening, the ０ It starts opening from time t １ After the throttle opening becomes constant, the throttle opening becomes constant at time t ｓ The wall temperature reaches a steady state at time t １ From t ｓ During this time, the wall temperature gradually increases due to changes in engine output caused by changes in the throttle opening.

[0066] At this time, the measured value of intake manifold pressure (solid line) gradually increases, while the measured value of air flow rate (solid line) gradually decreases. A difference occurs between the measured value of intake manifold pressure and the steady-state value of intake manifold pressure (dotted line). This difference is the correlation between the difference between the steady-state value of wall temperature (dotted line) and the measured value (solid line). When intake efficiency is corrected using equation (12), the intake efficiency correction value is calculated as a value greater than 0. As shown in the intake manifold pressure diagram, the estimated intake manifold pressure value (dashed line) of this embodiment (with correction) shows good agreement with the measured value. On the other hand, when intake efficiency is not corrected (when this embodiment is not applied), the estimated value (without correction) becomes the estimated intake manifold pressure shown by the dashed line, and there is a large error from the measured value.

[0067] Here, as a supplementary explanation, we will explain the derivation process of Equation 12 and explain that the difference between the measured intake manifold pressure and the steady-state intake manifold pressure value becomes apparent due to the influence of the wall temperature. The intake efficiency is a function of the intake manifold pressure, engine speed, and cylinder wall temperature.

[0068]

[0069] where η is the intake efficiency, pｉｎ 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-state temperature, we perform a Taylor expansion on the right-hand side.

[0070]

[0071]

[0072] Here, T ｗ，ｓｔ is the steady-state value of the wall temperature. Since the change in the gas temperature inside the cylinder due to the change in the wall temperature changes the intake efficiency, the intake efficiency can be considered as a function of the gas temperature inside the cylinder, so the formula can be further modified.

[0073]

[0074] Here, T ｃｙｌ is the gas temperature [K] inside the engine cylinder. Furthermore, equation (16) is transformed into a function of the gas temperature inside the engine cylinder.

[0075]

[0076] Here, we derive an equation for the partial derivative of intake efficiency with respect to the in-cylinder gas temperature. Equation 17 is derived by expressing the amount of gas taken into the cylinder using two equations. The amount of gas taken in during one combustion cycle is calculated by multiplying Equation 1 by the time for one combustion cycle (two engine revolutions).

[0077]

[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 in the intake pipe [K], V Ｄ is the displacement of one cylinder [m3], n ｃｙｌ is the number of cylinders [-]. Also, assuming that the pressure inside the cylinder at intake valve close (IVC) is equal to the intake pipe pressure and the temperature inside the cylinder is equal to the gas temperature inside the intake pipe, the amount of gas in one cylinder at the timing when the intake valve closes can be calculated using the following equation (19).

[0079]

[0080] Here, M ｃｙｌ，ｇａｓ is the amount of gas in the cylinder at the intake valve closing timing [kg], V ＩＶＣ is the cylinder volume at the intake valve closing timing. ｃｙｌ，ａｉｒ The sum of the above for the number of cylinders is the amount of gas taken in in one combustion cycle, and M １ｃｙｃ From this, we equate the product of Equation 18 and the number of cylinders of the engine with Equation 19, and rearrange it as an equation for intake efficiency to obtain the following Equation 20.

[0081]

[0082] By differentiating both sides of equation (20) with respect to the gas temperature in the cylinder, equation (21) is obtained, which is the partial derivative of the intake efficiency with respect to the gas temperature in the cylinder.

[0083]

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

[0085]

[0086]

[0087] Here, T ｃｙｌ，ｓｔ is the in-cylinder gas temperature [K] under steady-state cylinder wall temperature conditions. Next, by differentiating equation (19) under the condition that the in-cylinder mass is constant, the relationship between the in-cylinder gas temperature and the intake pipe pressure is obtained as equation (24).

[0088]

[0089] Furthermore, as shown in the following equation (25), the fluctuation amount δ of the intake pipe pressure ｐｉｎ Decide.

[0090]

[0091] When determined in this way, equation (23) can be transformed into equation (26), and it is understood that the intake efficiency correction amount is related to the change in intake pipe pressure.

[0092]

[0093] In this way, the intake efficiency correction formula is not derived simply from the correlation of phenomena, and although some approximation is necessary, it is a relationship derived based on a physical formula and does not correspond to a simple fitting. Next, a case where the air flow rate is used 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, C in formula (3) is set to a positive value. For example, if it is set to 1, the correction formula becomes formula (27) below.

[0094]

[0095] Here, m ｍ is the measured air flow rate, m ｓｔ is the steady-state air flow rate. ｓｔ 8A is a schematic diagram of a map for calculating the above. For example, as shown in FIG. 8A, a map may be used with the rotation speed and throttle opening as axes. Alternatively, as shown in FIG. 8B, a map may be used with the rotation speed and intake pipe pressure as axes. Furthermore, the axis of each map may be set to the gas temperature in the intake pipe. Furthermore, maps using different axes may be used by switching depending on the conditions. These maps are created from data acquired when the engine is in a steady state. When referring to the map of FIG. 8B, the measured value of the intake pipe pressure is used.

[0096] 9 is a diagram showing the change over time in the estimated intake manifold pressure value when the intermediate parameter (intake efficiency) is corrected based on the measured airflow rate. As in FIG. 7, the graph shows, from top to bottom, the throttle opening, wall temperature, intake efficiency correction value, intake manifold pressure, and airflow rate. The horizontal axis represents time. In the graph of wall temperature, the dotted line represents the steady-state value of the wall temperature, and the solid line represents the measured value. In the graph of intake manifold pressure, the solid line represents the measured value, the dashed line represents the estimated value according to the present application, and the dash-dotted line represents the estimated value without correction (correction coefficient K is 1).

[0097] In the graph of air flow rate, the dotted line indicates the steady value and the solid line indicates the measured value. １After the throttle opening becomes constant, the wall temperature reaches a steady value at time ts. １ From t ｓ During this time, the wall temperature gradually increases due to changes in engine output caused by changes in the throttle opening. At this time, a difference occurs between the measured air flow rate (solid line) and the steady-state air flow rate (dotted line). This difference is the correlation between the difference between the steady-state wall temperature value (dotted line) and the measured value (solid line).

[0098] By calculating the intake efficiency correction value using equation 27, it can be seen that the estimated intake pipe pressure value (dashed line) of this embodiment (with correction) shows good agreement with the measured value. On the other hand, if intake efficiency correction is not performed, the estimated intake pipe pressure value (without correction) will be the estimated intake pipe pressure result shown by the dashed line, and there will be a large error from the measured value.

[0099] Next, a case where the gas flow rate is used as the wall temperature correlation parameter will be described. Since the gas flow rate is a physical quantity that decreases as the wall surface temperature increases, C in Equation 3 is set to a positive value. For example, the gas flow rate can be set to 1, and the correction formula becomes Equation 28 below.

[0100]

[0101] Here, m ｇ，ｍ is the gas flow rate during operation, m ｇ，ｓｔ is the steady-state value of the gas flow rate. The gas flow rate is the flow rate of air and EGR gas, and in a system equipped with a flow meter that measures the EGR gas flow rate, it can be given as a measured value. Furthermore, if a flow meter that measures the EGR gas flow rate is not equipped, it must be estimated based on the intake pipe pressure, exhaust pressure, and EGR valve opening. For example, by creating in advance a compatibility map of the steady-state EGR gas flow rate based on the difference between the intake pipe pressure and the exhaust pressure and the EGR valve opening, it is possible to make an estimation based on this map during operation.

[0102] FIG. 10 shows the steady-state gas flow rate m ｇ，ｓｔ10A is a schematic diagram of a map for calculating the above. For example, as shown in FIG. 10A, the map can have the rotation speed, throttle opening, and EGR valve opening as axes. Alternatively, as shown in FIG. 10B, the map may have the rotation speed and intake pipe pressure as axes. Furthermore, the axis of each map may be set to the gas temperature in the intake pipe. Furthermore, maps using different axes may be switched depending on the conditions. These maps are created from data acquired when the engine is in a steady state. When referring to FIG. 10B, the measured value of the intake pipe pressure is used.

[0103] Fig. 11 is a diagram showing the change over time in the estimated intake manifold pressure value when the intermediate parameter (intake efficiency) is corrected based on the estimated gas flow rate value. As with Figs. 7 and 9, Fig. 11 shows, from top to bottom, the throttle opening, wall surface temperature, intake efficiency correction value, intake manifold pressure, and gas flow rate. In the diagram of 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 intake manifold pressure, the solid line indicates the measured value, the dashed line indicates the estimated value according to the present application, and the dash-dotted line indicates the estimated value without correction (correction coefficient K is 1). In the diagram of gas flow rate, the dotted line indicates the steady-state value, and the solid line indicates the measured or estimated value. The diagram of throttle opening shows the change over time at time t ０ It starts opening from time t １ This indicates that the throttle opening becomes constant thereafter.

[0104] After the throttle opening becomes constant, at time t ｓ The wall temperature reaches a steady state at time t １ From t ｓ Until then, the wall temperature gradually increases due to changes in engine output accompanying changes in throttle opening. At this time, a difference occurs between the measured or estimated gas flow rate and the steady-state gas flow rate value (dotted line). This difference is the correlation between the difference between the steady-state wall temperature value (dotted line) and the measured value (solid line). In this way, by calculating the intake efficiency correction value using Equation 28, the estimated intake manifold pressure value (dashed line) of this embodiment (with correction) shows good agreement with the measured value. On the other hand, if intake efficiency correction is not performed, that is, if no correction is performed, the estimated intake manifold pressure will be as shown by the dashed-dotted line, and there will be a large error from the measured value shown by the solid line.

[0105] As described above, by performing correction using estimated or measured values ​​of physical quantities that change with changes in the combustion chamber wall temperature, it is possible to correct the intake efficiency using data obtained in a steady state and a simple correction formula, and as a result, correction can be achieved with reduced adaptation work.

[0106] <Second Embodiment> Next, a second embodiment of the present invention will be described with reference to Figures 12 to 15. In this embodiment, the system configuration of the internal combustion engine, the hardware configuration of the ECU, and an example of intake metering control processing are the same as those described in Figures 1 to 3 in the first embodiment, and therefore redundant description will be omitted.

[0107] 12 is a functional block diagram showing the processing contents of the intake efficiency calculation unit 302. The basic intake efficiency calculation unit 1201 is a processing unit that calculates the reference intake efficiency based on the rotation speed and the estimated intake manifold pressure value. The reference intake efficiency is mapped using the rotation speed and the estimated intake manifold pressure as axes, and during operation, the value is searched and calculated based on the rotation speed and the estimated intake manifold pressure value. Note that this map is adapted to data measured when the combustion chamber wall surface temperature has reached a steady state.

[0108] The wall surface 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 surface temperature, which is a physical quantity that changes with changes in the combustion chamber wall surface temperature, and the wall surface temperature during operation.The wall surface temperature correction unit 1202 then determines whether the wall surface temperature is in a transient state and performs correction.The wall temperature difference calculation unit 1203 calculates the difference between the steady-state value of the wall surface temperature and the wall surface temperature during operation (the difference from the steady-state temperature).

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

[0110] 13 is a flowchart showing the processing contents of the wall surface temperature correction unit 1202 of the intake efficiency calculation unit 302. First, the wall surface temperature correction unit 1202 estimates a steady-state wall temperature value in step S1301. Next, the wall temperature difference calculation unit 1203 calculates the difference from the steady-state wall temperature value as shown in equation (29) in step S1302.

[0111]

[0112] Here, the correction T ｗ is the measured or estimated wall temperature, T ｗ，ｓｔ is the steady-state wall temperature value. Subsequently, in step S1303, the intake efficiency correction value K calculation unit 1204 calculates the intake efficiency correction value K as shown in equation (30).

[0113]

[0114] Here, T ｉｎ is the gas temperature in the intake pipe, and a measured value or an estimated value can be used. Note that equation 30 can also be derived by the following procedure. When the temperature of the air taken into the engine cylinder changes due to heat transfer on the cylinder wall surface, the energy conservation equation is given by the following equation.

[0115]

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

[31] is integrated using the factors other than the gas temperature in the cylinder as constants, and the initial value is the gas temperature T ｉｎ Then, the equation for the in-cylinder gas temperature is obtained as shown in [Equation 32].

[0117]

[0118]

[0119] Here, α may be calculated based on the operating conditions and various detected values, or may be calculated using an approximate value. For example, it is estimated to be a value of about 0.5 to 1. Next, by differentiating Equation 32, we obtain Equation 34, which is the partial derivative of the in-cylinder gas temperature with respect to the cylinder wall temperature.

[0120]

[0121] From the formulas

[16] ,

[33] , and

[34] , the following formula

[35] is obtained.

[0122]

[0123] Therefore, the intake efficiency correction amount K is expressed by the following formula (36).

[0124]

[0125] In this way, the intake efficiency correction amount K is not derived simply for the purpose of fitting, but is calculated based on an equation that governs physical phenomena. In step S1304, the wall temperature transient determination unit 1205 determines whether the wall surface temperature is in a transient state based on the following equation (37).

[0126]

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

[0128] 14 is a schematic diagram of a map for calculating the steady-state wall temperature. For example, the map may be based on the rotation speed and the gas flow rate. This map is created from data acquired when the engine is in a steady state.

[0129] Fig. 15 is a diagram showing the change over time in the estimated intake manifold pressure value when the intermediate parameter (intake efficiency) is corrected based on the difference between the estimated wall temperature value and the steady-state wall temperature value (difference from steady-state temperature). Fig. 15 shows, from top to bottom, the throttle opening, wall surface temperature, intake efficiency correction value, intake manifold pressure, and gas flow rate. The horizontal axis represents time. In the diagram of wall surface temperature, the dotted line represents the steady-state wall surface temperature value, and the solid line represents the measured value. In the diagram of intake manifold pressure, the solid line represents the measured value, the dashed line represents the estimated value according to the present application, and the dash-dotted line represents the estimated value without correction (correction coefficient K is 1).

[0130] The gas flow rate diagram shows measured or estimated values ​​with a solid line. The throttle opening diagram shows the throttle opening at time t ０ The throttle begins to open from time t １ After the throttle opening becomes constant, the throttle opening becomes constant at time t ｓ The wall temperature reaches a steady state at time t １ From t ｓ During this period, the wall temperature gradually increases due to the change in engine output caused by the change in throttle opening. Naturally, during this period, there is a difference between the wall temperature and the steady-state value of the wall temperature. By focusing on this difference, we found that it can be easily corrected using a model equation, and we derived the equation [Equation 36].

[0131] According to this embodiment, the intake efficiency correction value is appropriately calculated using equation (36), and the estimated intake manifold pressure value (dashed line) shows good agreement with the measured value. On the other hand, if the intake efficiency is not corrected, that is, if no correction is performed, the estimated intake manifold pressure will be as shown by the dashed-dotted line, and it can be seen that the error with the measured value will be large. As described above, according to the second embodiment, by using the difference from the steady-state value of the wall surface temperature, it is possible to correct the intake efficiency without having a map of intermediate parameters (intake efficiency) for the wall surface temperature.

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

[0133] Fig. 16 is a flowchart showing the processing contents of the wall surface temperature correction unit 402 of the intake efficiency calculation unit 302 in Fig. 4. First, in step S1601, the intake 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. This estimation can be made using the relationship shown in Fig. 6. Next, in step S1602, the intake efficiency correction value K calculation unit 403 calculates the intake efficiency correction value K based on the following equation.

[0134]

[0135] where C is a coefficient, p ｉｎ，ｅ is an 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. The coefficients C and D may be set to other values. The second term on the right side of Equation 38 is a term that corrects the difference between the engine wall temperature 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 engine wall temperature, which is not explicitly expressed by intake metering control but is implicitly recognized in the calculation, and the steady state. Next, in step S1603, the wall temperature transient determination unit 404 determines whether the wall temperature is in a transient state, that is, whether the wall temperature is deviating from the steady state, based on the following equation:

[0136]

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

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

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

[0140] In the example of FIG. 17, the throttle opening is ０ It starts opening from time t １ After the throttle opening becomes constant, the throttle opening becomes constant at time t ｓ The wall temperature reaches a steady state at time t １ From t ｓDuring this time, the wall temperature gradually increases due to changes in engine output caused by changes in throttle opening. At this time, the measured intake manifold pressure (solid line) gradually increases, and the measured air flow rate (solid line) gradually decreases. A difference occurs between the measured intake manifold pressure and the steady-state intake manifold pressure value (dotted line). This difference is the correlation between the difference between the steady-state wall temperature value (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 intake manifold pressure estimated value (dashed line) of this embodiment (with correction) shows good agreement with the measured value. Around time t1, a difference occurs between the estimated value and the measured value, but equation (38) corrects the error between the wall surface temperature implicitly recognized by intake metering control and the wall surface temperature during operation, so the estimated value changes over time in the direction of agreeing with the measured value. On the other hand, if the intake efficiency is not corrected, the estimated intake manifold pressure will be as shown by the dashed line, indicating an error.

[0142] As a result, even in the third embodiment, it is possible to correct the intake efficiency using data acquired in a steady state and a simple correction formula, and as a result, correction can be achieved with a reduced number of adjustment steps.

[0143] <Modifications> Note that the embodiments described above have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, some or all of the configurations and processes described in one embodiment may be combined with other embodiments.

[0144] Furthermore, in each block diagram, only control lines and information lines that are considered necessary for explanation are shown, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected. Furthermore, the process flow shown in each flowchart is only an example, and as long as the process results are the same, the order of some processes may be changed or multiple processes may be executed simultaneously.

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

[0146] The physical quantity that changes with the change in the combustion chamber wall temperature may be calculated based on one or both of the measurement value by the air flow sensor, the measurement or estimated value of the gas flow rate, and the measurement or 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 measurement or estimated value of the gas temperature in the intake pipe.

[0147] 2, the control device 100 is configured as a computer having a CPU and memory, and is configured to function as a control device by implementing a program that executes the processes described in each embodiment. Such a computer configuration is one example, and some 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] Furthermore, when the control device 100 is configured as a computer, the program to be implemented in the computer may be prepared in the memory within the control device 100, or may be stored on a recording medium such as an external memory, IC card, SD card, or optical disk and transferred.

[0149] 1...air flow sensor, 2...electronically controlled 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 thrust determination unit, 302... intake efficiency calculation unit, 303... cylinder inflow gas flow rate calculation unit, 304... cylinder flow rate 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 surface 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 surface 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 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, a calculation unit is provided that calculates an intermediate parameter indicating an intake efficiency for calculating the amount of air flowing into the cylinder 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 with a change in the combustion chamber wall surface temperature in the cylinder of the internal combustion engine. A control device for an internal combustion engine.

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

3. The calculation unit that calculates the intermediate parameter includes an estimated unit for an intake pipe pressure steady value that is the intake pipe pressure when the combustion chamber wall surface temperature reaches a steady state, and the estimated unit for the intake pipe pressure steady value 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 a throttle opening degree, an EGR valve opening degree, a measured value by an air flow rate sensor, a measured value or an estimated value of an EGR flow rate, an engine rotation speed, and a measured value or an estimated value of an intake pipe temperature. The control device for an internal combustion engine according to claim 3.

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

7. The calculation unit that calculates the correction value for the intermediate parameter includes an estimated unit for an air flow rate steady value that is the air flow rate when the combustion chamber wall surface temperature reaches a steady state, or an estimated unit for a gas flow rate steady value that is the gas flow rate when the combustion chamber wall surface temperature reaches a steady state, and the estimated unit for the gas flow rate steady value 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 a throttle opening degree and an engine rotation 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 degree, the EGR valve opening degree, 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 degree 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 the steady state. The estimation unit for the wall temperature steady value 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 a cylinder internal air amount calculation process for calculating the amount of air entering the cylinder of the internal combustion engine based on an air flow sensor, a calculation process for calculating an intermediate parameter indicating the intake efficiency for calculating the in-cylinder inflow air amount is performed 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 cylinder of the internal combustion engine. A control method for an internal combustion engine.

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