JP2011012632A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine equipped with an air flow meter outputting a positive flow rate when an actual flow rate is zero and capable of estimating the amount of air filling the cylinder with high accuracy when the air intake valve is driven again from a stop state.SOLUTION: The control device of an internal combustion engine is provided with an in-intake pipe pressure estimation means for estimating pressure in an intake pipe and an error estimation means for calculating a predicted output value of the air flow meter to calculate an error between pressure in the intake pipe calculated from the predicted output value and pressure in the intake pipe calculated from the actual output value of the air flow meter as error pressure. During a time period in which the intake valve is driven, the flow rate of air taken in the cylinder is calculated based on pressure obtained by subtracting the error pressure from the pressure in the intake pipe calculated by the in-intake pipe pressure estimation means, and when the air intake valve should be driven again from a stop state, the flow rate of the air taken in the cylinder is calculated based on the pressure in the intake pipe calculated by the in-intake pipe pressure estimation means.

Description

  The present invention relates to a control device for an internal combustion engine.

  In order to appropriately operate the internal combustion engine, it is preferable to make the air-fuel ratio at the time of combustion as close as possible to the target air-fuel ratio. For this purpose, there is known a method of estimating the amount of air charged in the cylinder when the intake valve is closed (hereinafter referred to as “cylinder charged air amount”) and determining the fuel injection amount in accordance with the cylinder charged air amount. ing. As a method of estimating the in-cylinder charged air amount, a map for calculating the in-cylinder charged air amount using the output value of the sensor for detecting various parameters of the internal combustion engine as a variable is prepared in advance. From this, a method for estimating the amount of air charged in the cylinder is known. In addition, a method is known in which model equations derived from models such as a throttle valve and an intake pipe are prepared in advance, and the in-cylinder charged air amount is estimated by numerical calculation using various parameter values and model equations of the internal combustion engine. ing.

  Among these methods, a numerical calculation method includes a throttle model that calculates the throttle valve passage air flow rate based on the throttle valve opening and the intake pipe pressure, and the intake air flow rate based on the throttle passage air flow rate and the cylinder intake air flow rate. An in-cylinder charged air amount model has been proposed that includes an intake pipe model that calculates the in-pipe pressure and the intake pipe temperature and an intake valve model that calculates the in-cylinder intake air flow rate based on the intake pipe pressure and the intake pipe temperature.

  In Japanese Patent No. 3760757, the intake pipe pressure is calculated from the sum of the throttle passage air amount calculated based on the throttle opening and the purge flow rate flowing into the intake pipe from the purge passage. An intake air amount calculation device is disclosed that calculates an intake pipe internal pressure from the intake air amount based on the calculated intake air amount and calculates an intake air amount taken into the engine based on the calculated intake pipe internal pressure.

Japanese Patent No. 3760757

  In many internal combustion engines, fuel cut control is performed to stop the supply of fuel to the combustion chamber during engine deceleration operation. If the intake valve and the exhaust valve are opened in the same manner as in normal operation during fuel cut control, air flows into the exhaust purification catalyst disposed in the engine exhaust passage. When air flows into the exhaust purification catalyst, oxygen poisoning of the so-called exhaust purification catalyst is caused, and the purification performance of the exhaust purification catalyst is lowered. For this reason, in many internal combustion engines, during fuel cut control, the intake valve is stopped in a closed state in order to prevent oxygen from flowing into the exhaust purification catalyst.

  In-cylinder charged air amount model that estimates the amount of air flowing into the cylinder using numerical calculation, the in-cylinder charged air amount including the effect of machine difference variation and errors caused by discretizing each model equation is calculated. Is done. In order to correct the calculation error, the actual output value of the air flow meter disposed in the engine intake passage is used to correct the calculated intake pipe pressure, and the cylinder intake air is corrected based on the corrected intake pipe pressure. The flow rate can be calculated.

  In an internal combustion engine that stops with the intake valve closed in fuel cut control or the like, the air flow rate in the engine intake passage becomes zero by stopping the intake valve with the intake valve closed. The intake pipe pressure is steady at almost atmospheric pressure. However, in the in-cylinder charged air quantity model that corrects the calculated intake pipe pressure using the actual output value of the air flow meter, the calculated value of the intake pipe pressure is obtained even though the intake valve is stopped in the closed state. There was a problem of rising. When the fuel cut control is completed and the intake valve is driven again, the flow rate of air flowing into the cylinder is calculated based on the calculated value of the increased intake pipe pressure. For this reason, the calculated cylinder air charge amount increases. Since fuel is injected from the fuel injection valve so as to achieve the target air-fuel ratio, the amount of fuel injection also increases. As a result, there is a problem that the actual air-fuel ratio in the cylinder becomes smaller than the target air-fuel ratio. That is, there is a problem that the air-fuel ratio at the time of actual combustion shifts to a richer side than the target air-fuel ratio.

  The present invention relates to an internal combustion engine control apparatus capable of accurately estimating the amount of air flowing into a cylinder when the intake valve is re-driven from a state where the intake valve is stopped in a closed state in an internal combustion engine where the intake valve is stopped in a closed state. The purpose is to provide.

  The first control device for an internal combustion engine of the present invention is capable of stopping the intake valve in a closed state during an operation period of the internal combustion engine, and an air flow meter that outputs a positive flow rate value when the actual flow rate is zero. A control device for an internal combustion engine arranged in an engine intake passage, which calculates a flow rate of air passing through the throttle valve based on an opening of the throttle valve, and calculates the flow rate of air passing through the throttle and the calculated flow rate of air passing through the cylinder Based on the previous in-cylinder intake air flow rate, the intake pipe pressure estimation means for calculating the intake pipe pressure and the actual opening of the throttle valve are detected, and the throttle valve is passed based on the detected actual opening. Calculate the flow rate of air passing through the throttle, calculate the expected output value that is expected to be output by the air flow meter based on the calculated flow rate of air passing through the throttle, and based on the expected output value Comprises an intake pipe pressure calculated, and error estimation means for calculating a difference between the calculated on the basis of the actual output value of the airflow meter intake pipe pressure as an error pressure Te. During the period when the intake valve is being driven, the current cylinder intake air flowing into the cylinder based on the pressure obtained by subtracting the error pressure calculated by the error estimation means from the intake pipe pressure calculated by the intake pipe pressure estimation means Calculate the flow rate. During the period when the intake valve is closed and stopped, the previous intake air flow rate in the cylinder is made zero, and the intake valve is re-driven during at least a part of the period when the intake valve is stopped and closed. If it should be, the current in-cylinder intake air flow rate flowing into the cylinder is calculated based on the pressure calculated by the intake pipe pressure estimation means.

  In the above invention, when the intake valve is to be redriven when the rate of increase in pressure calculated by the intake pipe pressure estimating means is greater than a predetermined determination value after the intake valve is stopped in the closed state. The current cylinder intake air flow rate is calculated based on the pressure obtained by subtracting the error pressure calculated by the error estimation means from the intake pipe pressure calculated by the intake pipe pressure estimation means, and the pressure rise calculated by the intake pipe pressure estimation means When the intake valve should be redriven when the rate is equal to or less than a predetermined determination value, it is preferable to calculate the current in-cylinder intake air flow rate based on the pressure calculated by the intake pipe pressure estimation means.

  In the above invention, the pressure obtained by subtracting the error pressure calculated by the error estimation means from the pressure calculated by the intake pipe pressure estimation means during the period in which the intake valve is stopped in the closed state is a predetermined maximum pressure value. When the intake valve should be re-driven when the value is larger than the above, it is preferable to calculate the current in-cylinder intake air flow rate based on a predetermined maximum pressure value.

  The control apparatus for a second internal combustion engine of the present invention is capable of stopping the intake valve in a closed state during the operation period of the internal combustion engine, and an air flow meter that outputs a positive flow rate value when the actual flow rate is zero. A control device for an internal combustion engine arranged in an engine intake passage, which calculates a flow rate of air passing through the throttle valve based on an opening of the throttle valve, and calculates the flow rate of air passing through the throttle and the calculated flow rate of air passing through the cylinder Based on the previous in-cylinder intake air flow rate, the intake pipe pressure estimation means for calculating the intake pipe pressure and the actual opening of the throttle valve are detected, and the throttle valve is passed based on the detected actual opening. Calculate the flow rate of air passing through the throttle, calculate the expected output value that is expected to be output by the air flow meter based on the calculated flow rate of air passing through the throttle, and based on the expected output value Comprises an intake pipe pressure calculated, and error estimation means for calculating a difference between the calculated on the basis of the actual output value of the airflow meter intake pipe pressure as an error pressure Te. During the period when the intake valve is being driven, the current cylinder intake air flowing into the cylinder based on the pressure obtained by subtracting the error pressure calculated by the error estimation means from the intake pipe pressure calculated by the intake pipe pressure estimation means Calculate the flow rate. While the intake valve is stopped in the closed state, the previous intake air flow rate in the cylinder is zero, and in the period in which the intake valve is stopped in the closed state, an error from the intake pipe pressure calculated by the intake pipe pressure estimation means If the intake valve is to be redriven when the pressure obtained by subtracting the error pressure calculated by the estimation means is greater than a predetermined maximum pressure value, the pressure in the cylinder is determined based on the predetermined maximum pressure value. The in-cylinder intake air flow rate this time flowing in is calculated.

  In the above invention, the predetermined maximum pressure value is an intake air amount that is calculated as the in-cylinder intake air flow rate when the actual value of the air flow meter is reached when the throttle valve is fully opened during the operation period to reach a steady state. It is preferable to update with the pressure value in the pipe.

  According to the present invention, in an internal combustion engine in which the intake valve is stopped in a closed state, the internal combustion engine control capable of accurately estimating the amount of air flowing into the cylinder when the intake valve is restarted from the closed state. An apparatus can be provided.

1 is a schematic diagram of an internal combustion engine in a first embodiment. 1 is a schematic perspective view of an air flow meter in Embodiment 1. FIG. 2 is an enlarged perspective view of a heat ray measuring unit of the air flow meter in Embodiment 1. FIG. It is a figure which shows the relationship between the output voltage of an airflow meter, and an airflow passage air flow rate. 3 is a block diagram of a first air model in Embodiment 1. FIG. It is a figure which shows the relationship between a throttle-valve opening degree and a flow coefficient. It is a figure which shows the relationship between a throttle-valve opening degree and opening cross-sectional area. It is a figure which shows function (PHI) (Pm / Pa). It is a figure which shows the basic concept of a throttle model. It is a figure which shows the basic concept of an intake pipe model. It is a figure which shows the basic concept of an intake valve model. It is a figure regarding the definition of cylinder filling air amount and cylinder intake air flow rate. FIG. 3 is a block diagram of a second air model in the first embodiment. It is a figure which shows the relationship between the depression amount of an accelerator pedal, and a target throttle valve opening degree. It is a figure which shows the relationship between a throttle passage air flow rate and complete heat dissipation. It is a figure which shows the relationship between the sum of delayed heat dissipation, and the estimated output value of an airflow meter. It is a time chart when performing control which stops an intake valve of an internal-combustion engine in a closed state. FIG. 6 is a block diagram during intake valve stop control in the second air model of the first embodiment. 6 is a graph of intake pipe pressure calculated from a model block of a second air model during intake valve stop control in the first embodiment. 5 is a flowchart of control when the intake valve should be re-driven from a state where the intake valve is stopped in a closed state in the first embodiment. It is a flowchart of control after re-driving from the state which the intake valve has stopped in the closed state. In Embodiment 2, it is a graph of the intake pipe internal pressure calculated from the model block of an air model during intake valve stop control. 9 is a flowchart for calculating a guard value for intake pipe pressure used in an air model in the second embodiment. In Embodiment 2, it is a figure which shows the relationship between the pressure in an intake pipe, and the in-cylinder intake air flow rate.

(Embodiment 1)
With reference to FIGS. 1 to 21, the control apparatus for an internal combustion engine in the first embodiment will be described.

  FIG. 1 is a schematic view of an internal combustion engine in the present embodiment. In the present embodiment, an internal combustion engine in which the engine body 1 is a cylinder injection type spark ignition type is shown. However, the present invention can be applied to another spark ignition type internal combustion engine such as a port injection type spark ignition type internal combustion engine or a compression self-ignition type internal combustion engine.

  The internal combustion engine in the present embodiment includes an engine body 1. The engine body 1 includes a cylinder block 2, a piston 3 that reciprocates within the cylinder block 2, and a cylinder head 4 that is fixed on the cylinder block 2. A combustion chamber 5 is formed between the piston 3 and the cylinder head 4. The cylinder head 4 is provided with an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 for each cylinder. Further, as shown in FIG. 1, a spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is disposed around the inner wall surface of the cylinder head 4. Further, a cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3. Further, the cylinder head 4 is provided with an intake valve control device 13 capable of continuously changing the phase angle and the valve lift amount of the intake valve 6.

  The intake port 7 of each cylinder is connected to a surge tank 15 via an intake branch pipe 14. The surge tank 15 is connected to an air cleaner 17 via an intake pipe 16. A throttle valve 19 driven by a step motor 18 is disposed in the intake pipe 16. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust pipe 20, and the exhaust pipe 20 is connected to a casing 22 containing an exhaust purification catalyst 21. In the following description, portions of the intake branch pipe 14, the surge tank 15, the intake pipe 16 and the like from the throttle valve 19 to the intake valve 6 are referred to as an intake pipe portion 23.

  The electronic control unit (ECU) 31 comprises a digital computer, and is connected to each other via a bidirectional bus 32, a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, An input port 36 and an output port 37 are provided.

  The intake pipe 16 upstream of the throttle valve 19 is provided with an air flow meter 41 for detecting the flow rate of intake air flowing through the intake pipe 16. Further, an intake air temperature sensor 42 for detecting the intake air temperature and an atmospheric pressure sensor 43 for detecting the atmospheric pressure are provided in the vicinity of the air cleaner 17. The throttle valve 19 is provided with a throttle valve opening sensor 44 that detects the opening of the throttle valve 19, and the throttle valve opening sensor 44 generates an output signal corresponding to the throttle valve opening. The air flow meter 41, the intake air temperature sensor 42, the atmospheric pressure sensor 43, and the throttle valve opening sensor 44 respectively output output signals corresponding to the intake air flow rate (mass flow rate), intake air temperature (atmospheric temperature), atmospheric pressure, and throttle valve opening. This output signal is input to the input port 36 via the corresponding AD converter 38.

  The accelerator pedal 45 is connected to a depression amount sensor 46 that generates an output voltage proportional to the depression amount of the accelerator pedal 45, and the output voltage of the depression amount sensor 46 is input to the input port 36 via the corresponding AD converter 38. Entered. The crank angle sensor 47 generates an output pulse every time the crankshaft rotates 15 degrees, for example, and this output pulse is input to the input port 36. The CPU 35 calculates the engine speed from the output pulse of the crank angle sensor 47.

  On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, the intake valve control device 13, and the step motor 18 via a corresponding drive circuit 39.

  FIG. 2 is a schematic perspective view of the air flow meter in the present embodiment, and FIG. 3 is an enlarged perspective view of a heat ray measuring unit of the air flow meter in the present embodiment. The air flow meter 41 of the present embodiment is a hot-wire flow meter, and is a flow meter that calculates the flow rate of the fluid based on the amount of heat taken away by the fluid. The air flow meter 41 includes a bypass passage that bypasses a part of the air flowing in the intake pipe 16 as shown in FIG. 2, a hot-wire metering unit 41a that measures the mass flow rate of the intake air bypassed to the bypass passage, A signal processing unit 41b that outputs a voltage corresponding to the measured mass flow rate.

  As shown in FIG. 3, the heat ray measuring unit 41 a includes an intake air temperature measurement resistor 41 a 1 made of platinum heat wire, a support unit 41 a 2 that holds the intake air temperature measurement resistor 41 a 1 connected to the signal processing unit 41 b, and a heating resistor. (Bobbin portion) 41a3 and a support portion 41a4 for connecting and holding the heating resistor 41a3 to the signal processing portion 41b. The signal processing unit 41b has a bridge circuit composed of an intake air temperature measurement resistor 41a1 and a heating resistor 41a3, and a temperature difference between the intake air temperature measurement resistor 41a1 and the heating resistor 41a3 is always constant by this bridge circuit. The power supplied to the heating resistor 41a3 is adjusted so that the power is maintained, and the supplied power is converted into a voltage and output.

  FIG. 4 shows the relationship between the output voltage of the air flow meter and the flow rate of air passing through the intake pipe in which the air flow meter is arranged. As the flow rate of air passing through the intake pipe (hereinafter referred to as “air flow air flow rate”) increases, the output voltage Vg increases.

  In the control apparatus for an internal combustion engine in the present embodiment, the combustion chamber 5 is filled when the intake valve 6 is closed in order to set the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio. The amount of air that has been discharged (hereinafter referred to as “cylinder charged air amount Mc”) is estimated, and fuel is used so that the air-fuel ratio of the mixture becomes the target air-fuel ratio based on the estimated cylinder charged air amount Mc. An amount of fuel (hereinafter referred to as “fuel injection amount”) to be injected into the combustion chamber 5 (or an engine intake passage in a port injection internal combustion engine or the like) by the injection valve 11 is determined. Therefore, in order to accurately set the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio, it is necessary to accurately estimate the cylinder charge air amount Mc. In the present embodiment, in-cylinder charged air amount Mc is calculated by numerical calculation using a throttle valve model, an intake pipe model, and an intake valve model.

  FIG. 5 shows a schematic diagram of the first air model in the present embodiment. The air model M1 as the first air model is a simple model among models applied to the internal combustion engine. Hereinafter, the air model M1 will be described.

  The air model M1 includes a throttle model M10, an intake pipe model M20, and an intake valve model M30. In the throttle model M10, the opening (throttle valve opening) θt of the throttle valve 19 detected by the throttle valve opening sensor 44 and the atmospheric pressure (or intake pipe) around the internal combustion engine detected by the atmospheric pressure sensor 43 are included. 16) Pa, the air temperature around the internal combustion engine detected by the intake air temperature sensor 42 (or the temperature of air sucked into the intake pipe 16) Ta, and an intake pipe model M20 described later. The previously calculated pressure in the intake pipe portion 23 (hereinafter referred to as “intake pipe pressure Pm”) is input, and the values of these input parameters are substituted into a model calculation formula of a throttle model M10 described later. Thus, the flow rate of air passing through the throttle valve 19 per unit time (hereinafter referred to as “throttle passage air flow rate mt”) is calculated.The throttle passage air flow rate mt calculated in the throttle model M10 is input to the intake pipe model M20.

  The intake pipe model M20 includes a throttle passage air flow rate mt calculated in the throttle model M10 and a flow rate of air flowing into the combustion chamber 5 per unit time calculated in the previous calculation (hereinafter referred to as “cylinder intake air”). The flow rate mc "is input, and the values of these input parameters are substituted into a model calculation formula of an intake pipe model M20, which will be described later, so that the pressure of the air present in the intake pipe portion 23 (intake air) The pipe pressure Pm) and the temperature of the air existing in the intake pipe portion 23 (hereinafter referred to as “intake pipe temperature Tm”) are calculated. The intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M20 are both input to the intake valve model M30, and the intake pipe pressure Pm is also input to the throttle model M10.

  In addition to the intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M20, an atmospheric temperature Ta is input to the intake valve model M30, and the values of these input parameters are set in the intake valve model M30 described later. By substituting in the model calculation formula, the current in-cylinder intake air flow rate mc is calculated. The in-cylinder charged air amount Mc is calculated using the current in-cylinder intake air flow rate mc. A fuel injection amount from the fuel injection valve is determined based on the cylinder charge air amount Mc. Further, the current in-cylinder intake air flow rate mc calculated in the intake valve model M30 is input to the intake pipe model M20 and used for the next calculation.

  As shown in FIG. 5, in the air model M1, the parameter value calculated in one model is used as an input value to another model. Therefore, in the entire air model M1, the actually input value is the throttle valve opening. There are only three parameters, θt, atmospheric pressure Pa, and atmospheric temperature Ta, and the cylinder charge air amount Mc is calculated from these three parameters.

  Next, each of the models M10 to M30 included in the air model M1 will be described. In the throttle model M10, the throttle passage air flow rate mt is calculated from the atmospheric pressure Pa, the atmospheric temperature Ta, the intake pipe pressure Pm, and the throttle valve opening θt based on the following equation (1). Here, the coefficient μt in the equation (1) is a flow coefficient in the throttle valve and is a function of the throttle valve opening θt. The flow coefficient μt in the throttle valve can be calculated from, for example, a map of the flow coefficient μt that is a function of the throttle valve opening θt stored in the ROM 34 of the ECU 31 in advance based on the graph shown in FIG. it can. The coefficient At represents the opening cross-sectional area of the throttle valve, and is a function of the throttle valve opening θt. The coefficient At can be calculated from, for example, a map of the opening cross-sectional area At, which is a function of the throttle valve opening degree θt, stored in advance in the ECU 31 based on the graph shown in FIG. The constant R is a gas constant, and is actually a value obtained by dividing the gas constant by the mass Mlmol of gas (air) per mol.

  Φ (Pm / Pa) is a function shown in the following formula (2), and κ in the formula (2) is a specific heat ratio (a constant value). Since this function Φ (Pm / Pa) can be expressed in a graph as shown in FIG. 8, such a graph is stored as a map in the ROM 34 of the ECU 31 and is actually calculated using the equation (2). Instead of this, the value of Φ (Pm / Pa) may be obtained from the map.

  Expressions (1) and (2) of the throttle model M10 are such that the gas pressure upstream of the throttle valve 19 is the atmospheric pressure Pa, the gas temperature upstream of the throttle valve 19 is the atmospheric temperature Ta, and the gas pressure downstream of the throttle valve 19 is Is the intake pipe pressure Pm, and the mass conservation law, the energy conservation law, and the momentum conservation law are applied to the model of the throttle valve 19 as shown in FIG. 9, and the gas equation of state, specific heat ratio definition formula, And by using the Meyer's relational expression.

  Referring to FIG. 5, in the intake pipe model M20, the intake pipe pressure is calculated from the throttle passage air flow rate mt, the cylinder intake air flow rate mc, and the atmospheric temperature Ta based on the following formulas (3) and (4). Pm and intake pipe temperature Tm are calculated. Vm in the equations (3) and (4) is a constant equal to the volume of the intake branch pipe 14, the surge tank 15, the intake pipe 16 and the like (intake pipe portion 23) from the throttle valve 19 to the intake valve 6. is there.

  Here, the intake pipe model M20 will be described with reference to FIG. When the total gas amount (total air amount) in the intake pipe portion 23 is M, the temporal change in the total gas amount M is the flow rate of the gas flowing into the intake pipe portion 23, that is, the throttle passage air flow rate mt, and the intake pipe portion. 23 is equal to the difference between the flow rate of the gas flowing out from the cylinder 23, that is, the in-cylinder intake air flow rate mc, and the following equation (5) is obtained by the law of conservation of mass. From (Pm · Vm = M · R · Tm), Equation (3) is obtained.

  Further, the temporal change amount of the gas energy M · Cv · Tm in the intake pipe portion 23 is equal to the difference between the energy of the gas flowing into the intake pipe portion 23 and the energy of the gas flowing out of the intake pipe portion 23. Therefore, when the temperature of the gas flowing into the intake pipe portion 23 is the atmospheric temperature Ta and the temperature of the gas flowing out from the intake pipe portion 23 is the intake pipe temperature Tm, the following equation (6) is obtained from the energy conservation law. Equation (4) is obtained from Equation (6) and the gas equation of state.

  Referring to FIG. 5, in the intake valve model M30, the in-cylinder intake air flow rate mc is calculated from the intake pipe internal pressure Pm, the intake pipe internal temperature Tm, and the atmospheric temperature Ta based on the following equation (7). . In the case of an internal combustion engine provided with a variable valve mechanism that can change the phase angle (valve timing) and operating angle of the intake valve 6 from the engine speed Ne, the constant a and the constant b in the equation (7). The value is determined from the phase angle and operating angle of the intake valve 6.

  The above-described intake valve model M30 will be described with reference to FIG. In general, the in-cylinder charged air amount Mc, which is the amount of air charged in the combustion chamber 5 when the intake valve 6 is closed, is determined when the intake valve 6 is closed (when the intake valve is closed). This is proportional to the pressure in the combustion chamber 5 when the intake valve 6 is closed. Further, the pressure in the combustion chamber 5 when the intake valve 6 is closed can be regarded as being equal to the pressure of the gas upstream of the intake valve 6, that is, the intake pipe pressure Pm. Therefore, the cylinder charge air amount Mc can be approximated as being proportional to the intake pipe pressure Pm.

  Here, the average air flow rate flowing out of the intake pipe portion 23 per a certain time (for example, a crank angle of 720 °), or the intake pipe portion 23 per a certain time (for example, a crank angle of 720 °). If the cylinder intake air flow rate mc is obtained by dividing the amount of air sucked into the combustion chambers 5 of all the cylinders by the above-mentioned fixed time, the cylinder charge air amount Mc is proportional to the intake pipe pressure Pm. The internal intake air flow rate mc is also considered to be proportional to the intake pipe internal pressure Pm. From this, the above formula (7) is obtained based on the theory and empirical rules. In Equation (7), the constant a is a proportionality coefficient, and the constant b is a value representing the burned gas remaining in the combustion chamber 5 (the amount of burned gas remaining in the combustion chamber 5 when the exhaust valve 8 is closed). Is equivalent to a value divided by time ΔT180 ° described later). In actual operation, the intake pipe temperature Tm may change greatly during transient operation. Therefore, a coefficient (Ta / Tm) derived based on theory and empirical rule is multiplied as a correction for this.

  FIG. 12 is an explanatory diagram of the in-cylinder intake air flow rate and the in-cylinder charged air amount. FIG. 12 illustrates a case where the internal combustion engine has four cylinders. The horizontal axis represents the rotation angle of the crankshaft, and the vertical axis represents the flow rate of air actually flowing from the intake pipe portion 23 into the combustion chamber 5 per unit time. Here, the cylinder intake air flow rate mc will be described. In a four-cylinder internal combustion engine, the intake valve 6 opens in the order of, for example, the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, and the intake pipes according to the valve opening amounts of the intake valves 6 corresponding to the respective cylinders. Air flows from the portion 23 into the combustion chamber 5 of each cylinder. For example, the displacement of the flow rate of the air flowing into the combustion chamber 5 of each cylinder from the intake pipe portion 23 is as shown by a broken line in FIG. 12, and this is summed up from the intake pipe portion 23 to the combustion chambers 5 of all cylinders. The flow rate of the air flowing into is as shown by the solid line in FIG. Further, for example, the in-cylinder charged air amount Mc to the first cylinder is as shown by hatching in FIG.

  On the other hand, the in-cylinder intake air flow rate mc is obtained by averaging the flow rate of the air flowing into the combustion chambers 5 of all the cylinders from the intake pipe portion 23 shown by the solid line, and is indicated by a one-dot chain line in the drawing. In the cylinder intake air flow rate mc indicated by the one-dot chain line, in the case of four cylinders, the crankshaft is 180 ° (that is, the angle 720 ° at which the crankshaft rotates during one cycle in the four-stroke internal combustion engine) The in-cylinder charged air amount Mc is obtained by multiplying the time ΔT180 ° required for rotation by an angle divided by the number. Therefore, the cylinder intake air amount Mc is calculated by multiplying the cylinder intake air flow rate mc calculated by the intake valve model M30 by ΔT180 ° (Mc = mc · ΔT180 °). More specifically, in consideration of the fact that the in-cylinder charged air amount Mc is proportional to the pressure when the intake valve is closed, the in-cylinder intake air flow rate mc when the intake valve is closed is multiplied by ΔT180 °. The filling air amount Mc.

  Next, a case where the air model M1 is mounted on a control device for an internal combustion engine and the in-cylinder charged air amount Mc is actually calculated will be described. The in-cylinder charged air amount Mc is expressed by solving the above equations (1), (3), (4), and (7) using the air model M1. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When the formula (1), the formula (3), the formula (4), and the formula (7) are discretized using the time t and the calculation interval Δt, the following formulas (8), (9), and (10) are respectively obtained. And Equation (11) is obtained. The intake pipe internal temperature Tm (t + Δt) is calculated by equation (12) from Pm / Tm (t + Δt) and Pm (t + Δt) calculated by equations (9) and (10), respectively.

  In the air model M1 implemented in this way, the throttle passage air flow rate mt (t) at time t calculated by the equation (8) of the throttle model M10 and the time calculated by the equation (11) of the intake valve model M30. The in-cylinder intake air flow rate mc (t) at t is substituted into the equations (9) and (10) of the intake pipe model M20, whereby the intake pipe internal pressure Pm (t + Δt) and the intake pipe internal temperature Tm (at time t + Δt) t + Δt) is calculated. Next, the calculated Pm (t + Δt) and Tm (t + Δt) are substituted into the equations (8) and (11) of the throttle model M10 and the intake valve model M30, whereby the throttle passage air flow rate mt (t + Δt) at time t + Δt. ) And the cylinder intake air flow rate mc (t + Δt). Then, by repeating such calculation, the cylinder intake air flow rate mc at any time t is calculated from the throttle valve opening θt, the atmospheric pressure Pa, and the atmospheric temperature Ta, and the calculated cylinder intake air flow rate mc Is multiplied by the time ΔT180 ° to calculate the in-cylinder charged air amount Mc at an arbitrary time t.

  At the time of starting the internal combustion engine, that is, at time t = 0, the intake pipe pressure Pm is equal to the atmospheric pressure (Pm (0) = atmospheric pressure), and the intake pipe temperature Tm is equal to the atmospheric temperature (Tm (0 ) = Ta), the calculation in each of the models M10 to M30 can be started.

  In the air model M1, the atmospheric temperature Ta and the atmospheric pressure Pa are assumed to be constant. However, the air model M1 may be a value that changes with time, for example, a value detected at time t by an intake air temperature sensor for detecting the atmospheric temperature. Is the atmospheric temperature Ta (t), and the value detected at time t by the atmospheric pressure sensor for detecting atmospheric pressure is substituted into the above equations (8), (10), and (11) as the atmospheric pressure Pa (t). You may do it.

  Or in order to consider the pressure loss in the air cleaner 17 arrange | positioned in the upstream of the throttle valve 19, the air cleaner model may be further added. The air cleaner model can calculate the air pressure at the outlet of the air cleaner 17 with respect to the atmospheric pressure at the inlet of the air cleaner 17 by, for example, a model equation based on Bernoulli's theorem. In this case, the air pressure at the outlet of the air cleaner calculated by the air cleaner model can be used as the air pressure input to the throttle model.

  Incidentally, as described above, the air model M1 is a simple model applied to an internal combustion engine, and an in-cylinder charged air amount Mc calculated by the air model M1 has an error with respect to an actual in-cylinder charged air amount. easy. Therefore, in the present embodiment, an air model that corrects the error of each model is used.

  FIG. 13 shows a schematic diagram of the second air model in the present embodiment. In the air model M2 as the second air model, in-cylinder charged air amount Mc is calculated based on the output value AFM of the air flow meter 41 in addition to the three parameters of the throttle valve opening θt, the atmospheric pressure Pa, and the atmospheric temperature Ta. To do. Hereinafter, the air model M2 will be described. In the description of the air model M2, detailed description will not be repeated for portions similar to the air model M1 as the first air model.

  The air model M2 includes an electronically controlled throttle model M40 and an air flow meter model (AFM model) M50 in addition to the throttle model M10, the intake pipe model M20, and the intake valve model M30. The electronically controlled throttle model M40 receives the output value Accp of the depression amount sensor 46 that generates an output voltage proportional to the depression amount of the accelerator pedal 45, and based on this, the throttle valve at a time T0 ahead of the current time. A throttle valve opening (hereinafter referred to as “throttle valve opening after a predetermined time”) θtf that is expected to reach 19 is calculated.

  The AFM model M50 is supplied with the throttle passage air flow rate mt calculated by the throttle model M10, and the input value is substituted into a model calculation formula of the AFM model M50, which will be described later. The output value (hereinafter referred to as “expected output value”) AFMmt that is expected to be output by the air flow meter 41 when the throttle passage air flow rate mt is assumed to be flowing in the intake pipe 16 where Calculated.

  That is, the output of the air flow meter 41 is specific to the actual air flow passing air flow rate (the air flow passing air flow rate and the throttle passing air flow rate are considered to be substantially the same, and will be described below as the throttle passing air flow rate). It has a response delay based on the response characteristics. The AFM model M50 is a model simulating this response characteristic, and calculates an expected output value in consideration of the response delay of the air flow meter 41.

  Here, the air model M2 can be divided into three model blocks M2 ′, M2 ″, and M2 ′ ″. The model block M2 ′ is a main model block for estimating the intake pipe pressure. The portion of the model block M2 ′ calculates an intake pipe internal pressure estimating means for calculating a throttle passage air flow rate passing through the throttle valve based on the opening degree of the throttle valve and calculating an intake pipe internal pressure based on the calculated throttle passage air flow rate. Corresponding to

  The model block M2 ″ and the model block M2 ′ ″ are error correction blocks for correcting an error included in the intake pipe pressure calculated by the main model block. The model block M2 '' detects an actual opening of the throttle valve, calculates a throttle passing air flow rate passing through the throttle valve based on the detected actual opening, and based on the calculated throttle passing air flow rate, An expected output value that is expected to be output by the air flow meter is calculated, and an intake pipe pressure is calculated based on the predicted output value.

  The model block M2 ′ ″ calculates the intake pipe pressure based on the actual output value of the air flow meter. The difference between the intake pipe pressure calculated by the model block M2 ″ and the intake pipe pressure calculated by the model block M2 ′ ″ corresponds to the error pressure included in the intake pipe pressure calculated by the model block M2 ′. To do. In the air model M2, the pressure in the intake pipe can be corrected by subtracting the error pressure from the pressure in the intake pipe calculated by the model block M2 ′.

  In the model block M2 ′, the throttle valve opening θtf is calculated by the electronically controlled throttle model M40 based on the output value Accp of the depression amount sensor 46. In the present embodiment, the model block M2 ′ is calculated based on the throttle valve opening θtf at the current time, while the time for transmitting the target throttle valve opening to the throttle valve is delayed by a predetermined time. That is, the actual throttle valve opening becomes the opening calculated by the electronic control throttle model M40 after a predetermined time. For this reason, the throttle valve opening degree of the electronically controlled throttle model M40 output at the current time substantially predicts the actual throttle valve opening degree after a predetermined time.

  Based on the calculated throttle valve opening degree θtf, a throttle model air flow rate mtf is calculated by the throttle model M10 ′. Then, the intake pipe pressure Pmf is calculated by the intake valve model M20 ′ based on the calculated throttle passage air flow rate mtf. The calculated intake pipe pressure Pmf is input to the throttle model M10 ′ and the intake valve model M30 ′. In the intake valve model M30 ′, the in-cylinder intake air flow rate mcf is calculated based on the intake pipe internal pressure Pmf and is input to the intake pipe model M20 ′.

  Therefore, in the entire model block M2 ′ of the air model M2, the cylinder intake air flow rate mcf after a predetermined time and the intake pipe pressure Pmf after the predetermined time are calculated by inputting the throttle valve opening θtf after the predetermined time. . Thus, by calculating the in-cylinder intake air flow rate mcf and the like after a predetermined time, the actual air-fuel ratio can be brought close to the target air-fuel ratio. During the transient operation of the internal combustion engine, the in-cylinder intake air flow rate changes every moment. Therefore, based on the current in-cylinder intake air flow rate (or the in-cylinder charged air amount calculated from the current in-cylinder intake air flow rate). Even if the fuel injection amount is calculated, the cylinder intake air flow rate may have already changed when the fuel is actually injected. As a result, the actual air-fuel ratio may be different from the target air-fuel ratio. In contrast, if the fuel injection amount is calculated based on the in-cylinder intake air flow rate after a predetermined time, the in-cylinder intake air flow rate calculated by the air model is obtained when the fuel is actually injected. The air-fuel ratio can be brought close to the target air-fuel ratio.

  In the second air model in the present embodiment, the output of the electronically controlled throttle model M40 is input to the throttle model M10 ′ in the model block M2 ′. However, the present invention is not limited to this form, and other estimated values or actual values are used. The throttle valve opening may be input to the throttle model M10 ′. For example, in the model block M2 ′, similarly to the first air model (see FIG. 5) in the present embodiment, the output value of the throttle valve opening sensor may be input to the throttle model M10 ′.

  Next, in the air model M2, the intake pipe internal pressure Pmf calculated in the model block M2 ′ is corrected based on the output of the air flow meter 41, and the in-cylinder charged air amount Mc is calculated based on the corrected intake pipe internal pressure. Can do.

  In the model block M2 ″, the same calculation as that of the air model M1 is performed based on the current throttle valve opening θtc detected by the throttle valve opening sensor 44. That is, the current throttle valve opening θtc and the current throttle passage air flow rate mtc are output to the throttle model M10 ″. The intake pipe model M20 ″ receives the current throttle passage air flow rate mtc and the current intake pipe internal pressure Pmc. The intake pipe pressure Pmc is input to the throttle model M10 ″ and the intake valve model M30 ″. In the intake valve model M30 ″, the current in-cylinder intake air flow rate mcc is calculated and input to the intake pipe model M20 ″.

  Based on the current throttle passage air flow rate mtc calculated in the above calculation, the AFM model M50 calculates an expected output value AFMmt that takes into account the response delay of the air flow meter 41. The calculated expected output value AFMmt is input to the intake pipe model M20 ′ ″ as the throttle passage air flow rate. Then, the intake pipe pressure Pmmdl is calculated by the intake pipe model M20 ′ ″ and the intake valve model M30 ′ ″ in the same manner as described above. The intake pipe pressure Pmmdl calculated in this way is calculated based on the current throttle valve opening θtc, and the intake pipe pressure when the throttle passage air flow rate is assumed to be equal to the output value that will be output by the air flow meter 41. Indicates pressure.

  On the other hand, in the model block M2 ′ ″, the actual output value AFM of the air flow meter 41 is input to the intake pipe model M20 ″ ″ as the throttle passage air flow rate. The intake pipe pressure Pmafm is calculated from the intake pipe model M20 ″ ″. The intake pipe model pressure Pmafm is input to the intake valve model M30 ″ ″, the in-cylinder intake air flow rate mcafm is calculated, and is input again to the intake pipe model M20 ″ ″. The intake pipe internal pressure Pmafm calculated in this way indicates the intake pipe internal pressure when it is assumed that the throttle passage air flow rate is equal to the output value of the air flow meter 41.

  The difference (Pmmdl-Pmafm) between the intake pipe pressure Pmmdl using the AFM model and the intake pipe pressure Pmafm based on the output of the air flow meter was calculated based on the current intake pipe pressure calculated by the air model and the air flow meter 41. It represents the error from the intake pipe pressure. By subtracting the error pressure (Pmmdl−Pmafm) from the intake pipe pressure Pmf calculated by the model block M2 ′, the intake pipe pressure (Pmf−Pmmdl + Pmafm) corrected for the error pressure can be calculated.

  Referring to FIG. 13, in the present embodiment, switch 51 is arranged at a portion that outputs error pressure (Pmmdl-Pmafm). During normal operation of the internal combustion engine, the switch 51 is in the connected state, and the error pressure (Pmmdl-Pmafm) is subtracted from the intake pipe pressure Pmf calculated by the main model block, and the intake pipe input to the intake valve model M30. The pressure Pmfin is calculated. Then, the intake pipe pressure Pmfin is input to the intake pipe model M30, and the cylinder charge air amount Mc is calculated based on the cylinder intake air flow rate mcfin calculated by the intake pipe model M30. A fuel injection amount is calculated on the basis of the in-cylinder charged air amount Mc.

  Next, the electronic control throttle model M40 and the AFM model M50 will be described.

  The electronically controlled throttle model M40 is a model that calculates the throttle valve opening degree θtf after a predetermined time T0 from the current time based on the depression amount of the accelerator pedal 45. In the present embodiment, a temporary target throttle valve opening degree θr1 is obtained based on the accelerator pedal depression amount Accp detected by the depression amount sensor 46 and a map created from the graph shown in FIG. A value obtained by delaying the provisional target throttle valve opening θr1 by a predetermined time T (for example, 64 msec) becomes the final target throttle valve opening θr of the throttle valve. Then, the ECU 31 sends a drive signal to the step motor 18 so as to achieve the target throttle valve opening θr.

  As described above, the target throttle valve opening degree θr of the throttle valve at the current time is the provisional target throttle valve opening degree θr1 determined according to the accelerator pedal depression amount Accp at the time before the predetermined time T from the current time. equal. If the operation delay time of the step motor 18 is ignored, the target throttle valve opening θr input to the step motor 18 is equal to the actual throttle valve opening. Based on this idea, in the electronically controlled throttle model M40, the temporary target throttle valve opening θr1 before the time (T−T0) from the current time (where 0 ≦ T0 ≦ T) is set to the predetermined time T0 from the current time. It is estimated as the throttle valve opening (throttle valve opening after a predetermined time) θtf at time t after that. In addition to the operation delay time of the step motor 18, the throttle valve opening θtf after a predetermined time may be set.

  Next, the AFM model M50 will be specifically described. 2 and 3, in the air flow meter 41, as described above, the heating resistor 41a3 is maintained so that the temperature difference between the intake temperature measuring resistor 41a1 and the heating resistor (bobbin portion) 41a3 is always kept constant. Adjust the power supplied to the. The airflow passing air flow rate is calculated based on the supplied power at that time. Here, since the supplied power indicates the amount of heat released from the bobbin portion 41a3 and the support portion 41a4 to the air passing through the intake pipe 16, the air flow meter 41 is based on the amount of heat released from the bobbin portion 41a3 and the support portion 41a4. In other words, the airflow passing air flow rate is calculated.

  More specifically, the bobbin portion 41a3 is formed by winding a platinum hot wire around a cylindrical ceramic bobbin and coating the outer periphery thereof with glass. For this reason, heat dissipation from the platinum heat wire to the surrounding air is delayed due to the glass layer interposed between the platinum heat wire and the surrounding air. Therefore, even when the flow rate of the air passing through the intake pipe 16 suddenly increases, the amount of heat released from the bobbin portion 41a3 per unit time (hereinafter simply referred to as “heat dissipation amount”) is not immediately available. It does not increase, but increases with some delay. In other words, the amount of heat released from the bobbin portion 41a3 has a response delay with respect to the actual airflow passing air flow rate. The same applies to the amount of heat released from the support portion 41a4. The amount of heat released from the support portion 41a4 has a response delay with respect to the actual airflow passing air flow rate.

It is known that this response delay can be approximated to a first-order delay, and the response delay of the heat radiation amount of the bobbin portion 41a3 is expressed by the following equation (13). Here, ω _b in the equation (13) is a heat dissipation amount of the bobbin portion 41a3 converted from the output value of the air flow meter 41, that is, a heat dissipation amount actually radiated from the platinum hot wire of the bobbin portion 41a3 as a result of the heat dissipation delay (hereinafter referred to as “heat dissipation amount”). , Referred to as “delayed heat release amount”). W _b in the equation (13) is a heat dissipation amount compensated for the response delay, that is, a heat dissipation amount radiated from the platinum heat wire of the bobbin portion 41a3 when it is assumed that no heat dissipation delay occurs (hereinafter referred to as “complete heat dissipation amount”). Designated). That is, the complete heat radiation amount W _b is equal to the heat radiation amount when the internal combustion engine is in steady operation, and is basically a function of only the flow rate of air passing through the intake pipe 16 near the air flow meter 41. Since the flow rate of air passing through the intake pipe 16 near the air flow meter 41 is substantially equal to the flow rate of air passing through the throttle, the complete heat radiation amount W _b can be considered as a function of the flow rate of air passing through the throttle. relationship between the true heat radiation amount W _b from can be represented as in Figure 15. Further, τ _b in the equation (13) is a time constant of a first-order lag in heat radiation from the bobbin portion 41a3, and a calculation method thereof will be described later.

Similarly, the response delay of the heat radiation amount of the support portion 41a4 is expressed by the following equation (14). The complete heat release amount W _b from the support portion 41a4 can also be considered as a function of the throttle passage air flow rate, and the relationship between the throttle passage air flow rate and the complete heat release amount W _s from the support portion 41a4 is as shown in the graph of FIG. Can be expressed as Further, τ _s in the equation (14) is a time constant of a first-order lag in heat dissipation from the support portion 41a4.

Delayed heat radiation amounts ω _b and ω _s from the bobbin portion 41a3 and the support portion 41a4 are calculated by the equations (13) and (14). In the air flow meter 41, the output voltage changes according to the amount of heat radiated from the bobbin portion 41a3 and the support portion 41a4 as a result of the heat radiation delay, that is, the amount of delayed heat radiation, so the equations (13) and (14) The output value (expected output value) AFMmt that the airflow meter 41 will output is calculated based on the sum of the delayed heat radiation amount calculated by (ω _b + ω _s ). In the present embodiment, the relationship between the sum of the delayed heat dissipation amount (ω _b + ω _s ) in the air flow meter 41 and the expected output value AFMmt of the air flow meter 41 is obtained in advance experimentally or by calculation, as shown in FIG. A map based on the graph is stored in the ROM 34 of the ECU 31. Then, the expected output value AFMmt of the air flow meter 41 is calculated using the map based on the sum of delayed heat dissipation ω _b + ω _s calculated from the equations (13) and (14). The calculation of the expected output value AFMmt of the air flow meter 41 based on the sum of delayed heat dissipation ω _b + ω _s using the above map can be expressed as the following equation (15).

The primary delay time constant τ _b of the bobbin portion 41a3 is calculated by the following equation (16), and the primary delay time constant τ _s of the support portion 41a4 is calculated by the following equation (17). In Expression (16) and Expression (17), u is an air flow rate per unit cross-sectional area in the flow path in the detection unit of the air flow meter 41, that is, in the bypass passage of the air flow meter 41. The air flow rate u per unit sectional area is calculated based on the output value AFM of the air flow meter 41 by a map or by a predetermined calculation formula. K _b , k _s , m _b , and m _s are constants obtained in advance by experiment or calculation, k _b and m _b are constants for the bobbin portion 41a3, and k _s and m _s are constants for the support portion 41a4. Respectively. Since the degree of response delay differs between the bobbin portion 41a3 and the support portion 41a4, a calculation for calculating an expected output value from the air flow rate through the throttle by setting the time constant by separating the bobbin portion 41a3 and the support portion 41a4. The accuracy is to be improved.

  Next, a description will be given of a case where the AFM model M50 is mounted on a control device for an internal combustion engine, and an expected output value AFMmt of the air flow meter 41 is calculated from the throttle passage air flow rate mt actually calculated by the throttle model M10. The expected output value AFMmt of the air flow meter 41 is expressed by solving the above equations (13) and (14) using the AFM model M50. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When the equations (13) and (14) are discretized using the time t and the calculation interval Δt, the following equations (18) and (19) are obtained, respectively.

In the AFM model M50 mounted in this way, the delayed heat release amount ω _b (t) from the bobbin portion 41a3, the delayed heat release amount ω _s (t) from the support portion 41a4 at time t, and the formula (8 ), The throttle passage air flow rate mt (t) at the time t calculated in step ( _b ) is substituted into the equations (18) and (19). The delayed heat radiation amount ω _s (t + Δt) from the portion 41a4 is calculated. Then, the predicted output value AFMmt (t + Δt) of the air flow meter 41 at time t + Δt is calculated by the equation (15) using these delayed heat radiation amounts ω _b (t + Δt) and ω _s (t + Δt).

  By using such an air model M2, the cylinder intake air flow rate can be calculated in consideration of the error pressure included in the air model.

  By the way, in the internal combustion engine of the present embodiment, fuel cut control is executed to stop the supply of fuel to the cylinder during engine deceleration operation. When air is circulated in the cylinder during the period when the fuel cut control is executed, that is, when air is introduced into the cylinder via the intake valve 6 and air is caused to flow out of the cylinder via the exhaust valve 8, A large amount of air flows into the exhaust purification catalyst 21.

  When air, particularly oxygen, flows into the exhaust purification catalyst 21, oxygen is adsorbed on the surface of the exhaust purification catalyst 21. Further, the noble metals supported on the exhaust purification catalyst 21 are combined with each other at a high temperature to become large particles, and the total surface area becomes small. This binding reaction is promoted by oxygen adsorbed on the surface of the exhaust purification catalyst 21. For this reason, when a large amount of air flows into the exhaust purification catalyst 21 and the amount of oxygen retained on the surface of the exhaust purification catalyst 20 increases, the oxidation ability of the noble metal may decrease (oxygen poisoning). . Therefore, it is preferable that oxygen does not flow into the exhaust purification catalyst 21 during fuel cut control.

  In the internal combustion engine of the present embodiment, intake valve stop control for stopping the intake valve 6 in the closed state is performed during the period during which fuel cut control is being executed. As a result, oxygen is suppressed from flowing into the exhaust purification catalyst 21 even during fuel cut control, and as a result, oxygen poisoning of the exhaust purification catalyst 21 is suppressed.

  FIG. 17 shows a time chart when the fuel cut control is performed. Normal operation is continued until time ts. Until time ts, the intake valve of one of the cylinders is opened continuously or intermittently, and air is sucked into the cylinder. At time ts, fuel cut control is started. During the fuel cut control period, intake valve stop control is performed to stop the intake valve in a closed state. At time ts, the in-cylinder intake air flow rate becomes zero. The actual intake pipe pressure is lower than atmospheric pressure until time ts. During the intake valve stop control period, the air flow in the intake pipe portion stops. The throttle valve 19 is not completely closed and air flows. For this reason, the pressure in the intake pipe portion 23 gradually increases and becomes a substantially constant value at atmospheric pressure.

  At time te, the fuel cut control is terminated and the intake valve stop control is terminated. At time te, the intake valve is driven again. Since the intake valve is driven again, the actual intake pipe pressure decreases again.

  FIG. 18 shows a block diagram of a second air model during intake valve stop control. When the intake valve stop control is being performed, air does not flow from the intake pipe portion 23 into the cylinder. In the air model M2, the previous in-cylinder intake calculated by the intake valve models M30 ′, M30 ″, M30 ′ ″, M30 ″ ″ in the respective model blocks M2 ′, M2 ″, M2 ′ ″. Without using the air flow rate, the previous in-cylinder intake air flow rate mc to be input to each of the intake pipe models M20 ′, M20 ″, M20 ′ ″, M20 ″ ″ is made zero. That is, in the model block M2 ′, the in-cylinder intake air flow rate mcf is set to zero. In the model block M2 ″, the in-cylinder intake air flow rate mcc is set to zero, and the in-cylinder intake air flow rate mcmdl is set to zero. In the model block M2 ′ ″, the in-cylinder intake air flow rate mcafm is set to zero. Thus, during the intake valve stop control, the previous in-cylinder intake air flow rate input to each intake pipe model is switched to zero.

  In each intake pipe model M20 ′, M20 ″, M20 ′ ″, M20 ″ ″, by substituting mc = 0 into Equation (3) and Equation (4), the following Equation (20) and Equation (21) can be derived. With the intake pipe model based on the equations (20) and (21), the intake pipe pressure Pm and the intake pipe temperature Tm in each model block can be calculated.

  Thus, the intake pipe pressures Pmf, Pmc, Pmmdl, and Pmafm can be calculated even during the intake valve stop control. From the model block M2 ′ as the main model block, the intake pipe pressure Pmf is calculated. From the model block M2 ″ and the model block M2 ′ ″ as error correction blocks, the intake pipe pressure Pmmdl and the intake pipe pressure Pmafm are calculated. Further, even during the intake valve stop control, the intake pipe pressure obtained by subtracting the error pressure (Pmmdl-Pmafm) from the intake pipe pressure Pmf calculated from the model block M2 ′ can be calculated.

  By the way, the air flow meter used in the control apparatus for an internal combustion engine in the present embodiment is a hot-wire flow meter. As described above, this air flow meter adjusts the power supplied to the heating resistor 41a3 so that the temperature difference between the intake temperature measuring resistor 41a1 and the heating resistor 41a3 is always kept constant. The voltage is output. However, even when the flow rate of air flowing through the air flow meter becomes zero, slight heat dissipation is continued from the heating resistor or the like. For this reason, the air flow meter in the present embodiment has a characteristic that the output flow rate value becomes positive even when the flow rate becomes zero.

  Referring to FIG. 4, the air flow meter in the present embodiment has a positive output voltage even when the air flow rate in the actual engine intake passage becomes zero. When the actual air flow rate becomes zero, the output voltage becomes the voltage Vg0. As described above, the air flow meter in the present embodiment outputs a signal indicating that the air flow rate is positive even if the actual air flow rate is zero.

  Referring to FIG. 18, in model block M2 ′ ″, the output value AFM of the air flow meter is input to intake pipe model M20 ″ ″. Even during the intake valve stop control period, the output value AFM of the air flow meter becomes positive. For this reason, the intake pipe pressure Pmafm calculated by the intake pipe model M20 ″ ″ increases with time.

  Referring to equation (4) of the intake pipe model described above, the flow rate mcafm of the gas flowing out from the intake pipe portion is zero, while the flow rate mt of the gas flowing into the intake pipe (the output value AFM of the air flow meter) is Become positive. For this reason, the variable (dPm / dt) becomes positive, and it can be seen that the intake pipe pressure Pmafm increases with time. The intake pipe pressure (Pmf−Pmmdl + Pmafm) obtained by correcting the error pressure calculated from the model block M2 ″ and the model block M2 ′ ″ increases with time.

  FIG. 19 shows a graph of the intake pipe pressure calculated from the main model block and the intake pipe pressure with the error pressure corrected in the second air model in the present embodiment. The horizontal axis is time, and the vertical axis is the estimated value of the intake pipe pressure. The solid line indicates the intake pipe pressure Pmf calculated from the model block M2 ′ as the main model block, and the broken line indicates the intake pipe pressure (Pmf−Pmmdl + Pmafm) obtained by correcting the error pressure.

  Until time ts, normal operation is performed. From time ts to time te, intake valve stop control is performed. The intake valve is driven again at time te. Until the time ts, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the error pressure corrected is used as the intake pipe pressure Pmfin input to the intake valve model M30. The intake valve pressure Pmf calculated from the model block M2 ′ and the error pressure calculated from the model blocks M2 ′, M2 ″, M2 ′ ″ were corrected by stopping the intake valve in the closed state at time ts. The intake pipe pressure (Pmf−Pmmdl + Pmafm) increases.

  At time ts1, the actual intake pipe pressure becomes substantially atmospheric pressure. In the period from time ts1 to time te, the intake pipe pressure Pmf calculated by the model block M2 ′ is substantially constant. However, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the error pressure corrected gradually increases. The increase in pressure is continued until the intake valve stop control is finished and the intake valve is driven again.

  When the drive of the intake valve is resumed at time te, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the corrected error pressure is larger than the actual intake pipe pressure. That is, the pressure is substantially higher than atmospheric pressure. Therefore, when the intake pipe pressure (Pmf−Pmmdl + Pmafm) with corrected error pressure is input to the intake valve model M30 when the drive of the intake valve is resumed, the in-cylinder intake air flow rate mcfin becomes the actual air flow rate. Greater than For this reason, more fuel is injected from the fuel injection valve, and the air-fuel ratio in the cylinder shifts to a richer side than the target air-fuel ratio.

  In the control apparatus for an internal combustion engine according to the present embodiment, when the intake valve is to be redriven during at least a part of the intake valve stop control period, the intake air used when the drive of the intake valve is resumed As the pipe internal pressure, the intake pipe internal pressure Pmf calculated from the model block M2 ′ as the main model block is adopted as the intake pipe internal pressure Pmfin input to the intake valve model M30. The current in-cylinder intake air flow rate mc is calculated based on the intake pipe pressure Pmf calculated from the model block M2 ′. This control makes it possible to accurately estimate the amount of air flowing into the cylinder when the intake valve is re-driven from a state where the intake valve is stopped in the closed state. As a result, the air-fuel ratio at the time of combustion in the cylinder can be brought close to the target air-fuel ratio. In the present embodiment, as shown in FIG. 18, by disconnecting the switch 51, the intake pipe pressure Pmfin input to the intake valve model M30 is used as the intake pipe pressure Pmf calculated by the model block M2 ′. Yes.

  Referring to FIG. 19, in the present embodiment, the period from time ts1 to time te is adopted as intake pipe internal pressure Pmfin for inputting intake pipe internal pressure Pmf calculated from model block M2 ′ to intake valve model M30. The period to be.

  FIG. 20 shows a flowchart of control when the intake valve is to be redriven in the control apparatus for an internal combustion engine of the present embodiment. FIG. 20 is a flowchart for selecting the intake pipe pressure Pmfin to be input to the intake valve model M30 in the first calculation when the drive of the intake valve is resumed.

  In step 101, it is determined whether or not a signal for restarting driving of the intake valve is transmitted. That is, it is determined whether or not the intake valve stop control has ended. In step 101, if the signal for resuming driving of the intake valve is not transmitted, this control is terminated. In step 101, if a signal for restarting driving of the intake valve is transmitted, the process proceeds to step 102.

  In step 102, it is determined whether or not the rate of increase of the intake pipe pressure Pmf calculated from the model block M2 ′ is greater than a predetermined determination value. That is, it is determined whether or not the intake pipe pressure Pmf is rising with a slope larger than a predetermined slope. In step 102, it is determined whether or not it is within the period from time ts to time ts1 shown in FIG. In step 102, when the rate of increase of the intake pipe pressure Pmf is larger than a predetermined determination value, the routine proceeds to step 103. In step 103, an intake pipe pressure (Pmf−Pmmdl + Pmafm) obtained by correcting the error pressure is selected as the intake pipe pressure Pmfin input to the intake valve model M30.

  If the calculated increase rate of the intake pipe pressure Pmf is equal to or smaller than a predetermined determination value in step 102, the process proceeds to step 104. That is, in the period after time ts1 shown in FIG. 19 and when the intake pipe pressure Pmf is substantially constant, the routine proceeds to step 104. In step 104, the intake pipe pressure Pmf calculated by the model block M2 ′ is selected as the intake pipe pressure Pmfin input to the intake valve model M30.

  Next, the process proceeds to step 105. In step 105, the current intake air flow rate mcfin in the cylinder is calculated by the intake valve model M30 using the intake pipe pressure Pmfin selected in step 103 or step 104.

  Referring to FIG. 19, in the present embodiment, when the intake valve is re-driven during the period from time ts to time ts1, the intake pipe pressure (Pmf− Pmmdl + Pmafm) is selected, and the current cylinder intake air flow rate mcfin is calculated. When the intake valve is re-driven during the period after time ts1, the in-cylinder intake air flow rate mcfin is calculated by selecting the intake pipe pressure Pmf calculated by the model block M2 ′.

  In the period from the start of the intake valve stop control until the pressure in the intake pipe becomes substantially constant (the period from time ts to time ts1), air flows into the intake pipe portion. For this reason, when the intake valve is re-driven during this period, the model block M2 ′ adopts the intake pipe pressure (Pmf−Pmmdl + Pmafm) in which the error pressure is corrected, as in normal operation. The accuracy is higher than when the intake pipe pressure Pmf is employed. After the intake valve is stopped in the closed state, when the intake valve is re-driven during the period until the intake pipe pressure becomes substantially constant, the cylinder pressure can be accurately determined by selecting the intake pipe pressure with the error pressure corrected. The internal intake air flow rate can be calculated. The cylinder charge air amount can be accurately calculated from the calculated cylinder intake air flow rate. In the subsequent control, the same control as in the normal operation can be performed.

  In the present embodiment, when the pressure in the intake pipe becomes substantially constant, the intake pipe internal pressure used to calculate the in-cylinder intake air flow rate is calculated from the intake pipe internal pressure with the error pressure corrected by the model block M2 ′. Although it is switched to the calculated intake pipe pressure, it is not limited to this form, and can be switched to any time during the period of intake valve stop control. For example, switching may be performed after a predetermined time has elapsed from when the pressure in the intake pipe becomes substantially constant.

  Next, control for calculating the in-cylinder intake air flow rate after re-driving the intake valve during a period after time ts when the intake pipe pressure is substantially constant will be described. Referring to FIG. 19, immediately after the drive of the intake valve is resumed at time te, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the corrected error pressure deviates from the actual intake pipe pressure. Therefore, immediately after the driving of the intake valve is resumed, the intake pipe pressure Pmf calculated by the model block M2 ′ is selected to calculate the in-cylinder intake air flow rate. When the intake pipe pressure decreases and becomes almost steady, the intake pipe flow rate is calculated by switching to the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the error pressure corrected.

  FIG. 21 shows a flowchart for selecting the intake pipe pressure to be input to the intake valve model during the period after the drive of the intake valve is resumed. In the present embodiment, the selection of the first intake pipe pressure when the intake valve is re-driven while the intake pipe pressure is substantially constant is selected according to the flowchart shown in FIG. In the second and subsequent calculations when the intake valve is re-driven, the intake pipe pressure is selected according to the flowchart shown in FIG.

  In step 111, it is determined whether or not the rate of change of the intake pipe pressure Pmf calculated by the model block M2 ′ is less than a predetermined determination value. In step 111, it is determined whether or not it is a period between time te and time te1 shown in FIG. That is, it is determined whether or not the intake pipe pressure Pmf is decreasing without substantially reaching a steady state.

  Referring to FIG. 21, when the change rate of intake pipe pressure Pmf calculated by model block M2 ′ is less than a predetermined determination value at step 111, the routine proceeds to step 112. That is, if it is the period from time te to time te1 shown in FIG. In step 112, the intake pipe pressure Pmf calculated by the model block M2 ′ is selected as the intake pipe pressure Pmfin input to the intake valve model M30.

  In step 111, if the change rate of the intake pipe pressure Pmf calculated by the model block M2 ′ is equal to or greater than a predetermined determination value, the process proceeds to step 113. If the intake pipe pressure is almost in a steady state, the routine proceeds to step 113. That is, if it is a period after time te1 shown in FIG. In step 113, an intake pipe pressure (Pmf−Pmmdl + Pmafm) obtained by correcting the error pressure is selected as the intake pipe pressure Pmfin input to the intake valve model M30.

  Next, the process proceeds to step 114. In step 114, the current in-cylinder intake air flow rate mcfin is calculated by the intake valve model M30 using the intake pipe pressure Pmfin selected in step 112 or step 113. An in-cylinder charged air amount is calculated from the calculated in-cylinder intake air flow rate.

  The control shown in FIG. 21 can be repeated until the intake pipe pressure becomes substantially steady. For example, in step 111, the calculation can be repeated until the rate of change of the intake pipe pressure Pmf is equal to or higher than a predetermined determination value. In this way, after the intake valve is re-driven during a period in which the intake pipe pressure is substantially constant, the estimated value of the intake pipe pressure input to the intake valve model is selected, so that the cylinder is The amount of air flowing into the can be calculated with high accuracy.

  In the present embodiment, the estimated value of the intake pipe pressure is switched based on the rate of change of the intake pipe pressure Pmf calculated by the model block M2 ′. The estimated value of the intake pipe pressure can be switched by an arbitrary control capable of determining whether or not. For example, when the intake valve is stopped in a closed state, the intake air flow rate mtf calculated from the throttle model M10 ′ in the model block M2 ′ becomes less than a predetermined determination value. The in-pipe pressure may be switched. Alternatively, the estimated value of the intake pipe pressure may be switched when the difference between the intake pipe pressure Pmf calculated in the model block M2 ′ and the atmospheric pressure Pa becomes less than a predetermined determination value.

  The air flow meter in the present embodiment is a hot-wire flow meter, but is not limited to this form, and this air flow meter is used when an air flow meter that outputs a positive flow value even when the actual air flow rate becomes zero is used. The invention can be applied. In addition, the calculation model included in the air model can be appropriately changed. For example, another correction term may be added to each calculation model.

(Embodiment 2)
With reference to FIG. 22 to FIG. 24, a control device for an internal combustion engine in the second embodiment will be described. The internal combustion engine in the present embodiment is the same as the internal combustion engine in the first embodiment (see FIG. 1). As in the first embodiment, the air model M2 for correcting the error pressure using the output value of the air flow meter is used as a model for estimating the amount of air flowing into the cylinder. Also, the intake valve stop control for stopping the intake valve in the closed state is the same as in the first embodiment (see FIGS. 13 and 18).

  Referring to FIG. 18, during the period in which the intake valve is stopped in the closed state, as in the first embodiment, in each model block M2 ′, M2 ″, M2 ′ ″, the intake pipe model M20 The previous in-cylinder intake air flow rates mcf, mcc, mcmd1, and mcafm input to “, M20 ″, M20 ′ ″, and M20 ″ ″ are set to zero. The control device for an internal combustion engine in the present embodiment also places the switch 51 in the connected state even during the period when the intake valve is stopped in the closed state. That is, the error pressure (Pmmdl-Pmafm) is subtracted from the intake pipe pressure Pmf.

  FIG. 22 shows a graph of the estimated value of the intake pipe pressure when performing the intake valve stop control in the present embodiment. In the present embodiment, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the corrected error pressure is guarded with a guard value as a predetermined maximum value so as not to exceed a predetermined value. As the guard value, for example, a value of almost atmospheric pressure can be adopted. In the present embodiment, the guard value is updated by calculating the intake pipe pressure PmWOT when the throttle valve is fully open and in a steady state. A method of calculating the intake pipe pressure PmWOT will be described later. The intake pipe pressure when the throttle valve is fully open is almost atmospheric pressure.

  The intake valve stop control is started at time ts. At time ts1, the intake pipe pressure has almost reached a steady state. However, as in the first embodiment, even if the actual air flow rate in the engine intake path is zero, the air flow meter outputs a positive flow rate, so that the error pressure is corrected in the intake pipe pressure (Pmf−Pmmdl + Pmafm). Will increase. At time tx, the intake pipe pressure with the corrected error pressure reaches the intake pipe pressure PmWOT as the guard value.

  At time te, the intake valve stop control is completed. At time te, when the intake valve is re-driven, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the corrected error pressure decreases. At time ty, the intake pipe pressure with the error pressure corrected reaches the guard value PmWOT. The intake pipe pressure continues to decrease until time te1, and is substantially in a steady state after time te1.

  In the present embodiment, when the intake valve is re-driven during the period from time ts to time tx, the intake pipe pressure (Pmf) with the error pressure corrected is used as the intake pipe pressure Pmfin input to the intake valve model M30. -Pmmdl + Pmafm). When the intake valve is re-driven during a period after time tx, the guard value PmWOT is selected as the intake pipe pressure Pmfin input to the intake valve model M30. In the period from time te to time ty, intake pipe pressure PmWOT is selected as the guard value. Further, in the period after time ty, the intake pipe pressure (Pmf−Pmmdl + Pmafm) with the corrected error pressure is selected.

  As described above, in the present embodiment, when the intake pipe pressure is calculated in consideration of the error and the intake pipe pressure is larger than a predetermined maximum value, the intake valve should be re-driven in advance. The in-cylinder intake air flow rate is calculated based on the determined maximum pressure value. With this control, the intake pipe pressure can be accurately estimated when the intake valve is re-driven from a state where the intake valve is closed and stopped. As a result, the in-cylinder intake air flow rate can be calculated with high accuracy.

  FIG. 23 shows a flowchart for calculating the guard value in the present embodiment. As the guard value in the present embodiment, an estimated value of the intake pipe internal pressure when the throttle valve opening is fully open and is in a steady state is employed. In the present embodiment, an operation time in which the throttle valve opening is in a steady state with the valve fully open is selected, and an estimated value of the intake pipe pressure is calculated during the operation. The calculated guard value for the intake pipe pressure is updated as appropriate. As the initial guard value, for example, a predetermined value near atmospheric pressure is stored in the ECU.

  In step 121, it is determined whether or not the opening degree TA of the throttle valve is fully open (WOT; Wide Open Throttle). In step 121, when the opening degree of the throttle valve is not fully opened, this control is finished. When the opening degree TA of the throttle valve is fully open, the routine proceeds to step 122.

  In step 122, it is determined whether or not the operating state of the internal combustion engine is substantially steady. In the present embodiment, it is determined whether or not the absolute value of the rate of change of the output value AFM of the air flow meter is less than a predetermined determination value. If the absolute value of the rate of change of the output value AFM of the air flow meter is equal to or greater than a predetermined determination value, it is determined that the operating state of the internal combustion engine is not steady, and this control is terminated. When the absolute value of the rate of change of the output value AFM of the air flow meter is less than a predetermined determination value, the process proceeds to step 123.

  In step 123, an intake pipe pressure PmWOT as a guard value is calculated. When the operation state of the internal combustion engine is steady, the output value AFM of the air flow meter becomes substantially equal to the in-cylinder intake air flow rate. For this reason, in the present embodiment, the output value AFM of the air flow meter is used as the in-cylinder intake air flow rate. An intake pipe pressure PmWOT used as a guard value is calculated from the in-cylinder intake air flow rate. In the present embodiment, the intake pipe pressure PmWOT is calculated backward from the in-cylinder intake air flow rate mcWOT using the above-described intake valve model equation (7).

  As described above, in the present embodiment, the intake pipe pressure calculated as the in-cylinder intake air flow rate when the throttle valve is fully opened and the output value of the air flow meter in the steady state is adopted as the guard value. ing. By this control, it is possible to calculate the guard value including the machine difference variation of each internal combustion engine. That is, each internal combustion engine component has machine difference variations due to manufacturing errors and the like. When the intake pipe pressure is almost atmospheric pressure, the intake pipe pressure PmWOT calculated from the actual output value of the air flow meter is adopted as a guard value, and when the intake valve is re-driven, the intake pipe pressure PmWOT is used to By calculating the intake air flow rate, the in-cylinder intake air flow rate can be accurately calculated.

  For example, when calculating the in-cylinder intake air flow rate in the air model, the intake pipe pressure Pm is input to the above-described equation (7). However, the constant a and the constant b in Equation (7) have an error due to machine difference variation. For this reason, when the atmospheric pressure is input to the intake pipe pressure Pm and the in-cylinder intake air flow rate is calculated by the equation (7), the influence of this machine difference variation remains.

  In the present embodiment, the intake pipe pressure PmWOT is calculated backward from the actual in-cylinder intake air flow rate mcWOT under the condition that the intake pipe pressure is atmospheric pressure. Since this value is calculated using, for example, the constant a and the constant b stored in the ECU 31 in the equation (7), the influence of individual differences of the respective internal combustion engines is taken into consideration. Therefore, by adopting the intake pipe pressure PmWOT as a guard value during the intake valve stop control, a more accurate in-cylinder intake air flow rate can be calculated when the intake valve is re-driven.

  FIG. 24 is a graph showing the relationship between the intake pipe pressure and the cylinder intake air flow rate. In the above description, the guard value is calculated by calculation based on Expression (7). However, the guard value is not limited to this form, and it is only necessary that the intake pipe pressure can be calculated based on the output value of the air flow meter. For example, the intake pipe pressure PmWOT at this time can be calculated from the graph shown in FIG. 24 using the output value AFMWOT of the air flow meter when the accelerator opening is fully open as the in-cylinder intake air flow rate. A map of the graph shown in FIG. 24 may be stored in the ECU 31, and the intake pipe pressure PmWOT may be calculated from the output value AFMWOT of the air flow meter.

  In the present embodiment, the calculated guard value is replaced with the previously calculated guard value. An internal combustion engine will deteriorate over time if used continuously. For this reason, the magnitude of machine difference variation changes as the internal combustion engine is used. By updating the intake pipe pressure PmWOT adopted as the guard value, it is possible to calculate the guard value including the influence of secular change in addition to the influence of machine difference variation.

  In the present embodiment, the intake pipe pressure calculated from the output value of the air flow meter is employed as the guard value. However, the present embodiment is not limited to this, and the intake pipe pressure PmWOT calculated by the air model may be employed. Absent. For example, referring to FIG. 13, when the throttle valve is fully opened and the internal combustion engine is in a steady state, the intake pipe pressure Pmafm calculated from the output value AFM of the air flow meter in the model block M2 ′ ″ is a guard value. May be adopted.

  Other configurations, operations, and effects are the same as those in the first embodiment, and thus description thereof will not be repeated here.

  The above embodiments can be combined as appropriate. For example, in the first embodiment, the estimated value of the intake pipe pressure is switched during a part of the intake valve stop control period, and the estimated value of the intake pipe pressure is guarded with a guard value during the other period. It doesn't matter.

  In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. Further, in the embodiment, changes included in the scope of claims are intended.

DESCRIPTION OF SYMBOLS 1 Engine main body 5 Combustion chamber 6 Intake valve 7 Intake port 8 Exhaust valve 11 Fuel injection valve 14 Intake branch pipe 15 Surge tank 16 Intake pipe 19 Throttle valve 41 Air flow meter 23 Intake pipe part 51 Switch

Claims (5)

A control device for an internal combustion engine in which an air flow meter that can stop the intake valve in a closed state during an operation period of the internal combustion engine and outputs a positive flow value when the actual flow rate is zero is disposed in the engine intake passage Because
Calculates the throttle passage air flow rate that passes through the throttle valve based on the throttle valve opening, and calculates the intake pipe pressure based on the calculated throttle passage air flow rate and the previous in-cylinder intake air flow rate that flows into the cylinder. Means for estimating the pressure in the intake pipe,
When the actual opening of the throttle valve is detected, the throttle passing air flow rate passing through the throttle valve is calculated based on the detected actual opening, and output by the air flow meter based on the calculated throttle passing air flow rate Error estimation means for calculating an expected predicted output value and calculating a difference between the intake pipe pressure calculated based on the expected output value and the intake pipe pressure calculated based on the actual output value of the air flow meter as an error pressure And
During the period when the intake valve is being driven, the current cylinder intake air flowing into the cylinder based on the pressure obtained by subtracting the error pressure calculated by the error estimation means from the intake pipe pressure calculated by the intake pipe pressure estimation means Calculate the flow rate,
During the period when the intake valve is closed and stopped, the previous intake air flow rate in the cylinder is made zero, and the intake valve is re-driven during at least a part of the period when the intake valve is stopped and closed. When it should be, the control apparatus for an internal combustion engine, characterized in that the current cylinder intake air flow rate flowing into the cylinder is calculated based on the pressure calculated by the intake pipe pressure estimation means. After the intake valve is stopped in the closed state, when the intake valve is to be redriven when the rate of increase in pressure calculated by the intake pipe pressure estimation means is greater than a predetermined determination value, the intake pipe pressure is estimated. Calculating the in-cylinder intake air flow rate this time based on the pressure obtained by subtracting the error pressure calculated by the error estimating means from the intake pipe pressure calculated by the means,
If the intake valve should be redriven when the rate of increase in pressure calculated by the intake pipe pressure estimation means is equal to or less than a predetermined determination value, the current in-cylinder is calculated based on the pressure calculated by the intake pipe pressure estimation means. The control apparatus for an internal combustion engine according to claim 1, wherein an intake air flow rate is calculated.   When the pressure obtained by subtracting the error pressure calculated by the error estimating means from the pressure calculated by the intake pipe pressure estimating means is larger than a predetermined maximum pressure value during the period when the intake valve is stopped in the closed state. 3. The control apparatus for an internal combustion engine according to claim 1, wherein when the intake valve is to be redriven, the current in-cylinder intake air flow rate is calculated based on a predetermined maximum pressure value. . A control device for an internal combustion engine in which an air flow meter that can stop the intake valve in a closed state during an operation period of the internal combustion engine and outputs a positive flow value when the actual flow rate is zero is disposed in the engine intake passage Because
Calculates the throttle passage air flow rate that passes through the throttle valve based on the throttle valve opening, and calculates the intake pipe pressure based on the calculated throttle passage air flow rate and the previous in-cylinder intake air flow rate that flows into the cylinder. Means for estimating the pressure in the intake pipe,
When the actual opening of the throttle valve is detected, the throttle passing air flow rate passing through the throttle valve is calculated based on the detected actual opening, and output by the air flow meter based on the calculated throttle passing air flow rate Error estimation means for calculating an expected predicted output value and calculating a difference between the intake pipe pressure calculated based on the expected output value and the intake pipe pressure calculated based on the actual output value of the air flow meter as an error pressure And
During the period when the intake valve is being driven, the current cylinder intake air flowing into the cylinder based on the pressure obtained by subtracting the error pressure calculated by the error estimation means from the intake pipe pressure calculated by the intake pipe pressure estimation means Calculate the flow rate,
During the period when the intake valve is stopped in the closed state, the previous cylinder intake air flow rate is made zero, and during the period when the intake valve is stopped in the closed state, an error from the intake pipe pressure calculated by the intake pipe pressure estimation means If the intake valve is to be redriven when the pressure obtained by subtracting the error pressure calculated by the estimation means is greater than a predetermined maximum pressure value, the pressure in the cylinder is determined based on the predetermined maximum pressure value. A control apparatus for an internal combustion engine, characterized by calculating a current in-cylinder intake air flow rate that flows in.   The preset maximum pressure value is updated with the intake pipe pressure value calculated as the in-cylinder intake air flow rate when the throttle valve is fully opened during operation and the steady state is reached. The control apparatus for an internal combustion engine according to claim 4, wherein

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