JP5240094B2 - Control device for internal combustion engine - Google Patents

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, a method is known in which the amount of air charged in the cylinder when the intake valve is closed is estimated, and the fuel injection amount is determined according to the amount of air charged in the cylinder. As a method for estimating the in-cylinder charged air amount, a map for calculating the in-cylinder charged air amount is prepared in advance using the output value of the sensor for detecting various parameters of the internal combustion engine as a variable. From this, a method for estimating the amount of air charged in the cylinder is known. In addition, there is a method in which model calculation formulas derived from models such as a throttle valve and an intake pipe are prepared in advance, and a cylinder charge air amount is estimated by numerical calculation using various parameter values and model calculation formulas of the internal combustion engine. Are known.

  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 inflow air flow rate. There has been proposed an air model composed of an intake pipe model for calculating the in-pipe pressure and the intake pipe temperature and an intake valve model for calculating the in-cylinder inflow air flow rate based on the intake pipe pressure and the intake pipe temperature (for example, Patent Document 1). reference). In this method, the cylinder charge air amount can be calculated based on the cylinder inflow air flow rate calculated from the air model.

JP-A-2005-69019 JP 2000-87767 A JP 2006-22708 A

  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 or exhaust valve is opened during fuel cut control in the same way as in normal operation, 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, many internal combustion engines continue to drive the intake valve during normal operation, and close the intake valve to prevent oxygen from flowing into the exhaust purification catalyst during fuel cut control. It is stopped in the state.

  In an internal combustion engine that stops the intake valve in a closed state in fuel cut control or the like, the actual air flow rate flowing out from the intake pipe becomes zero by stopping the intake valve in the closed state. During the period when the intake valve is stopped in the closed state, the throttle valve is maintained in a slightly open state, and therefore the intake pipe pressure rises. The intake pipe pressure is steady at almost atmospheric pressure.

  In the air model for estimating the in-cylinder inflow air flow rate, the air flow rate that has passed through the throttle valve is estimated. Based on the air flow rate that has passed through the throttle valve, the pressure in the intake pipe downstream of the throttle valve is estimated. This pressure is the pressure averaged over time. In the air model, the in-cylinder inflow air flow rate that flows into the cylinder is calculated using the calculated intake pipe pressure using the intake valve model calculation formula.

  In an internal combustion engine in which the intake valve is stopped in a closed state, when the intake valve is redriven from a state in which the intake valve is stopped in a closed state, the intake valve model calculation formula when the intake valve is continuously driven Can be used to calculate the in-cylinder inflow air flow rate. However, when the in-cylinder inflow air flow rate is calculated using the same model calculation formula as that when the intake valve is continuously driven, an error becomes large. That is, when the intake valve is re-driven, an error in the in-cylinder charged air amount calculated by the air model is large.

  The amount of fuel supplied into the cylinder is determined in accordance with the in-cylinder charged air amount. When the error in the cylinder inflow air flow rate increases, the error in the cylinder charge air amount also increases. For this reason, there is a problem that an error in the amount of fuel injected into the cylinder increases, and an error in the air-fuel ratio when the fuel burns increases.

  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 can stop the intake valve in a closed state during the operation period of the internal combustion engine, and can control the air pressure upstream of the intake valve based on the flow rate of air passing through the throttle valve. A control device for an internal combustion engine that calculates a certain intake pipe pressure and calculates a cylinder inflow air flow rate that flows into the cylinder based on the calculated intake pipe pressure. It is calculated from a model calculation formula including at least one constant as a variable. A constant during driving for calculating the in-cylinder inflow air flow rate while the intake valve continues to be driven, and the in-cylinder inflow air flow rate when the intake valve should be restarted from a closed state It has a constant at the time of re-driving for calculating. When the intake valve is to be re-driven from a closed state, the control device for the internal combustion engine calculates the in-cylinder inflow air flow rate by a model calculation formula using a constant at the time of re-drive.

  In the above invention, the in-cylinder inflow air flow rate is calculated by the model calculation formula of the following formula (1), and when the drive of the intake valve is continued, the constant a and b during driving are used. When the in-cylinder inflow air flow rate is calculated and the intake valve is to be re-driven from the closed state, the in-cylinder inflow air flow rate can be calculated using the constant a and the constant b during the re-drive. .

Where mc is the in-cylinder inflow air flow rate, Pm is the intake pipe internal pressure, Ta is the atmospheric temperature, and Tm is the intake pipe internal temperature.
In the above invention, it is preferable to have a plurality of re-driving constants depending on the operating state of the internal combustion engine, and to select the re-driving constant based on the operating state of the internal combustion engine. With this configuration, the estimation accuracy of the in-cylinder inflow air flow rate is improved.

  The control device for a second internal combustion engine of the present invention can stop the intake valve in a closed state during the operation period of the internal combustion engine, and can control the air pressure upstream of the intake valve based on the flow rate of air passing through the throttle valve. A control device for an internal combustion engine that calculates a certain intake pipe internal pressure and calculates a cylinder inflow air flow rate flowing into the cylinder based on the calculated intake pipe internal pressure, wherein the intake valve is stopped in a closed state When re-driving from the above, the in-cylinder inflow air flow rate is calculated based on a pressure obtained by subtracting a predetermined correction pressure from the calculated intake pipe pressure.

  In the above invention, it is preferable to have a plurality of predetermined correction pressures depending on the operating state of the internal combustion engine, and to select the predetermined correction pressure based on the operating state of the internal combustion engine. With this configuration, the estimation accuracy of the in-cylinder inflow air flow rate is improved.

  According to the present invention, it is possible to provide a control device for an internal combustion engine that can accurately estimate the amount of air flowing into a cylinder when the intake valve is re-driven from a closed state and stopped.

1 is an overall view of an internal combustion engine equipped with a control device of the present invention. 3 is a block diagram of an air model for calculating an in-cylinder charged air amount according to Embodiment 1. FIG. It is a graph which shows the relationship between a throttle opening and a flow coefficient. It is a graph which shows the relationship between throttle opening and opening cross-sectional area. It is a graph which shows the function (Pm / Pm). 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 inflow air flow volume. 2 is a time chart for explaining an operating state of the internal combustion engine in the first embodiment. It is a block diagram explaining the flow of the parameter of the air model during intake valve stop control. It is the schematic of a cylinder when an intake valve closes completely. It is a graph explaining the time fluctuation | variation of the pressure in an intake pipe when an internal combustion engine is drive | operated by the 1st engine speed. It is a graph explaining the time fluctuation of the intake pipe pressure when the internal combustion engine is operated at the second engine speed. 9 is a time chart when the intake valve stop control is terminated and the intake valve is re-driven in the second embodiment.

(Embodiment 1)
With reference to FIGS. 1 to 14, the control apparatus for an internal combustion engine in the first embodiment will be described. In this embodiment, a cylinder injection type spark ignition type internal combustion engine is illustrated, but the present invention is another spark ignition type internal combustion engine such as a port injection type spark ignition type, or a compression self-ignition type internal combustion engine. The present invention can also be applied.

  FIG. 1 is an overall schematic diagram of an internal combustion engine in the present embodiment. The internal combustion engine includes an engine body 1. The engine main body 1 in the present embodiment 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 cylinder (combustion chamber) 5 is formed between the piston 3 and the cylinder head 4. In the cylinder head 4, an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 are arranged for each cylinder 5. Further, a spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4. A fuel injection valve 11 that supplies fuel F into the cylinder 5 is disposed around the inner wall surface of the cylinder head 4. A cavity 12 is formed on the top surface of the piston 3 so as to extend from below the injection port of the fuel injection valve 11 to below the spark plug 10.

  The intake port 7 is connected to a surge tank 14 via an intake branch pipe 13 for each cylinder 5. The surge tank 14 is connected to the air cleaner 16 via the upstream side intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the upstream side intake pipe 15. On the other hand, the exhaust port 9 is connected to the exhaust pipe 19. The exhaust pipe 19 is connected to the exhaust purification catalyst 20.

  The intake valve 6 is provided with a variable valve mechanism 21 that can change the phase angle and the operating angle of the intake valve 6. The variable valve mechanism 21 can freely change the valve timing corresponding to the opening timing or closing timing of the intake valve 6 and the operating angle corresponding to the period during which the intake valve 6 is open. Further, the variable valve mechanism 21 can be stopped while the intake valve 6 is closed. That is, the closed state of the intake valve 6 can be maintained during a period corresponding to the intake process of the combustion cycle.

  The control device for an internal combustion engine in the present embodiment includes an electronic control unit 31. 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 internal combustion engine also includes a throttle opening sensor 43 for detecting the opening of the throttle valve 18. The output signal of the throttle opening sensor 43 is input to the input port 36 via the corresponding AD converter 38. The internal combustion engine includes an atmospheric pressure sensor 45 for detecting the pressure of the atmosphere around the internal combustion engine or the pressure of the air sucked into the upstream side intake pipe 15 through the air cleaner 16 (intake pressure), and the atmospheric pressure around the internal combustion engine. And an atmospheric temperature sensor 44 for detecting the temperature or the temperature of the air sucked into the upstream side intake pipe 15 through the air cleaner 16 (intake air temperature). These sensors 44 and 45 generate output voltages proportional to the atmospheric pressure and the atmospheric temperature, respectively, and these output voltages are input to the input port 36 via the corresponding AD converters 38. An air flow meter 42 for measuring the air flow rate is disposed in the upstream side intake pipe 15. The output signal of the air flow meter 42 is input to the input port 36 via the corresponding AD converter 38.

  A load sensor 47 that generates an output voltage proportional to the amount of depression of the accelerator pedal 46 is connected to the accelerator pedal 46. The output voltage of the load sensor 47 is input to the input port 36 via the corresponding AD converter 38. The internal combustion engine includes a crank angle sensor 48. For example, the crank angle sensor 48 generates an output pulse every time the crankshaft rotates 30 degrees, and the 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 48.

  On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, and the step motor 17 for the throttle valve via a corresponding drive circuit 39.

  By the way, the amount of fuel to be injected into the cylinder 5 from the fuel injection valve 11 (hereinafter referred to as “fuel injection amount”) is determined based on the amount of air charged in the cylinder 5. The fuel ratio is determined so as to become the target air-fuel ratio. Therefore, in order to set the air-fuel ratio of the air-fuel mixture in the cylinder 5 to the target air-fuel ratio, it is necessary to estimate the amount of air charged in the cylinder 5 (hereinafter referred to as “cylinder charged air amount”). In the present embodiment, the in-cylinder charged air amount is calculated by numerical calculation using a model calculation formula derived from the model of each device.

  FIG. 2 is a block diagram of an air model for estimating the in-cylinder charged air amount in the present embodiment. The air model shown in FIG. 2 is a simple model among many types of air models. In the following description, the air model shown in FIG. 2 is taken as an example, but the control device of the present invention is applied to an air model that calculates the amount of air charged in the cylinder using model calculation formulas of various devices. Can do.

  The air model M10 includes a throttle model M11 that models a throttle valve, an intake pipe model M12 that models an engine intake passage from the throttle valve to the intake valve, and an intake valve model M13 that models an intake valve. In the throttle model M11, the opening (throttle opening) θt of the throttle valve 18 detected by the throttle opening sensor 43 and the atmospheric pressure detected by the atmospheric pressure sensor 45 (or the intake air upstream of the throttle valve 18). In the intake pipe model M12, the pressure of air sucked into the pipe (Pa), the atmospheric temperature detected by the atmospheric temperature sensor 44 (or the temperature of air sucked into the intake pipe upstream of the throttle valve 18) Ta, and The calculated pressure (hereinafter referred to as “intake pipe pressure”) Pm in the engine intake passage from the throttle valve 18 to the intake valve 6 is input, and the value of each of these input parameters is used as a model calculation formula of the throttle model M11. By substituting, the flow rate of air passing through the throttle valve 18 per unit time (hereinafter referred to as “the flow rate of air passing through the throttle valve”). That) mt is calculated.

  Further, the intake pipe model M12 includes a throttle valve passage air flow rate mt calculated in the throttle model M11 described above and a flow rate of air flowing into the cylinder 5 per unit time calculated in the intake valve model M13 (hereinafter referred to as the following). "In-cylinder inflow air flow rate") mc and atmospheric temperature Ta are input. By substituting these input parameter values into the model calculation formula of the intake pipe model M12, the intake pipe pressure Pm and the temperature of the air in the engine intake passage from the throttle valve 18 to the intake valve 6 (hereinafter, “ Tm) ”(referred to as“ intake pipe temperature ”).

  The intake valve model M13 is supplied with the intake pipe pressure Pm, the intake pipe temperature Tm, and the atmospheric temperature Ta calculated in the intake pipe model M12. The in-cylinder inflow air flow rate mc is calculated by substituting these input parameter values into the model calculation formula of the intake valve model M13.

  In this method, the in-cylinder charged air amount Mc, which is the amount of air charged in the cylinder 5 when the intake valve 6 is closed, is calculated using the in-cylinder inflow air flow rate mc.

  In the air model M10, parameter values calculated in each model are used as parameter values input to another model. Therefore, in the entire air model M10, the actually input parameter values are the throttle opening θt and the atmospheric pressure Pa. , And the atmospheric temperature Ta. That is, the in-cylinder charged air amount Mc can be calculated from the three parameters.

  Next, the models M11 to M13 of each device will be described in detail. In the throttle model M11, the atmospheric pressure Pa, the atmospheric temperature Ta, the intake pipe pressure Pm, and the throttle opening θt are input to the following equation (2), and the throttle valve passing air flow rate mt is calculated by solving this equation. The

In Expression (2), μt is a flow coefficient in the throttle valve, which is a function of the throttle opening θt, and is determined from the map shown in FIG. At is the opening cross-sectional area of the throttle valve 18, which is a function of the throttle opening θt, and is determined from the map shown in FIG. The flow rate coefficient μt and the opening cross-sectional area At may be obtained from one map as a function of the throttle opening θt. R is a constant relating to the gas constant, and is a value obtained by dividing the so-called gas constant R ^* by the mass of air Ma per mole (R = R ^* / Ma).
Further, Φ (Pm / Pa) is a function having Pm / Pa as a variable, as shown in the following equation (3).

  In Expression (3), κ is a specific heat ratio, and is a constant value in the present embodiment.

  Note that there is a relationship as shown in FIG. 5 between the function Φ (Pm / Pa) and Pm / Pa. Therefore, instead of the equation (3), a map for calculating the function Φ (Pm / Pa) having Pm / Pa as a variable is stored in the ROM 34 in advance, and the function Φ (Pm / Pa) is calculated from Pm / Pa and this map. The value of Pa) may be calculated.

These equations (2) and (3) indicate that the pressure of the air upstream of the throttle valve 18 is atmospheric pressure Pa, the temperature of the air upstream of the throttle valve 18 is the atmospheric temperature Ta, and the air passing through the throttle valve 18 With respect to the throttle valve 18 with the pressure as the intake pipe pressure Pm, the law of conservation of mass and the law of conservation of energy between the air upstream of the throttle valve 18 and the air that has passed through the throttle valve 18 are based on the model shown in FIG. , And the relational expression established in the law of conservation of momentum, and the equation of state of gas, the specific expression of the specific heat ratio (κ = Cp / Cv), and the Mayer relational expression (Cp = Cv + R ^* ) . Here, Cp is a constant pressure specific heat, Cv is a quantitative specific heat, and R ^* is a so-called gas constant.

  Next, the intake pipe model M12 will be described. In the intake pipe model M12, the throttle valve passage air flow rate mt, the in-cylinder inflow air flow rate mc, and the atmospheric temperature Ta are input to the following equations (4) and (5), and by solving these equations, Pm and intake pipe temperature Tm are calculated.

  In the equations (4) and (5), V is the upstream intake pipe 15 from the throttle valve 18 to the intake valve 6, the surge tank 14, the intake branch pipe 13, and the intake port 7 (hereinafter collectively referred to as “intake The sum of the volume of the “tube portion”) and is usually a constant value.

  It should be noted that these equations (4) and (5) are related to the intake pipe portion on the basis of the model shown in FIG. It is derived from the relational expression that holds in the law of conservation of mass and the law of conservation of energy with the air flowing into the cylinder.

  Specifically, when the total amount of air in the intake pipe portion is M, the temporal change in the air amount M is caused by the flow rate of air flowing into the intake pipe portion (throttle valve passage air flow rate) mt and the intake pipe portion. Since it is equal to the difference between the flow rate of the air flowing out and flowing into the cylinder (cylinder inflow air flow rate) mc, the following equation (6) is established from the viewpoint of conservation of mass.

From the equation (6) and the gas equation of state (Pm · V = M · R ^* · Tm), the above equation (4) is derived.

  Further, the amount of time change of the energy amount M · Cv · Tm of the air in the intake pipe portion is the energy amount of air flowing into the intake pipe portion and the energy amount of air flowing out of the intake pipe portion and into the cylinder. Therefore, if the temperature of the air flowing into the intake pipe portion is the atmospheric temperature Ta, and the temperature of the air flowing out of the intake pipe portion and flows into the cylinder is the intake pipe temperature Tm, The following equation (7) is established.

  Then, the equation (5) is derived from the equation (7) and the gas state equation described above.

  Next, the intake valve model M13 will be described. In the intake valve model M13, the intake pipe pressure Pm, the intake pipe temperature Tm, and the atmospheric temperature Ta are input to the following equation (8), and by solving this equation, the cylinder inflow air flow rate mc is calculated.

  In equation (8), which is a model calculation formula for the intake valve model M13, the constant a is a proportionality coefficient, and the constant b is a value representing the amount of gas remaining in the cylinder 5 when the exhaust valve 8 is closed. . Further, the constant a and the constant b in the present embodiment are appropriately changed by detecting the engine speed NE as will be described later. A constant a and a constant b as a function of the engine speed NE are stored in the ROM 34 of the electronic control unit 31.

  Equation (8) is derived from theory and empirical rules regarding the intake valve 6 on the basis of the model as shown in FIG. 8 on the assumption that the in-cylinder inflow air flow rate mc is proportional to the intake pipe pressure Pm. Furthermore, when the operating state of the internal combustion engine is changing, that is, during transient operation, the intake pipe temperature Tm may change greatly. Therefore, as a correction coefficient for compensating for the change in the intake pipe temperature Tm, And Ta / Tm derived from the rule of thumb. Derivation of equation (8) will be described later.

  Note that the in-cylinder inflow air flow rate mc calculated by the equation (8) is an average value of the flow rate of air flowing out from the intake pipe portion per unit time. The in-cylinder charged air amount Mc in each cylinder 5 can be calculated by multiplying the time taken for the cycle by the number of cylinders.

  Next, the in-cylinder inflow air flow rate and the in-cylinder charged air amount will be described with reference to FIG. 9, taking an internal combustion engine having four cylinders as an example. The horizontal axis is the crank angle (rotation angle), and the vertical axis is the amount of air flowing from the intake pipe portion into the cylinder 5 per unit time. In the example shown in FIG. 9, the intake stroke is performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. When the intake stroke is performed in this way, the flow rate of air flowing into each cylinder 5 from the intake pipe portion changes as indicated by the broken line in FIG. 9, and as a result, the flow rate of air flowing out from the intake pipe portion is 9 will change as indicated by the solid line in FIG.

  The average value of the flow rate of air flowing out from the intake pipe portion (solid line in FIG. 9) is the in-cylinder inflow air flow rate mc, which is indicated by a one-dot chain line. Therefore, the in-cylinder charged air amount Mc in each cylinder 5 is equal to the in-cylinder inflow air flow rate mc (the dashed line in FIG. 9) and the time required for one cycle of the internal combustion engine (in the example shown in FIG. Is calculated by multiplying the time obtained by dividing the time (degree required for rotation) by the number of cylinders, that is, the time required for the crankshaft to rotate 180 degrees in the example shown in FIG. The in-cylinder charged air amount Mc in each cylinder 5 calculated in this way corresponds to, for example, the hatched portion in FIG.

  Next, a method for calculating the in-cylinder charged air amount Mc when the air model M10 described above is mounted on an internal combustion engine will be described.

  The in-cylinder charged air amount Mc is obtained from the equations (2) to (5) and (8) of each model of the air model M10. These five equations are calculated by the electronic control unit 31 when mounted on the internal combustion engine. Discretized for processing. That is, assuming that the time is t and the calculation interval (calculation period) is Δt, these five equations are discretized as shown in the following equations (9) to (13).

  According to the air model M10 discretized and mounted in the internal combustion engine in this way, the throttle valve passing air flow rate mt (t) at the time t calculated in the throttle model M11 and the time t calculated in the intake valve model M13. The in-cylinder inflow air flow rate mc (t) and the intake pipe temperature Tm (t) at time t are input to the expressions (11) and (12) of the intake pipe model M12, and these expressions (11) and ( By solving 12), the intake pipe pressure Pm (t + Δt) and the intake pipe temperature Tm (t + Δt) at time (t + Δt) are calculated.

  Then, the intake pipe pressure Pm (t + Δt) calculated in the intake pipe model M12 and the throttle opening θt (t) at time t are input to the equations (9) and (10) of the throttle model M11, and these equations are solved. Thus, the throttle valve passing air flow rate mt (t + Δt) at time (t + Δt) is calculated.

  Further, the intake pipe pressure Pm (t + Δt) and the intake pipe temperature Tm (t + Δt) calculated in the intake pipe model M12 are input to the expression (13) of the intake valve model M13, and the time (t + Δt) is obtained by solving this expression. The in-cylinder inflow air flow rate mc (t + Δt) at is calculated.

  By repeating such calculation, the in-cylinder inflow air flow rate mc at any time is calculated. Then, as described above, the in-cylinder inflow air amount Mc of each cylinder at an arbitrary time is obtained by multiplying the thus calculated in-cylinder inflow air flow rate mc by the time obtained by dividing the time required for one cycle by the number of cylinders as described above. Calculated.

  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 Pa (Pm (0) = Pa), while the intake pipe temperature Tm is equal to the atmospheric temperature Ta. (Tm (0) = Ta) and calculation in each of the models M11 to M13 is started.

  Further, as the atmospheric pressure Pa and the atmospheric temperature Ta used in the air model M10 described above, the atmospheric pressure and the atmospheric temperature when the calculation of the air model M10 is started may be always used, or the atmospheric pressure Pa (t at time t ) And the atmospheric temperature Ta (t). Thus, an estimated value can be calculated using the model formula of each device.

  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 5 during engine deceleration operation. When the fuel cut control is executed in this way, if air is circulated in the cylinder 5, that is, air is caused to flow into the cylinder 5 via the intake valve 6, and air is supplied from the cylinder 5 via the exhaust valve 8. When it flows out, a large amount of air flows into the exhaust purification catalyst 20.

  When air, particularly oxygen, flows into the exhaust purification catalyst 20, oxygen is adsorbed on the surface of the exhaust purification catalyst 20. Further, the noble metals supported on the exhaust purification catalyst 20 are combined with each other at a high temperature to become large particles, and this binding reaction is promoted by oxygen adsorbed on the surface of the exhaust purification catalyst 20. For this reason, when a large amount of air flows into the exhaust purification catalyst 20 and the amount of oxygen retained on the surface of the exhaust purification catalyst 20 increases, the oxidation ability and the like of the noble metal decreases (oxygen poisoning).

  For this reason, in the internal combustion engine of the present embodiment, when the fuel cut control is executed, the intake valve stop control for stopping the intake valve 6 in the closed state is executed. As a result, oxygen is suppressed from flowing into the exhaust purification catalyst 20 even during fuel cut control, and as a result, oxygen poisoning of the exhaust purification catalyst 20 is suppressed.

  FIG. 10 shows a time chart when the fuel cut control is performed in the internal combustion engine in the present embodiment. Until time ts, normal operation in which the intake valve is continuously driven is executed. In the internal combustion engine in the present embodiment, air is continuously flowing into the cylinders until the time ts because the intake valve of any of the cylinders is open. Until the time ts, the actual intake pipe pressure is lower than the atmospheric pressure.

  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 inflow air flow rate becomes zero. During the intake valve stop control period, the air flow in the intake pipe portion stops. The throttle valve 19 is not completely closed but is maintained in a slightly open state, and air flows therethrough. For this reason, the pressure in the intake pipe 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. The intake valve is driven again at time te. When the intake valve is driven again, the actual pressure in the intake pipe decreases again to a pressure corresponding to the operating state of the engine body.

  FIG. 11 shows a block diagram of an air model when intake valve stop control is performed. When the intake valve stop control is being executed, air does not flow from the intake pipe portion into the cylinder. Therefore, in the present embodiment, during the intake valve stop control, the calculation of the in-cylinder inflow air flow rate by the intake valve model M13 is stopped and the in-cylinder inflow air flow rate mc input to the intake pipe model M12 is zero. It is said.

  In the intake pipe model M12, the following expressions (14) and (15) are derived by substituting mc = 0 into the above expressions (4) and (5). The intake pipe internal pressure Pm and the intake pipe internal temperature Tm are calculated from the equations (14) and (15). Even during the period when the intake valve stop control is being executed, the intake pipe pressure Pm can be continuously calculated.

  After the intake valve has been re-driven, the cylinder charge air amount can be estimated using an air model during normal operation. For example, as shown in FIG. 2, the intake pipe pressure Mm and the intake pipe temperature Tm are calculated by the intake pipe model M12, and the inflow cylinder air amount mc calculated by the intake valve model M13 is used. Mc can be calculated.

  Next, the derivation of the model calculation formula of the intake valve model in the present embodiment will be exemplified.

  FIG. 12 is a schematic view of a cylinder portion of the internal combustion engine in the present embodiment. FIG. 12 is a schematic view when the intake valve is completely closed in the intake process of the combustion cycle. That is, the moment when the intake valve 6 is closed and the cylinder 5 is in a sealed space is shown. When the intake valve 6 is completely closed, the relationship between the pressure Pc in the cylinder 5, the temperature Tc in the cylinder 5, the volume Vc in the cylinder 5, and the air amount Mt existing in the cylinder 5 depends on the gas equation of state. It can be defined by the following equation (16).

  Here, the intake pipe pressure Pm when the intake valve 6 is completely closed can be regarded as equal to the pressure Pc in the cylinder 5 (Pc≈Pm). Therefore, the following formula (17) can be obtained by substituting Pc = Pm into the formula (16).

  Next, a new air amount (in-cylinder charged air amount) Mc flowing into the cylinder 5 in the intake process, an air amount Me remaining in the cylinder 5 at the start of the intake process, and the intake valve 6 in the intake process The relationship with the air amount Mt existing in the cylinder 5 when is completely closed is expressed by the following equation (18).

  From the above equations (17) and (18), the in-cylinder charged air amount Mc, which is a new amount of air flowing into the cylinder 5 in the intake stroke, can be expressed by the following equation (19).

  From the equation (19), the cylinder charge air amount Mc can be considered to be proportional to the intake pipe pressure Pm. Here, the in-cylinder charged air amount Mc is obtained by setting the flow rate mc of the air flowing into the cylinder 5 during the valve opening period of the intake valve 6 (cylinder inflow air flow rate) mc over the valve opening period of the intake valve 6 over time. It is obtained by integrating. That is, there is a relationship between the in-cylinder charged air amount Mc and the in-cylinder inflow air flow rate mc that the time integral value of the in-cylinder inflow air flow rate mc is the in-cylinder charged air amount Mc. In the above equation (19), if approximately Mc = mc · to (to: intake valve opening time) is substituted and transformed, the in-cylinder inflow air flow rate mc is expressed by the following equation (20). be able to.

  In the equation (20), the term [Vc / (to · R · Tc)] is a constant a, the term (Me / to) is a constant b, and a correction coefficient for compensating for the change in the intake pipe temperature Tm ( By multiplying (Ta / Tm), the above equation (8) can be derived.

  By the way, referring to the above equation (19), the in-cylinder charged air amount Mc is proportional to the pressure in the intake pipe portion 13 when the intake valve is completely closed (the moment when the cylinder is sealed). That is, when the intake pipe pressure when the intake valve 6 is completely closed is high, the in-cylinder charged air amount Mc increases, and when the intake pipe pressure when the intake valve 6 is completely closed is small, The in-cylinder charged air amount Mc is reduced.

  FIG. 13 shows a graph of the intake pipe internal pressure when the internal combustion engine of the present embodiment is operated at the first engine speed. The horizontal axis is time, and the vertical axis is the intake pipe pressure. In the example shown in FIG. 13, the intake valve is continuously driven, and the operation state of the internal combustion engine is steady.

  During the period in which the drive of the intake valve continues, the intake pipe pressure decreases as the intake valve of any cylinder opens and air flows into the cylinder in the intake process of the combustion cycle. The reduced intake pipe pressure is recovered by closing the intake valve. As described above, since the intake pipe pressure fluctuates as the intake valve is driven, the actual intake pipe pressure pulsates. The intake valve is completely closed at time tc during the period in which the actual intake pipe internal pressure rises and falls. That is, the closing of the intake valve is completed at time tc.

  On the other hand, the intake pipe pressure Pm calculated by the air model in the present embodiment is an average value of pulsating pressure. In the example shown in FIG. 13, when the actual intake pipe pressure is larger than the intake pipe pressure Pm calculated by the intake pipe model M12, the intake valve is completely closed.

  Referring to the above equation (19), the in-cylinder charged air amount depends on the intake pipe pressure at the moment when the intake valve is completely closed. For this reason, in the example shown in FIG. 13, when the in-cylinder charged air amount Mc is calculated using the intake pipe pressure Pm calculated by the intake pipe model M12, a value smaller than the actual in-cylinder charged air amount is calculated. . For this reason, in the intake valve model M13 in the present embodiment, the constants a and b in the equation (8) for calculating the in-cylinder inflow air flow rate mc are adapted. For example, in the example shown in FIG. 13, a large constant is used as the constant a. In equation (8), which is a model calculation formula of the intake valve model, the timing at which the intake valve is completely closed with respect to the pulsation of the intake pipe pressure can be taken into account by using the matched constants a and b. The estimation accuracy of the inner filling air flow rate is improved.

  Here, in the pressure range where pulsation occurs, the intake pipe pressure when the intake valve is completely closed depends on the operating state of the internal combustion engine. For example, when the intake valve is completely closed in the pressure range in which the intake pipe pressure pulsates, it depends on the engine speed of the internal combustion engine.

  FIG. 14 shows a graph of the intake pipe internal pressure when the internal combustion engine of the present embodiment is operated at the second engine speed. The example shown in FIG. 14 also shows a case where the operating state of the internal combustion engine is steady. At time tc, the intake valve is completely closed. In the example shown in FIG. 14, the intake valve is completely closed when the actual intake pipe pressure is smaller than the intake pipe pressure Pm calculated by the intake pipe model M12. When the in-cylinder charged air amount is calculated using the intake pipe pressure Pm calculated by the intake pipe model, the actual in-cylinder charged air amount becomes larger. For this reason, in the example shown in FIG. 14, for example, it is preferable to adopt a small constant as the constant a in the model calculation formula of the intake valve model.

  Thus, in the example of the first engine speed shown in FIG. 13, the intake valve is completely closed at a relatively high pressure in the pressure range in which the pressure in the intake pipe pulsates, and the second shown in FIG. In this example of the engine speed, the intake valve is completely closed at a relatively low pressure. Even in one internal combustion engine, when the engine speed is different, the time when the intake valve is completely closed differs. For this reason, depending on the engine speed, the optimum constants a and b in the model calculation formula of the intake valve model are different from each other.

  In the control device for an internal combustion engine in the present embodiment, a plurality of constants a and b, which are functions of the engine speed, are stored in the electronic control unit 31. The engine speed is detected when the intake valve is continuously driven. Based on the detected engine speed, constants a and b corresponding to the engine speed are selected from a plurality of constants a and b. The in-cylinder inflow air flow rate is calculated by the equation (8) using the selected constants a and b.

  For example, as shown in FIG. 13, a large constant a is selected from a plurality of constants a for the engine speed at which the intake valve is completely closed when the actual intake pipe pressure is relatively high. As shown in FIG. 14, in the engine speed at which the intake valve is completely closed when the actual intake pipe pressure is relatively low, a small constant a is selected from a plurality of constants a.

  In the air model in the present embodiment, the in-cylinder inflow air flow rate in which the influence of the pulsation of the intake pipe pressure is corrected can be calculated by selecting a constant a and a constant b that are adapted as a function of the engine speed. As a result, the in-cylinder charged air amount can be calculated with higher accuracy.

  The constants a and b in the model calculation formula of the intake valve model can be determined by experiments. For example, when the internal combustion engine is steadily operating at one engine speed, the measured value of the air flow meter corresponds to the air flow rate flowing into the cylinder. For this reason, the constants a and b are set so that the measured value of the air flow meter and the in-cylinder inflow air flow rate calculated by the air model coincide with each other while the internal combustion engine is constantly operated at one engine speed. Can be adapted. Thus, the constants a and b are accurate when the intake pipe pressure when the intake valve is continuously operated is input to the model calculation formula of the intake valve model and calculated. Is preferably adapted to calculate.

  Thus, the constant of the model calculation formula of the intake valve model can be selected according to the operating state such as the engine speed. As the operating state, in addition to the engine speed, the driving state of the variable valve mechanism can be exemplified. The constant of the model calculation formula of the intake valve model can be selected by using the valve opening time or valve closing time (valve timing) or the operating angle of the variable valve mechanism as a function. As other operating conditions, for example, in an internal combustion engine equipped with a swirl control valve (SCV) for promoting combustion by generating a swirling flow in the air flowing into the cylinder, the swirl control valve is opened and closed. The state can be exemplified. The constant of the model calculation formula of the intake valve model can be selected according to the open / close state of the swirl control valve.

  Or, if the internal combustion engine is equipped with a variable intake system (ACIS: Acoustic Control Induction System) that adjusts the intake flow rate by changing the length of the intake pipe section, The constant of the model calculation formula of the valve model can be selected. Alternatively, when the internal combustion engine performs fuel supply by in-cylinder injection and fuel supply by port injection at the same time, the ratio of the fuel injection amount of in-cylinder injection and the fuel injection amount of port injection is used as a function, and the intake valve A constant for the model calculation formula of the model can be selected.

  By the way, referring to FIG. 10, when the normal operation in which the intake valve continues to be driven is performed, the actual intake pipe pressure pulsates, while the intake valve stop control is started and a predetermined time elapses. After that, the actual pressure in the intake pipe becomes almost steady. That is, the actual intake pipe pressure when the intake valve stops in the closed state and becomes a steady state is hardly pulsating, is atmospheric pressure, and is substantially constant. Also at this time, the internal combustion engine is driven at a predetermined engine speed.

  In the intake valve model equation (8), the driving constants a and b employed when the drive of the intake valve is continued take into account the influence of pulsation depending on the engine speed as described above. ing. When the intake valve is to be redriven at time te, an error increases if the in-cylinder inflow air flow rate is calculated using the constants a and b during driving when the intake valve continues to be driven. In other words, when the pulsation hardly appears in the actual intake pipe pressure, applying the constants a and b during driving of the intake valve increases the error.

  For example, when the throttle valve is fully opened and the operation state of the internal combustion engine becomes steady, the actual intake pipe internal pressure becomes substantially atmospheric pressure, and becomes substantially equal to the intake pipe internal pressure during intake valve closing control. However, pulsation occurs in the pressure in the intake pipe while the intake valve is driven. Therefore, even if the actual operating conditions such as the actual pressure in the intake pipe and the engine speed are the same, the air flow rate that flows into the cylinder when the intake valve is fully driven and the intake valve is re-driven The flow rate of air flowing into the cylinder at this time is different from each other. As described above, if the constants a and b used during driving of the intake valve are used to calculate the in-cylinder inflow air flow rate when the intake valve should be redriven, an error increases.

  In the internal combustion engine of the present embodiment, the intake valve stop control is performed in addition to the constants a and b during driving for calculating the in-cylinder inflow air flow rate when the driving of the intake valve is continued. When the intake valve is to be re-driven, the re-driving constants a and b for calculating the in-cylinder inflow air flow rate are provided. That is, in the model calculation formula of the intake valve model, in addition to the constants a and b used during normal operation, the constants a and b used when the intake valve should be redriven are stored in the electronic control unit 31, for example. When the intake valve should be re-driven from the closed state, the in-cylinder inflow air flow rate is calculated using the constants a and b at the time of re-drive. This control makes it possible to accurately estimate the in-cylinder inflow air flow rate when the intake valve is driven again. The in-cylinder charged air amount can be accurately estimated. As a result, the air-fuel ratio when the fuel burns can be brought close to the target air-fuel ratio. The constants a and b at the time of re-driving can be adapted by the same method as the constants a and b during driving.

  After the intake valve is driven again, in the second and subsequent calculations of the air model, the constants a and b in the model calculation formula of the intake valve model can adopt constants during driving of the intake valve. In the air model of the present embodiment, the in-cylinder inflow air flow rate is calculated by a differential equation. That is, the calculation result before a minute time is used for the current calculation. For this reason, the estimation accuracy of the cylinder inflow air flow rate immediately after the reactivation of the intake valve is improved, so that the estimation accuracy of the cylinder inflow air flow rate calculated thereafter is also improved.

  In addition, the constants a and b at the time of re-driving of the intake valve are prepared in advance as a plurality of constants a and b depending on the operating state in the same manner as the constants a and b during driving of the intake valve. The constants a and b at the time of re-driving can be selected based on the operating state. A plurality of constants a and b depending on the operating state can be stored in the electronic control unit 31, and the operating state can be detected when the intake valve should be re-driven to select the optimum constants a and b. This control can improve the estimation accuracy of the in-cylinder charged air amount.

  For example, the control device for an internal combustion engine can include a plurality of constants a and b that are functions of the engine speed NE as constants a and b for the model calculation formula of the intake valve model. Alternatively, it is possible to provide a plurality of constants a and b that are functions of the timing and operating angle of the opening or closing of the intake valve in the variable valve mechanism. Or in an internal combustion engine provided with a swirl control valve, a plurality of constants a and b corresponding to the open / closed state of the swirl control valve can be provided. Alternatively, an internal combustion engine including a variable intake system can include a plurality of constants a and b corresponding to the state of the variable intake system. Or, in the case of an internal combustion engine that simultaneously performs fuel supply by in-cylinder injection and fuel supply by port injection, a plurality of constants that are functions of the ratio between the fuel injection amount of in-cylinder injection and the fuel injection amount of port injection a and b can be provided.

  In this embodiment, when the intake valve is to be driven again, all constants in the model calculation formula of the intake valve model are changed. However, the present invention is not limited to this mode, and one or more constants may be changed. it can. For example, in the model calculation formula of the intake valve model in the present embodiment, only the constant a may be changed without changing the constant b.

  In the present embodiment, as a model calculation formula for calculating the in-cylinder charged air amount, the in-cylinder inflow air flow rate is calculated using the above-described equation (8), and the in-cylinder inflow amount is calculated from the calculated in-cylinder inflow air flow rate. Although the amount of charged air is calculated, the present invention is not limited to this form, and the present invention is applied to an air model that calculates the inflow air flow rate in the cylinder by a model calculation formula including at least one constant with the intake pipe pressure as a variable. Can do.

(Embodiment 2)
With reference to FIG. 15, a control apparatus for an internal combustion engine in the second embodiment will be described. The configuration of the internal combustion engine in the present embodiment is the same as that in the first embodiment (see FIG. 1). Use of the air model M10 to estimate the amount of air flowing into the cylinder is the same as in the first embodiment (see FIG. 2). 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. 10 and 11).

  FIG. 15 is an enlarged view of the time chart when the intake valve stop control is terminated and normal operation is resumed in the internal combustion engine in the present embodiment. In the present embodiment, a four-cylinder internal combustion engine will be described as an example. The internal combustion engine in the present embodiment includes a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder. The intake process is performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder.

  At time te, the intake valve stop control is terminated and the intake valve is driven again. During the intake valve stop control period, the actual intake pipe pressure is substantially atmospheric pressure and is substantially constant. When the intake valve is driven again, the actual intake pipe pressure decreases with time until the intake pipe pressure during normal operation is reached. At time te, driving of the intake valve of the first cylinder is started, and at time tx, driving of the intake valve of the first cylinder is completed. For example, the actual intake pipe pressure at time tx is decreased by ΔP from the pressure during the intake valve stop control. The actual average intake pipe pressure from time te to time tx is, for example, a pressure obtained by subtracting approximately half of ΔP from the pressure during intake valve stop control.

  Referring to FIG. 2, the intake pipe pressure Pm in the air model M10 employs time-averaged intake pipe pressure. When the intake valve is to be redriven, the intake pipe pressure Pm calculated by the intake pipe model M12 is almost atmospheric pressure. In the calculation of the air model M10 when the intake valve is to be redriven, when the intake pipe pressure Pm calculated during the intake valve stop control period is input, the average intake pipe pressure immediately after the intake valve is redriven is greater than the average intake pipe pressure. A large pressure is input. For this reason, the error of the estimated cylinder air charge amount increases. For example, when calculated based on a pressure larger than the actual average intake pipe pressure, the cylinder charge air amount calculated by the air model becomes larger than the actual cylinder fill air amount.

  When the intake valve is to be redriven, the control apparatus for an internal combustion engine according to the present embodiment uses a cylinder based on a pressure obtained by subtracting a predetermined correction pressure Pmd from the intake pipe pressure Pm calculated by the intake pipe model M12. The inflow air flow rate is calculated. The correction pressure Pmd is, for example, the difference between the pressure in the intake pipe in a steady state during intake valve stop control and the average pressure in the period from opening to closing of the first cylinder immediately after re-driving the intake valve. Can be adopted. Referring to FIG. 15, correction pressure Pmd employs a differential pressure between the average value of the intake pipe pressure during intake valve stop control before time te and the average value of the intake pipe pressure from time te to time tx. can do. Alternatively, a value that is approximately ½ of the pressure drop ΔP can be adopted as the correction pressure Pmd.

  Alternatively, the correction pressure Pmd is not limited to this form. For example, the pressure in the intake pipe in a steady state during the intake valve stop control and the time when one calculation of the air model M10 is performed from the moment when the intake valve is redriven are passed. You may employ | adopt the differential pressure | voltage with the average pressure in the period until it does. Such a correction pressure Pmd can be obtained by numerical calculation using a highly responsive flow meter, pressure gauge, or model equation.

  In the present embodiment, the correction pressure Pmd used when the intake valve should be redriven is determined in advance and stored in the electronic control unit 31. When the intake valve is to be driven again, in the first calculation of the air model for calculating the in-cylinder inflow air flow rate, a pressure (Pm−) obtained by subtracting the correction pressure Pmd from the intake pipe pressure Pm calculated by the intake pipe model M12. Pmd) is input to the intake valve model M13. That is, the in-cylinder inflow air flow rate is calculated based on the intake pipe internal pressure taking into account the pressure drop ΔP of the intake pipe internal pressure immediately after the intake valve is re-driven.

  In the intake valve model M13 in the present embodiment, when the correction pressure Pmd is taken into consideration, the equation (8) as a model calculation equation can be transformed into the following equation (21). The in-cylinder inflow air flow rate can be calculated based on the following equation (21).

  Further, an expression obtained by discretizing the expression (21) can be expressed by the following expression (22).

  In this way, when the intake valve stop control is terminated and the intake valve is to be re-driven, the cylinder inflow air flow rate is calculated based on the intake pipe internal pressure obtained by subtracting a predetermined correction pressure. The amount of air filled inside can be estimated with high accuracy.

  Incidentally, the correction pressure Pmd depends on the operating state of the internal combustion engine. The control device for the internal combustion engine can include a plurality of correction pressures Pmd depending on the operating state. The correction pressure Pmd can be selected according to the operating state of the internal combustion engine. For example, the correction pressure Pmd depends on the cylinder volume when the intake valve is completely closed. For this reason, when the internal combustion engine includes a variable valve mechanism, the correction pressure Pmd can be made a function of the valve timing when the intake valve should be redriven. A plurality of correction pressures Pmd having the valve timing as a function can be stored in the ROM 34 of the electronic control unit 31, and the correction pressure Pmd can be selected according to the valve timing when the intake valve should be re-driven.

  As described above, the in-cylinder inflow air flow rate can be estimated more accurately by selecting a predetermined correction pressure based on the operating state of the internal combustion engine. As the operating state of the internal combustion engine, in addition to the operating state of the variable valve mechanism, the open / closed state of the swirl control valve can be exemplified as in the first embodiment.

  In the second and subsequent calculations of the air model M10 after the intake valve is driven again, for example, the in-cylinder charged air amount can be calculated by the air model M10 during normal operation. In the intake valve model, the in-cylinder inflow air flow rate can be calculated using the model calculation formula of the above-described formula (8).

  Also in the control apparatus for the internal combustion engine in the present embodiment, since the current parameter value is estimated using the calculation result before a minute time, the first estimation accuracy of the air model when the intake valve should be re-driven is improved. By doing so, the estimation accuracy after the second time is also improved.

  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. 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 Cylinder 6 Intake valve 7 Intake port 8 Exhaust valve 11 Fuel injection valve 23 Intake pipe part 18 Throttle valve M10 Air model M11 Throttle model M12 Intake pipe model M13 Intake valve model

Claims (5)

The intake valve can be stopped in a closed state during the operation period of the internal combustion engine, and the intake pipe internal pressure, which is the air pressure upstream of the intake valve, is calculated based on the flow rate of air passing through the throttle valve. A control device for an internal combustion engine that calculates a cylinder inflow air flow rate flowing into the cylinder based on
The in-cylinder inflow air flow rate is calculated from a model calculation formula including at least one constant with the intake pipe pressure as a variable.
A constant during driving for calculating the in-cylinder inflow air flow rate when the intake valve continues to drive , and a state in which the intake valve stops in the closed state and the intake pipe pressure is almost constant at atmospheric pressure. It has a constant at the time of re-driving to calculate the in-cylinder inflow air flow rate when it should be driven,
The constant at the time of re-driving is different from the constant during driving,
When the intake valve continues to be driven, calculate the in-cylinder inflow air flow rate by a model calculation formula using constants during driving,
When to be re-driven from the state in which the intake valve is stopped at the closed state, calculates the cylinder flow-in air flow rate by the model equation using constants at the time of re-driving in the first calculation, re driving the intake valve A control device for an internal combustion engine, wherein the control unit calculates an in- cylinder inflow air flow rate by switching to a model calculation formula using a constant during driving later . The in-cylinder inflow air flow rate is calculated by the following formula (1) model calculation formula,
When the intake valve continues to be driven, the in-cylinder inflow air flow rate is calculated using the constants a and b being driven,
The in-cylinder inflow air flow rate is calculated using a constant a and a constant b at the time of re-driving when the intake valve is to be re-driven from a stopped state in a closed state. Control device for internal combustion engine.

(Where mc is the in-cylinder inflow air flow rate, Pm is the intake pipe pressure, Ta is the atmospheric temperature, and Tm is the intake pipe temperature)   3. The re-driving constant is selected based on the operating state of the internal combustion engine, and has a plurality of re-driving constants depending on the operating state of the internal combustion engine. Control device for internal combustion engine. The intake valve can be stopped in a closed state during the operation period of the internal combustion engine, and the intake pipe pressure calculated as the air pressure upstream of the intake valve is calculated based on the flow rate of air passing through the throttle valve. A control device for an internal combustion engine that calculates a cylinder inflow air flow rate flowing into the cylinder based on
When the intake valve is closed and stopped, the pressure inside the intake pipe is almost constant at atmospheric pressure,
When the intake valve should be re-driven from a closed state, the in-cylinder inflow air flow rate is calculated based on a pressure obtained by subtracting a predetermined correction pressure from the calculated intake pipe pressure ,
The control apparatus for an internal combustion engine, wherein the predetermined correction pressure is set based on a decrease amount of the pressure in the intake pipe after the intake valve is re-driven .   5. A plurality of predetermined correction pressures depending on the operating state of the internal combustion engine, and the predetermined correction pressure is selected based on the operating state of the internal combustion engine. Control device for internal combustion engine.

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