JP4544110B2 - In-cylinder intake fresh air volume estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake fresh air amount estimation device for an internal combustion engine that estimates an amount of fresh air (in-cylinder intake fresh air amount) or the like sucked into a cylinder of the internal combustion engine.

  In order to control the air-fuel ratio of the air-fuel mixture combusted by the internal combustion engine to a desired value and to appropriately control the ignition timing, the amount of fresh air sucked into the cylinder of the internal combustion engine (hereinafter referred to as “in-cylinder”). It is necessary to accurately calculate “Intake fresh air volume Ma”. Fresh air is the atmosphere and does not include combustion gas (burned gas). Normally, this in-cylinder intake fresh air amount Ma is estimated from the output value of an air flow sensor provided in the intake passage of the internal combustion engine. However, in a transient operation where the throttle valve opening changes rapidly, the behavior of the output value of the air flow sensor does not match the actual behavior of the intake fresh air amount. It is generally difficult to accurately obtain the in-cylinder intake fresh air amount Ma under all operating conditions.

Therefore, in recent years, a model that expresses the behavior of air in the intake passage is constructed using equations obtained based on physical laws such as the energy conservation law and the momentum conservation law. Various attempts have been made to accurately estimate the amount Ma (a value corresponding to the amount Ma) (for example, see Patent Document 1).
JP 2004-339958 A

  In the above document, a model (cylinder model) related to the cylinder (gas in the cylinder) is constructed based on the law of conservation of mass and the law of conservation of energy, and a technique for estimating the in-cylinder intake fresh air amount Ma using this model is described. ing.

  More specifically, the cylinder model is constructed based on the following equations (1) and (2).

  Equation (1) is based on the law of conservation of mass. Equation (1) indicates that “the amount of change in the in-cylinder gas amount Mc, which is the amount of gas in the cylinder consisting of fresh air and burned gas, over time (dMc / dt)” The intake valve passage gas flow rate mi, which is the flow rate of the gas sucked into the inside (hereinafter referred to as “intake valve passage gas”) and the gas (hereinafter referred to as “intake valve passage gas flow rate mi”) , Which is referred to as “exhaust valve passage gas”), which is equal to the sum of the exhaust valve passage gas flow rate me ”. In this case, both the intake valve passage gas flow rate mi and the exhaust valve passage gas flow rate me are defined to be positive values when gas flows into the cylinder.

  Equation (2) is an equation based on the law of conservation of energy. Equation (2) shows that “time variation (dE / dt) of the energy E of the gas in the cylinder” is “energy Ei ′ given to the gas in the cylinder per unit time by the intake valve passing gas”, “exhaust “Energy Ee ′ given to the gas in the cylinder per unit time by the valve passing gas” and “amount of heat given to the gas in the cylinder from the cylinder wall surface per unit time (hereinafter referred to as“ transfer heat flow rate ”) Qw It represents that it is equal to a value obtained by subtracting “the work W ′ performed on the piston per unit time by the gas in the cylinder” from the sum of “”.

  On the other hand, the energy Ei ′ given to the gas in the cylinder per unit time by the intake valve passage gas, as shown in the following equation (3), the intake valve passage gas flow rate mi and the intake valve passage gas temperature (intake gas temperature) ) Proportional to Ti. Here, Cpi is the constant pressure specific heat of the intake valve passage gas. Further, the energy Ee ′ given to the gas in the cylinder per unit time by the exhaust valve passage gas is expressed by the exhaust valve passage gas flow rate me and the exhaust valve passage gas temperature (exhaust gas temperature) as shown in the following equation (4). ) Proportional to Te. Here, Cpe is the constant pressure specific heat of the exhaust valve passage gas.

Ei '＝ mi ・ Cpi ・ Ti… (3)

Ee '＝ me ・ Cpe ・ Te… (4)

  Therefore, in the cylinder model, the expression obtained by applying the relation between the expressions (3) and (4) to the expression (2) is based on the law of conservation of energy, and by combining the expression with the expression (1), the cylinder model The pressure of the internal gas (hereinafter referred to as “cylinder gas”) (hereinafter referred to as “cylinder gas pressure Pc”) and the temperature of the cylinder gas (hereinafter referred to as “cylinder gas temperature Tc”) Called.). Then, the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc thus obtained are applied to the following formulas (5) to (8), whereby the intake valve passage gas flow rate mi and the exhaust valve passage gas flow rate are applied. me is updated. Equations (5) to (8) are equations based on general equations for obtaining the flow rate of the fluid passing through the throttle portion. Pi is the intake valve upstream gas pressure, and Pe is the exhaust gas pressure. Ri, Re, and Rc are gas constants, Cdi and Cde are flow coefficients, and Ai and Ae are channel cross-sectional areas.

  The intake valve passage gas flow rate mi updated by equation (5) or (6) and the exhaust valve passage gas flow rate me updated by equation (7) or (8) are expressed by the above equations (1) to (4). The new in-cylinder gas pressure Pc and in-cylinder gas temperature Tc are obtained. The new in-cylinder gas pressure Pc and in-cylinder gas temperature Tc are again applied to the above equations (5) to (8), and further new intake valve passage gas flow rate mi and exhaust valve passage gas flow rate me are obtained. .

  Thus, the intake valve passage gas flow rate mi, the exhaust valve passage gas flow rate me, the in-cylinder gas pressure Pc, and the in-cylinder gas temperature Tc are sequentially updated. The updated intake valve passage gas flow rate mi is integrated from the time when the intake valve is opened to the time when the intake valve is closed, thereby estimating the in-cylinder intake fresh air amount Ma. The updated exhaust valve passage gas flow rate me is integrated from when the intake valve is opened to when the exhaust valve is closed, whereby the amount of burnt gas remaining in the cylinder (hereinafter referred to as “in-cylinder residual gas amount”). .) Me is estimated.

  In general, the intake valve and the exhaust valve of an internal combustion engine sometimes take a state of being opened simultaneously. That is, as indicated by the curve LIN and the curve LEX in FIG. 18A, the lift amount of the intake valve and the exhaust valve is indicated by the predetermined crank angle θ0 (the crank angle of the intake valve before the intake top dead center (TDC)). The valve is opened at time t0). The exhaust valve is still open at this time t0, and is then closed when the crank angle reaches a predetermined crank angle θ2 (time t2) after the intake top dead center (TDC). A period during which both the intake valve and the exhaust valve are open (time t0 to t2) is referred to as a valve overlap period (VOL).

  Since the initial period of the valve overlap period is the second half of the exhaust stroke, the volume of the combustion chamber (cylinder) is decreasing. Accordingly, since the intake valve upstream gas pressure Pi is smaller than the cylinder gas pressure Pc (and the exhaust gas pressure Pe), the burned gas in the cylinder passes through the periphery of the intake valve (or the exhaust system (exhaust port and exhaust pipe). ) Is burned back to the intake passage (intake system, that is, the intake port and the intake pipe constituting the intake passage downstream of the throttle valve) around the exhaust valve, the cylinder and the intake valve). . In this case, since the intake valve passage gas flow rate mi is a negative value calculated by the equation (6), as shown by the solid line in FIG. 18B, the integrated value of the intake valve passage gas flow rate mi is It decreases from time t0 and becomes a negative value.

  Thereafter, when the crank angle reaches a predetermined crank angle θ1 after the intake top dead center (TDC), the exhaust valve is substantially closed (time t1). This time is the initial stage of the intake stroke, and since the volume of the combustion chamber (cylinder) is increasing, the intake valve upstream gas pressure Pi becomes larger than the in-cylinder gas pressure Pc. Therefore, the burned gas blown back into the intake passage starts to be sucked again into the cylinder through the periphery of the intake valve. In this case, since the intake valve passage gas flow rate mi is calculated by the equation (5) and becomes a positive value, as shown by a solid line in FIG. It starts increasing from time t1. At time t3, when all the burned gas blown back into the intake passage is sucked into the cylinder, fresh air starts to be sucked into the cylinder. The integrated value of the intake valve passage gas flow rate mi becomes “0” at time t3, and since fresh air is sucked into the cylinder after time t3, the value finally represents the in-cylinder intake fresh air amount Ma. Become.

  By the way, when the burned gas blows back into the intake passage, the in-cylinder gas pressure Pc decreases and becomes smaller than the exhaust gas pressure Pe. As a result, the burned gas discharged to the exhaust system is discharged to the exhaust valve. Flows back into the cylinder through the periphery of Hereinafter, this phenomenon is referred to as “backflow of burned gas from the exhaust system”. When a backflow of burned gas from the exhaust system occurs, the exhaust gas pressure decreases. The degree of the decrease in the exhaust gas pressure increases as the valve overlap period increases.

  On the other hand, in the above-mentioned document, the exhaust gas pressure is calculated from a general formula for obtaining the pressure loss of the pipeline without considering the decrease in the exhaust gas pressure due to the backflow of burned gas from the exhaust system. That is, in the equation (7) for obtaining the exhaust valve passage gas flow rate me used when the backflow of burned gas from the exhaust system occurs, the exhaust gas pressure Pe is higher than the actual exhaust gas pressure. Set to pressure. Therefore, the calculated value (positive value) of the exhaust valve passage gas flow rate me becomes larger than the actual value of the exhaust valve passage gas flow rate.

  As a result, the in-cylinder gas pressure Pc calculated by the equations (1) to (4) becomes larger than the actual in-cylinder gas pressure. Therefore, the in-cylinder gas pressure Pc is greater than the actual in-cylinder gas pressure in the equation (6) for determining the intake valve passage gas flow rate mi used when the burned gas is blown back into the intake passage. Also set to high pressure. Therefore, the calculated value (negative value) of the intake valve passage gas flow rate mi becomes smaller (the absolute value becomes larger) than the actual intake valve passage gas flow rate value. In other words, the total amount of burned gas blown back into the intake passage calculated (the absolute value of the minimum value (negative value) of the integrated value of the intake valve passage gas flow rate mi) becomes larger than the actual value.

  As a result, as shown by the broken line in FIG. 18B, the calculated fresh air intake start time t4 (the time point at which the integrated value of the intake valve passage gas flow rate mi returns to “0”) is actual. There is a tendency that the in-cylinder inhalation fresh air amount Ma is different from the actual in-cylinder inhalation fresh air amount because the time is later than the fresh air inhalation start time t3. This tendency becomes more prominent as the valve overlap period is longer.

  The present invention has been made in order to cope with the above problem, and its purpose is that the valve overlap period is long in consideration of a decrease in exhaust gas pressure due to a backflow of burned gas from the exhaust system. However, an object of the present invention is to provide an in-cylinder intake fresh air amount estimation device for an internal combustion engine that can accurately estimate the in-cylinder intake fresh air amount.

  An in-cylinder intake fresh air amount estimation device for an internal combustion engine according to the present invention calculates in-cylinder gas pressure, in-cylinder gas pressure calculation means, intake gas pressure acquisition means for acquiring intake gas pressure, and exhaust gas pressure. Exhaust gas pressure calculating means, intake valve passing gas flow rate calculating means for calculating an intake valve passing gas flow rate, exhaust valve passing gas flow rate calculating means for calculating an exhaust valve passing gas flow rate, and the calculated intake valve passing gas flow rate And in-cylinder intake fresh air amount estimation means for estimating the in-cylinder intake fresh air amount.

  The cylinder gas pressure calculation means calculates the cylinder gas pressure based on at least the calculated intake valve passage gas flow rate and the calculated exhaust valve passage gas flow rate. The in-cylinder gas pressure calculating means is preferably configured to calculate the in-cylinder gas pressure based on, for example, an energy conservation law and a mass conservation law.

  The intake valve passage gas flow rate calculating means calculates the intake valve passage gas flow rate based on at least the acquired intake gas pressure and the calculated in-cylinder gas pressure. For example, the intake valve passage gas flow rate calculating means calculates the intake air flow based on an equation for calculating a gas flow rate that passes through the throttle portion formed when a gas passage formed around the intake valve is regarded as a throttle portion. Suitably configured to calculate the valve passing gas flow rate.

  The exhaust valve passage gas flow rate calculating means calculates the exhaust valve passage gas flow rate based on at least the calculated exhaust gas pressure and the calculated in-cylinder gas pressure. For example, the exhaust valve passage gas flow rate calculation means calculates the exhaust gas flow based on an equation for calculating a gas flow rate that passes through the throttle portion formed when the gas passage formed around the exhaust valve is regarded as a throttle portion. Suitably configured to calculate the valve passing gas flow rate.

  A feature of the in-cylinder intake fresh air amount estimation device according to the present invention is that the exhaust gas pressure calculation means uses the backflow of burnt gas from the exhaust passage that is generated during a valve overlap period into the cylinder. This is because the exhaust gas pressure is calculated in consideration of the decrease in the exhaust gas pressure.

  According to this, since the exhaust gas pressure can be accurately calculated during the valve overlap period, the exhaust valve passage gas flow rate calculated based on the exhaust gas pressure can be accurately calculated. Therefore, since the cylinder gas pressure calculated based on the exhaust valve passage gas flow can be calculated with high accuracy, the intake valve passage gas flow calculated based on the cylinder gas pressure can be calculated with high accuracy. Therefore, the in-cylinder intake fresh air amount calculated based on the intake valve passage gas flow rate can also be accurately estimated. Thereby, even if the valve overlap period is long, the in-cylinder intake fresh air amount can be accurately estimated.

  In this case, the exhaust gas pressure calculating means is configured to calculate the exhaust gas pressure based on a parameter representing an operating state of the internal combustion engine including a parameter representing the open / close state of the intake valve and the exhaust valve. Is preferred. Here, the parameters representing the opening / closing states of the intake valve and the exhaust valve are, for example, the operating speed of the internal combustion engine, the opening / closing timing of the intake valve (the advance amount of the intake valve), the opening / closing timing of the exhaust valve (the exhaust valve Advance amount), intake valve lift amount (maximum lift amount), and the like.

  The degree of reduction in exhaust gas pressure due to the above-described “backflow of burnt gas from the exhaust system” increases as the degree of backflow of burnt gas from the exhaust system increases. The degree of backflow of burned gas from the exhaust system increases as the degree of burnt gas blowback to the intake passage increases. On the other hand, the degree of backflow of burned gas from the exhaust system greatly depends on the open / close state of the exhaust valve, and the degree of return of burnt gas to the intake passage greatly depends on the open / close state of the intake valve.

  From the above, the degree of decrease in the exhaust gas pressure due to “backflow of burned gas from the exhaust system” greatly depends on the open / close state of the intake valve and the exhaust valve. The above configuration is based on such knowledge. According to this, since it is possible to accurately estimate the degree of decrease in exhaust gas pressure due to “backflow of burnt gas from the exhaust system”, it is possible to accurately calculate the exhaust gas pressure during the valve overlap period. .

  In this case, the exhaust gas pressure calculation means is a time integral value of the passage area of the gas passage formed around the intake valve over the valve overlap period (hereinafter referred to as “opening area integrated value”). A burned gas blowback amount that is a total amount of burned gas blown back from the cylinder to the intake passage is calculated based on a value corresponding to the above, and the exhaust gas pressure is calculated based on the burned gas blowback amount. May be configured.

  As described above, the degree of reduction in exhaust gas pressure due to “backflow of burnt gas from the exhaust system” increases as the degree of blown back burned gas into the intake passage increases. In other words, the degree of decrease in the exhaust gas pressure due to “backflow of burnt gas from the exhaust system” greatly depends on the burned gas blowback amount itself. On the other hand, the burned gas blow-back amount uses an integrated opening area value that can be calculated based on the above-described parameters indicating the open / close state of the intake valve and the exhaust valve (for example, at the start of the valve overlap period). It is possible to easily estimate (predict) (details will be described later).

  The above configuration is based on such knowledge. This also makes it possible to accurately estimate the degree of decrease in exhaust gas pressure due to “backflow of burned gas from the exhaust system”, and therefore, it is possible to accurately calculate the exhaust gas pressure during the valve overlap period.

  Further, in the in-cylinder intake fresh air amount estimation device according to the present invention, the exhaust gas pressure calculating means sets a virtual region having a predetermined volume in the exhaust passage, and the gas flowing into and out of the volume is set. Based on the assumption that the flow rate is equal to the exhaust valve passage gas flow rate calculated by the exhaust valve passage gas flow rate calculation means, the same is obtained from the mass change of the gas in the volume obtained based on the exhaust valve passage gas flow rate. The exhaust gas pressure may be calculated by calculating the pressure change of the gas in the volume and considering the pressure change of the gas in the calculated volume.

  According to this, it is possible to simplify the calculation by assuming that the pressure change of the gas in the predetermined volume of the virtual region is equal to the decrease (change) of the exhaust gas pressure due to “backflow of burned gas from the exhaust system”. Thus, it is possible to accurately estimate the degree of decrease in exhaust gas pressure due to “backflow of burned gas from the exhaust system”. As a result, the exhaust gas pressure during the valve overlap period can be calculated with high accuracy.

  The exhaust gas pressure calculation means calculates a change in the exhaust gas pressure from a change in the exhaust valve passage gas flow rate calculated by the exhaust valve passage gas flow rate calculation means, and the calculated exhaust gas pressure The exhaust gas pressure may be calculated in consideration of the change.

  It is considered that the actual fluctuation of the exhaust gas pressure largely depends on the inertia of the gas flowing through the exhaust passage. Therefore, the fluctuation of the exhaust gas pressure largely depends on the change of the flow velocity of the gas flowing through the exhaust passage, and hence the change of the exhaust valve passage gas flow rate. From the above, even with the above configuration, it is possible to accurately estimate the degree of reduction in exhaust gas pressure due to “backflow of burned gas from the exhaust system”, so the exhaust gas pressure during the valve overlap period can be accurately estimated. Can be calculated.

  In the in-cylinder intake fresh air amount estimation device according to the present invention, the intake valve passage gas flow rate calculating means positively adjusts the intake valve passage gas flow rate when gas is being sucked into the cylinder from the intake passage. As one of the negative signed gas flow rates, when the gas is blown back from the inside of the cylinder into the intake passage, the intake valve passage gas flow rate is set as either the positive or negative signed gas flow rate. The in-cylinder intake fresh air amount estimating means is configured to calculate the in-cylinder intake fresh air amount based on an integrated value of the calculated intake valve passage gas flow rate from the time when the intake valve is opened. It is preferably configured to estimate the amount of fresh intake air.

  In a general internal combustion engine, the intake valve opens in the latter half of the exhaust stroke and before the exhaust valve is closed. At this time, since the intake gas pressure is smaller than the in-cylinder gas pressure, the above-described burned gas blows back into the intake passage. In this case, the intake valve passage gas flow rate calculation means calculates the intake valve passage gas flow rate as a value having one of positive and negative signs.

  Thereafter, when the intake stroke proceeds to the timing at which the exhaust valve substantially closes, the intake gas pressure becomes greater than the in-cylinder gas pressure. Accordingly, the burnt gas blown back into the intake passage is again sucked into the cylinder through the periphery of the intake valve. In this case, the intake valve passage gas flow rate calculation means calculates the intake valve passage gas flow rate as a value having a positive or negative sign.

  Therefore, if the intake valve passage gas flow rate is accurately calculated, the integrated value of the intake valve passage gas flow rate after the intake valve is opened is the total amount of burned gas blown back into the intake passage. It returns to the initial integrated value when the intake valve is opened when it is drawn into the cylinder.

  That is, for convenience of explanation, the intake valve passage gas flow rate calculation means is configured such that when the gas flows backward from the cylinder to the intake passage, the intake valve passage gas flow rate having a negative sign, the gas flows into the cylinder from the intake passage. Assuming that the intake valve passage gas flow rate having a positive sign is calculated in the case of forward flow, and that the initial value at the start of integration of the intake valve passage gas flow rate (when the intake valve opens) is assumed to be 0 The integrated value of the intake valve passage gas flow rate becomes a negative value and decreases after the intake valve is opened. The integrated value of the intake valve passage gas flow starts to increase when the burned gas blown back to the intake passage starts to be sucked into the cylinder again, and the burned gas blown back to the intake passage. When all of these are sucked into the cylinder, they return to zero. Thereafter, the integrated value of the intake valve passage gas flow rate becomes a positive value and increases. That is, the integrated value of the intake valve passage gas flow rate when the intake valve is closed is a value representing the in-cylinder intake fresh air amount itself. The above configuration is based on such knowledge. According to this, it is possible to estimate the in-cylinder intake fresh air amount only by performing simple integration of the intake valve passage gas flow rate.

(First embodiment)
Hereinafter, an in-cylinder intake fresh air amount estimation device for an internal combustion engine according to the present invention (this device can also be referred to as an in-cylinder intake air amount estimation device, an in-cylinder intake gas amount estimation device, and an in-cylinder residual gas amount estimation device). ) Will be described with reference to the drawings. This in-cylinder intake fresh air amount estimation device is a part of the fuel injection amount control device. FIG. 1 shows a schematic configuration of a system in which such a fuel injection amount control device is applied to a spark ignition type multi-cylinder (four-cylinder) internal combustion engine 10. FIG. 1 shows only a cross section of a specific cylinder, but the other cylinders have the same configuration.

  The internal combustion engine 10 includes a cylinder block unit 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head unit 30 fixed on the cylinder block unit 20, and a gasoline mixture to the cylinder block unit 20. An intake system 40 for supplying and an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft that drives the intake valve 32, and a phase angle of the intake camshaft and the intake valve 32. The intake valve control device 33 capable of continuously changing the intake valve lift amount (maximum intake valve lift amount), the actuator 33a of the intake valve control device 33, the exhaust port 34 communicating with the combustion chamber 25, and the exhaust port 34 are opened and closed. An exhaust valve 35, an exhaust cam shaft that drives the exhaust valve 35, and an exhaust valve control device 36 that can continuously change the phase angle of the exhaust cam shaft, an actuator 36a of the exhaust valve control device 36, a spark plug 37, an ignition An igniter 38 including an ignition coil for generating a high voltage to be applied to the plug 37 and a fuel The has an injector (fuel injection means) 39 for injecting into the intake port 31.

  The intake system 40 is provided in the intake pipe 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and the intake pipe 41. And a throttle valve 43 for varying the opening cross-sectional area of the intake passage. The throttle valve 43 is rotationally driven in the intake pipe 41 by a throttle valve actuator 43a made of a DC motor.

  The exhaust system 50 includes an exhaust manifold 51 communicating with the exhaust port 34, an exhaust pipe 52 connected to the exhaust manifold 51, and a catalytic converter (three-way catalyst device) 53 interposed in the exhaust pipe 52.

On the other hand, this system includes a hot-wire air flow meter 61, an intake air temperature sensor 62, an atmospheric pressure sensor (a throttle valve upstream pressure sensor) 63, a throttle position sensor 64, an intake side cam position sensor 65, an exhaust side cam position sensor 66, an intake valve. A lift amount sensor 67, a crank position sensor 68, a water temperature sensor 69, an air-fuel ratio sensor (O ₂ sensor) 70, and an accelerator opening sensor 71 are provided.

  The air flow meter 61 actually measures the flow rate of air flowing through the intake passage of the internal combustion engine 10 (intake air flow rate), and outputs a signal representing the measured intake air flow rate AFM. The intake air temperature sensor 62 is provided in the air flow meter 61, detects the temperature of the intake air, and outputs a signal representing the intake air temperature Ta. The atmospheric pressure sensor 63 detects the pressure upstream of the throttle valve 43 (that is, atmospheric pressure) and outputs a signal indicating the throttle valve upstream pressure Pa. The throttle position sensor 64 detects the opening (throttle valve opening) of the throttle valve 43 and outputs a signal representing the throttle valve opening TA.

  The intake side cam position sensor 65 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (ie, every time the crankshaft 24 rotates 180 °). . This signal represents the opening / closing timing (intake valve advance amount) VVTin of the intake valve 32. Similarly, the exhaust side cam position sensor 66 generates a signal having one pulse every time the exhaust camshaft rotates 90 °, and this signal indicates the opening / closing timing of the exhaust valve 35 (exhaust valve advancement). Angular amount) VVTex.

  The intake valve lift amount sensor 67 detects the lift amount of the intake valve 32 and outputs a signal representing the intake valve lift amount Li that takes a value of “0” when the intake valve 32 is fully closed. The crank position sensor (engine speed sensor) 68 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °. It has become. This signal represents the engine speed NE.

The water temperature sensor 69 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal representing the cooling water temperature THW. The O ₂ sensor 70 outputs a signal corresponding to the oxygen concentration in the exhaust gas flowing into the catalytic converter 53 (a value corresponding to the air-fuel ratio of the exhaust gas). The accelerator opening sensor 71 outputs a signal representing the accelerator pedal operation amount Accp operated by the driver.

  The electric control device 80 is a microcomputer including a CPU 81, a ROM 82, a RAM 83, a backup RAM 84, an interface 85, and the like connected to each other by a bus. The ROM 82 stores a table (map) and constants in advance. The RAM 83 temporarily stores data as required by the CPU 81. The backup RAM 84 stores data while the power is turned on and holds the stored data while the power is shut off. The interface 85 includes an AD converter, is connected to the sensors 61 to 71, supplies signals from the sensors 61 to 71 to the CPU 81, and controls the actuator 33a and exhaust valve control of the intake valve control device 33 in accordance with instructions from the CPU 81. Drive signals are sent to the actuator 36a, igniter 38, injector 39, throttle valve actuator 43a, etc. of the device 36.

  Next, a method for determining the fuel injection amount (a method for estimating the in-cylinder intake fresh air amount Ma) by the fuel injection amount control device configured as described above will be described.

(Method for determining fuel injection amount fc and method for estimating in-cylinder intake fresh air amount Ma)
The fuel injection amount control device must inject fuel into the cylinder before the intake valve 32 of the cylinder in the intake stroke is closed. For this reason, the fuel injection amount control device uses the intake valve 32 to reduce the in-cylinder intake fresh air amount Ma that would be taken into the cylinder when the intake valve 32 is closed (that is, when the intake valve is closed). The fuel injection amount (basic injection amount) fc is determined based on the formula fc = kλ · Ma before the valve is closed. Here, kλ is a coefficient based on the set air-fuel ratio that changes according to the operating state. Then, the fuel injection amount control device injects the fuel of the determined fuel injection amount fc from the injector 39 of the cylinder in the intake stroke before the intake valve 32 of the cylinder is closed.

  Hereinafter, the fuel injection amount control device will be specifically described. FIG. 2 is a functional block diagram of the fuel injection amount control device. The fuel injection amount control device uses a simulation model consisting of an electronically controlled throttle model M1, a throttle model M2, an intake pipe model M3, an intake valve model M4, a cylinder model M5, and an exhaust valve model M6, and in-cylinder intake fresh air amount Ma Is supposed to be estimated.

  Calculations in these models M1 to M6 are achieved by the CPU 81 executing a program corresponding to each model every elapse of a predetermined time (program execution interval time Δt). In addition, the differential equations and integral equations described below are actually discretized to obtain their solutions. Further, the fuel injection amount control device includes a throttle valve electronic control logic A1, and controls the opening degree of the throttle valve 43 via a throttle valve actuator 43a. Hereinafter, each model will be described in order.

(Electronic control throttle model M1 and throttle valve electronic control logic A1)
The electronically controlled throttle model M1 is a model that estimates the throttle valve opening degree θt at a time t that is a predetermined time T0 ahead of the current time based on the accelerator pedal operation amount Accp up to the current time.

  More specifically, the throttle valve electronic control logic A1 is an actual value detected by the table shown in FIG. 3 that defines the relationship between the accelerator pedal operation amount Accp and the target throttle valve opening θr and the accelerator opening sensor 71. Based on the (current) accelerator pedal operation amount Accp, the provisional target throttle valve opening θr1 is determined every elapse of a predetermined time (for example, 2 msec). The table (map) that defines the relationship between the accelerator pedal operation amount Accp and the target throttle valve opening θr defines these relationships so that the accelerator pedal operation amount Accp increases and the target throttle valve opening θr increases. ing.

  Further, the throttle valve electronic control logic A1 is determined by a value obtained by delaying the provisional target throttle valve opening θr1 by a predetermined time T (for example, 64 msec), that is, at a time before the predetermined time T. The provisional target throttle valve opening θr1 is determined as the final target throttle valve opening θr at the present time. Then, the throttle valve electronic control logic A1 sends a drive signal to the throttle valve actuator 43a so that the actual throttle valve opening TA becomes the current target throttle valve opening θr.

  Thus, the target throttle valve opening θr is equal to the provisional target throttle valve opening θr1 determined in accordance with the accelerator pedal operation amount Accp at the time point a predetermined time T before the current time, and therefore the predetermined time from the current time. The target throttle valve opening degree θr at time t ahead of T0 is equal to the provisional target throttle valve opening degree θr1 before the time (T−T0) from the present time. Further, the provisional target throttle valve opening degree θr1 before the time (T−T0) from the present time is equal to the throttle valve opening degree θt at time t if the operation delay time of the throttle valve actuator 43a is ignored.

  Based on this idea, the electronically controlled throttle model M1 estimates the throttle valve opening θt at time t that is a predetermined time T0 ahead of the current time. That is, the provisional target throttle valve opening θr1 before the time (T−T0) from the current time is estimated as the throttle valve opening θt at the time t that is a predetermined time T0 from the current time. The throttle valve opening degree θt may be estimated in consideration of the operation delay time of the throttle valve actuator 43a.

(Throttle model M2)
In the throttle model M2, an air flow rate (hereinafter referred to as “throttle passage air flow rate”) mt passing through the throttle valve 43 is regarded as a throttle portion (orifice) as an air passage formed around the throttle valve 43. This is a model that is estimated based on the following formulas (9) to (11), which are general formulas for calculating the air flow rate that passes through the throttle portion that is established at the same time.

  In the above equations (9) to (11), Ct (θt) is a flow coefficient that changes according to the throttle valve opening θt, and At (θt) is the throttle opening area (intake air that changes according to the throttle valve opening θt) The opening area of the pipe 41), Pa is the upstream pressure of the throttle valve (ie, atmospheric pressure), Pm is the air pressure in the intake pipe downstream of the throttle valve 43 (intake pipe pressure), Ta is the intake air temperature (atmospheric temperature), and Tm is the throttle. An intake pipe air temperature downstream of the valve 43, R is a gas constant, and κ is a specific heat ratio (here, κ is treated as a constant value).

  Expression (11) is an expression that defines the function Φ, and the upper part of expression (11) is used when the flow velocity is lower than the sound velocity, and the lower portion is used when the flow velocity becomes the sound velocity. The throttle model M2 uses the formula (9) when the throttle valve upstream pressure Pa is a forward flow larger than the intake pipe air pressure Pm (Pa ≧ Pm), and the throttle valve upstream pressure Pa is smaller than the intake pipe air pressure Pm. In case (Pa <Pm), use equation (10).

  In the above equations (9) and (10), θt is an estimated throttle valve opening at a time t that is a predetermined time T0 ahead of the current time estimated by the electronic control throttle model M1. The throttle model M2 obtains the flow coefficient Ct (θt) using the table shown in FIG. 4 that defines the relationship between the throttle valve opening θt and the flow coefficient Ct (θt) and the estimated throttle valve opening θt, The opening area At (θt) is obtained using the table shown in FIG. 5 that defines the relationship between the throttle valve opening θt and the opening area At (θt) and the estimated throttle valve opening θt.

  The throttle model M2 uses the table shown in FIG. 6 that defines the relationship between the throttle valve opening degree θt and the product values Ct (θt) · At (θt) and the estimated throttle valve opening degree θt. (Θt) · At (θt) may be obtained at a time. The throttle model M2 includes a table MapCt (θt, Pm) that defines the relationship between the throttle valve opening θt, the intake pipe air pressure Pm, and the flow coefficient Ct (θt, Pm), and the estimated throttle valve opening θt. Further, it may be configured to obtain a flow coefficient Ct (θt, Pm) instead of the flow coefficient Ct (θt) using an intake pipe air pressure Pm acquired from an intake pipe model M3 described later.

  The throttle model M2 acquires the throttle valve upstream pressure Pa and the intake air temperature Ta from the atmospheric pressure sensor 63 and the intake air temperature sensor 62, respectively, and the intake pipe air pressure Pm and the intake pipe air temperature Tm from the intake pipe model M3 described later. Obtaining and calculating the above equation (9) or (10) using these values, the throttle passage air flow rate mt at time t is estimated. As will be described later, the intake pipe model M3 performs calculation using the throttle passage air flow rate mt that is the output of the throttle model M2. Therefore, the intake pipe air pressure Pm and the intake pipe air temperature Tm acquired by the throttle model M2 from the intake pipe model M3 are the same as those of the intake pipe model M3 at the previous calculation timing (before the program execution interval time Δt). This is the calculated value. This calculation method is similarly used in other models.

(Intake pipe model M3)
The intake pipe model M3 includes the following expression (12) and expression (13), throttle passage air flow rate mt, throttle passage air temperature (that is, intake air temperature) Ta, and intake pipe based on the law of conservation of mass and the law of conservation of energy, respectively. This is a model for obtaining the intake pipe air pressure (intake gas pressure) Pm and the intake pipe air temperature Tm from the intake valve passage gas flow rate mi, which is the flow rate of air flowing out of the air. In the following equations (12) and (13), Vm is the volume of the intake passage from the throttle valve 43 to the intake valve 32 (hereinafter simply referred to as “intake pipe section”).

d (Pm / Tm) / dt = (R / Vm) ・ (mt−mi) (12)

dPm / dt = κ ・ (R / Vm) ・ (mt ・ Ta−mi ・ Tm) (13)

  The intake pipe model M3 acquires the throttle passage air flow rate mt in the above equations (12) and (13) from the throttle model M2, and acquires the intake valve passage gas flow rate mi from an intake valve model M4 described later. Then, the calculation based on the equations (12) and (13) is performed to obtain the intake pipe air pressure Pm and the intake pipe air temperature Tm at a time t that is a predetermined time T0 from the present time. Note that the derivation process of the equations (12) and (13) describing the intake pipe model M3 is described in detail in, for example, the above-mentioned Patent Document 1 and the like, so detailed description thereof is omitted here. To do.

(Intake valve model M4)
In the intake valve model M4, the intake valve passage gas flow rate mi that is the air flow rate that passes around the intake valve 32 shown in FIG. 7 is regarded as the throttle portion (orifice). This is a model that is estimated based on the following formulas (14) to (16), which are general formulas for calculating the air flow rate that passes through the throttle portion that is established at the same time.

  In Expressions (14) to (16), Cdi (Li) is a flow coefficient that changes in accordance with the lift amount Li of the intake valve 32, and Ai (Li) is the periphery of the intake valve 32 that changes in accordance with the lift amount Li. , Ti is the gas temperature upstream of the intake valve 32 (the temperature of the gas passing through the intake valve, hereinafter referred to as “intake valve passage gas temperature Ti”), Pi is the intake air Gas pressure upstream of the valve 32 (hereinafter referred to as “intake valve upstream gas pressure Pi”), Tc is the in-cylinder gas temperature (gas temperature in the cylinder 21), and Pc is the in-cylinder gas pressure (cylinder 21). Gas pressure).

  Expression (16) is an expression that defines the function Φ described in Expression (11). The upper part of Expression (16) is used when the flow velocity is less than the sound speed, and the lower part is used when the flow velocity becomes the sound speed. The intake valve model M4 uses equation (14) when the intake valve upstream gas pressure Pi is greater than the in-cylinder gas pressure Pc, and when the intake valve upstream gas pressure Pi is less than the in-cylinder gas pressure Pc. Use equation (15). Thus, the intake valve passage gas flow rate mi is positive when the gas is sucked into the cylinder 21 and negative when the gas (burned gas) is blown back from the cylinder 21 into the intake passage. It is prescribed to take.

  The intake valve model M4 estimates the intake valve lift amount Li (t) at a time t that is a predetermined time T0 ahead of the current time. This estimation may be made based on the current lift amount Li detected by the intake valve lift amount sensor 67 and the engine rotational speed NE, and depends on the operation state including the current crank angle and the engine rotational speed NE. You may make based on the lift amount map set beforehand. The intake valve model M4 includes the table shown in FIG. 8 that defines the relationship between the intake valve lift amount Li and the product values Cdi (Li) · Ai (Li), and the estimated intake valve lift amount Li (t). Based on the above, the product value Cdi (Li) · Ai (Li) used in the equation (14) and the equation (15) is obtained.

  The intake valve model M4 sets the intake valve upstream gas pressure Pi to a value equal to the intake pipe air pressure Pm acquired from the intake pipe model M3, as will be described in detail later with reference to a flowchart. In the intake valve model M4, the intake valve passage gas temperature Ti in the equation (14) is equal to the intake pipe air temperature Tm acquired from the intake pipe model M3 when the cylinder 21 is sucking fresh air. If the cylinder 21 sucks the burned gas blown back into the intake passage, it is set to a value equal to the blown-back gas temperature Tp acquired as described later. The intake valve model M4 acquires in-cylinder gas pressure Pc and in-cylinder gas temperature Tc from a cylinder model M5 described later. The intake valve model M4 estimates the intake valve passage gas flow rate mi at time t by performing calculations based on the above equations (14) to (16) using these variables.

<Blow-back gas temperature Tp>
In the intake valve model M4, a gas blown back into the intake passage (specifically, in the intake port 31) from the inside of the cylinder 21 (hereinafter referred to as “blow-back gas”) is sucked into the cylinder 21. The blowback gas temperature Tp, which is the temperature used as the intake valve passage gas temperature Ti, is acquired based on the following formula (17) based on the energy of the blowback gas and the amount of the blowback gas.

  In the above equation (17), tivo is when the intake valve 32 is opened (that is, when the burned gas starts to be blown back into the intake passage). Trev is the time when the blown-back gas starts to be sucked into the cylinder 21 again (that is, when the blow-back of the burned gas into the intake passage is completed).

  The numerator on the right side of equation (17) is the energy of the blown-back gas at time trev. This is based on the fact that the energy given to the blowback gas per unit time by the intake valve passing gas is represented by “(−mi) · Cp · Tc”. The denominator on the right side of equation (17) is the amount of blown-back gas at time Trev. Cp is the constant pressure specific heat of the blown back gas (burned gas), and Cp is treated as a constant value here. This equation (17) is derived from the relationship that “the energy of the gas at a certain time is equal to the product of the amount of gas at that time, the constant-pressure specific heat of the gas, and the temperature of the gas at that time”. It is a formula.

  Thus, the intake valve model M4 performs the integral calculation (integration) based on the equation (17) to obtain the temperature of the blown-back gas at the time trev, and acquires this temperature as the blown-back gas temperature Tp. In the intake valve model M4, the blown-back gas temperature Tp acquired in this way is set to the period during which the blow-back gas is sucked into the cylinder 21 as described above (that is, when mi> 0 and the intake valve is opened when mi is opened. (The period when the integrated value <0 from 0) is used as the intake valve passage gas temperature Ti in the above equation (14).

(Cylinder model M5)
In the cylinder model M5, the in-cylinder gas pressure Pc and the in-cylinder gas are determined according to the following formula (18) and the following formula (19) based on the mass conservation law and the energy conservation law for the air in the cylinder 21 (combustion chamber 25). This is a model for obtaining the temperature Tc. As shown in FIG. 7, Vc is the volume of the cylinder 21 (combustion chamber 25), Ti is the intake valve passage gas temperature (intake gas temperature), mi is the intake valve passage gas flow rate, me is the exhaust valve passage gas flow rate, Te Is the exhaust gas temperature (exhaust valve passing gas temperature).

  κc, κi, and κe are the specific heat ratio of the gas in the cylinder 21 (in-cylinder gas specific heat ratio), the specific heat ratio of the intake valve passage gas, and the specific heat ratio of the exhaust gas (exhaust valve passage gas), respectively. Treat as κ. Rc, Ri, and Re are the gas constant of the gas in the cylinder 21, the gas constant of the gas passing through the intake valve, and the gas constant of the exhaust gas, respectively, and are treated as a constant value R here. Qw ′ is the amount of heat (transfer heat flow rate, heat flow) per unit time transferred from the cylinder 21 (cylinder wall surface) to the gas in the cylinder 21. Note that the derivation process of the equations (18) and (19) describing the cylinder model M5 is described in detail in, for example, the above-described Patent Document 1 and the like, and thus detailed description thereof is omitted here.

  The intake valve passage gas flow rate mi at time t in the equations (18) and (19) is given by the intake valve model M4, and the exhaust valve passage gas flow rate me is given by the exhaust valve model M6 described later. The cylinder volume Vc at time t can be obtained from the actual crank angle detected by the crank position sensor 68 and the engine speed NE. The intake valve passage gas temperature Ti at time t is acquired in the same manner as the intake valve model M4 described above. The exhaust gas temperature Te is the exhaust gas amount Ge per unit time obtained by integrating (integrating and integrating time) the exhaust valve passage gas flow rate me of all cylinders (or the intake valve passages of all cylinders). The intake gas amount Ga per unit time obtained by integrating (time integration) the gas flow rate mi), the fuel amount Gf per unit time obtained by integrating (time integration) the fuel injection amount fc of all cylinders, and It is obtained as a function (map value) of the engine speed NE. An exhaust gas temperature sensor may be installed in the exhaust port 34, and the exhaust gas temperature Te may be obtained from the output of the exhaust gas temperature sensor.

  Since the transfer heat flow rate Qw 'is relatively small, it is ignored in this example. The cylinder model M5 calculates the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc at time t by performing calculations based on the above equations (18) and (19) using these variables.

(Exhaust valve model M6)
In the exhaust valve model M6, the air flow rate (that is, the exhaust valve passage gas flow rate) me passing around the exhaust valve 35 shown in FIG. 7, and the air passage formed around the exhaust valve 35 are throttled (orifice). The following formulas (20) and (21) corresponding to the above formulas (14) and (15), respectively, which are general formulas for calculating the air flow rate passing through the throttle part established when This is a model estimated based on the above equation and the above equation (16) which is the definition equation of Φ.

  In Expressions (20) and (21), Cde (Le) is a flow coefficient that changes in accordance with the lift amount Le of the exhaust valve 35, and Ae (Le) is the periphery of the exhaust valve 35 that changes in accordance with the lift amount Le. , Te is the exhaust gas temperature, Pc is the in-cylinder gas pressure, and Pe is the exhaust gas pressure (the pressure of the gas downstream of the exhaust valve 35).

The exhaust valve model M6 uses the equation (20) when the exhaust gas pressure Pe is larger than the in-cylinder gas pressure Pc, and uses the equation (21) when the exhaust gas pressure Pe is smaller than the in-cylinder gas pressure Pc. Thus, the exhaust valve passage gas flow rate me takes a positive value when gas is sucked into the cylinder 21 from the exhaust system, and takes a negative value when gas is discharged from the cylinder 21 to the exhaust system. It is stipulated in.
The exhaust valve model M6 estimates the exhaust valve lift amount Le (t) at a time t that is a predetermined time T0 ahead of the current time. This estimation can be performed based on the current crank angle and the engine speed NE. The exhaust valve model M6 includes the table shown in FIG. 9 that defines the relationship between the exhaust valve lift amount Le and the product values Cde (Le) · Ae (Le), and the estimated exhaust valve lift amount Le (t). Based on the above, the product values Cde (Le) · Ae (Le) used in the above equations (20) and (21) are obtained.

  The exhaust valve model M6 integrates the exhaust gas temperature Te, the exhaust gas amount Ge obtained by integrating (time integration) the exhaust valve passage gas flow rate me, and the fuel injection amounts fc of all cylinders ( It is obtained as a function (map value) of the fuel amount Gf per unit time obtained by time integration) and the engine speed NE. The exhaust valve model M6 acquires the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc from the cylinder model M5, and acquires the exhaust gas pressure Pe as described later. The exhaust valve model M7 estimates the exhaust valve passage gas flow rate me at time t by calculating the above equation (20) or the above equation (21) using these variables.

<Exhaust gas pressure Pe>
In general, it is known that the pressure loss of a pipe line can be approximated by a quadratic expression of the flow rate of gas flowing in the pipe line. Therefore, the exhaust gas pressure is the exhaust gas amount Ge per unit time obtained by integrating (time integration) the exhaust valve passage gas flow rate me of all the cylinders (or the intake valve passage gas of all the cylinders). It can be obtained as a function (for example, basic exhaust gas pressure Pe0 = a · Ge + b · Ge ² : a and b are constants) obtained by integrating (time integration) the flow rate mi. .

  By the way, when the intake valve 32 is opened and the above-described combustion gas is blown back into the intake passage, the in-cylinder gas pressure Pc decreases. As a result, immediately after the intake valve 32 is opened, the in-cylinder gas pressure Pc becomes smaller than the exhaust gas pressure, and the burned gas discharged into the exhaust system flows back into the cylinder 21 through the periphery of the exhaust valve 35. (Backflow of the burned gas from the exhaust system is generated). When a backflow of burned gas from the exhaust system occurs, the exhaust gas pressure decreases.

  The backflow of burned gas from the exhaust system continues until the exhaust valve 35 is substantially closed (immediately before the end of the valve overlap period). Therefore, the degree of the decrease in the exhaust gas pressure due to the backflow of the burned gas from the exhaust system becomes larger as the valve overlap period is longer.

  Here, when the valve overlap period is long, that is, when the degree of decrease in the exhaust gas pressure due to the backflow of burned gas from the exhaust system is large, the exhaust gas pressure obtains the pressure loss of the above-mentioned pipeline. It became clear that it became smaller than the basic exhaust gas pressure Pe0 obtained from the quadratic equation. In other words, when the valve overlap period is long, it has been found that the exhaust gas pressure cannot be accurately approximated by the above-described secondary expression for calculating the pressure loss of the pipe line. Accordingly, in order to accurately obtain the exhaust gas pressure including the case where the valve overlap period is long, it is necessary to correct the basic exhaust gas pressure Pe0 obtained from the above-described quadratic expression for obtaining the pressure loss of the pipe line. is there.

  On the other hand, the degree of decrease in the exhaust gas pressure due to the above-described backflow of burned gas from the exhaust system increases as the amount (total amount) of backflow of burned gas from the exhaust system increases. The total amount of the burned gas that flows backward from the exhaust system increases as the amount (total amount) of the burned gas blown back into the intake passage increases.

  The total amount of the burned gas that flows backward from the exhaust system greatly depends on the exhaust valve advance amount VVTex of the exhaust valve 35 and the engine speed NE. In addition, it is considered that the total amount of burnt gas that flows backward from the exhaust system also greatly depends on the difference between the exhaust gas pressure and the intake pipe air pressure Pm (intake gas pressure) (Pe0−Pm, intake / exhaust pressure difference). The total amount of burned gas blown back into the intake passage greatly depends on the intake valve advance angle amount VVTin of the intake valve 32, the maximum lift amount Limax, and the engine speed NE.

  From the above, the exhaust valve model M6 introduces the pressure correction coefficient Kp (0 <Kp ≦ 1), the pressure correction coefficient Kp, the engine speed NE, the intake / exhaust pressure difference (Pe0-Pm), the intake valve advance This is obtained based on a table prepared in advance through experiments or the like using the angular amount VVTin, the exhaust valve advance amount VVTex, and the maximum lift amount Limax of the intake valve 32 as arguments. The exhaust valve model M6 acquires a value obtained by multiplying the basic exhaust gas pressure Pe0 by the pressure correction coefficient Kp as the exhaust gas pressure Pe in the above equation (20). In this example, the exhaust valve model M6 uses the product value (constant) of the pressure correction coefficient Kp obtained when the intake valve 32 is opened and the basic exhaust gas pressure Pe0 over the subsequent valve opening period of the intake valve 32. Thus, it continues to be used as the exhaust gas pressure Pe in the above equation (20).

  This fuel injection amount control apparatus integrates the intake valve passage gas flow rate mi obtained by such a series of calculations from time tivo when the intake valve 32 opens to time tivc when the intake valve 32 closes. The cylinder intake fresh air amount Ma sucked into the cylinder 21 in one intake stroke is estimated, and the fuel injection amount fc is determined based on this value Ma. The integrated value Mi of the intake valve passage gas flow rate mi is “0” when all the gas blown back into the intake passage is re-inhaled if an initial value 0 is given at the time tivo when the intake valve 32 opens. As a result, the value indicates the in-cylinder intake fresh air amount Ma. The above is the principle for determining the in-cylinder intake fresh air amount Ma and the fuel injection amount fc.

(Actual operation)
Next, with respect to the actual operation of the fuel injection amount control apparatus according to the first embodiment of the present invention, FIG. 10, the flowchart of FIG. 11 showing the routine (program) executed by the CPU 81, and the time chart of FIG. The description will be given with reference.

  The CPU 81 is configured to execute a series of routines shown in FIGS. 10 and 11 for a specific cylinder (a certain cylinder) every elapse of a predetermined time (program execution interval time Δt). The time on this routine is a time t that is a predetermined time T0 ahead of the present time. That is, for example, the intake valve 32 actually changes from the closed state to the open state after a predetermined time T0 has elapsed from the time when it is determined that the intake valve 32 has shifted from the closed state to the open state by executing this routine. Transition. The CPU 81 executes the same routine independently for the other cylinders.

  When the predetermined timing is reached, the CPU starts the processing of this routine from step 1000, proceeds to step 1005, and determines whether or not it is immediately after the intake valve 32 of a specific cylinder shifts from the closed state to the opened state. judge. Now, assuming that the intake valve 32 of a specific cylinder is in a closed state, the CPU 81 makes a “No” determination at step 1005 to proceed to step 1010, where the intake valve 32 is in an open state. It is determined whether or not.

  In this case, since the intake valve 32 of the specific cylinder is in the closed state, the CPU 81 makes a “No” determination at step 1010 to proceed to step 1015, and the intake valve 32 shifts from the open state to the closed state. It is determined whether it is immediately after. Even in this case, since the intake valve 32 is in the closed state, the CPU 81 makes a “No” determination at step 1015 to proceed to step 1095 to end the present routine tentatively. Such processing is repeatedly performed until the intake valve 32 shifts from the closed state to the open state.

  Thereafter, when the crank angle reaches the valve opening crank angle θ0 before the intake top dead center TDC, the intake valve 32 shifts from the valve closed state to the valve open state (see time t0 in FIG. 12). In this case, the CPU 81 determines “Yes” when the process proceeds to step 1005, proceeds to step 1020, and acquires the intake pipe air pressure Pm and the intake pipe air temperature Tm estimated by the intake pipe model M3.

Next, in step 1025, the CPU 81 sets the intake valve upstream gas pressure Pi to a value equal to the acquired intake pipe air pressure Pm, and in the subsequent step 1030, the equation (Pe0 = a · Ge + b) described in step 1030 is set.・ Ge ² ,
The basic exhaust gas pressure Pe0 is obtained according to constants a and b. Here, Ge is an exhaust gas amount per unit time obtained by integrating (time integration) the exhaust valve passage gas flow rates me of all the cylinders, and is separately calculated by a routine (not shown).

  Next, the CPU 81 proceeds to step 1035, where the intake gas amount Ga per unit time obtained by integrating (time integration) the intake valve passage gas flow rates mi of all cylinders, and the fuel injection amounts of all cylinders. The exhaust gas temperature Te (= MapTe) from the fuel amount Gf per unit time obtained by integrating fc (time integration) and the engine speed NE, and a table MapTe that defines the relationship between these values and the exhaust gas temperature Te (Ga, Gf, NE)).

  Subsequently, the CPU 81 proceeds to step 1040 to obtain the intake / exhaust pressure difference ΔP by subtracting the acquired intake pipe air pressure Pm from the acquired basic exhaust gas pressure Pe0. Next, the CPU 81 proceeds to step 1045, where the engine speed NE, the intake / exhaust pressure difference ΔP, the intake valve advance angle amount VVTin, the exhaust valve advance angle amount VVTex, the maximum lift amount Limax of the intake valve 32, and the like. The pressure correction coefficient Kp is obtained from the table MapKp that defines the relationship between the value of the pressure and the pressure correction coefficient Kp, and the exhaust gas is obtained by multiplying the obtained basic exhaust gas pressure Pe0 by the pressure correction coefficient Kp in the subsequent step 1050. Find the pressure Pe.

  Subsequently, the CPU 81 performs initial setting of each value in step 1055. Specifically, the CPU 81 sets the exhaust gas pressure Pe as the in-cylinder gas pressure Pc, and sets the exhaust gas temperature Te as the in-cylinder gas temperature Tc. This is because the exhaust valve 35 is opened at the time t0 when the intake valve 32 is opened (refer to the lift amount of the exhaust valve 35 indicated by the broken line LEX in FIG. 12), and therefore the cylinder gas pressure Pc. And based on the knowledge that the in-cylinder gas temperature Tc will be approximate to the exhaust gas pressure Pe and the exhaust gas temperature Te, respectively.

  Further, the CPU 81 sets the intake valve passage gas temperature Ti to a value equal to the exhaust gas temperature Te. This is because the intake valve 32 and the exhaust valve 35 are both open, so that the gas in the exhaust port 34 is blown back to the intake port 31 having a low pressure through the cylinder 21, so that the intake valve passage gas temperature Ti is equal to the cylinder. This is because the inner gas temperature Tc (≈the exhaust gas temperature Te) is reached. Further, the CPU 81 sets the integrated value Mi of the intake valve passage gas flow rate mi from the time when the intake valve 32 is opened to the initial value “0”, and the exhaust valve passage gas from when the intake valve 32 is opened. The integrated value Me of the flow rate me is set to the initial value “0”.

  Next, the CPU 81 proceeds to step 1060 to set both the energy integration value SE of the blow back gas and the total amount SC of the blow back gas to “0”.

  Next, the CPU 81 proceeds to step 1105 in FIG. 11, and calculates the intake valve passage gas flow rate mi by the intake valve model M4. In this case, since the intake valve upstream gas pressure Pi (= intake pipe air pressure Pm) is smaller than the in-cylinder gas pressure Pc (= exhaust gas pressure Pe), the burned gas flows backward from the cylinder 21 to the intake port 31. That is, the intake valve passage gas flow rate mi is obtained using the equation (15). Therefore, the intake valve passage gas flow rate mi is a negative value.

  Next, the CPU 81 proceeds to step 1110, and adds the product value (Δt · mi) of the program execution interval time Δt and the intake valve passage gas flow rate mi to the integrated value Mi of the intake valve passage gas flow rate mi at that time, to thereby obtain a new intake air. An integrated value Mi of the valve passage gas flow rate mi is obtained, and in the subsequent step 1115, the exhaust valve passage gas flow rate me is calculated by the exhaust valve model M6. In this case, since the exhaust gas pressure Pe is equal to or higher than the in-cylinder gas pressure Pc, gas flows into the cylinder 21 from the exhaust port 34 (reverses flow). That is, the exhaust valve passage gas flow rate me is obtained using the equation (20). Therefore, the exhaust valve passage gas flow rate me is a positive value. At this time, as the exhaust gas pressure Pe in the equation (20), a value (constant) obtained by correcting the basic exhaust gas pressure Pe0 acquired in step 1050 with the pressure correction coefficient Kp is used.

  Next, in step 1120, the CPU 81 determines whether or not the integrated value Mi of the intake valve passage gas flow rate mi is greater than the initial value “0” (whether or not it is a positive value). If the integrated value Mi is a negative value, the gas is being blown back from the cylinder 21 to the intake passage, or the blown back gas (blow-back gas) is re-inhaled into the cylinder 21. Indicates that it is in a stage. On the other hand, if the integrated value Mi is a positive value, it indicates that all of the blown-back gas is re-inhaled into the cylinder 21 and fresh air is inhaled into the cylinder 21.

  At present, the intake valve passage gas flow rate mi is a negative value, and therefore the integrated value Mi of the intake valve passage gas flow rate mi is a negative value. Therefore, the CPU 81 makes a “No” determination at step 1120. Then, the routine proceeds to step 1125, where it is determined whether or not the intake valve upstream gas pressure Pi set to a value equal to the intake pipe air pressure Pm is smaller than the in-cylinder gas pressure Pc in step 1025. That is, in step 1125, it is determined whether gas is flowing into the cylinder 21 from the intake passage or whether gas is being blown back from the cylinder 21 to the intake passage.

  Since the present time is immediately after the intake valve 32 is opened, the intake valve upstream gas pressure Pi is smaller than the in-cylinder gas pressure Pc, so the CPU 81 determines “Yes” in step 1125 and proceeds to step 1130. A new blown gas is obtained by adding the value Δt · mi · Cp · Tc corresponding to the blown gas energy from the previous execution of this routine to the current execution of this routine to the integral value SE of the blown gas energy at that time. Get the integral value SE of the energy.

  Next, in step 1135, the CPU 81 adds a value Δt · mi corresponding to the amount of blowback gas from the previous execution of this routine to the current execution of this routine to the total amount SC of the blowback gas at that time to newly blow back. Get the total amount of gas SC. Then, in step 1140, the CPU 81 obtains the blow back gas temperature Tp according to the equation (Tp = SE / (Cp · SC)) shown in step 1140.

  Thereafter, the CPU 81 calculates the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc from the cylinder model M5 in step 1145, and in step 1150, adds the program execution interval time Δt to the integrated value Me of the exhaust valve passage gas flow rate me at that time. And the product value (Δt · me) of the exhaust valve passage gas flow rate me and a new integrated value Me of the exhaust valve passage gas flow rate me is obtained. The integrated value Me of the exhaust valve passage gas flow rate me is hereinafter referred to as “in-cylinder residual gas amount”.

  In step 1155, the CPU 81 sets the intake valve upstream gas pressure Pi to a value equal to the intake pipe air pressure Pm determined by the intake pipe model M3 at that time, and in step 1160, the intake gas amount at that time is set. The exhaust gas temperature Te (= MapTe (Ga, Gf, NE)) is obtained from Ga, the fuel amount Gf, the engine speed NE, and the table MapTe in the same manner as in Step 1035, and the process proceeds to Step 1095 to end the series of this routine once. To do.

  Thereafter, when the program execution interval time Δt elapses, the CPU 81 starts the processing of this routine again from step 1000 in FIG. At this time, the intake valve 32 is open. Accordingly, the CPU 81 makes a “No” determination in step 1005 and also makes a “Yes” determination in step 1010 for determining whether or not the intake valve 32 is in an open state (whether or not the valve is open). , The process proceeds to step 1105 to step 1120 in FIG.

  At this time, since sufficient time has not passed since the intake valve 32 is opened, the gas is still flowing back from the exhaust port 34 to the cylinder 21 (Pc <Pe), and the intake port 31 from the cylinder 21 The gas is still flowing back (Pi <Pc). Accordingly, the expression (15) is continuously used in step 1105 to obtain the intake valve passage gas flow rate mi, and the intake valve passage gas flow rate mi is still a negative value. As a result, the integrated value Mi of the intake valve passage gas flow rate mi updated in step 1110 is still a negative value.

  In step 1115, the equation (20) is continuously used to obtain the exhaust valve passage gas flow rate me. That is, as the exhaust gas pressure Pe in the equation (20), a value (constant) obtained by correcting the basic exhaust gas pressure Pe0 acquired in step 1050 with the pressure correction coefficient Kp is used.

  As described above, at this time, the integrated value Mi of the intake valve passage gas flow rate mi is negative, and the intake valve upstream gas pressure Pi is smaller than the in-cylinder gas pressure Pc. Accordingly, the CPU 81 proceeds to step 1120 and steps 1125 to 1140 to update the blow back gas temperature Tp, and thereafter executes steps 1145 to 1160 to end the present routine tentatively. Thereafter, the processing described above is repeatedly executed.

  Thus, when the integrated value Mi of the intake valve passage gas flow rate mi is a negative value and the intake valve upstream gas pressure Pi is smaller than the in-cylinder gas pressure Pc, the blow-back gas temperature Tp is updated. In this case, the intake valve passage gas flow rate mi is obtained by equation (15).

  In addition, when the in-cylinder gas pressure Pc is smaller than the exhaust gas pressure Pe (that is, while the gas is flowing backward from the exhaust port 34 to the cylinder 21, therefore, the gas is flowing backward from the cylinder 21 to the intake port 31). As the exhaust gas pressure Pe in the equation (20), the value (constant) obtained by correcting the basic exhaust gas pressure Pe0 acquired in step 1050 with the pressure correction coefficient Kp is continuously used. As a result, the exhaust gas pressure Pe is closer to the actual value than the basic exhaust gas pressure Pe0, so the exhaust valve passage gas flow rate me is calculated with high accuracy.

  Thereafter, when time elapses and the time t1 shown in FIG. 12 (the crank angle becomes the crank angle θ1 slightly after the intake top dead center TDC), the exhaust valve 35 is substantially closed. At this time, the piston 22 is lowered and the volume of the combustion chamber 25 is increased. As a result, the intake valve passage gas pressure Pi becomes larger than the in-cylinder gas pressure Pc, and the burnt gas (blow-back gas) blown back into the intake port 31 is sucked into the cylinder 21 through the periphery of the intake valve 32. Start to be.

  As a result, the CPU 81 obtains the intake valve passage gas flow rate mi using the equation (14) in step 1105. Further, since the integrated value Mi of the intake valve passage gas flow rate mi is still a negative value, the CPU 81 still determines “No” in step 1120, while determining “No” in step 1125 and step 1165. Then, the intake valve passage gas temperature Ti is set to a value equal to the blowback gas temperature Tp obtained by the calculation in step 1140.

  Accordingly, in step 1105 at the next execution of this routine, a value equal to the blowback gas temperature Tp is used as the intake valve passage gas temperature Ti in the equation (14). As a result, the intake valve passage gas temperature Ti becomes a value very close to the actual intake valve passage gas temperature, so that the intake valve passage gas flow rate mi is accurately calculated. Further, since the intake valve passage gas flow rate mi becomes a positive value, the integrated value Mi of the intake valve passage gas flow rate mi increases after time t1.

  However, since the integrated value Mi of the intake valve passage gas flow rate mi is still a negative value, the CPU 81 determines “No” in step 1120 and executes steps 1125 and 1165. Therefore, the intake valve passage gas temperature Ti in the equation (14) becomes the blow-back gas temperature Tp even at the next execution of this routine.

  When this state continues, the integrated value Mi of the intake valve passage gas flow rate mi becomes “0” at time t3 ′. In the present embodiment, this time t <b> 3 ′ corresponds to a time when all of the blown-back gas is sucked into the cylinder 21 and fresh air starts to be sucked into the cylinder 21.

  If this routine is executed immediately after this time t3 ′, the CPU 81 determines “Yes” when the routine proceeds to step 1120 and proceeds to step 1170, where the intake pipe model M3 estimates the intake valve passage gas temperature Ti. A value equal to the intake pipe air temperature Tm is set.

  As a result, when the CPU 81 proceeds to step 1105 at the next execution of this routine, the intake valve passage gas flow rate mi is calculated by setting the intake valve passage gas temperature Ti in the above equation (14) to the intake pipe air temperature Tm. . Thus, since fresh air should be sucked into the cylinder 21 after the time t3 ′, the intake valve passage gas flow rate mi is set by setting the intake valve passage gas temperature Ti to the intake pipe air temperature Tm. Calculated more accurately.

  Thereafter, when the crank angle reaches the valve closing crank angle θ5, the intake valve 32 shifts from the valve opening state to the valve closing state (see time t5 in FIG. 12). At this time, the CPU 81 makes a “No” determination at step 1005 and step 1010, and determines at step 1015 whether or not the intake valve 32 has transitioned from the valve opening state to the valve closing state. Since this determination result is “Yes”, the CPU 81 proceeds from step 1015 to step 1065, where the integrated value Mi of the intake valve passage gas flow rate mi from when the intake valve 32 calculated up to that point is opened. Is stored as in-cylinder intake fresh air amount Ma.

  In step 1070, the CPU 81 obtains the fuel injection amount fc based on the in-cylinder intake fresh air amount Ma, and in subsequent step 1075, the in-cylinder intake fresh air amount Ma, the in-cylinder residual gas amount Me, and the engine speed NE. And ignition timing map Mapθig, ignition timing θig (= Mapθig (Ma, Me, NE)) is determined, and the routine proceeds to step 1095 to end the present routine tentatively. As described above, the present fuel injection amount control apparatus determines engine control parameters such as the fuel injection amount fc and the ignition timing θig based on the in-cylinder intake fresh air amount Ma and the in-cylinder residual gas amount Me.

  As described above, in the in-cylinder intake fresh air amount estimation device of the first embodiment, the intake valve 32 is in the latter half of the exhaust stroke (when the crank angle becomes the crank angle θ0 before the intake top dead center TDC). It is applied to the internal combustion engine 10 having a valve overlap which is opened and the exhaust valve 35 is opened at that time. The exhaust valve 35 is closed immediately after the start of the intake stroke (when the crank angle becomes the crank angle θ2 immediately after the intake top dead center TDC).

  The in-cylinder intake fresh air amount estimation device of the first embodiment includes an in-cylinder gas pressure calculating means (step 1145) for calculating an in-cylinder gas pressure Pc that is a pressure in the cylinder 21 of the internal combustion engine 10, and an internal combustion engine. Intake gas pressure acquisition means (step 1020) for acquiring the intake gas pressure Pm, which is the pressure of the gas in the intake passage (intake port 31 and intake pipe 41), and the exhaust passage (exhaust port 34, exhaust of the internal combustion engine 10) Exhaust gas pressure calculating means (step 1030, step 1045 and step 1050) for calculating the exhaust gas pressure Pe, which is the pressure of the gas in the manifold 51 and the exhaust pipe 52), is provided.

  Further, this in-cylinder intake fresh air amount estimation device calculates the intake valve passage gas flow rate mi that is the flow rate of the gas that passes around the intake valve 32 that communicates and blocks the cylinder 21 and the intake passage. An exhaust valve passage gas flow rate me, which is a flow rate of gas passing through the periphery of the exhaust valve 35 that communicates and shuts off the cylinder 21 and the exhaust passage, and the flow rate calculation means (steps 1170, 1165, 1105, and 1145) is calculated. The exhaust valve passage gas flow rate calculating means (step 1115 and step 1145), and the cylinder for estimating the cylinder intake fresh air amount Ma which is the amount of fresh air sucked into the cylinder 21 based on the intake valve passage gas flow rate mi. An internal intake fresh air amount estimation means (step 1110 and step 1065) is provided.

  The in-cylinder gas pressure calculating means calculates the in-cylinder gas pressure Pc based on at least the intake valve passage gas flow rate mi and the exhaust valve passage gas flow rate me (see equations (18) and (19)). The intake valve passage gas flow rate calculating means calculates the intake valve passage gas flow rate mi based on at least the intake gas pressure Pm and the in-cylinder gas pressure Pc (see equations (14) and (15)). The exhaust valve passage gas flow rate calculation means calculates the exhaust valve passage gas flow rate me based on at least the exhaust gas pressure Pe and the in-cylinder gas pressure Pc (see equations (20) and (21)).

  As described above, the exhaust gas pressure calculating means reversely flows the burned gas into the cylinder 21 from the exhaust passage that occurs during the valve overlap period in which both the intake valve 32 and the exhaust valve 35 are open. In order to take into account the decrease in exhaust gas pressure due to the internal combustion engine, the internal combustion engine includes parameters (intake valve advance amount VVTin, intake valve maximum lift amount Limax, exhaust valve advance amount VVTex) representing the open / close state of the intake valve 32 and the exhaust valve 35 A pressure correction coefficient Kp (0 <Kp ≦ 1) is obtained based on parameters representing the operating state of the engine 10 (engine speed NE, intake / exhaust pressure difference ΔP), and the pressure is set to the basic exhaust gas pressure Pe0 (see step 1030). The exhaust gas pressure Pe is calculated by multiplying the correction coefficient Kp.

  As a result, the exhaust gas pressure Pe can be accurately calculated during the valve overlap period. Therefore, since the exhaust valve passage gas flow rate me calculated based on the exhaust gas pressure Pe can be calculated with high accuracy, the in-cylinder gas pressure Pc calculated based on the exhaust valve passage gas flow rate me can be calculated with high accuracy. Therefore, since the intake valve passage gas flow rate mi calculated based on the in-cylinder gas pressure Pc can be calculated with high accuracy, the in-cylinder intake fresh air amount Ma calculated based on the intake valve passage gas flow rate mi is also accurately estimated. Can be done. Thereby, even if the valve overlap period is long, the in-cylinder intake fresh air amount Ma can be accurately estimated.

  The intake valve passage gas flow rate calculating means has either a positive or negative signed gas flow rate (in this example, a positive sign) when gas is sucked into the cylinder 21 from the intake passage. The gas flow rate) is calculated as the intake valve passage gas flow rate mi every elapse of a predetermined time Δt (steps 1105 and (14)). Further, the intake valve passage gas flow rate calculation means calculates the positive or negative signed gas flow rate when the gas is blown back from the cylinder 21 to the intake passage (in this example, a gas flow rate having a negative sign). ) As the intake valve passage gas flow rate mi every time the predetermined time Δt elapses (steps 1105 and (15)).

  On the other hand, as described above, the in-cylinder intake fresh air amount estimation means integrates the calculated intake valve passage gas flow rate mi from the time when the intake valve 32 is opened to obtain the integrated value Mi (step 1110). The initial value of the integrated value Mi set when the intake valve 32 is opened is 0 in this example. Accordingly, the integrated value Mi of the intake valve passage gas flow rate mi returns to 0 when all of the burned gas blown back into the intake passage is sucked into the cylinder 21, and the intake valve 32 is closed thereafter. The integrated value Ma of the intake valve passage gas flow rate mi at the time of the valve is a value representing the in-cylinder intake fresh air amount Ma itself. Therefore, the in-cylinder intake fresh air amount Ma can be estimated by simply performing the integration of the intake valve passage gas flow rate mi.

(Second Embodiment)
Next, a fuel injection amount control device (in-cylinder intake fresh air amount estimation device) according to a second embodiment of the present invention will be described. In the second embodiment, a burned gas blowback amount Grev that is the total amount of burnt gas blown back from the cylinder 21 to the intake passage over the valve overlap period is calculated, and the pressure is calculated based on the burnt gas blowback amount Grev. This is different from the first embodiment in that the correction coefficient Kp is calculated.

  Based on this difference, the CPU 81 of the second embodiment performs the routine shown by the flowchart in FIG. 13 instead of the routine of FIG. 10 executed by the CPU 81 of the first embodiment and the CPU 81 of the first embodiment executed by FIG. A series of routines consisting of the same routines are executed. In the routine shown in FIG. 13, steps that are the same as the steps in the routine shown in FIG. 10 are given the same step numbers as the step numbers in FIG. Hereinafter, the routine of FIG. 13 unique to the second embodiment will be described.

  The routine shown in FIG. 13 differs from the routine shown in FIG. 10 only in that steps 1040 and 1045 in FIG. 10 are replaced with steps 1305, 1310 and 1315. When the intake valve 32 is opened, in step 1305, the passage area time integrated value AOL, which is the time integral value of the passage area of the gas passage formed around the intake valve 32 over the valve overlap period, is determined as the engine speed NE. The intake valve advance amount VVTin, the exhaust valve advance amount VVTex, the maximum lift amount Limax of the intake valve 32, and a table MapAOL that defines the relationship between these values and the passage area time integral value AOL. The table MapAOL can be easily prepared from these values and design specifications relating to the passage area of the gas passage formed around the intake valve 32 in the engine 10.

  In step 1310, the burned gas blow-back amount Grev is used to calculate the flow rate of air passing through the throttle portion established when the air passage formed around the intake valve 32 is regarded as a throttle portion (orifice). This is obtained based on the following formula (22) applying the above formula and the above formula (16) which is the definition formula of Φ. Here, as AOL, Pe0, Te, and Pm, the values acquired in step 1305, step 1030, step 1035, and step 1020 are used, respectively. In the equation (22), it is assumed that the in-cylinder gas pressure Pc is equal to the basic exhaust gas pressure Pe0.

  In step 1315, the pressure correction coefficient Kp (0 <Kp ≦ 1) is obtained from the burned gas blowback amount Grev and the table MapKp that defines the relationship between the burned gas blowback amount Grev and the pressure correction coefficient Kp. This is based on the knowledge that the degree of decrease in the exhaust gas pressure due to the backflow of the burned gas from the exhaust system will largely depend on the burned gas blowback amount Grev itself. Thereby, the pressure correction coefficient Kp becomes a smaller value as the burned gas blow-back amount Grev is larger.

  The pressure correction coefficient Kp thus determined is multiplied by the basic exhaust gas pressure Pe0 in step 1050, and this product value (constant) is the step in FIG. 11 over the period during which the intake valve 32 is open. It is used as the exhaust gas pressure Pe of the equations (20) and (21) used in 1115. In this second embodiment, Step 1030, Step 1305, Step 1310, Step 1315, and Step 1050 correspond to the exhaust gas pressure calculation means.

  As described above, the in-cylinder intake fresh air amount estimation device of the second embodiment is applied to the internal combustion engine 10 having the valve overlap as in the first embodiment. The exhaust gas pressure calculation means of the second embodiment is based on parameters (intake valve advance amount VVTin, intake valve maximum lift amount Limax, exhaust valve advance amount VVTex) representing the open / closed states of the intake valve 32 and the exhaust valve 35. Then, a value (passage area time integral value AOL) corresponding to the time integral value of the passage area of the gas passage formed around the intake valve 32 over the valve overlap period is calculated, and based on this passage area time integral value AOL Thus, the burned gas blowback amount Grev is obtained (see step 1310, equation (22)).

  This exhaust gas pressure calculating means is based on the knowledge that the degree of reduction in exhaust gas pressure due to the backflow of burned gas from the exhaust system will depend largely on the burned gas blowback amount Grev itself. A pressure correction coefficient Kp (0 <Kp ≦ 1) is obtained based on the gas blowback amount Grev, and the exhaust gas pressure Pe is calculated by multiplying the basic exhaust gas pressure Pe0 (see step 1030) by the pressure correction coefficient Kp. This also allows the exhaust gas pressure Pe to be accurately calculated during the valve overlap period, as in the first embodiment. Therefore, even if the valve overlap period is long, the in-cylinder intake fresh air amount Ma can be accurately estimated.

(Third embodiment)
Next, a fuel injection amount control device (in-cylinder intake fresh air amount estimation device) according to a third embodiment of the present invention will be described. In the third embodiment, the change in pressure of the gas in the virtual region set in the exhaust passage is sequentially obtained during the valve opening period of the intake valve 32, and the basic exhaust gas pressure Pe0 is sequentially corrected by this change in pressure. Thus, it is different from the first and second embodiments in which the exhaust gas pressure Pe is made constant over the valve opening period of the intake valve 32 in that the exhaust gas pressure Pe is sequentially calculated and changed.

  More specifically, in the third embodiment, a virtual region with a volume V is assumed in the exhaust passage near the exhaust valve 35 (specifically, in the exhaust port 34). It is assumed that the gas flowing out from the volume V (or flowing into the volume V) is only the gas that passes around the exhaust valve 35. In other words, it is assumed that the gas that has entered the volume V does not flow toward the downstream (three-way catalyst device 53 side) of the exhaust passage, and that the gas does not flow into the volume V from the three-way catalyst device 53 side. To do. According to this assumption, the flow rate of the gas flowing out from the volume V becomes equal to the exhaust valve passage gas flow rate me, so that the decrease amount of the gas in the volume V during the minute time dt is (me · dt).

  On the other hand, if the pressure of the gas in the volume V is the gas pressure Pv, the gas constant of the gas is R, the amount (mass) of the gas is Gv, and the temperature of the gas is equal to the exhaust gas temperature Te, The equation of state for the gas in the volume V is expressed according to the following equation (23). Therefore, in this case, the decrease in the gas pressure Pv due to the decrease in the gas amount in the volume V during the minute time dt (the gas pressure decrease amount Pdown) is expressed according to the following equation (24) based on the equation (23). be able to.

Pv ・ V = Gv ・ R ・ Te (23)

Pdown = ((R ・ Te) / V) ・ (me ・ dt) (24)

  However, in practice, it is considered that when the gas amount Gv in the volume V decreases, the gas pressure Pv in the volume V decreases with a certain delay. In order to reflect the delay in the change of the gas pressure Pv in the gas pressure drop amount Pdown in the above equation (24), the “reduction amount of the gas in the volume V during the minute time dt (me・ Integration processing may be applied to “dt)”. From the above, the gas pressure drop amount Pdown can be expressed according to the equation (25).

  In the third embodiment, it is assumed that the gas pressure decrease amount Pdown calculated according to the equation (25) is equal to the decrease (change) in the exhaust gas pressure due to the “backflow of burned gas from the exhaust system”. In the third embodiment, while the backflow of burned gas from the exhaust system is occurring, the gas pressure drop Pdown is sequentially obtained according to the equation (25), and the gas pressure drop from the basic exhaust gas pressure Pe0 (constant). By reducing Pdown, exhaust gas pressure Pe is calculated and changed sequentially.

  Next, the operation of the fuel injection amount control apparatus according to the third embodiment will be described. The CPU 81 of the third embodiment is shown in the flowcharts of FIGS. 14 and 15 corresponding to FIGS. 10 and 11, respectively, instead of the routines of FIGS. 10 and 11 executed by the CPU 81 of the first embodiment. Run a series of routines. In the routines shown in FIG. 14 and FIG. 15, the same step numbers as those in the previous routine are assigned to the same steps as those in the previous routine.

  In the routine shown in FIG. 14, steps 1310 and 1050 in FIG. 13 are replaced with steps 1405 and 1410, step 1315 in FIG. 13 is deleted, and step 1415 is added after step 1060 in FIG. Only the point differs from the routine shown in FIG. The routine shown in FIG. 15 differs from the routine shown in FIG. 11 only in that steps 1505 to 1525 are added between step 1160 and step 1095 in FIG. Hereinafter, such differences will be mainly described.

  When the intake valve 32 is opened, the CPU 81 of the third embodiment executes steps 1005, 1020 to 1035, and 1305, and then, in step 1405, the volume V of the virtual region is calculated in step 1305. It is obtained from the value AOL and the function funcV that defines the relationship between the passage area time integrated value AOL and the volume V.

  Thereby, the volume V is set to a smaller value as the passage area time integrated value AOL is larger. This is because the larger the passage area time integrated value AOL, the larger the decrease in the exhaust gas pressure Pe due to the “backflow of burned gas from the exhaust system”, and the amount of gas pressure decrease obtained according to the above equation (25) Pdown is based on the fact that the smaller the volume V, the larger the value calculated. That is, by this, the larger the passage area time integrated value AOL, the larger the gas pressure drop amount Pdown is calculated.

  Next, the CPU 81 proceeds to step 1410, sets the exhaust gas pressure Pe to a value equal to the basic exhaust gas pressure Pe0 calculated in step 1030, executes the subsequent steps 1055, 1060, and then in step 1415. Then, the accumulated amount SM of decrease in the gas in the volume V is set to “0”.

  Next, the CPU 81 starts the processing of the routine of FIG. 15 and executes the processing of step 1160, and then proceeds to step 1505, where the exhaust gas pressure Pe (currently equal to the basic exhaust gas pressure Pe0) is calculated in step 1145. If it is determined whether or not the in-cylinder gas pressure Pc is greater than the in-cylinder gas pressure Pc (that is, whether or not the backflow of burned gas from the exhaust system has occurred). The gas pressure drop amount Pdown is set to “0”, and the process proceeds to step 1515.

  The present time is immediately after the intake valve 32 is opened, and the in-cylinder gas pressure Pc is reduced to be lower than the exhaust gas pressure Pe due to the start of the return of burnt gas to the intake passage. Accordingly, the CPU 81 makes a “Yes” determination at step 1505 to proceed to step 1520, where the accumulated amount of decrease SM of the gas in the volume V at that time is calculated from the previous execution of this routine to the current execution of this routine. A value Δt · me corresponding to the amount of gas decrease in the volume V is added to obtain (update) the gas decrease amount integrated value SM in the new volume V.

  Subsequently, the CPU 81 proceeds to step 1525, in which the exhaust gas temperature Te acquired in step 1160, the volume V acquired in step 1405, the accumulated reduction amount SM of the gas in the updated volume V, and the above ( Based on the equation described in step 1525 corresponding to equation 25), the gas pressure drop amount Pdown is obtained, and the process proceeds to step 1515.

  When the CPU 81 proceeds to step 1515, the exhaust gas pressure Pe is set / updated to a value obtained by subtracting the obtained gas pressure drop amount Pdown from the basic exhaust gas pressure Pe0 obtained in step 1030, and then proceeds to step 1095. The routine is temporarily terminated.

  Thereafter, when the program execution interval time Δt elapses, the CPU 81 starts the processing of the routine of FIG. 14 again. At this time, the intake valve 32 is open. Therefore, the CPU 81 starts processing of the routine of FIG. 15 through steps 1005 and 1010. In this case, when the CPU 81 proceeds to step 1115, the exhaust valve passage gas flow rate me is obtained using the value set and updated in step 1515 at the time of the previous execution of this routine as the exhaust gas pressure Pe in the equation (20). .

  Thereafter, the CPU 81 updates the exhaust gas pressure Pe by executing the processing from step 1505 onward. At this time, since sufficient time has not passed since the intake valve 32 opened, the gas still flows back from the exhaust port 34 to the cylinder 21 (Pc <Pe). Accordingly, “Yes” is determined in step 1505, and the gas pressure drop amount Pdown is calculated in step 1525.

  In this way, while the gas is still flowing back from the exhaust port 34 to the cylinder 21 (Pc <Pe) (that is, during the valve overlap period), it is obtained at step 1525 every time the program execution interval time Δt elapses. The exhaust gas pressure Pe is sequentially set / updated in step 1515 using the gas pressure drop amount Pdown thus set, and the value of the exhaust gas pressure Pe thus set / updated is the value at the next execution of this routine. In step 1115, the exhaust gas pressure Pe in the equation (20) is sequentially used. In the third embodiment, step 1030, step 1305, step 1405, and steps 1505 to 1525 correspond to exhaust gas pressure calculation means.

  As described above, the in-cylinder intake fresh air amount estimation device of the third embodiment is applied to the internal combustion engine 10 having the valve overlap as in the first embodiment. The exhaust gas pressure calculation means of the third embodiment sets a virtual region having a predetermined volume V in the exhaust passage (in the exhaust port 34), and the flow rate of the gas flowing into and out of the volume V is the exhaust valve passage gas flow rate. Under the assumption that it is equal to me, the pressure change of the gas in the volume V (gas pressure drop amount) from the mass change of the gas in the volume V obtained based on the exhaust gas flow rate me (the integrated value SM thereof) Pdown) is sequentially calculated (steps 1525 and 1510), and the exhaust gas pressure Pe is sequentially set and updated to a value obtained by subtracting the gas pressure decrease amount Pdown from the basic exhaust gas pressure Pe0 (step 1515).

  According to this, as compared with the first and second embodiments in which the exhaust gas pressure Pe is constant over the period during which the intake valve 32 is open (and therefore over the valve overlap period), The exhaust gas pressure Pe can be calculated with higher accuracy during the overlap period, and as a result, the in-cylinder intake fresh air amount Ma can be estimated with higher accuracy even when the valve overlap period is long. .

(Fourth embodiment)
Next, a fuel injection amount control device (in-cylinder intake fresh air amount estimation device) according to a fourth embodiment of the present invention will be described. In the fourth embodiment, the change amount of the exhaust gas pressure Pe is obtained from the change of the exhaust valve passage gas flow rate me, and the basic exhaust gas pressure Pe0 is sequentially corrected based on the change amount of the exhaust gas pressure Pe to obtain the exhaust gas pressure Pe. The third embodiment is different from the third embodiment in that it is sequentially calculated and changed.

  In the fourth embodiment, as in the third embodiment, the exhaust gas pressure Pe is obtained by subtracting the gas pressure decrease amount Pdown from the basic exhaust gas pressure Pe0. In the fourth embodiment, the inertia of the gas flowing through the exhaust passage is taken into account when determining the gas pressure drop amount Pdown.

  More specifically, it is considered that the actual fluctuation of the exhaust gas pressure largely depends on the inertia of the gas flowing through the exhaust passage. Therefore, the fluctuation of the exhaust gas pressure Pe greatly depends on the change in the flow velocity of the gas flowing through the exhaust passage, and increases as the change in the flow velocity of the gas flowing through the exhaust passage increases.

  On the other hand, the change in the flow velocity of the gas flowing through the exhaust passage can be considered to be equal to the change in the exhaust valve passage gas flow rate me. Depends heavily on From the above, the gas pressure drop amount Pdown can be expressed according to the following equation (26). Here, C is a gain, which will be described later.

  In the fourth embodiment, while the backflow of burned gas from the exhaust system is occurring, the gas pressure drop amount Pdown is sequentially obtained according to the equation (26), and the gas pressure drop amount is calculated from the basic exhaust gas pressure Pe0 (constant). By reducing Pdown, exhaust gas pressure Pe is calculated and changed sequentially.

  Next, the operation of the fuel injection amount control apparatus according to the fourth embodiment will be described. The CPU 81 of the fourth embodiment is shown in the flowcharts of FIGS. 16 and 17 corresponding to FIGS. 14 and 15, respectively, instead of the routines of FIGS. 14 and 15 executed by the CPU 81 of the third embodiment. Run a series of routines. In the routines shown in FIG. 16 and FIG. 17, the same step numbers as those in the previous routine are assigned to the same steps as those in the previous routine.

  The routine shown in FIG. 16 differs from the routine shown in FIG. 14 only in that step 1405 in FIG. 14 is replaced with step 1605 and step 1415 in FIG. 14 is deleted. The routine shown in FIG. 17 is shown in FIG. 15 only in that steps 1520 and 1525 in FIG. 15 are replaced with steps 1705 and 1710 and that step 1715 is added between steps 1515 and 1095 in FIG. Different from routine. Hereinafter, such differences will be mainly described.

  When the intake valve 32 is opened, the CPU 81 of the fourth embodiment executes steps 1005, 1020 to 1035, and 1305, and then, in step 1605, the gain C is set to the passage area time integrated value AOL obtained in step 1305. And the function funcC that defines the relationship between the passage area time integrated value AOL and the gain C.

  Thereby, the gain C is set to a larger value as the passage area time integrated value AOL is larger. This is because the larger the passage area time integrated value AOL, the greater the decrease in the exhaust gas pressure Pe due to the “backflow of burned gas from the exhaust system”, and the amount of gas pressure decrease obtained according to the above equation (26). Pdown is based on the fact that the larger the gain C is, the larger the value is calculated. That is, by this, the larger the passage area time integrated value AOL, the larger the gas pressure drop amount Pdown is calculated.

  Next, after executing step 1410, step 1055, and 1060, the CPU 81 starts the processing of the routine of FIG. 17, and after executing the processing of step 1160, proceeds to step 1505 to determine “No”. Proceeding to 1510, the gas pressure decrease amount Pdown is set to “0”, and proceeding to step 1515.

  The present time is immediately after the intake valve 32 is opened, and the in-cylinder gas pressure Pc is reduced to be lower than the exhaust gas pressure Pe due to the start of the return of burnt gas to the intake passage. Therefore, the CPU 81 makes a “Yes” determination at step 1505 to proceed to step 1705, where the exhaust valve passage gas flow rate me acquired at step 1115 and the step 1715 described later when the routine is executed last time are obtained. The differential value Δme of the exhaust valve passage gas flow rate is obtained from the previous exhaust valve passage gas flow rate meb and the formula described in step 1705.

  Subsequently, the CPU 81 proceeds to step 1710, the differential value Δme of the acquired exhaust valve passage gas flow rate, the gain C acquired in step 1605, and the equation described in step 1710 corresponding to the above equation (26), Based on the above, the gas pressure drop amount Pdown is obtained, and the process proceeds to step 1515.

  When the CPU 81 proceeds to step 1515, the exhaust gas pressure Pe is set / updated to a value obtained by subtracting the obtained gas pressure drop amount Pdown from the basic exhaust gas pressure Pe0 obtained in step 1030. After setting the value of the exhaust valve passage gas flow rate meb to the value of the exhaust valve passage gas flow rate me acquired at step 1115 at this time, the routine proceeds to step 1095 to end the present routine tentatively.

  Thereafter, when the program execution interval time Δt elapses, the CPU 81 starts the processing of the routine of FIG. 16 again. At this time, the intake valve 32 is open. Therefore, the CPU 81 starts processing of the routine of FIG. 17 through steps 1005 and 1010. In this case, when the CPU 81 proceeds to step 1115, the exhaust valve passage gas flow rate me is obtained using the value set / updated in step 1515 at the previous execution of this routine as the exhaust gas pressure Pe in the equation (20). .

  Thereafter, the CPU 81 updates the exhaust gas pressure Pe by executing the processing from step 1505 onward. At this time, since sufficient time has not passed since the intake valve 32 opened, the gas still flows back from the exhaust port 34 to the cylinder 21 (Pc <Pe). Accordingly, “Yes” is determined in step 1505, and the gas pressure drop amount Pdown is calculated in step 1710.

  As described above, while the gas is still flowing back from the exhaust port 34 to the cylinder 21 (Pc <Pe) (that is, during the valve overlap period), it is obtained at step 1710 every time the program execution interval time Δt elapses. The exhaust gas pressure Pe is sequentially set / updated in step 1515 using the gas pressure drop amount Pdown thus set, and the value of the exhaust gas pressure Pe thus set / updated is the value at the next execution of this routine. In step 1115, the exhaust gas pressure Pe in the equation (20) is sequentially used. In the fourth embodiment, Step 1030, Step 1305, Step 1605, Step 1505, 1510, 1515, 1705, 1710, and 1715 correspond to the exhaust gas pressure calculating means.

  As described above, the in-cylinder intake fresh air amount estimation device of the fourth embodiment is applied to the internal combustion engine 10 having the valve overlap as in the first embodiment. The exhaust gas pressure calculating means of the fourth embodiment sequentially calculates the change in the exhaust gas pressure Pe (gas pressure drop Pdown) from the change in the exhaust valve passage gas flow rate me (steps 1710 and 1510), and the exhaust gas pressure Pe. Are sequentially set and updated to a value obtained by subtracting the gas pressure drop Pdown from the basic exhaust gas pressure Pe0 (step 1515).

  According to this, as in the third embodiment, compared to the first and second embodiments in which the exhaust gas pressure Pe is constant over the period during which the intake valve 32 is open, the valve overlap period is longer. Thus, the exhaust gas pressure Pe can be calculated with higher accuracy, and as a result, the in-cylinder intake fresh air amount Ma can be estimated with higher accuracy even when the valve overlap period is long.

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, in each of the above embodiments, the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc are obtained from the cylinder model M5 based on the mass conservation law and the energy conservation law in the cylinder 21, but are different from the cylinder model M5. The in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc may be obtained by calculation using a model (formula).

  Further, in each of the above embodiments, the intake gas temperature (intake pipe air pressure Pm) is obtained by the intake pipe model M3 based on the mass conservation law and the energy conservation law for the air in the intake pipe 41, but the intake pipe The intake pipe air pressure Pm may be detected by an intake pressure sensor that directly detects the air pressure in 41.

In each of the above embodiments, the basic exhaust gas pressure Pe0 used when calculating the exhaust gas pressure Pe is a unit obtained by integrating (time integration) the exhaust valve passage gas flow rates me of all the cylinders. It is obtained by a function of the exhaust gas amount Ge per hour (Pe0 = a · Ge + b · Ge ² : a and b are constants), but the intake valve passage gas flow rate mi of all cylinders is integrated (time integration). May be obtained by a function of the intake gas amount Ga obtained per unit time (for example, Pe0 = c · Ga + d · Ga ² : c and d are constants).

  In addition, in the first and second embodiments, the pressure correction coefficient Kp is based on parameters representing the open / closed states of the intake valve 32 and the exhaust valve 35 (intake valve advance amount VVTin, exhaust valve advance amount VVTex, etc.). The exhaust gas pressure Pe is obtained by multiplying the basic exhaust gas pressure Pe0 by this pressure correction coefficient Kp, and the pressure correction value is calculated based on the parameters representing the open / closed states of the intake valve 32 and the exhaust valve 35. Then, the exhaust gas pressure Pe may be obtained by adding or subtracting this pressure correction value to or from the basic exhaust gas pressure Pe0.

1 is a schematic configuration diagram of a system in which a fuel injection amount control device including an in-cylinder intake fresh air amount estimation device for an internal combustion engine according to a first embodiment of the present invention is applied to a spark ignition type multi-cylinder internal combustion engine. FIG. 2 is a functional block diagram showing a connection relationship of various models adopted by the electric control device shown in FIG. 1 to estimate an in-cylinder intake fresh air amount and the like. It is a figure which shows the table which prescribed | regulated the relationship between the accelerator pedal operation amount and target throttle valve opening which CPU shown in FIG. 1 refers. It is a figure which shows the table which prescribed | regulated the relationship between the throttle-valve opening degree which the CPU shown in FIG. 1 refers, and a flow coefficient. It is a figure which shows the table which prescribed | regulated the relationship between the throttle-valve opening degree and opening area which CPU shown in FIG. 1 refers. It is a figure which shows the table which prescribed | regulated the relationship between the throttle valve opening degree, the product of a flow coefficient, and an opening area which CPU referred to in FIG. FIG. 2 is a diagram conceptually showing a cylinder and its vicinity in order to explain variables used by the CPU shown in FIG. 1 when calculating each value. It is a figure which shows the table which prescribed | regulated the relationship between the intake valve lift amount which CPU shown in FIG. 1 refers, and the product value of a flow coefficient and opening area. It is a figure which shows the table which prescribed | regulated the relationship between the exhaust valve lift amount which CPU shown in FIG. 1 refers, and the product value of a flow coefficient and opening area. 3 is a flowchart showing a first half of a routine executed by a CPU shown in FIG. 1. 3 is a flowchart showing a second half of a routine executed by the CPU shown in FIG. 1. (A) is the graph which showed the valve lift amount of the intake valve and the exhaust valve with respect to time passage, (B) is the graph which showed the change of the integrated value of the intake valve passage gas flow rate with time passage. It is the flowchart which showed the first half part of the routine which CPU of the cylinder intake fresh air quantity estimation apparatus which concerns on 2nd Embodiment of this invention performs. It is the flowchart which showed the first half part of the routine which CPU of the cylinder intake fresh air amount estimation apparatus which concerns on 3rd Embodiment of this invention performs. It is the flowchart which showed the second half part of the routine which CPU of the cylinder intake fresh air amount estimation apparatus which concerns on 3rd Embodiment of this invention performs. It is the flowchart which showed the first half part of the routine which CPU of the cylinder intake fresh air amount estimation apparatus which concerns on 4th Embodiment of this invention performs. It is the flowchart which showed the second half part of the routine which CPU of the cylinder intake fresh air amount estimation apparatus which concerns on 4th Embodiment of this invention performs. (A) is the graph which showed the valve lift amount of the intake valve and the exhaust valve with respect to time passage, (B) is the graph which showed the change of the integrated value of the intake valve passage gas flow rate with time passage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 33 ... Intake valve control device, 34 ... Exhaust port, 35 ... Exhaust valve, 36 ... Exhaust valve control device, 39 ... Injector 41 ... Intake pipe 52 ... Exhaust pipe 80 ... Electric control device 81 ... CPU

Claims (8)

In-cylinder gas pressure calculating means for calculating an in-cylinder gas pressure that is a pressure in a cylinder of the internal combustion engine;
An intake gas pressure acquisition means for acquiring an intake gas pressure which is a pressure of a gas in the intake passage of the internal combustion engine;
Exhaust gas pressure calculating means for calculating an exhaust gas pressure which is a pressure of a gas in an exhaust passage of the internal combustion engine;
An intake valve passage gas flow rate calculating means for calculating an intake valve passage gas flow rate that is a flow rate of gas passing through the periphery of the intake valve that communicates and blocks the cylinder and the intake passage;
An exhaust valve passage gas flow rate calculating means for calculating an exhaust valve passage gas flow rate that is a flow rate of gas passing through the periphery of the exhaust valve that communicates and blocks the cylinder and the exhaust passage;
In-cylinder intake fresh air amount estimation means for estimating an in-cylinder intake fresh air amount that is an amount of fresh air sucked into the cylinder based on the calculated intake valve passage gas flow rate;
With
The in-cylinder gas pressure calculating means calculates the in-cylinder gas pressure based on at least the calculated intake valve passage gas flow rate and the calculated exhaust valve passage gas flow rate,
The intake valve passage gas flow rate calculating means calculates the intake valve passage gas flow rate based on at least the acquired intake gas pressure and the calculated in-cylinder gas pressure,
The exhaust valve passage gas flow rate calculating means is configured to calculate the exhaust valve passage gas flow rate based on at least the calculated exhaust gas pressure and the calculated in-cylinder gas pressure. In the inhalation fresh air volume estimation device,
The exhaust gas pressure calculating means includes
Considering a decrease in the exhaust gas pressure due to the backflow of burnt gas from the exhaust passage into the cylinder that occurs during the valve overlap period, in which both the intake valve and the exhaust valve are open. An in-cylinder intake fresh air amount estimation device for an internal combustion engine configured to calculate the exhaust gas pressure. The in-cylinder intake fresh air amount estimation device for an internal combustion engine according to claim 1,
The exhaust gas pressure calculating means includes
In-cylinder intake fresh air amount estimation device for an internal combustion engine configured to calculate the exhaust gas pressure based on a parameter representing an operating state of the internal combustion engine including a parameter representing an open / close state of the intake valve and the exhaust valve . In the in-cylinder intake fresh air amount estimation device for an internal combustion engine according to claim 2,
The exhaust gas pressure calculating means includes
Based on a value corresponding to a time integral value of the passage area of the gas passage formed around the intake valve over the valve overlap period, the total amount of burned gas blown back from the cylinder to the intake passage. An in-cylinder intake fresh air amount estimation device for an internal combustion engine configured to calculate a fuel gas blowback amount and calculate the exhaust gas pressure based on the burnt gas blowback amount. The in-cylinder intake fresh air amount estimation device for an internal combustion engine according to claim 1,
The exhaust gas pressure calculating means includes
Assuming that a virtual region having a predetermined volume is set in the exhaust passage, and the flow rate of the gas flowing into and out of the volume is equal to the exhaust valve passage gas flow rate calculated by the exhaust valve passage gas flow rate calculation means Therefore, a change in the pressure of the gas in the volume is calculated from a change in the mass of the gas in the volume obtained based on the flow rate of gas passing through the exhaust valve, and the change in the pressure of the gas in the volume is taken into account. An in-cylinder intake fresh air amount estimation device for an internal combustion engine configured to calculate the exhaust gas pressure. The in-cylinder intake fresh air amount estimation device for an internal combustion engine according to claim 1,
The exhaust gas pressure calculating means includes
A change amount of the exhaust gas pressure is calculated from a change in the exhaust valve passage gas flow rate calculated by the exhaust valve passage gas flow rate calculation means, and the exhaust gas pressure is taken into consideration in consideration of the calculated change amount of the exhaust gas pressure. An in-cylinder intake fresh air amount estimation device for an internal combustion engine configured to calculate In the in-cylinder intake fresh air amount estimation device according to any one of claims 1 to 5,
The intake valve passage gas flow rate calculating means includes:
When gas is sucked into the cylinder from the intake passage, the flow rate of the intake valve passage gas is set to one of positive and negative signed gas flow rates, and the gas is blown back from the cylinder to the intake passage. The intake valve passage gas flow rate is calculated as a positive or negative signed gas flow rate every time a predetermined time elapses,
The in-cylinder intake fresh air amount estimation means includes:
In-cylinder intake fresh air amount estimation device for an internal combustion engine configured to estimate the in-cylinder intake fresh air amount based on an integrated value of the calculated intake valve passage gas flow rate from when the intake valve is opened . The in-cylinder intake fresh air amount estimation device for an internal combustion engine according to any one of claims 1 to 6,
The intake valve passage gas flow rate calculating means includes:
The intake valve passage gas flow rate is calculated based on an equation for calculating a gas flow rate that passes through the throttle portion formed when the gas passage formed around the intake valve is regarded as a throttle portion. In-cylinder intake fresh air volume estimation device. The in-cylinder intake fresh air amount estimation device for an internal combustion engine according to any one of claims 1 to 7,
The exhaust valve passage gas flow rate calculating means includes:
The exhaust valve passage gas flow rate is calculated based on an equation for calculating a gas flow rate that passes through the throttle portion formed when the gas passage formed around the exhaust valve is regarded as a throttle portion. In-cylinder intake fresh air volume estimation device.

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