JP2007016660A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of appropriately controlling the internal combustion engine in transient operation. <P>SOLUTION: This control device is provided with an air model M30 estimating cylinder air quantity KL and an injection fuel quantity determination means M40 determining injection fuel quantity τ based on cylinder air quantity KL. A throttle model M31 including the air model M30 estimates throttle pass-through air quantity mt with using a flow coefficient μ as an index indicating degree of turbulence of flow. This control device acquires throttle valve drive speed v and determines the flow coefficient based on the acquired throttle valve drive speed, and applies the determined flow coefficient to the throttle model. Consequently, the flow coefficient during opening of a throttle valve is changing (transient operation) can be estimated at high accuracy. As a result, fuel injection quantity can be appropriately determined and the internal combustion engine 10 can be appropriately controlled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for estimating a flow rate of air passing around a throttle valve disposed in an intake passage of an internal combustion engine and controlling the internal combustion engine based on the estimated flow rate of air.

  A conventional control device for an internal combustion engine needs to determine the amount of air (in-cylinder air amount) introduced into the combustion chamber in order to control the internal combustion engine. The in-cylinder air amount is obtained based on the flow rate of air passing around the throttle valve (throttle passage air flow rate). Accordingly, one of the conventional devices obtains the throttle passage air flow rate using a physical model representing the behavior of air passing around the throttle valve. This physical model uses a throttle valve opening (throttle valve opening) and a flow coefficient as an index indicating the degree of turbulence in the flow, for example, when obtaining the flow rate of air passing through the throttle (for example, Patent Documents). 1).

  The conventional apparatus previously stores a table that defines the relationship between the flow coefficient when the throttle valve opening is constant (during steady operation) and the throttle valve opening, and this table and the throttle valve opening. The flow rate coefficient is determined based on the degree, and the throttle passage air flow rate is estimated based on the determined flow coefficient and the throttle valve opening. Further, this apparatus estimates the in-cylinder air amount based on the estimated throttle passage air flow rate, determines the fuel injection amount based on the estimated in-cylinder air amount, and controls the internal combustion engine.

According to the above-described conventional apparatus, the actual flow coefficient is estimated with high accuracy during the steady operation, and therefore the throttle passage air flow rate is estimated with high accuracy. As a result, the internal combustion engine can be appropriately controlled.
JP 2005-36672 A

  However, when the throttle valve opening is changing (during transient operation), the flow of air passing around the throttle valve is more likely to be disturbed than during steady operation, so the actual flow coefficient is It becomes smaller than the value during operation. Therefore, since the actual flow coefficient cannot be estimated with high accuracy during transient operation, there is a possibility that the internal combustion engine cannot be appropriately controlled by the conventional device.

  The present invention has been made to address the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can appropriately control the internal combustion engine during transient operation.

In order to achieve this object, a control device for an internal combustion engine according to the present invention includes:
An intake passage that introduces air taken from outside into the cylinder, a throttle valve that is disposed in the intake passage and can be adjusted to change the amount of air that flows through the intake passage, and the throttle Applied to an internal combustion engine comprising: a throttle valve driving means for driving a valve; and a throttle valve opening obtaining means for obtaining the opening of the throttle valve;
Throttle passing air flow rate, which is the flow rate of air passing around the throttle valve based on a physical model representing the behavior of air passing around the throttle valve using the opening degree of the throttle valve and the flow coefficient A throttle passage air flow rate estimating means for estimating
The internal combustion engine is controlled based on the estimated throttle passage air flow rate.

The control device further includes a throttle valve drive speed acquisition means for acquiring a throttle valve drive speed, which is a speed at which the throttle valve is driven by the throttle valve drive means,
Flow coefficient determination means for determining a flow coefficient based on the acquired throttle valve drive speed.
The throttle passage air flow rate estimation means is configured to estimate the throttle passage air flow rate by applying the acquired throttle valve opening and the determined flow rate coefficient to the physical model.

  The throttle valve driving speed, which is the speed at which the throttle valve is driven, well represents the degree of turbulence in the flow of air that passes around the throttle valve. Accordingly, by determining the flow coefficient based on the acquired throttle valve drive speed as in the above configuration, the actual flow coefficient when the throttle valve opening is changing (during transient operation) can be increased with high accuracy. Is estimated. Thereby, the throttle passage air flow rate can be estimated with high accuracy. As a result, for example, when the control amount of the internal combustion engine such as the amount of fuel to be injected (injected fuel amount) is determined based on the estimated throttle passage air flow rate, the internal combustion engine is appropriately controlled by the determined control amount. be able to.

  In this case, it is preferable that the flow coefficient determination means is configured such that the determined flow coefficient decreases as the acquired throttle valve drive speed increases.

  As the throttle valve driving speed increases, the flow of air passing around the throttle valve is greatly disturbed, so the actual flow coefficient decreases. Therefore, by configuring the flow coefficient determining means so that the flow coefficient determined as the throttle valve driving speed increases as in the above configuration, the actual flow coefficient corresponding to the throttle valve driving speed can be increased with high accuracy. Can be estimated.

In this case, the control device includes throttle valve downstream pressure acquisition means for acquiring a throttle valve downstream pressure, which is a pressure of air downstream of the throttle valve,
The flow coefficient determination means preferably further determines the flow coefficient based on the acquired throttle valve downstream pressure.

  The degree to which the air flow is disturbed by driving the throttle valve varies depending on the throttle valve downstream pressure. Therefore, by determining the flow coefficient taking into account the throttle valve downstream pressure in addition to the throttle valve drive speed as in the above configuration, the actual flow coefficient can be accurately determined even if the throttle valve downstream pressure changes. Can be estimated.

  In this case, it is preferable that the flow coefficient determination means is configured such that the determined flow coefficient decreases as the acquired throttle valve downstream pressure decreases.

  As the throttle valve downstream pressure decreases, the difference between the throttle valve downstream pressure and the air pressure upstream of the throttle valve (throttle valve upstream pressure) increases, so that the air flow is reduced by driving the throttle valve. The degree of disturbance is increased. Therefore, as in the above configuration, the actual flow coefficient according to the throttle valve downstream pressure is highly accurate by configuring the flow coefficient determination means so that the flow coefficient determined as the throttle valve downstream pressure decreases. Can be estimated.

In this case, the control device includes engine rotation speed acquisition means for acquiring the engine rotation speed,
The flow coefficient determination means preferably further determines the flow coefficient based on the acquired engine speed.

  The degree to which the air flow is disturbed by driving the throttle valve varies depending on the engine speed. Accordingly, by determining the flow coefficient in consideration of the engine speed in addition to the throttle valve driving speed as in the above configuration, the actual flow coefficient is estimated with high accuracy even if the engine speed changes. be able to.

  In this case, it is preferable that the flow coefficient determination means is configured such that the determined flow coefficient decreases as the acquired engine rotation speed increases.

  As the engine speed increases, the flow rate of air passing through the throttle increases, and the degree to which the air flow is disturbed by driving the throttle valve increases. Therefore, by configuring the flow coefficient determination means so that the flow coefficient determined as the engine rotation speed increases as in the above configuration, the actual flow coefficient corresponding to the engine rotation speed can be obtained with high accuracy. Can be estimated.

  Hereinafter, embodiments of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a system in which the control device according to the first embodiment of the present invention is applied to a spark ignition type multi-cylinder (four-cylinder) internal combustion engine. 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 portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and fuel and air in the cylinder block portion 20. And an exhaust system 50 for releasing the exhaust gas from the cylinder block 20 to the outside.

  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 cylinder 21, the head of the piston 22, and the cylinder head portion 30 form a combustion chamber (cylinder) 25.

  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 continuously changes the phase angle of the intake camshaft. The variable intake timing device 33, the actuator 33 a of the variable intake timing device 33, the exhaust port 34 communicating with the combustion chamber 25, the exhaust valve 35 that opens and closes the exhaust port 34, the exhaust camshaft 36 that drives the exhaust valve 35, and the spark plug 37 Further, an igniter 38 including an ignition coil that generates a high voltage to be applied to the spark plug 37 and an injector 39 as a fuel injection valve are provided.

  The injector 39 injects fuel of the injected fuel amount τ into the intake port 31 in response to an instruction signal sent out by an electric control device 70 described later achieving a function of fuel injection valve control means described later. It has become.

  The intake system 40 includes an intake manifold 41 that communicates with the intake port 31, a surge tank 42 that communicates with the intake manifold 41, and one end connected to the surge tank 42 to form an intake passage together with the intake port 31, the intake manifold 41, and the surge tank 42. An intake duct 43, an air filter 44 disposed in the intake duct 43 in order from the other end of the intake duct 43 toward the downstream (surge tank 42), a throttle valve 45, and a throttle valve actuator 45a as a throttle valve driving means are provided. ing. Note that the intake passage from the throttle valve 45 to the intake valve 32 constitutes an intake pipe portion as a throttle valve downstream portion.

  The throttle valve 45 is rotatably supported by the intake duct 43, and the opening degree can be adjusted by being driven by a throttle valve actuator 45a. As a result, the throttle valve 45 makes the passage cross-sectional area of the intake duct 43 variable. The opening degree of the throttle valve 45 (throttle valve opening degree) is defined by the angle rotated from the position of the throttle valve 45 in the state where the passage cross-sectional area is minimized (the throttle valve is fully closed).

  The throttle valve actuator 45a formed of a DC motor has an actual throttle valve opening θta that is set to a target throttle valve in accordance with a drive signal sent out by an electric control device 70 described later achieving a function of throttle valve control means described later. The throttle valve 46 is driven so that the opening degree θtt is obtained.

  The exhaust system 50 includes an exhaust pipe 51 including an exhaust manifold that communicates with the exhaust port 34 and forms an exhaust passage together with the exhaust port 34, and a three-way catalyst device 52 disposed in the exhaust pipe 51.

  On the other hand, this system includes a pressure sensor 61, a temperature sensor 62, a throttle position sensor 63 as a throttle valve opening acquisition means, a cam position sensor 64, a crank position sensor 65 as an engine rotation speed acquisition means, and an operating state quantity acquisition means. The accelerator opening sensor 66 and the electric control device 70 are provided.

  The pressure sensor 61 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The pressure sensor 61 detects the pressure of the air upstream of the throttle valve 45 (the throttle valve upstream pressure, that is, the intake pressure), and outputs a signal representing the intake pressure Pa. The temperature sensor 62 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The temperature sensor 62 detects the temperature of the air upstream of the throttle valve 45 (the throttle valve upstream temperature, that is, the intake air temperature), and outputs a signal representing the intake air temperature Ta.

  The throttle position sensor 63 detects the opening (throttle valve opening) of the throttle valve 45 and outputs a signal representing the throttle valve opening θta. The cam position sensor 64 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °). The crank position sensor 65 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 °. This signal represents the engine speed NE. The accelerator opening sensor 66 detects the operation amount of the accelerator pedal 67 operated by the driver, and outputs a signal representing the operation amount (accelerator pedal operation amount) Accp of the accelerator pedal.

  The electric control device 70 is connected to each other via a bus 71, a ROM 72 pre-stored with programs executed by the CPU 71, tables (look-up tables, maps), constants, and the like, and the CPU 71 temporarily stores data as necessary. The microcomputer includes a RAM 73, a backup RAM 74 that stores data while the power is turned on, and retains the stored data while the power is shut off, an interface 75 including an AD converter, and the like. The interface 75 is connected to the sensors 61 to 66, supplies signals from the sensors 61 to 66 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, the injector 39, and the throttle of the variable intake timing device 33. A drive signal (instruction signal) is sent to the valve actuator 45a.

  Next, how the internal combustion engine control apparatus configured as described above controls the internal combustion engine 10 will be described.

  This control device controls the amount of air (in-cylinder air amount) introduced into the combustion chamber 25 so that the air-fuel ratio of the air-fuel mixture formed in the combustion chamber 25 matches the target air-fuel ratio determined according to the operating state. ) And the amount of fuel injected from the injector 39 (injected fuel amount) is determined based on the estimated in-cylinder air amount.

  In order to estimate the in-cylinder air amount, this control device uses a physical model constructed based on physical laws such as an energy conservation law, a momentum conservation law, and a mass conservation law. This physical model is a well-known model disclosed in Japanese Patent Laid-Open Nos. 2001-41095 and 2003-184613. This physical model includes a throttle model that estimates a throttle passing air flow rate that is a flow rate of air passing around the throttle valve 45 in the intake passage. In this throttle model, a flow coefficient is used as an index representing the degree of turbulence of the flow.

  FIG. 2 is a graph conceptually showing the relationship between the change in the throttle valve opening and the actual change in the flow coefficient. FIG. 2A is a graph showing changes in the opening degree of the throttle valve 45 driven at different speeds. A straight line Mt1 in FIG. 2 (B) shows the difference between the throttle valve opening and the flow rate coefficient in steady operation in the above-described prior art when the throttle valve opening changes as shown by the straight line O1 in FIG. 2 (A). The change of the flow coefficient (conventional flow coefficient) determined based on the relationship is shown. A straight line Mt2 in FIG. 2 (B) shows the change in the conventional flow coefficient when the throttle valve opening changes as shown by the straight line O2 in FIG. 2 (A).

  A curve M1 in FIG. 2B shows a change in the actual flow coefficient when the throttle valve opening changes as shown by the straight line O1 in FIG. A curve M2 in FIG. 2 (B) shows a change in the actual flow coefficient when the throttle valve opening changes as indicated by the straight line O2 in FIG. 2 (A).

  As shown in FIG. 2, the actual flow coefficient is smaller than the conventional flow coefficient while the throttle valve opening is changing (increasing). Further, as the throttle valve driving speed, which is the speed at which the throttle valve 45 is driven, is increased, the flow of air passing around the throttle valve 45 is greatly disturbed, so that the actual flow coefficient is further reduced.

  Further, as the air pressure downstream of the throttle valve 45 (throttle valve downstream pressure, ie, the intake pipe pressure) decreases, the throttle valve downstream pressure and the air pressure upstream of the throttle valve 45 (throttle valve upstream pressure, That is, the difference between the intake pressure and the intake pressure becomes large, so that the degree to which the air flow is disturbed by driving the throttle valve 45 becomes large. Therefore, as shown in FIG. 3, even when the throttle valve 45 is driven at a constant speed, the actual flow coefficient becomes smaller than the conventional flow coefficient as the throttle valve downstream pressure Pm decreases.

  Therefore, this control device acquires the throttle valve driving speed and the throttle valve downstream pressure during the transient operation, and determines the flow coefficient based on the acquired throttle valve driving speed and the throttle valve downstream pressure. The flow coefficient is applied to the throttle model.

  Therefore, according to this control device, since the actual flow coefficient is estimated with high accuracy when the throttle valve opening is changing (during transient operation), the in-cylinder air amount is estimated with high accuracy. be able to. Thereby, since the amount of injected fuel can be determined appropriately, an air-fuel mixture having the target air-fuel ratio can be formed in the combustion chamber 25, and the internal combustion engine 10 can be controlled appropriately.

  More specifically, as shown in FIG. 4 which is a functional block diagram, this control device includes a throttle valve control means C10, a fuel injection valve control means C20, a throttle valve drive speed acquisition means M10, a flow rate. The coefficient determination means M20, the air model M30, and the injected fuel amount determination means M40 are provided.

  The throttle valve control means C10 is a ROM 72 that defines the relationship between the accelerator pedal operation amount Accp and the target throttle valve opening θtt, and the relationship in which the target throttle valve opening θtt monotonously increases with respect to the accelerator pedal operation amount Accp. To remember. The throttle valve control means C10 determines the target throttle valve opening θtt based on the actual accelerator pedal operation amount Accp detected by the table and the accelerator opening sensor 67, and according to the determined target throttle valve opening θtt. The drive signal is sent to the throttle valve actuator 45a.

  The fuel injection valve control means C20 sends an instruction signal to the injector (fuel injection valve) 39 in accordance with the injected fuel quantity τ determined by the injected fuel quantity determining means M40 described later.

  The throttle valve drive speed acquisition means M10 calculates a throttle valve drive speed v (v = dθta / dt) that is a speed at which the throttle valve 45 is driven based on the throttle valve opening degree θta detected by the throttle position sensor 63. It is like that.

  During transient operation, the flow coefficient determination means M20 is configured to detect the throttle valve opening θta, the throttle valve drive speed v calculated by the throttle valve drive speed acquisition means M10, and the throttle valve 45 estimated by the air model M30. The flow coefficient μ is determined on the basis of the air pressure (the downstream pressure of the throttle valve, that is, the pressure in the intake pipe) Pm. On the other hand, during steady operation, the flow coefficient determining means M20 determines the flow coefficient μ based on the throttle valve opening θta, the intake pipe pressure Pm, and the engine speed NE. Yes.

  The air model M30 is a physical model constructed based on the above physical laws, and includes a throttle model M31, an intake valve model M32, an intake pipe model M33, and an intake valve model M34. The throttle model M31 estimates the throttle passage air flow rate mt based on the throttle valve opening θta detected by the throttle position sensor 63 and the flow coefficient μ determined by the flow coefficient determination means M20. Yes.

  The intake valve model M32, the intake pipe model M33, and the intake valve model M34 estimate the in-cylinder air amount KL based on the throttle passage air flow rate mt estimated by the throttle model M31.

  The injected fuel amount determining means M40 is based on the in-cylinder air amount KL estimated by the air model M30 and the target air-fuel ratio (AbyF) determined according to the operating state, and the injected fuel amount τ (τ = k・ KL / AbyF, k is a constant.)

Here, the air model M30 will be described in detail.
As will be described later, a part of a mathematical formula (hereinafter also referred to as “generalized mathematical formula”) derived based on the physical law representing the models M31 to M34 included in the air model M30 is part of the inside of the intake pipe portion. It includes a time differential term for the air pressure Pm and temperature Tm. The air model M30 discretizes the mathematical formula including the time differential term so that the calculation by the microcomputer is possible, and based on the discretized mathematical formula and the physical quantity estimated as the physical quantity at the time of the current computation. The physical quantity at the next calculation time after a predetermined calculation cycle from the simultaneous point is estimated.

  The air model M30 repeats such estimation, thereby estimating the physical quantity at the next calculation time point (time point after the calculation cycle from the current time) every time the calculation cycle elapses. That is, the air model M30 sequentially estimates the physical quantity for each calculation cycle by repeatedly estimating the physical quantity. In the following explanation, the variable representing each physical quantity with (k-1) is the physical quantity at the current computation time estimated at the k-1th estimation time (previous computation time). It is a variable that represents. In addition, the variable representing each physical quantity to which (k) is attached is a variable representing each physical quantity at the next computation time estimated at the k-th estimation time (current computation time).

  Hereinafter, the throttle model M31, the intake valve model M32, the intake pipe model M33, and the intake valve model M34 constituting the air model M30 will be individually and specifically described. In addition, since the derivation | leading-out of the expression showing each model is disclosed in detail in the above-mentioned gazette and is well-known, detailed description is abbreviate | omitted in this specification.

(Throttle model M31)
The throttle model M31 is a generalized mathematical expression representing this model, and the following formulas (1) and (2) obtained based on physical laws such as energy conservation law, momentum conservation law, mass conservation law, and state equation. ) Is a model for estimating the flow rate of air passing through the periphery of the throttle valve 45 (throttle passage air flow rate) mt. In the following equation (1), μ is a flow coefficient, At (θt) is a throttle opening cross-sectional area that changes in accordance with the throttle valve opening θt (opening cross-sectional area around the throttle valve 45 in the intake passage), and Pa is a throttle. A throttle valve upstream pressure (ie, intake pressure) that is the pressure of air in the intake passage upstream of the valve 45, and Pm is an intake pipe pressure that is the pressure of air in the intake pipe (ie, from the throttle valve 45 to the intake valve 32). Throttle valve downstream pressure which is the pressure of the air in the intake passage until), Ta is the temperature of the throttle valve upstream which is the temperature of the air in the intake passage upstream of the throttle valve 45 (ie, the intake temperature), R is the gas constant and κ is the specific heat ratio of air.

  Here, the throttle opening cross-sectional area At (θt) on the right side of the equation (1) is a value determined according to the throttle valve opening θt. Therefore, the throttle model M31 stores a table MAPAT that defines the relationship between the throttle valve opening degree θt and the throttle opening sectional area At (θt) in the ROM 72, and the throttle valve opening detected by the throttle position sensor 63 is stored. The throttle opening cross-sectional area At (θta) (= MAPAT (θta)) is obtained based on the degree θta.

  Further, the throttle model M31 stores a table MAPΦ for defining the relationship between the value Pm / Pa and the value Φ (Pm / Pa) in the ROM 72, and is estimated at the time of the k−1th estimation by the intake pipe model M33 described later. The value Φ (Pm (k−k−)) is obtained from the value Pm (k−1) / Pa obtained by dividing the pressure Pm (k−1) in the intake pipe section divided by the intake pressure Pa detected by the pressure sensor 61 and the table MAPΦ. 1) / Pa) (= MAPΦ (Pm (k-1) / Pa)).

  The throttle model M31 includes the throttle opening sectional area At (θta) and the value Φ (Pm (k-1) / Pa) obtained as described above, the flow coefficient μ determined by the flow coefficient determination means M20, and the above The throttle passage air flow rate mt (k−1) is obtained by applying the intake pressure Pa and the intake air temperature Ta detected by the temperature sensor 62 to the above equation (1).

(Intake valve model M32)
The intake valve model M32 is an intake pipe section temperature that is the temperature of the intake pipe section Pm and the temperature of air in the intake pipe section (that is, a throttle valve that is the temperature of air in the intake passage from the throttle valve 45 to the intake valve 32). This is a model for estimating the in-cylinder inflow air flow rate mc, which is the flow rate of the air that passes around the intake valve 32 and flows into the cylinder (inside the combustion chamber 25) from the downstream temperature Tm or the like. Since the pressure in the cylinder in the intake stroke (including when the intake valve 32 is closed) can be regarded as the pressure upstream of the intake valve 32, that is, the intake pipe pressure Pm, the in-cylinder inflow air flow rate mc is the intake valve flow rate. It can be considered that it is proportional to the pressure Pm in the intake pipe when the valve is closed. In view of this, the intake valve model M32 is a generalized mathematical expression representing this model, and the inflow air flow rate mc in the cylinder is obtained according to the following equation (3) based on an empirical rule.
mc = (Ta / Tm) ・ (c ・ Pm−d) (3)

  In the above equation (3), the value c is a proportional coefficient and the value d is a value reflecting the amount of burnt gas remaining in the cylinder. The value c can be obtained from the table MAPC that defines the relationship between the engine speed NE and the opening / closing timing VT of the intake valve 32 and the value c, the current engine speed NE, and the current opening / closing timing VT of the intake valve 32 ( c = MAPC (NE, VT)). The intake valve model M32 stores the table MAPC in the ROM 72. Similarly, the value d is obtained from the table MAPD that defines the relationship between the engine speed NE and the opening / closing timing VT of the intake valve 32 and the value d, the current engine speed NE, and the current opening / closing timing VT of the intake valve 32. (D = MAPD (NE, VT)). The intake valve model M32 stores the table MAPD in the ROM 72.

  The intake valve model M32 includes an intake pipe internal pressure Pm (k-1) and an intake pipe internal temperature Tm (k-1) estimated at the time of the (k-1) th estimation by an intake pipe model M33 described later, and the current intake air temperature. Ta is applied to the above equation (3) to estimate the in-cylinder inflow air flow rate mc (k-1).

(Intake pipe model M33)
The intake pipe model M33 is a generalized mathematical expression representing this model. The following expression (4), expression (5), and intake pipe based on the mass conservation law and the energy conservation law regarding the air in the intake pipe section, respectively. From the flow rate of air flowing into the section (that is, the flow rate of air passing through the throttle) mt, the intake air temperature Ta, and the flow rate of air flowing out of the intake pipe section (that is, the flow rate of air flowing into the cylinder) mc This is a model for obtaining pressure (Pm) and intake pipe internal temperature (throttle valve downstream temperature) Tm. In the following formulas (4) and (5), Vm is the volume of the intake pipe portion (the intake passage from the throttle valve 45 to the intake valve 32).
d (Pm / Tm) / dt = (R / Vm) ・ (mt−mc) (4)
dPm / dt = κ ・ (R / Vm) ・ (mt ・ Ta−mc ・ Tm) (5)

The intake pipe model M33 includes the following expression (6) and expression (7) obtained by discretizing the above expressions (4) and (5) by the difference method, and the throttle passing air acquired by the throttle model M31. The flow rate mt (k-1), the in-cylinder inflow air flow rate mc (k-1) acquired by the intake valve model M32, the current intake air temperature Ta, and this model were estimated at the time of the k-1th estimation. The latest intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (k) are estimated based on the intake pipe internal pressure Pm (k-1) and the intake pipe internal temperature Tm (k-1). However, when the intake pipe pressure Pm and the intake pipe temperature Tm have never been estimated (when this model is used for the first estimation (in this example, when the internal combustion engine starts operating)), the intake pipe The model M33 employs the intake pressure Pa and the intake air temperature Ta as the intake pipe internal pressure Pm (0) and the intake pipe internal temperature Tm (0), respectively.
(Pm / Tm) (k) = (Pm / Tm) (k-1) + Δt ・ (R / Vm) ・ (mt (k-1) −mc (k-1)) (6)
Pm (k) = Pm (k-1) + Δt ・ κ ・ (R / Vm) ・ (mt (k-1) ・ Ta−mc (k-1) ・ Tm (k-1)) (7)

(Intake valve model M34)
The intake valve model M34 includes a model similar to the intake valve model M32. In the intake valve model M34, the latest intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (k) estimated at the time of the k-th estimation by the intake pipe model M33, and the current intake air temperature Ta are obtained. This is a generalized formula that represents this model, and is applied to the formula (3) (mc = (Ta / Tm) ・ (c ・ Pm−d)) based on the above empirical rule. k). The intake valve model M34 is closed after the intake valve 32 calculated based on the current in-cylinder inflow air flow rate mc (k) from the current engine speed NE and the current open / close timing VT of the intake valve 32 is opened. The in-cylinder air amount KL, which is the amount of air introduced into the cylinder at the time when the intake valve 32 is closed in the intake stroke, is obtained by multiplying the time to valve (intake valve opening time) Tint. .

  Next, the actual operation of the electric control device 70 will be described with reference to FIGS.

(In-cylinder air volume estimation)
The CPU 71 of the electric control device 70 executes the in-cylinder air amount estimation routine shown in the flowchart in FIG. 5 every elapse of a predetermined calculation cycle Δt (8 ms in this example), thereby allowing the in-cylinder at the next calculation time point to be calculated. Estimate the air volume KL. Note that the execution of the in-cylinder air amount estimation routine corresponds to the achievement of the function of the in-cylinder air amount estimation means.

  More specifically, when the predetermined timing is reached, the CPU 71 starts processing from step 500 and proceeds to step 505 to obtain the throttle passage air flow rate mt (k-1) by the throttle model M31. The process proceeds to step 600 shown in the flowchart of FIG. Note that the execution of the routine of FIG. 6 corresponds to the achievement of the function of the throttle passing air flow rate estimating means.

  Next, the CPU 71 proceeds to step 605 and reads the throttle valve opening degree θta detected by the throttle position sensor 63.

  Next, the CPU 71 proceeds to step 610 and reads At (k−1) as the throttle opening cross-sectional area At of the equation (1) in the table MAPAT and the step 605 (the current calculation time point). That is, it is obtained from the throttle valve opening θta at the present time.

  Then, the CPU 71 proceeds to step 615 and proceeds to step 700 shown in the flowchart of FIG. 7 in order to determine the flow coefficient μ (k−1). Note that the execution of the routine of FIG. 7 corresponds to the achievement of the function of the flow coefficient determination means M20.

  Next, the CPU 71 proceeds to step 705, and the throttle valve opening θta at the time of the current calculation and the throttle valve set at step 630 (to be described later) at the time of the previous execution of the routine of FIG. It is determined whether or not the absolute value of the difference between the opening θtap is greater than zero. That is, it is determined whether or not the throttle valve opening degree θta and the throttle valve opening degree θtap are different.

  Now, a case where the driver starts depressing the accelerator pedal 67 will be described. In this case, the accelerator pedal operation amount Accp detected by the accelerator opening sensor 66 increases. Therefore, since the load on the internal combustion engine 10 increases, in order to increase the amount of air introduced into the cylinder, the throttle valve control means C10 sends a drive signal to the throttle valve actuator 45a so that the throttle valve opening increases. Send it out. Thereby, the throttle valve 45 is driven so that the opening degree increases.

  In this case, the throttle valve opening θta at the current calculation time is larger than the throttle valve opening θtap at the previous calculation time. Accordingly, the CPU 71 determines “Yes” in step 705, proceeds to step 710, and determines whether or not the value of the transient state flow coefficient adoption flag Xk is “0”.

  Here, the transient state flow coefficient adoption flag Xk is a flag indicating whether or not the transient state flow coefficient μk calculated as the flow coefficient at the time of transient operation was adopted as the flow coefficient during the previous execution of this routine. If the value is “1”, the transient flow coefficient μk is adopted as the flow coefficient, and if it is “0”, the steady state flow coefficient μt calculated as the flow coefficient during steady operation is adopted as the flow coefficient. Indicates. As will be described later, the value of the transient state flow coefficient adoption flag Xk is set to “1” when the throttle valve opening starts to change (see step 730), and then the transient state flow coefficient μk is When the value becomes sufficiently close to the steady state flow coefficient μt, it is set to “0” (see Steps 765 to 775).

  The present time is a point in time when the operating state of the internal combustion engine 10 has changed from a steady operating state (a state where the throttle valve opening is constant) to a transient operating state (a state where the throttle valve opening is increasing). Therefore, since the throttle valve opening was substantially constant until the previous execution of this routine, the value of the transient state flow coefficient adoption flag Xk is “0” at the present time.

  Accordingly, the CPU 71 makes a “Yes” determination at step 710, proceeds to step 715, and enters the transient state initial throttle valve opening θta0, which is the throttle valve opening at the time when the operating state of the internal combustion engine 10 becomes the transient operation state. Is set to the throttle valve opening θtap at the time of the previous calculation. Furthermore, in step 715, the CPU 71 sets the transient initial intake pipe internal pressure Pm0, which is the intake pipe internal pressure at the time when the operating state of the internal combustion engine 10 becomes a transient operation state, at the time of execution of the routine of FIG. The intake pipe internal pressure Pm (k-2) at the time of the previous calculation obtained in step 515 described later is set.

  In addition, in step 715, the CPU 71 calculates the throttle valve driving speed v by dividing the difference between the throttle valve opening θta at the current calculation time and the throttle valve opening θtap at the previous calculation time by the calculation cycle Δt. And the transient state elapsed time t, which is the time that has elapsed since the operating state of the internal combustion engine 10 became the transient operation state, is set to Δt. Note that the execution of the process of step 715 corresponds to the achievement of the function of the throttle valve drive speed acquisition means.

  Then, the CPU 71 proceeds to step 720, and the relationship among the transient state flow coefficient μk, the transient state initial throttle valve opening θta0, the transient state initial intake pipe pressure Pm0, the throttle valve drive speed v, and the transient state elapsed time t. Based on the transient state flow coefficient table fk that defines the transient state initial throttle valve opening θta0, transient state initial intake pipe pressure Pm0, throttle valve drive speed v, and transient state elapsed time t set in step 715 above. Determine the transient flow coefficient μk.

  Here, the transient state flow coefficient table fk is created based on experimentally measured values, and is stored in the ROM 72 in advance. The transient state flow coefficient μk obtained from the transient state flow coefficient table fk decreases rapidly in a short period after the throttle valve opening starts to change (increase or decrease), and then with time, By gradually increasing, the steady state flow coefficient μt is approached.

  Therefore, by determining the transient state flow coefficient μk based on the transient state flow coefficient table fk, the actual flow coefficient when the throttle valve opening is changing (during transient operation) is estimated with high accuracy. be able to.

  Further, the transient state flow coefficient μk obtained from the transient state flow coefficient table fk decreases as the throttle valve drive speed v increases. In addition, the transient state flow coefficient μk decreases as the transient state initial intake pipe pressure Pm0 decreases.

  Accordingly, the transient state flow coefficient μk can be determined in consideration of the degree of turbulence of the air flow in accordance with the throttle valve drive speed v and the transient state initial intake pipe pressure Pm0. It is possible to estimate the actual flow coefficient according to the speed v and the transient state initial intake pipe pressure Pm0 with high accuracy.

  As a result, as will be described later, when the throttle passage air flow rate mt and the cylinder air amount KL are estimated based on the determined transient state flow coefficient μk, the throttle passage air flow rate mt and the cylinder air amount KL can be obtained with high accuracy. Can be estimated.

  Then, the CPU 71 proceeds to step 725 and sets the flow coefficient μ (k−1) to the transient state flow coefficient μk determined in step 720. Next, the CPU 71 proceeds to step 730, sets the value of the transient state flow coefficient adoption flag Xk to 1, and in step 735, the value obtained by adding the transient period elapsed time t to the transient state elapsed time t and the calculation period Δt. Set to.

  Next, the CPU 71 proceeds to step 620 in FIG. 6 via step 795, and the current calculation time point obtained in step 515 (to be described later) at the time of execution of the routine of FIG. The value Pm (k-1) / Pa obtained by dividing the pressure Pm (k-1) in the intake pipe at the present time by the intake pressure Pa detected by the pressure sensor 61, and the value Φ (Pm (k-1) / Pa )

  Then, the CPU 71 proceeds to step 625, the values obtained in step 610, step 615 and step 620, respectively, and the equation shown in step 625 based on equation (1) representing the throttle model M31, Based on the intake pressure Pa and the intake air temperature Ta detected by the temperature sensor 62, a throttle passage air flow rate mt (k-1) at the time of the current calculation is obtained.

  Next, the CPU 71 proceeds to step 630 to set the throttle valve opening θtap as the past throttle valve opening to the throttle valve opening θta read in step 605 at the time of execution of this routine. The process proceeds to step 510 in FIG.

  Next, the CPU 71 proceeds to step 510, and calculates the coefficient c of the equation (3) representing the intake valve model M32 from the table MAPC, the current engine speed NE, and the current open / close timing VT of the intake valve 32. Ask. Similarly, the value d is obtained from the table MAPD, the current engine speed NE, and the current open / close timing VT of the intake valve 32.

  Then, the CPU 71 obtains the equation shown in step 510 based on the equation (3) representing the intake valve model M32 in step 510 and the current time obtained in step 515, which will be described later at the time of the previous execution of this routine. Based on the intake pipe internal pressure Pm (k-1) and intake pipe internal temperature Tm (k-1) and the intake air temperature Ta, the in-cylinder inflow air flow rate mc (k- Find 1).

  Next, the CPU 71 proceeds to step 515 and formulas (6) and (7) obtained by discretizing the formulas (4) and (5) representing the intake pipe model M33 (the formulas shown in step 515 (difference formulas). )), The throttle passage air flow rate mt (k-1) obtained in step 505, the in-cylinder inflow air flow rate mc (k-1) obtained in step 510, and the intake air temperature Ta. Based on the value obtained by dividing the intake pipe internal pressure Pm (k) at the next calculation time and the intake pipe internal pressure Pm (k) by the intake pipe internal temperature Tm (k) at the next calculation time {Pm / Tm } (K). That is, in step 515, the intake pipe internal pressure Pm (k) at the next calculation time and the intake pipe internal pressure Pm (k-1) and the intake pipe internal temperature Tm (k-1) at the current calculation time are calculated. An intake pipe temperature Tm (k) is obtained. Note that the execution of the processing of step 515 corresponds to the achievement of part of the function of the throttle valve downstream pressure acquisition means.

  Thereafter, the CPU 71 proceeds to step 520 to obtain the in-cylinder inflow air flow rate mc (k) at the next calculation time using the equation (3) representing the intake valve model M34. At this time, the values obtained in step 510 are used as the value c and the value d. For the intake pipe internal pressure Pm (k) and the intake pipe internal temperature Tm (k), the values (latest values) at the next calculation time obtained in step 515 are used.

  Then, the CPU 71 proceeds to step 525 and closes the intake valve opening time (the intake valve 32 is opened after the intake valve 32 is opened) determined by the current engine speed NE and the current opening / closing timing VT of the intake valve 32. In step 530, the in-cylinder inflow air flow rate mc (k) at the next calculation time is multiplied by the intake valve opening time Tint to calculate the in-cylinder air amount KL. Proceed to to end the present routine.

  As described above, the in-cylinder air amount estimation routine is executed every time the calculation period Δt elapses, whereby the in-cylinder air amount KL at each calculation time point is sequentially estimated.

  On the other hand, the CPU 71 executes a routine for determining an injected fuel amount (not shown) at a predetermined timing.

  The amount of injected fuel needs to be determined at a time before the injection start timing in consideration of the time required for the CPU 71 to determine the amount of injected fuel. Therefore, this control device executes an injection fuel amount determination routine every time immediately after the start of the intake stroke.

  Then, the CPU 71 divides the constant k by a value obtained by dividing the latest in-cylinder air amount KL obtained at the time of execution of the injection fuel amount determination routine by the target air-fuel ratio AbyF determined according to the operating state of the internal combustion engine 10. By multiplying, the amount of injected fuel τ is determined.

  Thereafter, during the period in which the accelerator pedal operation amount Accp is increasing, the absolute value of the difference between the throttle valve opening θta at the current calculation time and the throttle valve opening θtap at the previous calculation time is greater than zero. Therefore, when the CPU 71 starts the processing of the routine of FIG. 7, when the CPU 71 proceeds to step 705, it determines “Yes”, proceeds to step 710, and the value of the transient state flow coefficient adoption flag Xk is “0”. Is determined.

  At this time, the value of the transient state flow coefficient adoption flag Xk is set to “1” in the above step 730 at the time of the previous execution of this routine. Accordingly, the CPU 71 makes a “No” determination at step 710, proceeds to step 720, and determines the transient state flow coefficient μk as described above. Then, the CPU 71 executes the processing of the above steps 725 to 735 and once ends the processing of this routine.

  Thus, according to this control apparatus, the actual flow coefficient when the throttle valve opening is changing (during transient operation) is estimated with high accuracy. Thereby, since the throttle passage air flow rate mt is estimated with high accuracy, the in-cylinder air amount KL can be estimated with high accuracy. As a result, the amount of injected fuel τ can be appropriately determined, and the internal combustion engine 10 can be appropriately controlled.

  Thereafter, when the driver stops the depression of the accelerator pedal 67 (that is, when the position of the accelerator pedal 67 is maintained), the accelerator pedal operation amount Accp detected by the accelerator opening sensor 66 becomes constant. The valve opening degree θtt is also constant. Therefore, the throttle valve 45 is controlled so that the opening degree is constant. In such a state, the throttle valve opening degree θtap at the time of the previous calculation becomes equal to the throttle valve opening degree θta at the time of the current calculation. Therefore, when the CPU 71 starts the processing of the routine of FIG. 7, when the CPU 71 proceeds to step 705, it determines “No”, proceeds to step 750, and the value of the transient state flow coefficient adoption flag Xk is “1”. Is determined.

  At this time, the value of the transient state flow coefficient adoption flag Xk is set to “1” in the above step 730 at the time of the previous execution of this routine. Accordingly, the CPU 71 makes a “Yes” determination at step 750 and proceeds to step 755 to determine the relationship among the steady state flow coefficient μt, the throttle valve opening θta, the intake pipe internal pressure Pm, and the engine speed NE. The steady-state flow coefficient table ft to be defined, the throttle valve opening θta read in step 605 at the time of execution of the routine of FIG. 6 this time, and obtained at step 515 at the time of execution of the routine of FIG. The steady-state flow coefficient μt is determined based on the intake pipe internal pressure Pm (k−1) at the time of the current calculation and the current engine speed NE.

  Here, the steady state flow coefficient table ft is created based on experimentally measured values, and is stored in the ROM 72 in advance. The steady-state flow coefficient μt acquired from the steady-state flow coefficient table ft decreases as the throttle valve opening θta increases.

  Next, the CPU 71 proceeds to step 760 to determine the transient state flow coefficient μk as in step 720 described above. Then, the CPU 71 proceeds to step 765 and the absolute value of the difference between the steady state flow coefficient μt determined in step 755 and the transient state flow coefficient μk determined in step 760 is sufficiently small (to zero). It is determined whether or not it is greater than a predetermined value α. That is, it is determined whether or not the steady state flow coefficient μt and the transient state flow coefficient μk are sufficiently close to each other.

  This time is a time immediately after the driving of the throttle valve 45 is finished. Accordingly, since the flow disturbance remains while the throttle valve 45 is being driven, the degree of the flow disturbance is larger than that in the steady operation state. Accordingly, since the transient state flow coefficient μk is smaller than the steady state flow coefficient μt, the CPU 71 determines “Yes” in step 765, executes the processing of step 725 to step 735, and temporarily executes the processing of this routine. finish.

  Thereafter, with the passage of time, the turbulence of the flow becomes substantially equal to that during steady operation. At this time, when the CPU 71 starts the processing of the routine of FIG. 7, when the CPU 71 proceeds to step 765, it determines “No”, proceeds to step 770, and sets the flow coefficient μ (k−1) to the above. The steady state flow coefficient μt determined in step 755 is set. Next, the CPU 71 proceeds to step 775, sets the value of the transient state flow coefficient adoption flag Xk to “0”, executes the subsequent processing of step 735, and temporarily ends the processing of this routine.

  Furthermore, when the CPU 71 starts processing of the routine at the next timing when the processing of the routine of FIG. 7 is executed, the CPU 71 determines “No” when it proceeds to step 750, and proceeds to step 780. Thus, the steady state flow coefficient μt is determined in the same manner as in step 755 above. Next, the CPU 71 executes the processing of step 770, step 775, and step 735, and once ends the processing of this routine. Accordingly, during steady operation, the steady state flow coefficient μt is employed as the flow coefficient.

  As described above, the first embodiment of the control apparatus for an internal combustion engine according to the present invention acquires the throttle valve driving speed v during transient operation, and based on the acquired throttle valve driving speed v, the flow coefficient μ To decide. Thereby, the actual flow coefficient at the time of transient operation can be estimated with high accuracy.

  Further, the first embodiment is configured such that the flow coefficient μ determined as the throttle valve driving speed v increases. Thereby, the actual flow coefficient according to the throttle valve drive speed v can be estimated with high accuracy.

  In addition, in the first embodiment, in addition to the throttle valve drive speed v, the intake pipe pressure (throttle valve downstream pressure) Pm (actually, the transient initial pressure in the intake pipe Pm0) is taken into consideration. Determine μ. As a result, the actual flow coefficient can be estimated with high accuracy regardless of the value of the pressure Pm in the intake pipe during transient operation.

  Further, the first embodiment is configured such that the flow coefficient μ determined as the intake pipe internal pressure Pm (actually the transient initial intake pipe internal pressure Pm0) decreases. Thereby, the actual flow coefficient according to the intake pipe internal pressure Pm can be estimated with high accuracy.

  Thus, according to the first embodiment, the actual flow coefficient when the throttle valve opening is changing (during transient operation) is estimated with high accuracy. As a result, the throttle passage air flow rate mt can be estimated with high accuracy based on the estimated flow rate coefficient. Therefore, the injected fuel amount τ can be appropriately determined, and the internal combustion engine 10 can be appropriately controlled.

  In the first embodiment, the throttle valve downstream pressure (intake pipe section pressure) Pm is estimated by the air model M30. However, the intake pipe section pressure Pm is detected by a pressure sensor that detects the air pressure in the intake pipe section. May be detected.

  In the first embodiment, based on the transient state flow coefficient table fk defining the relationship between the transient state initial intake pipe part pressure Pm0 and the transient state flow coefficient μk, and the transient state initial intake pipe part pressure Pm0. The transient flow coefficient μk was estimated, but the transient flow rate coefficient μk based on the table defining the relationship between the intake pipe pressure Pm and the transient flow coefficient μk and the intake pipe pressure Pm at each calculation point May be estimated.

(Second Embodiment)
Next, a second embodiment of the control device for an internal combustion engine according to the present invention will be described. This second embodiment differs from the first embodiment only in that the transient state flow coefficient μk is determined based on the engine rotational speed NE instead of the transient state initial intake pipe pressure Pm0. Therefore, such differences will be described below.

  By the way, when the engine rotational speed NE is increased, the throttle passage air flow rate mt is increased, so that the degree to which the air flow is disturbed by driving the throttle valve 45 is increased. Therefore, as shown in FIG. 8, as the engine rotational speed NE increases, the actual flow coefficient is determined based on the relationship between the throttle valve opening and the flow coefficient during steady operation in the prior art. The coefficient (conventional flow coefficient) becomes even smaller.

  Therefore, the control device according to the second embodiment acquires the throttle valve driving speed v and the engine rotational speed NE during transient operation, and the flow rate based on the acquired throttle valve driving speed v and engine rotational speed NE. The coefficient μ is determined, and the determined flow coefficient μ is applied to the throttle model M31.

  Therefore, according to this control device, since the actual flow coefficient when the throttle valve opening is changing (during transient operation) is estimated with high accuracy, the throttle passage air flow rate mt and the cylinder air amount KL are estimated. Can be estimated with high accuracy. As a result, the amount of injected fuel τ can be appropriately determined, so that an air-fuel mixture having a target air-fuel ratio determined according to the operating state of the internal combustion engine 10 can be formed in the combustion chamber 25. 10 can be appropriately controlled.

  More specifically, this control device replaces the transient state flow coefficient table fk stored in the ROM 72 in the first embodiment with a transient state flow coefficient μk, a transient state initial throttle valve opening θta0, A transient state flow coefficient table fkn that defines the relationship among the engine speed NE, the throttle valve drive speed v, and the transient state elapsed time t is stored in the ROM 72.

  The transient flow coefficient table fkn is created based on experimentally measured values. The transient state flow coefficient μk obtained from the transient state flow coefficient table fkn decreases rapidly in a short period after the throttle valve opening starts to change (increase or decrease), and then with time, By gradually increasing, the steady state flow coefficient μt is approached.

  Further, the transient state flow coefficient μk decreases as the throttle valve drive speed v increases. In addition, the transient state flow coefficient μk decreases as the engine speed NE increases.

  This control device performs the processing of step 720 and step 760 of FIG. 7 in the transient state flow coefficient table fkn, the current engine speed NE, and the transient state initial stage set in step 715 of the routine of FIG. The routine is executed by substituting the process for determining the transient state flow coefficient μk based on the throttle valve opening θta0, the throttle valve drive speed v, and the transient state elapsed time t.

  Thereby, the actual flow coefficient according to the engine speed NE can be estimated with high accuracy.

  As described above, the second embodiment of the control apparatus for an internal combustion engine according to the present invention determines the flow coefficient μ in consideration of the engine rotational speed NE in addition to the throttle valve driving speed v. Thereby, the actual flow coefficient according to the engine speed NE can be estimated with high accuracy. As a result, the throttle passage air flow rate mt can be estimated with high accuracy based on the estimated flow rate coefficient. Therefore, the in-cylinder air amount KL can be estimated with high accuracy, and the injected fuel amount τ can be appropriately determined.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in each of the above embodiments, the injected fuel amount τ is determined in accordance with the in-cylinder air amount KL obtained based on the determined flow coefficient μ, and the intake valve 32 and the exhaust valve 34 are further opened and closed. Timing, fuel injection timing, ignition timing, and the like may be determined.

  In each of the above embodiments, the current injected fuel amount τ is determined based on the current throttle valve opening detected by the throttle position sensor 63. However, the throttle valve opening at a time earlier than the current time is determined. The injected fuel amount τ at the previous time point may be determined based on the throttle valve opening at the previous time point estimated by the estimating means.

  In addition, in each of the above embodiments, the transient state flow coefficient μk is determined based on either the throttle valve downstream pressure Pm or the engine rotational speed NE, but the throttle valve downstream pressure Pm and the engine rotational speed NE The transient flow coefficient μk may be determined based on both.

1 is a schematic configuration diagram of a system in which a control device according to a first embodiment of the present invention is applied to a spark ignition type multi-cylinder internal combustion engine. It is the graph which showed notionally the relationship between the change of a throttle valve opening degree, and the change of a flow coefficient. It is the graph which showed notionally the relation between the throttle valve downstream pressure and the change of the actual flow coefficient. It is a functional block diagram of the means and model for determining the amount of injected fuel. It is the flowchart which showed the program for estimating the in-cylinder air quantity which CPU shown in FIG. 1 performs. It is the flowchart which showed the program for estimating the throttle passage air flow rate which CPU shown in FIG. 1 performs. It is the flowchart which showed the program for determining the flow coefficient which CPU shown in FIG. 1 performs. It is the graph which showed notionally the relationship between engine rotation speed and the change of an actual flow coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 34 ... Exhaust port, 35 ... Exhaust valve, 39 ... Injector, 41 ... Intake manifold, 42 ... Surge tank, 43 ... Intake duct, 44 ... Air filter, 45 ... Throttle valve, 45a ... Throttle valve actuator, 51 ... Exhaust pipe, 61 ... Pressure sensor, 62 ... Temperature sensor, 63 ... Throttle position sensor, 65 ... Crank position sensor, 66 ... Open accelerator Degree sensor, 67 ... accelerator pedal, 70 ... electric control device, 71 ... CPU, 72 ... ROM, 73 ... RAM.

Claims (6)

An intake passage that introduces air taken from outside into the cylinder, a throttle valve that is disposed in the intake passage and can be adjusted to change the amount of air that flows through the intake passage, and the throttle Applied to an internal combustion engine comprising: a throttle valve driving means for driving a valve; and a throttle valve opening obtaining means for obtaining the opening of the throttle valve;
Throttle passing air flow rate, which is the flow rate of air passing around the throttle valve based on a physical model representing the behavior of air passing around the throttle valve using the opening degree of the throttle valve and the flow coefficient A throttle passage air flow rate estimating means for estimating
A control device for an internal combustion engine that controls the internal combustion engine based on the estimated throttle passage air flow rate,
Throttle valve drive speed acquisition means for acquiring a throttle valve drive speed that is a speed at which the throttle valve is driven by the throttle valve drive means;
Flow coefficient determination means for determining a flow coefficient based on the acquired throttle valve drive speed, and
The throttle passage air flow rate estimating means is configured to apply the acquired throttle valve opening degree and the determined flow rate coefficient to the physical model to estimate the throttle passage air flow rate. Engine control device. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, wherein the flow coefficient determination means is configured such that the determined flow coefficient decreases as the acquired throttle valve drive speed increases. A control device for an internal combustion engine according to claim 1 or 2,
A throttle valve downstream pressure acquisition means for acquiring a throttle valve downstream pressure which is a pressure of air downstream of the throttle valve;
The control apparatus for an internal combustion engine, wherein the flow coefficient determining means further determines the flow coefficient based on the acquired throttle valve downstream pressure. The control apparatus for an internal combustion engine according to claim 3,
The control apparatus for an internal combustion engine, wherein the flow coefficient determination means is configured such that the determined flow coefficient decreases as the acquired throttle valve downstream pressure decreases. A control device for an internal combustion engine according to any one of claims 1 to 4,
An engine rotation speed acquisition means for acquiring the engine rotation speed;
The internal combustion engine control device, wherein the flow coefficient determination means further determines the flow coefficient based on the acquired engine rotation speed. The control apparatus for an internal combustion engine according to claim 5,
The control apparatus for an internal combustion engine, wherein the flow coefficient determination means is configured so that the determined flow coefficient decreases as the acquired engine rotation speed increases.

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