JP2008144680A - Air quantity estimation device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air quantity estimation device for an internal combustion engine capable of reducing calculation load while keeping estimation accuracy of cylinder air quantity as high as possible. <P>SOLUTION: The estimation devise estimates cylinder air quantity KL with using a first air model M10 constructed under an assumption that thermal energy (thermal transmission energy) transmitted from a wall surface of an intake passage to air in the intake passage is zero when temperature Tim, Tst of wall surfaces of the intake passage is low and throttle valve opening TAe is large (when conditions of quantity of operation state are satisfied). On the other hand, cylinder air quantity KL is estimated by estimating heat transfer energy and applying the estimated heat transfer energy to a second air model M20 constructed based on the energy conservation law with considering heat transfer energy. As the result, calculation load can be reduced with keeping estimation accuracy of cylinder air quantity KL when the conditions of quantity of operation state are satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for estimating the amount of air introduced into a cylinder of an internal combustion engine.

  Conventionally, based on the energy conservation law regarding the air in the intake pipe portion (including the surge tank and the intake manifold) from the throttle valve to the intake valve in the intake passage for introducing the air taken from outside into the cylinder of the internal combustion engine 2. Description of the Related Art An air amount estimation device for an internal combustion engine that estimates an air amount (in-cylinder air amount) introduced into a cylinder by using a built physical model is known. In the energy conservation law that became the basis for constructing this physical model, the heat energy (heat transfer energy) transferred from the wall surface of the intake pipe to the air in the intake pipe is determined as the increase in the energy of the air in the intake pipe. It is handled.

In this air amount estimation device, since the change in the in-cylinder air amount due to the transfer of thermal energy from the wall surface of the intake pipe portion to the air in the intake pipe portion is taken into account, the in-cylinder air amount is compared by this thermal energy. Even in the case of a large change, the in-cylinder air amount is estimated with high accuracy (see, for example, Patent Document 1).
JP 2004-293546 A

  By the way, in the process of estimating the in-cylinder air amount using the physical model constructed by considering heat transfer energy (hereinafter also referred to as “the former physical model”), the heat transfer energy is 0. This is more complicated than the case of using a physical model (hereinafter also referred to as “the latter physical model”) constructed based on the energy conservation law regarding the air in the intake pipe section under the assumption that Therefore, the calculation load when calculating the in-cylinder air amount using the former physical model is higher than that when using the latter physical model.

  On the other hand, the smaller the heat energy ratio, which is the ratio of heat transfer energy to the increase in the air energy in the intake pipe section, the smaller the degree of influence that the change in heat transfer energy has on the change in the in-cylinder air amount. Therefore, the magnitude of the difference between the in-cylinder air amount estimated using the former physical model and the in-cylinder air amount estimated using the latter physical model is also reduced. Therefore, when the thermal energy ratio is sufficiently small, the in-cylinder air amount is estimated with sufficiently high accuracy even if the latter physical model is used. However, in the conventional air amount estimation device, the cylinder air amount is always estimated using the former physical model, and thus the calculation load may become uselessly high.

  The present invention has been made based on such knowledge, and its purpose is to estimate the air amount of an internal combustion engine that can reduce the calculation load while maintaining the estimation accuracy of the in-cylinder air amount as high as possible. To provide an apparatus.

In order to achieve the above object, an air amount estimation device for an internal combustion engine according to the present invention includes a first in-cylinder air amount estimation unit, a second in-cylinder air amount estimation unit, an operating state amount condition determination unit, and an in-cylinder air. Quantity estimation switching means.
The first in-cylinder air amount estimating means has zero heat transfer energy, which is heat energy transmitted from the wall surface of the intake passage for introducing air taken from outside into the cylinder to air in a predetermined region of the intake passage. The in-cylinder air amount, which is the amount of air introduced into the cylinder, is estimated by using the first physical model constructed based on the energy conservation law for the air in the predetermined region under the assumption It is means to do.

  The second in-cylinder air amount estimation means estimates the heat transfer energy and treats the heat transfer energy as an increase in the energy of the air in the predetermined region as an energy conservation law for the air in the predetermined region. The in-cylinder air amount is estimated by applying the heat transfer energy estimated to the second physical model constructed based on the energy conservation law.

  The operating state quantity condition determining means acquires the operating state quantity of the internal combustion engine that affects the heat energy ratio that is the ratio of the heat transfer energy to the increase in the energy of air in the predetermined region. The difference between the in-cylinder air amount that would be estimated by the first in-cylinder air amount estimating means and the in-cylinder air amount that would be estimated by the second in-cylinder air amount estimating means Is a means for determining whether or not the operating state quantity condition that the size is within a range that is smaller than a predetermined size is satisfied.

  The in-cylinder air amount estimation switching means causes the first in-cylinder air amount estimation means to estimate the in-cylinder air amount when it is determined by the operating state quantity condition determining means that the operating state quantity condition is satisfied, The cylinder air amount is estimated by the second cylinder air amount estimating means when it is determined by the operation state quantity condition determining means that the condition of the operation state quantity is not satisfied.

  According to this, when the operating state quantity condition is satisfied, the in-cylinder air quantity is determined using the first physical model constructed based on the energy conservation law under the assumption that the heat transfer energy is zero. Presumed. At this time, the in-cylinder air amount that would be estimated using the first physical model and the energy conservation law in which the heat transfer energy is treated as an increase in the energy of the air in the predetermined region are constructed. The magnitude of the difference between the in-cylinder air amount that would be estimated using the physical model 2 is relatively small. Therefore, the in-cylinder air amount can be estimated with sufficiently high accuracy even when the first physical model is used. Furthermore, the calculation load can be reduced as compared with the case where the second physical model is used. That is, when the operating state quantity condition is satisfied, the calculation load can be reduced while maintaining the estimation accuracy of the cylinder air quantity as high as possible.

  On the other hand, when the operating state quantity condition is not satisfied, the in-cylinder air quantity is estimated using the second physical model. Thereby, even if the in-cylinder air amount changes relatively greatly due to heat transfer energy, the in-cylinder air amount can be estimated with high accuracy.

  In this case, the operating state quantity condition determining means acquires the temperature of the wall surface of the intake passage as the operating state quantity, and satisfies the operating state quantity condition when the temperature of the wall surface is lower than a predetermined threshold temperature. Then, it is preferable to be configured to determine.

  As the temperature of the wall surface of the intake passage (wall surface temperature) decreases, the difference between the wall surface temperature and the temperature of the air in the predetermined region decreases, so the heat transfer energy decreases. Therefore, when the wall surface temperature is sufficiently low, the thermal energy ratio is sufficiently small. As a result, the influence of the heat transfer energy on the in-cylinder air amount is sufficiently small, so that the in-cylinder air amount that would be estimated using the first physical model and the second physical model are used for estimation. The magnitude of the difference from the in-cylinder air amount that would be performed is sufficiently small. Therefore, if the cylinder air amount is estimated based on the first physical model when the wall surface temperature is lower than the threshold temperature as in the above configuration, the calculation load is maintained while maintaining the estimation accuracy of the cylinder air amount as high as possible. Can be reduced.

Moreover, in another aspect of the air amount estimation device for an internal combustion engine according to the present invention,
The operating state quantity condition determining means obtains, as the operating state quantity, an opening degree of a throttle valve that is disposed in the intake passage and changes the flow rate of air passing through the intake passage by changing the opening degree. In addition, it is preferable that when the opening degree of the throttle valve is larger than a predetermined threshold opening degree, it is determined that the operation state quantity condition is satisfied.

  As the opening degree of the throttle valve (throttle valve opening degree) disposed in the intake passage increases, the flow rate of air passing through the intake passage increases. Accordingly, the energy held by the air flowing into the predetermined area of the intake passage (the energy of the air flowing into the predetermined area, that is, the inflow energy) is increased. Accordingly, when the throttle valve opening is sufficiently large, the ratio of the inflow energy to the increase in the energy of the air in the predetermined region of the intake passage is sufficiently large, so that the thermal energy ratio is sufficiently small. As a result, the influence of the heat transfer energy on the in-cylinder air amount is sufficiently small, so that the in-cylinder air amount that would be estimated using the first physical model and the second physical model are used for estimation. The magnitude of the difference from the in-cylinder air amount that would be performed is sufficiently small. Therefore, if the cylinder air amount is estimated based on the first physical model when the throttle valve opening is larger than the threshold opening as in the above configuration, the estimation accuracy of the cylinder air amount is maintained as high as possible. The calculation load can be reduced.

<Configuration>
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an air amount estimating 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 air amount estimation device according to an 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 air and fuel in the cylinder block portion 20. And an exhaust system 50 for releasing the exhaust gas from the cylinder block unit 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 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 fuel injection means for injecting fuel to be supplied into the combustion chamber 25 in response to the instruction signal into the intake port 31. I have.

  The intake system 40 includes an intake manifold 41 including a plurality of independent passages that communicate with the intake ports 31 of the cylinders, a surge tank 42 that communicates with all the passages of the intake manifold 41, and an intake air that has one end connected to the surge tank 42. A duct 43, an air filter 44, a throttle valve 45, and a throttle valve actuator 45a as a throttle valve driving means are provided in the intake duct 43 in order from the other end of the intake duct 43 to the downstream (surge tank 42). Yes. The intake port 31, the intake manifold 41, the surge tank 42, and the intake duct 43 form an intake passage through which air taken from the outside of the internal combustion engine 10 is introduced into the cylinder. Further, the intake passage from the throttle valve 45 to the intake valve 32 constitutes an intake pipe portion. In the present specification, the intake pipe portion is also referred to as a predetermined region of the intake passage.

  The throttle valve 45 is rotatably supported by the intake duct 43. The throttle valve 45 is driven by a throttle valve actuator 45a to change the passage sectional area of the intake duct 43 by changing the opening degree. With such a configuration, the throttle valve 45 can change the flow rate of air passing through the intake duct 43 (intake passage).

  The throttle valve actuator 45a formed of a DC motor is operated by an electric control device 70, which will be described later, in accordance with a drive signal sent by the electronic control throttle valve logic, which will be described later. The throttle valve 45 is driven so that the valve opening) TA matches the target throttle valve opening TAt.

  The exhaust system 50 is connected to the exhaust port 34 of each cylinder, the exhaust manifold 52 connected to the exhaust manifold 51 and forming an exhaust passage together with the exhaust port 34 and the exhaust manifold 51, and the exhaust pipe 52 disposed in the exhaust pipe 52. A three-way catalyst 53 is provided as a purification catalyst.

  On the other hand, this system includes a hot-wire air flow meter 61, an intake air temperature sensor 62, an intake air pressure sensor 63, a throttle position sensor 64, a cam position sensor 65, a crank position sensor 66, a coolant temperature sensor 67, and an accelerator pedal operation amount detection means. The accelerator opening sensor 68 and the electric control device 70 are provided.

The air flow meter 61 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The air flow meter 61 detects the flow rate of air passing through the intake duct 43 (that is, the intake flow rate) and outputs a signal representing the intake flow rate Ga.
The intake air temperature sensor 62 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The intake air temperature sensor 62 detects an air temperature (ie, intake air temperature) Ta upstream of the throttle valve 45 and outputs a signal representing the intake air temperature Ta.
The intake pressure sensor 63 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The intake pressure sensor 63 detects air pressure (ie, intake pressure) Pa upstream of the throttle valve 45 and outputs a signal representing the intake pressure Pa.

The throttle position sensor 64 detects the opening degree (throttle valve opening degree) TAa of the throttle valve 45 and outputs a signal representing the throttle valve opening degree TAa.
The cam position sensor 65 outputs a signal (G2 signal) having a pulse that is generated every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °).
The crank position sensor 66 outputs a signal having a narrow pulse generated every time the crankshaft 24 rotates 10 ° and a wide pulse generated every time the crankshaft 24 rotates 360 °. . This signal represents the engine speed NE.

  The cooling water temperature sensor 67 detects the temperature (cooling water temperature) Tw of the cooling water circulating in the side wall of the cylinder 21 and outputs a signal representing the cooling water temperature Tw.

  The accelerator opening sensor 68 detects the operation amount Accp of the accelerator pedal 81 operated by the driver, and outputs a signal representing the operation amount (accelerator pedal operation amount) Accp of the accelerator pedal 81.

  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 68, supplies signals from the sensors 61 to 68 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 valve of the variable intake timing device 33. A drive signal (instruction signal) is sent to the actuator 45a.

<Overview of operation>
Next, how the air amount estimation device for an internal combustion engine configured as described above estimates the amount of air introduced into the cylinder (in-cylinder air amount) will be described.

  In the internal combustion engine 10 to which this air amount estimation device is applied, the injector 39 is disposed upstream of the intake valve 32, and therefore, when the intake stroke ends when the intake valve 32 is closed (intake valve closed). By the time). Therefore, in order to determine the fuel injection amount that matches the air-fuel ratio of the mixed gas formed in the cylinder with the target air-fuel ratio, this air amount estimation device closes the intake valve at a predetermined time before fuel injection. It is necessary to estimate the in-cylinder air amount KL at the time of valve operation.

  Therefore, this air amount estimation device uses a physical model constructed based on physical laws such as the energy conservation law, the momentum conservation law, and the mass conservation law. The pressure Pm and the temperature Tm are estimated, and the in-cylinder air amount KL at the previous point is estimated based on the estimated pressure Pm and temperature Tm of the air in the intake pipe at the previous point.

  By the way, as the temperature of the inner wall surface (surge tank wall surface temperature) Tst of the surge tank 42 and the temperature of the inner wall surface of the intake manifold 41 (intake manifold wall surface temperature) Tim are lowered, the intake pipe portion extends from these wall surfaces (wall surface of the intake passage). The heat transfer energy, which is the heat energy transferred to the air in the (predetermined region of the intake passage), becomes small. Accordingly, the heat energy ratio, which is the ratio of the heat transfer energy in the increased amount of air energy in the intake pipe portion, is also reduced. That is, when both the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim are sufficiently low, the pressure Pm and the temperature Tm of the air in the intake pipe portion hardly change due to the heat transfer energy.

  Further, as the opening degree (throttle valve opening degree) TA of the throttle valve 45 increases, the flow rate of the air passing through the intake pipe portion increases. Therefore, inflow energy becomes large. That is, since the ratio of the inflow energy in the increase in the energy of the air in the intake pipe portion is increased, the thermal energy ratio is decreased. Therefore, when the throttle valve opening degree TA is sufficiently large, the pressure Pm and the temperature Tm of the air in the intake pipe portion hardly change due to the heat transfer energy.

  Therefore, the air amount estimation device includes (1) a condition that the surge tank wall surface temperature Tst is lower than a predetermined threshold temperature α, (2) a condition that the intake manifold wall surface temperature Tim is lower than a predetermined threshold temperature β, and (3) When any of the conditions that the throttle valve opening TA is larger than the predetermined threshold opening γ is satisfied (that is, when an operating state quantity condition described later is satisfied), the heat transfer energy is The first physical model constructed based on the energy conservation law that is not considered is used as the physical model for estimating the pressure Pm and temperature Tm of the air in the intake pipe and the in-cylinder air amount KL. Thereby, the air amount estimation device can estimate the in-cylinder air amount KL with high accuracy.

  On the other hand, when any one of the above conditions (1) to (3) is not satisfied, the pressure Pm and the temperature Tm in the intake pipe portion change relatively greatly by the heat transfer energy. Therefore, the air amount estimation device uses the second physical model constructed based on the energy conservation law that takes heat transfer energy into consideration, and calculates the air pressure Pm and temperature Tm in the intake pipe section and the in-cylinder air amount KL. Used as the above physical model for estimation. As a result, the air amount estimation device can estimate the in-cylinder air amount KL with high accuracy even if the pressure Pm and the temperature Tm of the air in the intake pipe section change relatively greatly due to heat transfer energy.

  As a result, while ensuring the estimation accuracy of the in-cylinder air amount KL, if any of the above conditions (1) to (3) is satisfied, the first physical model is used, so the calculation load is reduced. Can be reduced. In the present specification, each of the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim is also referred to as the temperature of the wall surface of the intake passage.

  More specifically, as shown in FIG. 2 which is a functional block diagram, this air amount estimation device is an electronically controlled throttle valve logic A1, an injection amount determining logic A2, an electronically controlled throttle valve model M1, an intake passage portion. A wall surface temperature estimation unit M2, an air model selection unit M3, a first air model M10 as a first physical model, and a second air model M20 as a second physical model are provided.

(Electronic control throttle valve logic A1)
The electronically controlled throttle valve logic A1 is a table that defines the relationship between the accelerator pedal operation amount Accp and the provisional target throttle valve opening degree TAt1, and the provisional target throttle valve opening degree TAt1 monotonically increasing with respect to the accelerator pedal operation amount Accp. Has MapTAt.

  The electronically controlled throttle valve logic A1 determines the temporary target throttle valve opening degree TAt1 (= MapTAt (Accp)) based on the table MapTAt and the detected accelerator pedal operation amount Accp, and has a predetermined delay time from the present time. The target value (target throttle valve opening) TAt of the throttle valve opening at the previous time point by TD (64 ms in this example) TAt is set to the provisional target throttle valve opening TAt1 determined at the present time. .

  In other words, the electronically controlled throttle valve logic A1 sets the current target throttle valve opening TAt to the provisional target throttle valve opening TAt1 determined at the time before the current time by the delay time TD. . The electronic control throttle valve logic A1 sends a drive signal corresponding to the set target throttle valve opening degree TAt to the throttle valve actuator 45a.

(Injection amount determination logic A2)
The injection amount determination logic A2 includes an in-cylinder air amount KL estimated by either the first air model M10 or the second air model M20, and a target air-fuel ratio AbyF determined according to the operating state of the internal combustion engine 10. , The fuel injection amount fi (fi = Kf · KL / AbyF, Kf is a constant) is determined, and an instruction signal corresponding to the determined fuel injection amount fi is sent to the injector 39. Yes.

(Electronic control throttle valve model M1)
The electronically controlled throttle valve model M1 has a delay time TD from the current time (from the current time) based on the target throttle valve opening degree TAt up to a time point TD ahead of the current time set by the electronically controlled throttle valve logic A1. The throttle valve opening (predicted throttle valve opening) TAe up to the previous time point is estimated.

  In the electronically controlled throttle valve model M1, the actual throttle valve opening TA becomes the target throttle valve opening TAt without delay after the drive signal corresponding to the target throttle valve opening TAt is sent to the throttle valve actuator 45a. The model is based on the assumption that it follows, and the predicted throttle valve opening degree TAe at a time point ahead of the current time point by the delay time TD is set to the target throttle valve opening degree TAt at the same time point.

  It should be noted that there is a relatively large delay from when the drive signal corresponding to the target throttle valve opening degree TAt is sent to the throttle valve actuator 45a until the actual throttle valve opening degree TA follows the target throttle valve opening degree TAt. In this case, the electronic control throttle valve model M1 is preferably configured to calculate the predicted throttle valve opening degree TAe taking this delay into account.

(Intake passage wall surface temperature estimating means M2)
The intake passage wall surface temperature estimation means M2 includes a table MapTst that is a table that defines the relationship between the surge tank wall surface temperature Tst, the coolant temperature Tw, and the intake air temperature Ta, and is preset based on experimentally measured values. The intake passage wall surface temperature estimating means M2 is based on the table MapTst, the cooling water temperature Tw detected by the cooling water temperature sensor 67, and the intake air temperature Ta detected by the intake air temperature sensor 62. Tst is calculated.

  The intake passage wall surface temperature estimation means M2 further includes a table MapTim that is a table that defines the relationship between the intake manifold wall surface temperature Tim and the coolant temperature Tw, and is preset based on experimentally measured values. The intake passage wall surface temperature estimating means M2 calculates the intake manifold wall surface temperature Tim based on the table MapTim and the coolant temperature Tw detected by the coolant temperature sensor 67.

(Air model selection unit M3)
The air model selection unit M3 includes a predicted throttle valve opening degree TAe estimated by the electronically controlled throttle valve model M1, a surge tank wall surface temperature Tst and an intake manifold wall surface temperature Tim estimated by the intake passage wall surface temperature estimation means M2. Based on this, it is determined which one of the first air model M10 and the second air model M20 is to be used (one of the first air model M10 and the second air model M20 is selected).

  The air model selection unit M3 selects the first air model M10 when the operating state quantity condition is satisfied, and selects the second air model M20 when the operating state quantity condition is not satisfied. Here, the operating state quantity condition is (1) the surge tank wall surface temperature Tst is lower than the predetermined threshold temperature α, and (2) the intake manifold wall surface temperature Tim is lower than the predetermined threshold temperature β, and ( 3) The condition is that the predicted throttle valve opening degree TAe is larger than a predetermined threshold opening degree γ.

  In addition, the threshold temperature α, the threshold temperature β, and the threshold opening γ are the in-cylinder air amount KL estimated by the first air model M10 described later, and the second air pressure described later, as long as the above-described operation state amount condition is satisfied. It is set in advance so that the magnitude of the difference from the in-cylinder air amount KL estimated by the air model M20 is smaller than a predetermined magnitude.

(First air model M10)
The first air model M10 is constructed based on the throttle valve opening (predicted throttle valve opening) TAe estimated by the electronically controlled throttle valve model M1 and physical laws such as the energy conservation law, the momentum conservation law, and the mass conservation law. The in-cylinder air amount KL at a time earlier than the current time is estimated based on the physical model thus made. This physical model is disclosed in detail in JP2003-184613A and JP200141095A.
As shown in FIG. 3, the first air model M10 includes a throttle model M11, an intake valve model M12, a first intake pipe model M13, and an intake valve model M14.

  As will be described later, some of the mathematical formulas (hereinafter also referred to as “generalized mathematical formulas”) derived based on the physical laws representing the models M11 to M14 are part of the air pressure Pm and the intake pipe portion. Includes a time derivative term for temperature Tm. The first air model M10 discretizes the mathematical expression including the time derivative term so that the calculation by the microcomputer is possible, and based on the discrete mathematical expression and the physical quantity estimated as the physical quantity at a certain time point. The physical quantity at a previous time after a predetermined minute time (time step Δt) from the simultaneous point is estimated.

  And the 1st air model M10 estimates the physical quantity of the further previous time by repeating such estimation. That is, the first air model M10 sequentially estimates the physical quantity for each minute time by repeatedly estimating the physical quantity. In the following description, among the variables representing physical quantities, the variables with (k-1) are variables representing physical quantities estimated at the k-1th estimation time (previous calculation time). . Of the variables representing the physical quantity, the variable with (k) is a variable representing the physical quantity estimated at the time of the k-th estimation (current calculation time).

  Hereinafter, the models M11 to M14 constituting the first air model M10 will be described individually and specifically. In addition, since the derivation | leading-out of the expression showing each model is disclosed in detail in the gazette mentioned above, detailed description is abbreviate | omitted in this specification.

(Throttle model M11)
The throttle model M11 is a generalized mathematical expression representing this model, and the following formula (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), Ct (TA) is a flow coefficient that changes according to the throttle valve opening TA, At (TA) is a throttle opening cross-sectional area that changes according to the throttle valve opening TA (the throttle in the intake passage) (Open sectional area around the valve 45), Pa is the throttle valve upstream pressure (ie, intake pressure), which is the pressure of air in the intake passage upstream of the throttle valve 45, and Pm is the intake pressure, which is the pressure of air in the intake pipe section In-pipe pressure (that is, throttle valve downstream pressure, which is the pressure of air in the intake passage from the throttle valve 45 to the intake valve 32), Ta is the temperature of air in the intake passage upstream of the throttle valve 45, and upstream of the throttle valve Temperature (ie, intake air temperature), R is a gas constant, and κ is a specific heat ratio of air.

  Here, the product Ct (TA) · At (TA) of the flow coefficient Ct (TA) on the right side of the equation (1) and the throttle opening cross-sectional area At (TA) can be determined based on the throttle valve opening TA. Known empirically. Therefore, the throttle model M11 stores a table MapCTAT that defines the relationship between the throttle valve opening TA and the values Ct (TA) · At (TA) in the ROM 72. The table MapCTAT and the electronically controlled throttle valve The value Ct (TAe) · At (TAe) (= MapCTAT (TAe)) is obtained based on the predicted throttle valve opening degree TAe estimated by the model M1.

  Further, the throttle model M11 stores a table MapΦ for defining the relationship between the value Pm / Pa and the value Φ (Pm / Pa) in the ROM 72, and the k-1th estimation is performed by the first intake pipe model M13 described later. From the value Pm (k-1) / Pa obtained by dividing the intake pipe pressure Pm (k-1) estimated by the intake pressure Pa detected by the intake pressure sensor 63 and the table MapΦ, the value Φ (Pm (k-1) / Pa) (= MapΦ (Pm (k-1) / Pa)) is obtained.

  The throttle model M11 has the values Ct (TAe) · At (TAe) and Φ (Pm (k-1) / Pa) obtained as described above, and the intake pressure detected by the intake pressure Pa and intake temperature sensor 62. The temperature Ta is applied to the above equation (1) to obtain the throttle passage air flow rate mt (k−1).

(Intake valve model M12)
The intake valve model M12 includes an intake pipe section temperature Pm and an intake pipe section temperature that is 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 air that flows around the intake valve 32 and flows into the cylinder (combustion chamber 25) from the downstream temperature Tm or the like. The pressure in the cylinder during 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. 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 M12 is a generalized mathematical expression that represents the in-cylinder inflow air flow rate mc 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 table MapC is stored 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 table MapD is stored in the ROM 72.

  The intake valve model M12 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-1th estimation by a first intake pipe model M13, which will be described later. The intake air temperature Ta is applied to the above equation (3) to estimate the in-cylinder inflow air flow rate mc (k-1).

(First intake pipe model M13)
The first intake pipe model M13 is a generalized mathematical expression representing the present model, and represents the following expression (4) based on the law of conservation of mass regarding the air in the intake pipe portion (predetermined region of the intake passage). The following formula (5) based on the energy conservation law regarding the air in the intake pipe when assuming that the heat transfer energy is 0, which is a generalized equation, the flow rate of air flowing into the intake pipe (ie, From the flow rate of air passing through the throttle (mt), the intake air temperature Ta, and the flow rate of air flowing out from the intake pipe (that is, the flow rate of air flowing into the cylinder) mc, the pressure in the intake pipe (throttle valve downstream pressure) Pm and the temperature in the intake pipe (throttle) This is a model for determining the 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 first intake pipe model M13 includes the following equation (6) and equation (7) obtained by discretizing the equations (4) and (5) by the difference method, and the throttle obtained by the throttle model M11. Passing air flow rate mt (k-1), in-cylinder inflow air flow rate mc (k-1) acquired by the intake valve model M12, current intake air temperature Ta, and estimated at the time of the (k-1) th estimation by this model The latest intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (based on the intake pipe internal pressure Pm (k-1), intake pipe internal temperature Tm (k-1), and time step Δt. k) is estimated. However, when the estimation of the intake pipe internal pressure Pm and the intake pipe internal temperature Tm has never been performed (when the first estimation is performed by this model (in this example, when the operation of the internal combustion engine 10 is started)), The one intake pipe model M13 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)

Here, the derivation process of the equation (4) and the equation (5) describing the first intake pipe model M13 will be described. First, Equation (4) based on the mass conservation side for the air in the intake pipe section is studied. Assuming that the total air amount in the intake pipe is M, the amount of change (time change) per unit time of the total air amount M is the same as the throttle passage air flow rate mt corresponding to the flow rate of air flowing into the intake pipe. Since this is the difference between the in-cylinder inflow air flow rate mc corresponding to the flow rate of air flowing out from the intake pipe, the following equation (8) based on the law of conservation of mass is obtained.
dM / dt = mt−mc (8)

Further, assuming that the pressure and temperature of the air in the intake pipe are spatially uniform, the following equation (9) based on the state equation is obtained. Then, substituting the following equation (9) into the above equation (8) to eliminate the total air amount M and considering that the volume Vm of the intake pipe portion does not change, the above equation (4) based on the law of conservation of mass Is obtained.
Pm ・ Vm ＝ M ・ R ・ Tm (9)

  Next, the above equation (5) based on the energy conservation law for the air in the intake pipe section will be examined. The amount of change (d (M ・ Cv ・ Tm) / dt) per unit time of the energy M ・ Cv ・ Tm (Cv is the constant volume specific heat of air) of the air in the intake pipe Increase in air energy (energy given to the air in the intake pipe per unit time) and decrease in air energy in the intake pipe per unit time (deprived from the air in the intake pipe per unit time) Energy). In the following, it is assumed that all of the energy of the air in the intake pipe part contributes to the temperature rise (that is, the kinetic energy is ignored).

  Assuming that the heat transfer energy, which is the heat energy transferred from the wall surface of the intake pipe portion to the air in the intake pipe portion, is 0, the increase in the energy of the air in the intake pipe portion is the intake pipe per unit time. It is only the energy (the energy of the air that flows into the intake pipe unit per unit time, that is, the inflow energy) held by the air that flows into the section. This inflow energy is expressed as Cp · mt · Ta. Here, Cp is the constant pressure specific heat of air. On the other hand, the decrease in the energy of the air in the intake pipe portion is the energy (the energy of the air flowing out from the intake pipe portion, that is, the outflow energy) Cp · mt · Tic held by the air flowing out from the intake pipe portion.

Accordingly, the following equation (10) based on the energy conservation law regarding the air in the intake pipe portion is obtained.
d (M ・ Cv ・ Tm) / dt = Cp ・ mt ・ Ta−Cp ・ mc ・ Tm (10)

By the way, the specific heat ratio κ is expressed by the following formula (11), and the Meyer relationship is expressed by the following formula (12). Therefore, the above formula (9) (Pic · Vic = M · R · Tic), the following formula (11) and the following formula The equation (5) is obtained by modifying the equation (10) using the equation (12). Here, it is considered that the volume Vm of the intake pipe portion does not change.
κ = Cp / Cv (11)
Cp = Cv + R (12)

(Intake valve model M14)
The intake valve model M14 includes a model similar to the intake valve model M12. In the intake valve model M14, 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 first intake pipe model M13, the current intake air temperature Ta, and Is the 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. Find mc (k). The intake valve model M14 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 until valve opening (intake valve opening time) Tint.

(Second air model M20)
The second air model M20 differs from the first air model M10 only in that it includes a second intake pipe model M23 instead of the first intake pipe model M13 and a heat transfer model M24. Hereinafter, this difference will be mainly described.

  The second air model M20 includes a throttle valve opening (predicted throttle valve opening) TAe estimated by the electronically controlled throttle valve model M1, a surge tank wall surface temperature Tst estimated by the intake passage wall surface temperature estimating means M2, and an intake. Estimate the in-cylinder air amount KL at a time earlier than the current time based on the manifold wall temperature Tim and a physical model constructed based on physical laws such as the energy conservation law, momentum conservation law, and mass conservation law It has become. This physical model is disclosed in detail in Japanese Patent Application Laid-Open No. 2004-293546.

As shown in FIG. 4, the second air model M20 includes a throttle model M21, an intake valve model M22, a second intake pipe model M23, a heat transfer model M24, and an intake valve model M25.
The throttle model M21, the intake valve model M22, and the intake valve model M25 are the same models as the throttle model M11, the intake valve model M12, and the intake valve model M14 provided in the first air model M10.

(Second intake pipe model M23)
In the second intake pipe model M23, instead of the above equation (5) based on the energy conservation law regarding the air in the intake pipe section when the heat transfer energy is assumed to be 0, the heat transfer energy is the air in the intake pipe section. This is different from the first intake pipe model M13 in the first air model M10 only in that a mathematical formula based on an energy conservation law that is handled as an increase in the amount of energy is used.

More specifically, the increase in the energy of the air in the intake pipe portion is the sum of the heat transfer energy and the inflow energy unless it is assumed that the heat transfer energy is zero. Therefore, the mathematical formula based on the energy conservation law for the air in the intake pipe in this model is the thermal energy (heat transfer energy per unit time) Q transferred from the wall of the intake pipe to the air in the intake pipe per unit time Is added to the inflow energy. That is, by adding the heat transfer energy Q to the right side of the above formula (10), the following formula (13) is obtained as a formula based on the above energy conservation law.
d (M ・ Cv ・ Tm) / dt = Cp ・ mt ・ Ta−Cp ・ mc ・ Tm + Q (13)

Similar to the first intake pipe model M13, the above expression (9), the above expression (11), and the above expression (12) are used to modify the above expression (13) to generalize this model. Among the above formulas, the following formula (14) which is a formula based on the energy conservation law regarding the air in the intake pipe portion is obtained.
dPm / dt = κ ・ (R / Vm) ・ (mt ・ Ta−mc ・ Tm + Q / Cp)… (14)

The second intake pipe model M23 includes the above expression (6), the following expression (15) obtained by discretizing the above expression (14) by the difference method, and the throttle passage air flow rate mt (k obtained by the throttle model M21. -1), in-cylinder inflow air flow rate mc (k-1) acquired by the intake valve model M22, heat transfer energy Q (k-1) acquired by a heat transfer model M24 described later, and the current intake air Based on the temperature Ta, the intake pipe internal pressure Pm (k-1) and the intake pipe internal temperature Tm (k-1) estimated at the time of the (k-1) th estimation by this model, and the time step Δt, the latest Intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (k) are estimated.
Pm (k) = Pm (k-1) + Δt ・ κ ・ (R / Vm) ・ (mt (k-1) ・ Ta−mc (k-1) ・ Tm (k-1)
+ Q (k-1) / Cp)… (15)

(Heat transfer model M24)
The heat transfer model M24 is a model for estimating the heat transfer energy Q per unit time used in the second intake pipe model M23 from the surge tank wall surface temperature Tst, the intake manifold wall surface temperature Tim, the intake pipe internal temperature Tm, and the like.

The heat transfer energy Q is transferred from the inner wall surface of the surge tank 42 to the air in the surge tank 42 (surge tank heat transfer energy) Qst and from the inner wall surface of the intake manifold 41 to the air in the intake manifold 41. The sum of the heat energy (intake manifold heat transfer energy) Qim is expressed as the following equation (16).
Q = Qst + Qim (16)

By the way, since air stays in the surge tank 42 for a relatively long time, it is considered that heat transfer between the inner wall surface of the surge tank 42 and the air in the surge tank 42 is mainly heat transfer by natural convection. be able to. Therefore, the heat transfer model M24 is a generalized mathematical expression representing a part of this model, and the surge tank heat transfer energy Qst is obtained according to the following formula (17) and the following formula (18) based on an empirical rule.
Qst ＝ Ast ・ hwst ・ (Tst−Tm) (17)
hwst = f1 (Tst−Tm) (18)

  Here, Ast is a value corresponding to the surface area of the inner wall surface of the surge tank 42, and hwst is a natural convection heat transfer coefficient. Further, as shown in FIG. 5, the function f1 is a function having a substantially constant value regardless of the temperature difference (Tst−Tm) that is the difference between the surge tank wall surface temperature Tst and the intake pipe internal temperature Tm. . The function f1 may be a function having a larger value as the temperature difference (Tst−Tm) becomes larger (a function f1 that increases monotonously with respect to the temperature difference (Tst−Tm)).

On the other hand, since air passes in the intake manifold 41 in a relatively short time, heat transfer between the inner wall surface of the intake manifold 41 and the air in the intake manifold 41 is mainly by forced convection. Can be considered. Therefore, the heat transfer model M24 is a generalized mathematical expression representing a part of the model, and the intake manifold heat transfer energy Qim is obtained according to the following formula (19) and the following formula (20) based on an empirical rule.
Qim ＝ Aim ・ hwim ・ (Tim−Tm)… (19)
hwim ＝ f2 (mc)… (20)

Here, Aim is a value corresponding to the surface area of the inner wall surface of the intake manifold 41, and hwim is a forced convection heat transfer coefficient. Further, as shown in FIG. 6, the function f2 is a function having a larger value as the in-cylinder inflow air flow rate mc increases. In this example, f2 = kmc · mc ^0.8 (kmc is a constant).

  The heat transfer model M24 includes the intake pipe temperature Tm (k-1) estimated at the time of the (k-1) th estimation by the second intake pipe model M23 and the surge tank wall surface estimated by the intake passage wall surface temperature estimation means M2. The heat transfer energy Q (k−1) is estimated by applying the temperature Tst and the intake manifold wall surface temperature Tim to the above equations (16) to (20).

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

(Target throttle valve opening setting)
The CPU 71 of the electric control device 70 executes a target throttle valve opening setting routine (not shown) for achieving the function of the electronic control throttle valve logic A1 every elapse of a predetermined calculation cycle Δt1 (2 ms in this example). It is like that.

  Therefore, when the predetermined timing is reached, the CPU 71 maintains the target throttle valve opening degree TAt (1) to TAt (Ntd) set by the execution of this routine until the previous time while maintaining the order of values. Shift from TAt (0) to TAt (Ntd-1). Here, Ntd is a value (32 in this example) obtained by dividing the delay time TD (64 ms in this example) by the calculation cycle Δt1.

  Next, the CPU 71 reads the accelerator pedal operation amount Accp detected by the accelerator opening sensor 68, and based on the read accelerator pedal operation amount Accp and the table MapTAt, the temporary target throttle valve opening amount TAt1 (= MapTAt (Accp)). Then, the CPU 71 determines the target value (target throttle valve opening) TAt (Ntd) of the throttle valve opening at the time point (the time when the throttle valve opening can be estimated) ahead of the current time by the delay time TD. Set to provisional target throttle valve opening TAt1.

  Then, the CPU 71 sends a drive signal corresponding to the set current target throttle valve opening degree TAt (0) to the throttle valve actuator 45a. In this way, a drive signal based on the accelerator pedal operation amount Accp detected at the time point before the current time by the delay time TD is sent to the throttle valve actuator 45a at the current time point. Thereby, the actual throttle valve opening TA coincides with the current target throttle valve opening TAt (0) without much delay after the throttle valve actuator 45a receives the drive signal.

(Throttle valve opening estimation)
On the other hand, the CPU 71 executes a throttle valve opening estimation routine (not shown) for achieving the function of the electronic control throttle valve model M1 following the target throttle valve opening setting routine.

  Therefore, when the execution of the target throttle valve opening setting routine is finished, the CPU 71 starts the processing of the throttle valve opening estimation routine, and predicts the predicted throttle valve opening TAe (Ntd at a time earlier than the current time by the delay time TD. ) Is set to the target throttle valve opening degree TAt (Ntd) at a time point earlier than the current time set in the target throttle valve opening degree setting routine by the delay time TD. Therefore, the CPU 71 executes this routine to estimate (predict) the throttle valve opening TA from the present time to the previous time by the delay time TD (ie, the predicted throttle valve opening TAe ( 0) to TAe (Ntd) are always maintained.

(Air model selection)
On the other hand, the CPU 71 executes the air model selection routine shown in the flowchart of FIG. 7 every elapse of a predetermined calculation cycle Δt2 (8 ms in this example).

  Therefore, when the predetermined timing comes, the CPU 71 starts processing from step 700 and proceeds to step 705 to read the intake air temperature Ta detected by the intake air temperature sensor 62. Next, the CPU 71 proceeds to step 710 and reads the cooling water temperature Tw detected by the cooling water temperature sensor 67.

  Then, the CPU 71 proceeds to step 715, and based on the table MapTst, the intake air temperature Ta read in the step 705, and the cooling water temperature Tw read in the step 710, the heat energy. Estimate (acquire) the surge tank wall surface temperature Tst as one of the operating state quantities affecting the ratio. Next, the CPU 71 proceeds to step 720, and as one of the operation state quantities affecting the heat energy ratio based on the table MapTim and the cooling water temperature Tw read in the step 710. Estimate (acquire) intake manifold wall surface temperature Tim.

  Next, the CPU 71 proceeds to step 725 to calculate a predetermined time interval from the present time based on the predicted throttle valve opening degree TAe (m) (m is an integer of 0 to Ntd) set by the throttle valve opening degree estimation routine. The predicted throttle valve opening degree TAe (n) estimated as the throttle valve opening degree closest to the time point after Δt0 is read as the predicted throttle valve opening degree TA (k). That is, the CPU 71 acquires the predicted throttle valve opening degree TA (k) as one of the operation state quantities that influence the thermal energy ratio.

  Here, the time interval Δt0 is a predetermined fuel injection amount determination time before the fuel injection start timing of a specific cylinder (the final time when the fuel injection amount needs to be determined, in this example, the crank angle of the specific cylinder is From the start of the intake stroke (when the intake valve 32 of the cylinder is opened) to the end of the intake stroke from the top dead center (increase the crank angle advanced by 75 ° from the intake top dead center) Until the intake valve 32 is closed). The value k is an integer to which 1 is added every time execution of this routine is started, and represents the number of times execution of this routine is started.

  Hereinafter, for convenience of explanation, the time corresponding to the predicted throttle valve opening TA (k-1) read in step 725 at the previous calculation time (when this routine is executed for the (k-1) th time) is the previous time. Estimated time t1 is set, and the time corresponding to the predicted throttle valve opening TA (k) read in step 725 at the current calculation time (time when this routine is executed k times) is set as the current estimated time t2. (Refer to FIG. 8, which is a schematic diagram showing the relationship among the time when the throttle valve opening can be estimated, the predetermined time interval Δt0, the previous estimated time t1, and the current estimated time t2.)

  Then, the CPU 71 proceeds to step 730 and determines whether or not the driving state quantity condition is satisfied (the driving state quantity condition is satisfied). Here, the operating state quantity condition is (1) the surge tank wall surface temperature Tst estimated in the above step 715 is lower than the threshold temperature α, and (2) the intake manifold wall surface estimated in the above step 720. The temperature Tim is lower than the threshold temperature β, and (3) the predicted throttle valve opening TA (k−1) read in step 725 at the previous calculation time is larger than the threshold opening γ. This is the condition described above. In addition, that the process of step 715-step 730 is performed respond | corresponds to the function of a driving | running state amount condition determination means being achieved.

  First, at the time immediately after the operation of the internal combustion engine 10 is started, when the driver operates the accelerator pedal 81, the accelerator pedal operation amount Accp becomes relatively large. As a result, the throttle valve opening TA is set to the threshold value. The case where the opening degree γ becomes larger will be described. In this case, since the temperature of the internal combustion engine 10 is relatively low, the surge tank wall surface temperature Tst is lower than the threshold temperature α, and the intake manifold wall surface temperature Tim is lower than the threshold temperature β.

Accordingly, the CPU 71 determines “Yes” in step 730 and proceeds to step 735 to set the value of the use air model flag Xam to “1”. Here, the used air model flag Xam is a flag representing an air model to be used. If the value is “1”, the first air model M10 is to be used, and if it is “2”. Indicates that the second air model M20 is scheduled to be used. As will be described later, the value of the operating air model flag Xam is set to “1” when the operating state quantity condition is satisfied (the operating state quantity condition is satisfied) in this routine, and the operating state quantity condition is satisfied. It is set to “2” when not (operating state quantity condition is not satisfied). Note that the execution of the process of step 735 corresponds to the achievement of part of the function of the cylinder air amount estimation switching means.
Then, the CPU 71 proceeds to step 799 to end this routine once.

(In-cylinder air volume estimation)
On the other hand, the CPU 71 executes an in-cylinder air amount estimation routine shown by a flowchart in FIG. 9 following the air model selection routine.

  Accordingly, when the predetermined timing is reached, the CPU 71 starts the process from step 900 and proceeds to step 905, where the throttle model M11 (or the throttle model M21) uses the throttle passage air flow rate mt (k−1) at the previous estimated time t1. )

  More specifically, the CPU 71 determines a value based on the predicted throttle valve opening TA (k−1) read in the step 725 at the previous execution of the air model selection routine and the table MapCTAT. Calculate CtAt (TA (k-1)).

  Further, the CPU 71 detects the intake air pressure detected by the intake pressure sensor 63 at the previous estimated time point t1 obtained in step 920 or step 955, which will be described later, at the previous execution of this routine. A value Φ (Pm (k−1) / Pa) is obtained based on the value Pm (k−1) / Pa divided by Pa and the table MapΦ.

  In addition, the CPU 71 determines the value CtAt (TA (k-1)) and the value Φ (Pm (k-1) / Pa) obtained, and the intake air temperature Ta detected by the intake air pressure Pa and the intake air temperature sensor 62. Is applied to the equation shown in step 905 based on the equation (1) representing the throttle model M11 to obtain the throttle passage air flow rate mt (k-1).

Next, the CPU 71 proceeds to step 910 to obtain the in-cylinder inflow air flow rate mc (k-1) at the previous estimated time t1 from the intake valve model M12 (or intake valve model M22).
More specifically, the CPU 71 determines the values c and c based on the engine speed NE detected by the crank position sensor 66, the current open / close timing VT of the intake valve 32, the table MapC, and the table MapD. Determine the value d. Further, the CPU 71 applies the obtained value c and value d to the equation shown in step 910 based on the equation (3) representing the intake valve model M12 to thereby calculate the in-cylinder inflow air flow rate mc (k-1). Ask.

  Then, the CPU 71 proceeds to step 915 to determine whether or not the value of the use air model flag Xam is “1”. At this time, since the value of the use air model flag Xam is “1”, the CPU 71 determines “Yes” in step 915 and proceeds to step 920. Note that the execution of the processing of step 915 corresponds to the achievement of part of the function of the cylinder air amount estimation switching means.

In step 920, the CPU 71 obtains the (latest) intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (k) at the current estimated time t2 from the first intake pipe model M13.
More specifically, the CPU 71 calculates the time step Δt (= t2−t1) that is the difference between the current estimated time t2 and the previous estimated time t1, and the obtained throttle passage air flow rate mt (k−1). The in-cylinder inflow air flow rate mc (k-1) obtained above, the intake pipe internal pressure Pm (k-1) and the intake pipe internal temperature Tm () at the previous estimated time t1 obtained during the previous execution of this routine (k-1) and (6) and (7) obtained by discretizing the equations (4) and (5) representing the first intake pipe model M13 (the equation (difference equation) shown in step 920) ) To obtain the intake pipe internal pressure Pm (k) and the intake pipe internal temperature Tm (k) at the estimated time t2.

Then, the CPU 71 proceeds to step 925 to obtain the (latest) in-cylinder inflow air flow rate mc (k) at the current estimated time t2 from the intake valve model M14 (or intake valve model M25).
More specifically, the CPU 71 obtains the intake pipe internal pressure Pm (k) and the intake pipe internal temperature Tm (k) at the current estimated time t2 obtained in step 920, and obtained in the above step 910. The in-cylinder inflow air flow rate mc (k) is obtained by applying the value c and the value d to the equation shown in step 925 based on the equation (3) representing the intake valve model M14.

Next, the CPU 71 proceeds to step 930, and based on the detected engine speed NE and the current opening / closing timing VT of the intake valve 32, the intake valve opening time (intake air to introduce air into the cylinder) The time from when the valve 32 is opened until it is closed) Tint is obtained, and in the subsequent step 935, the intake valve opening time Tint obtained in the same step 925 is calculated as the in-cylinder inflow air flow rate mc ( By multiplying k), the in-cylinder air amount KL at the present estimated time t2 is obtained.
Then, the CPU 71 proceeds to step 999 to end this routine once.

  The in-cylinder air amount KL estimated as described above will be further described. Here, for convenience of explanation, the calculation period Δt2 of the in-cylinder air amount estimation routine is sufficiently shorter than the time that elapses while the crankshaft 24 rotates by 360 °, and the time interval Δt0 is Consider the case where there is no significant change. At this time, the current estimation time point t2 shifts to the previous time point approximately by the calculation cycle Δt2 every time the above-described in-cylinder air amount estimation routine is executed. When this routine is executed at the fuel injection amount determination time, the current estimated time t2 substantially coincides with the intake stroke end time (when the intake valve 32 of the specific cylinder is closed). Therefore, the in-cylinder air amount KL calculated at this time is an estimated value of the in-cylinder air amount at the end of the intake stroke.

  Note that the execution of the processing of Step 905, Step 910 and Step 920 to Step 935 corresponds to the achievement of the function of the first in-cylinder air amount estimation means.

(Fuel injection amount determination)
On the other hand, the CPU 71 executes a fuel injection amount determination routine (not shown) every time the fuel injection amount determination time comes. Note that the execution of the fuel injection amount determination routine corresponds to the achievement of the function of the injection amount determination logic A2.

  Therefore, when the predetermined timing is reached, the CPU 71 starts the process of the fuel injection amount determination routine, determines the target air-fuel ratio AbyF according to the operating state of the internal combustion engine 10, and the latest obtained at the time of execution of the routine. The fuel injection amount fi is determined by multiplying the value obtained by dividing the in-cylinder air amount KL by the determined target air-fuel ratio AbyF by a constant Kf. Then, the CPU 71 sends an instruction signal corresponding to the determined fuel injection amount fi to the injector 39. In this example, the constant Kf is set to “1”, and the target air-fuel ratio AbyF is set to the stoichiometric air-fuel ratio.

  As described above, when the operating state quantity condition is satisfied, the in-cylinder air quantity using the first air model M10 constructed based on the energy conservation law under the assumption that the heat transfer energy is zero. KL is estimated.

  In this case, since the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim are sufficiently low, the heat transfer energy is sufficiently small. Further, in this case, since the throttle valve opening TA is sufficiently large, the flow rate of air passing through the intake pipe portion is sufficiently large. Therefore, the thermal energy ratio is sufficiently small.

  As a result, the in-cylinder air amount KL can be estimated with sufficiently high accuracy by using the first air model M10. Furthermore, the calculation load can be reduced as compared with the case where the second air model M20 is used. That is, when the operating state quantity condition is satisfied, the calculation load can be reduced while maintaining the estimation accuracy of the cylinder air quantity KL as high as possible.

  Next, the description will be continued with respect to the case where the accelerator pedal operation amount Accp becomes relatively small as the driver operates the accelerator pedal 81, and as a result, the throttle valve opening degree TA becomes smaller than the threshold opening degree γ.

  In this case, when the CPU 71 starts the processing of the air model selection routine of FIG. 7 and proceeds to step 730, the CPU 71 determines “No” in step 730 and proceeds to step 740. In step 740, the CPU 71 sets the value of the use air model flag Xam to “2”, proceeds to step 799, and once ends this routine. Note that the execution of the processing of step 740 corresponds to the achievement of part of the function of the cylinder air amount estimation switching means.

  Further, when the CPU 71 starts executing the in-cylinder air amount estimation routine of FIG. 9, the CPU 71 proceeds to step 915 in which it is determined whether or not the value of the use air model flag Xam is “1”. In step 915, “No” is determined, and the process proceeds to step 950, and the process proceeds to step 1000 shown in the flowchart of FIG. 10 in order to obtain the heat transfer energy Q (k−1) by the heat transfer model M24.

  Then, the CPU 71 proceeds to step 1005 and reads the intake water temperature Ta detected by the intake air temperature sensor 62 and reads the cooling water temperature Tw detected by the cooling water temperature sensor 67 in the subsequent step 1010.

  Next, the CPU 71 proceeds to step 1015 to determine the surge tank wall surface temperature Tst based on the intake air temperature Ta read in step 1005, the coolant temperature Tw read in step 1010, and the table MapTst. presume. Note that the execution of the processing of step 1015 corresponds to the achievement of part of the function of the intake passage wall surface temperature estimation means M2.

  Then, the CPU 71 proceeds to step 1020, and at the previous execution of the in-cylinder air amount estimation routine, the intake pipe portion internal temperature Tm (k-1) at the previous estimated time t1 obtained in step 920 or step 955 described later. ) Is obtained from the value Tst−Tm (k−1) obtained by subtracting from the surge tank wall surface temperature Tst estimated in step 1015 and the function f1 to obtain the natural convection heat transfer coefficient hwst.

  Next, the CPU 71 proceeds to step 1025 to represent the value Tst−Tm (k−1) and the natural convection heat transfer coefficient hwst obtained in step 1020 as the heat transfer model M24 (17). The surge tank heat transfer energy Qst is estimated by applying to the equation shown in step 1025 based on the equation.

  Next, the CPU 71 proceeds to step 1030 to estimate the intake manifold wall surface temperature Tim based on the cooling water temperature Tw read in step 1010 and the table MapTim. The execution of the process of step 1030 corresponds to the achievement of a part of the function of the intake passage wall surface temperature estimating means M2.

  Then, the CPU 71 proceeds to step 1035, and the in-cylinder inflow air flow rate mc (k-1) at the previous estimated time t1 obtained in the step 910 when the in-cylinder air amount estimation routine is executed this time, and the above The forced convection heat transfer coefficient hwim is obtained based on the function f2.

  Next, the CPU 71 proceeds to step 1040, and at the previous execution of the in-cylinder air amount estimation routine, the intake pipe section internal temperature Tm (k-1) at the previous estimated time t1 obtained in step 920 or step 955 described later. ) Is subtracted from the intake manifold wall surface temperature Tim estimated in step 1030, and the forced convection heat transfer coefficient hwim determined in step 1035 is the heat transfer model. The intake manifold heat transfer energy Qim is estimated by applying the equation shown in step 1040 based on the equation (19) representing M24.

Then, the CPU 71 proceeds to step 1045 to add the intake manifold heat transfer energy Qim estimated at step 1040 to the surge tank heat transfer energy Qst estimated at step 1025, thereby transferring the heat transfer at the previous estimated time t1. Estimate energy Q (k-1).
Then, the CPU proceeds to step 955 in FIG.

In step 955, the CPU 71 obtains the (latest) intake pipe internal pressure Pm (k) and intake pipe internal temperature Tm (k) at the current estimated time t2 from the second intake pipe model M23.
More specifically, the CPU 71 obtains the heat transfer energy Q (k−1) at the previous estimated time t1 estimated in step 950, the time step Δt (= t2−t1), and the above-described calculation. Throttle passage air flow rate mt (k-1), the above-obtained in-cylinder inflow air flow rate mc (k-1), and the intake pipe internal pressure Pm (at the previous estimated time t1 obtained at the previous execution of this routine) k-1) and the intake pipe internal temperature Tm (k-1), and the expressions (6) and (15) obtained by discretizing the expressions (4) and (14) representing the second intake pipe model M23 ( Applying to the equation (difference equation) shown in step 955, the intake pipe internal pressure Pm (k) and the intake pipe internal temperature Tm (k) at the current estimated time t2 are obtained.

Next, the CPU 71 proceeds to the steps after step 925, obtains the in-cylinder air amount KL at the current estimation time t2, and once ends the routine of FIG.
Note that the execution of the processing of Step 905, Step 910, Step 950, Step 955, and Step 925 to Step 935 corresponds to the achievement of the function of the second cylinder air amount estimation means.

Thus, when the operating state quantity condition is not satisfied, the in-cylinder air quantity KL is estimated using the second air model M20.
In this case, since the throttle valve opening TA is relatively small, the flow rate of air passing through the intake pipe is relatively small. That is, since the inflow energy is relatively small, the thermal energy ratio is relatively large.

  Therefore, as described above, by using the second air model M20, it is possible to estimate the in-cylinder air amount KL with high accuracy even if the in-cylinder air amount KL changes relatively largely due to the heat transfer energy Q. it can.

  On the other hand, when the surge tank 42 is heated by the heat energy generated in the combustion chamber 25 as the internal combustion engine 10 is operated, the surge tank wall surface temperature Tst becomes higher than the threshold temperature α, or the intake manifold 41 The case where the intake manifold wall surface temperature Tim becomes higher than the threshold temperature β by being heated will continue to be described.

  In this case as well, the cylinder air amount KL is estimated using the second air model M20, as in the case where the throttle valve opening TA is smaller than the threshold opening γ. In this case, since the surge tank wall surface temperature Tst or the intake manifold wall surface temperature Tim is relatively high, the heat transfer energy is relatively large. Therefore, in this case, the thermal energy ratio is relatively large. Therefore, as described above, by using the second air model M20, it is possible to estimate the in-cylinder air amount KL with high accuracy even if the in-cylinder air amount KL changes relatively largely due to the heat transfer energy Q. it can.

  As described above, according to the embodiment of the air amount estimation device for the internal combustion engine according to the present invention, the cylinder is obtained by using the first air model M10 (first physical model) when the operating state amount condition is satisfied. The calculation load can be reduced while maintaining the estimation accuracy of the internal air amount KL as high as possible. On the other hand, when the operating state quantity condition is not satisfied, the in-cylinder air can be obtained even if the in-cylinder air amount KL is changed by the heat transfer energy Q by using the second air model M20 (second physical model). The quantity KL can be estimated with high accuracy.

  In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in the above embodiment, (1) the condition that the surge tank wall surface temperature Tst is lower than the threshold temperature α, (2) the condition that the intake manifold wall surface temperature Tim is lower than the threshold temperature β, and (3) The throttle valve opening TA is configured to select an air model to be used based on all three conditions including the condition that the threshold opening γ is larger than the threshold opening γ. (1) to ( The air model to be used may be selected based on one or only two of the three conditions of 3).

  More specifically, the above embodiment uses the conditions (1) and (2) regardless of the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim (the temperature of the intake passage wall surface). It may be configured to select an air model to be used based only on the condition (3). On the other hand, the above embodiment is used based on both the above condition (1) and the above condition (2) regardless of the throttle valve opening TA (without using the above condition (3)). It may be configured to select a scheduled air model. Furthermore, the air model to be used may be selected based on only one of the condition (1) and the condition (2).

In the above embodiment, instead of the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim, a temperature Twall representative of the temperature of the wall surface of the intake passage is acquired, and the acquired temperature Twall is lower than a predetermined threshold temperature. Or may be configured to select the air model that is to be used.
Further, in the above embodiment, the cooling water temperature Tw may be adopted as a physical quantity representing the temperature of the wall surface of the intake passage.

  In the above embodiment, the heat transfer model M24 is a model that takes into account heat transfer by natural convection of air in the surge tank 42 and heat transfer by forced convection of air in the intake manifold 41. However, heat transfer by forced convection of air in the surge tank 42 may be further taken into consideration, and heat transfer by natural convection of air in the intake manifold 41 may be further taken into consideration. The heat transfer model M24 may be a model for obtaining the heat transfer energy Q without distinguishing between heat transfer by natural convection and heat transfer by forced convection.

  In addition, the above-described embodiment is configured to estimate the surge tank wall surface temperature Tst and the intake manifold wall surface temperature Tim based on a pre-stored table. However, the surge tank is based on a physical model or the like without using a table. The tank wall surface temperature Tst and the intake manifold wall surface temperature Tim may be estimated. Moreover, the said embodiment may be provided with the sensor which detects surge tank wall surface temperature Tst and intake manifold wall surface temperature Tim.

1 is a schematic configuration diagram of a system in which an air amount estimation device for an internal combustion engine according to an embodiment of the present invention is applied to a spark ignition multi-cylinder internal combustion engine. FIG. 5 is a functional block diagram of means and a model for determining a fuel injection amount by estimating an in-cylinder air amount. It is a detailed functional block diagram of the 1st air model shown in FIG. It is a detailed functional block diagram of the 2nd air model shown in FIG. It is a graph which shows the function for determining the natural convection heat transfer coefficient used by the heat transfer model shown in FIG. It is a graph which shows the function for determining the forced convection heat transfer coefficient used by the heat transfer model shown in FIG. It is the flowchart which showed the program for selecting the air model which the CPU shown in FIG. 1 performs and is going to be used. FIG. 6 is a schematic diagram showing a relationship among a throttle valve opening estimation possible time, a predetermined time interval Δt0, a previous estimated time t1, and a current estimated time t2. 2 is a flowchart showing a program executed by the CPU shown in FIG. 1 for estimating an in-cylinder air amount. It is the flowchart which showed the program for the heat | fever transfer energy which is a program which CPU shown in FIG. 1 performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder block part, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 34 ... Exhaust port, 35 ... Exhaust valve, 39 ... Injector, 40 ... Intake system, 41 ... Intake manifold, 42 ... Surge tank, 43 ... Intake duct, 45 ... Throttle valve, 45a ... Throttle valve actuator, 62 ... Intake temperature sensor, 63 ... Intake pressure sensor, 64 ... Throttle position sensor, 67 ... Coolant temperature sensor, 68 ... Open accelerator Degree sensor, 70 ... electric control device, 71 ... CPU, 81 ... accelerator pedal, A1 ... electronically controlled throttle valve logic, A2 ... injection amount determining logic, M1 ... electronically controlled throttle valve model, M2 ... intake passage wall surface temperature estimating means , M3 ... Air model selection unit, M10 ... First air model, M20 ... Second air model, 13 ... first intake pipe model, M23 ... second intake pipe model, M24 ... heat transfer model.

Claims (3)

An air amount estimation device for an internal combustion engine,
Under the assumption that the heat transfer energy, which is the heat energy transferred from the wall of the intake passage for introducing the air taken in from the outside into the cylinder to the air in the predetermined region of the intake passage, is zero. First in-cylinder air amount estimation means for estimating an in-cylinder air amount that is the amount of air introduced into the cylinder by using a first physical model constructed based on an energy conservation law relating to air; ,
The heat transfer energy is estimated, and is constructed based on an energy conservation law relating to air in the predetermined region, wherein the heat transfer energy is handled as an increase in the energy of air in the predetermined region. Second in-cylinder air amount estimating means for estimating the in-cylinder air amount by applying the heat transfer energy estimated to the second physical model;
An operating state quantity of the internal combustion engine that affects a heat energy ratio that is a ratio of the heat transfer energy to an increase in air energy in the predetermined region is acquired, and the acquired operating state quantity is the first The magnitude of the difference between the in-cylinder air amount that would be estimated by the in-cylinder air amount estimation unit and the in-cylinder air amount that would be estimated by the second in-cylinder air amount estimation unit is larger than a predetermined size. Driving state quantity condition determining means for determining whether or not the driving state quantity condition of being within the range to be reduced is satisfied,
The in-cylinder air amount is estimated by the first in-cylinder air amount estimating unit when the operating state amount condition determining unit determines that the operating state amount condition is satisfied, while the operating state amount condition determining unit In-cylinder air amount estimation switching means for estimating the in-cylinder air amount by the second in-cylinder air amount estimating means when it is determined that the operating state quantity condition is not satisfied,
An air amount estimation device comprising: In the internal combustion engine air amount estimation device according to claim 1,
The operating state quantity condition determining means acquires the temperature of the wall surface of the intake passage as the operating state quantity, and determines that the operating state quantity condition is satisfied when the temperature of the wall surface is lower than a predetermined threshold temperature. An air amount estimation device configured as described above. In the internal combustion engine air amount estimation device according to claim 1,
The operating state quantity condition determining means obtains, as the operating state quantity, an opening degree of a throttle valve that is disposed in the intake passage and changes the flow rate of air passing through the intake passage by changing the opening degree. And an air amount estimating device for an internal combustion engine configured to determine that the operating state amount condition is satisfied when the opening degree of the throttle valve is larger than a predetermined threshold opening degree.

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