JPH08232751A - Suction air amount estimating device for internal combustion engine - Google Patents

Abstract

PURPOSE: To perform accurate estimation of a cylinder suction air amount by a method wherein the fluctuation of a filling air amount are detected by a detecting means and the primary delay correction factor of a throttle opening is individually set according to a case wherein a filling air amount is increased and a case wherein a filling air amount is decreased. CONSTITUTION: When a suction air amount is estimated by a control unit 50, an amount Gc of suction air to a combustion chamber when an engine is in a steady operation state is determined based on the number of revolutions of an engine and a pressure in a chamber. Further, based on a throttle opening and the pressure in the chamber, the first effective opening area A of a throttle is determined. The primary delay value of an effective opening area A is then determined and the value forms the second effective opening area B of the throttle and an actual suction amount Gc is determined by a formula of Gc= Gc'×(A/B). In this case, the fluctuation of a filling air amount is detected and according to a detecting result, the primary delay correction factor of the throttle opening is set. Based on the primary delay correction factor, the primary delay value of the first effective opening area A is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount estimating apparatus for an internal combustion engine, which estimates the amount of air taken into the internal combustion engine.

[0002]

2. Description of the Related Art In recent years, a method has been proposed in which a fluid dynamics model is applied to the intake system of an internal combustion engine, and a correct cylinder intake air amount is estimated by a model formula. The applicant of the present invention has previously considered that the throttle valve is an orifice in Japanese Patent Laid-Open No. 6-74076, and calculates the throttle passing air amount from the differential pressure before and after the throttle valve using a throttle type flow rate principle formula. We proposed a method to calculate the cylinder intake air amount based on.

[0003]

However, such a fluid dynamics model is premised on an ideal state, and it is difficult to accurately specify various constants (specific heat ratio etc.) used in modeling. In addition, since the equation of fluid dynamics requires calculation of exponentiation, square root, etc., an approximate value is practically used. For these reasons, the modeling error cannot be wiped out.

Therefore, it is extremely important how to reduce the error between the cylinder intake air amount obtained from this model and the actual cylinder intake air amount. In order to improve this point, the present applicant absorbs the error of the model formula without requiring complicated calculation while assuming the fluid dynamics model, and transient state and deterioration of engine operation, variation, secular change, etc. And a method of more accurately estimating the cylinder intake air amount is proposed (Japanese Patent Application No. 5-208835).

The object of the present invention is to further improve the method already proposed, further reduce the error between the cylinder intake air amount obtained from the fluid dynamics model and the actual cylinder intake air amount, and improve the cylinder intake air amount. It is an object of the present invention to provide an intake air amount estimation device for an internal combustion engine, which can estimate more accurately.

[0006]

Therefore, the intake air amount estimating apparatus for an internal combustion engine according to the first aspect of the present invention is configured so that the engine speed Ne,
Based on the first means for detecting the operating state of the internal combustion engine, which includes the throttle opening θTH and the chamber pressure Pb, and at least the engine speed Ne and the chamber pressure Pb detected by the first means, the steady state is established. Second means for determining the intake air amount Gc 'into the combustion chamber during operation, and at least the first means
Means for obtaining the first effective opening area A of the throttle on the basis of the throttle opening θTH and the chamber pressure Pb detected by the means, and the first-order lag value of the first effective opening area A of the throttle. And the fourth effective means for determining the value as the second effective opening area ADELAY of the throttle, the first effective opening area A determined by the third means and the second effective opening area ADELAY determined by the fourth means. By correcting the intake air amount Gc 'on the basis of the following equation, the actual intake air amount Gc is calculated as Gc = Gc' × (A /
ADELAY) and a fifth means for calculating, and the intake system from the throttle to the combustion chamber is modeled and regarded as one chamber, and based on this intake system model, the actual intake air amount sucked into this combustion chamber In the intake air amount estimating apparatus for an internal combustion engine for estimating Gc, the fourth means receives a detection means for detecting an increase or a decrease in the filling air amount Gb filled in the chamber and a detection result of the detection means. Based on the setting means for individually setting the first-order lag correction coefficient B of the throttle opening depending on whether the filled air amount Gb increases or decreases, and the first-order lag correction coefficient B set by this setting means. And a calculating means for obtaining a first-order lag value of the first effective opening area A of the throttle.

Further, in the intake air amount estimating apparatus for an internal combustion engine according to a second aspect of the present invention, the above-mentioned detecting means is means for detecting an increase or decrease in the filled air amount Gb based on an increase or decrease in the throttle opening θTH. Configure as.

Further, in the intake air amount estimating apparatus for an internal combustion engine according to a third aspect, the detecting means according to the first and second aspects is provided with the intake manifold volume change, the valve timing change of the internal combustion engine, the atmospheric pressure change and the target. Based on at least one of the changes in the air-fuel ratio,
It is configured as a means for detecting the increase or decrease of the filling air amount Gb.

In the present invention, the steady operation state means a period during which the increase / decrease of the filling air amount Gb is substantially constant and substantially constant, and the transient operation state means the filling air amount Gb.
The period during which b is fluctuating.

[0010]

In the intake air amount estimating apparatus for the internal combustion engine according to the first aspect, the detecting means detects the increase or decrease of the filling air amount Gb, and based on the detection result, the setting means detects the filling air amount Gb. The first-order lag correction coefficient B for the throttle opening is individually set depending on whether the value increases or decreases. By performing such a setting, the behavior of the intake air differs when the filling air amount Gb increases and decreases, but the intake air behaves appropriately when the filling air amount Gb increases and decreases. The first-order delay correction coefficient B of the throttle opening is set.

Further, in the intake air amount estimating apparatus for the internal combustion engine according to the second aspect of the present invention, attention is paid to the movement of the throttle valve which is a main factor when the filling air amount Gb changes. That is,
When the throttle valve shifts in the opening direction, the operating state is in the accelerating state, and in this case, the filling air amount Gb tends to increase. Further, when the throttle valve shifts in the closing direction, the operating state is in a decelerating state, and in this case, the filling air amount Gb tends to decrease. In this way, by detecting the movement of the throttle valve by the detecting means, it is possible to detect the increase or decrease of the filling air amount Gb.

Further, in the intake air amount estimating apparatus for the internal combustion engine according to the third aspect, the filling air amount Gb is caused not only by the movement of the throttle valve but also by the volume change of the intake manifold.
Is increased or decreased, the increase or decrease of the filling air amount Gb can be detected by detecting them by the detection means.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a four-cylinder internal combustion engine, in which the intake air introduced from an air cleaner 14 arranged at the tip of an intake passage 12 is adjusted in its flow rate by a throttle valve 16 and a surge tank. It is introduced into the first to fourth cylinders via the intake manifold 18 and the intake manifold 20. An injector 2 is provided near the intake valve (not shown) of each cylinder.
2 is provided and fuel is injected from here. The air-fuel mixture in which the injected fuel and intake air are integrated is ignited by a spark plug in each cylinder and burned to drive a piston of the internal combustion engine. The exhaust gas after combustion is discharged to the exhaust manifold 24 through the exhaust valve, and the exhaust pipe 26
After that, it is purified by the three-way catalytic converter 28 and discharged to the outside of the engine.

A crank angle sensor 34 for detecting the crank angle position of the piston is provided in the distributor (not shown) of the internal combustion engine. In addition to this, a throttle for detecting the opening degree θTH of the throttle valve 16 is provided. An opening sensor 36 and an intake pressure sensor 38 for detecting the intake pressure (chamber pressure) Pb downstream of the throttle valve 16 as an absolute pressure are also provided. An atmospheric pressure sensor 40 that detects the atmospheric pressure Pa, an intake air temperature sensor 42 that detects the temperature TA of the intake air, and a humidity sensor 44 that detects the humidity of the intake air are provided upstream of the throttle valve 16. . Further, the intake passage 12 is provided with a bypass passage 32 for bypassing the intake passages before and after the throttle valve 16 for adjusting the secondary air amount. By driving the solenoid valve 90, the bypass passage 32 is provided. Open and close. In the exhaust system, a wide-range air-fuel ratio 46 including an oxygen concentration detecting element is provided downstream of the exhaust manifold 24 and upstream of the three-way catalytic converter 28 to detect the air-fuel ratio of the exhaust gas. The outputs of these sensors 34 and the like are output to the control unit 5
Sent to 0.

FIG. 2 shows the details of the control unit. The output of the wide range air-fuel ratio sensor 46 is input to the detection circuit 52 and the air-fuel ratio A / F is detected. The output of the detection circuit 52 is A /
CPU 56, ROM 58 and R via D conversion circuit 54
It is taken into the microcomputer composed of AM60 and stored in RAM60. Similarly, the analog output of the throttle opening sensor 36 and the like is supplied to the level conversion circuit 6
2, multiplexer 64 and second A / D conversion circuit 66
Is input to the microcomputer via the. In addition, the output of the crank angle sensor 34 is the waveform shaping circuit 68.
After the waveform is shaped by, the output value is counted by the counter 70, and the count value is input into the microcomputer. In the microcomputer, the CPU 56 calculates a control value, which will be described later, according to the instruction stored in the ROM 58, and drives the injector 22 of each cylinder via the drive circuit 72.

Here, the basic principle of the method for estimating the cylinder intake air amount using the fluid dynamics model, which is adopted in this embodiment, will be schematically described (see Japanese Patent Application No. 6-197, 23).
No. 8).

In this method, the behavior of air in the intake system of an internal combustion engine is modeled by a physical formula (FIG. 3), and the amount of air passing through the throttle Gth and the amount of air filled in the chamber Gb are used to calculate the cylinder interior. This is a method of estimating the intake air amount (actual intake air amount) Gc that is taken into the air. It should be noted that the term "chamber" as used herein means not only a so-called surge tank-corresponding portion but also all portions through which air flows from the throttle to the intake port, and means an effective volume that actually acts as a chamber. .

First, as shown in FIG. 4, a throttle projection area (throttle projection area in the longitudinal direction of the intake pipe) S is obtained from the throttle opening θTH according to a preset characteristic. On the other hand, as shown in FIG. 5, the throttle opening θTH
And a coefficient C (product of flow coefficient α and expansion correction coefficient ε of gas) according to another characteristic set for the intake pressure (chamber pressure) Pb, and multiplied by both to obtain the effective opening area A of the throttle. Since the throttle does not function as a throttle in the so-called throttle fully open region, the throttle fully open region is obtained as a critical value for each engine speed, and when the detected throttle opening exceeds this critical value, This critical value is the throttle opening.

Next, the air amount Gb in the chamber is obtained from the equation 1 based on the equation of state of the gas, and the air amount ΔGb filled in the chamber this time is obtained from the pressure change ΔP in the chamber according to the equation 2. If the amount of air filled in the chamber this time is naturally not taken into the cylinder combustion chamber, the amount of intake air Gc per unit time ΔT is
It can be expressed as in Equation 3.

[0021]

[Equation 1]

[0022]

[Equation 2]

[0023]

(Equation 3)

On the other hand, as shown in FIG. 6, the above-mentioned ROM 58 shows the fuel injection amount Timap in the steady operation state as the engine speed Ne based on the so-called speed density method.
It is set in advance so that it can be retrieved from the intake pressure Pb and the intake pressure Pb, and is stored as a map. Further, since the fuel injection amount Timap retrieved here is set according to the target air-fuel ratio A / F which is determined according to the engine speed Ne and the intake pressure Pb, as shown in FIG. Basic value of fuel ratio A / F KBS
Is stored in advance as a map so that it can be freely searched from the engine speed Ne and the intake pressure Pb. The fuel injection amount Timap is set so as to satisfy the steady operation state in the fluid dynamics model described above. The valve opening time of the injector 22 is directly set as a unit.

Here, under a certain condition in a steady operation state (condition defined by the engine speed Ne1 and the intake pressure Pb1), the fuel injection amount Timap1 determined by the map search becomes as shown in the equation (4). .

[0026]

[Equation 4]

By preparing this map value so as to satisfy the above-mentioned model formula, the fuel injection amount Timap1 'in the steady operation state determined based on the fluid dynamics model.
Naturally agrees with the fuel injection amount Timap1 determined by the map search.

On the other hand, the fuel injection amount Timap1 'in the steady operation state and the fuel injection amount Timap2' in the transient operation state, which are determined based on the fluid dynamics model, are obtained by changing the target air-fuel ratio to the theoretical air-fuel ratio (14.7: 1), it can be expressed by Equation 5 and Equation 6.

[0029]

(Equation 5)

[0030]

(Equation 6)

In both of these equations, comparing the throttle passing air amount Gth1 in the steady operation state and the throttle passing air amount Gth2 in the transient operation state, only the effective opening areas A1 and A of the throttle differ. Therefore, the throttle passing air amount Gth2 in the transient operation state can be expressed by the equation (7).

[0032]

(Equation 7)

Based on the equations (3) and (7), the ratio of the effective opening area of the throttle valve in the steady state to the effective opening area of the throttle valve in the transient state is used to determine the throttle passing air amount Gth1 in the steady state. In addition, the throttle passing air amount Gth2 in the transient operation state can be expressed.

Further, assuming that the current effective opening area of the throttle valve is A and the effective opening area of the throttle valve in the steady operation state is A1, the effective opening area A1 of the throttle valve in the steady operation state is the current throttle value. It can be grasped as the primary delay of the effective opening area A of the valve (Fig. 8). That is, when the first-order lag of A is called "ADELAY", it can be seen that A1 and ADELAY have almost the same value. Therefore, when approximating the model using the concept of the fluid dynamics model, A / (first-order lag of A) may be used.

As shown in FIG. 9, in the transient operation state, at the moment when the throttle is opened, the differential pressure before and after the throttle is large, so the amount of air passing through the throttle flows all at once, and gradually falls to a steady state. The throttle passing air amount Gth in the state can be expressed by this ratio A / ADELAY, and in the steady operation state, this value becomes "1" as shown in the lower graph of FIG. Below, this ratio is
OA ".

Further, the effective opening area of the throttle greatly depends on the throttle opening, and changes in a state of almost following the change of the throttle opening (FIG. 10). Therefore, the first-order lag value of the effective opening area described above is treated equivalently to the first-order lag value of the throttle opening. Furthermore, in order to eliminate the delay in which the chamber filling air amount ΔGb is reflected in the intake air amount Gc, in addition to this first-order delay of the throttle opening, the first-order delay of the value ΔGb is considered.

In this way, the intake air amount Gc can be obtained based on the throttle passing air amount Gth by calculating the chamber filling air amount Gb from the throttle passing air amount Gth. This simplifies the configuration and reduces the amount of calculation. Specifically, the intake air amount Gc per unit time ΔT can be expressed by the equation (8).
Further, when the equations 9 and 10 are expressed in the form of transfer function,
Equation 11 is derived. As shown in the equation (11), the intake air amount Gc can be obtained from the primary delay value of the throttle passing air amount Gth.

[0038]

(Equation 8)

[0039]

[Equation 9]

[0040]

[Equation 10]

[0041]

[Equation 11]

Therefore, such a series of arithmetic processing is shown as a block diagram in FIG. Since the intake air amount Gc can be treated in the same manner as the fuel injection amount, the intake air amount is treated as the fuel injection amount in the following block diagrams and the like for convenience. Further, in the figure, "(1-
B) / (z-B) "is a transfer function of a discrete system and means a first-order delay.

Therefore, under certain conditions during steady operation (conditions defined by the engine speed Ne and the intake pressure Pb)
When the fuel injection amount determined by the map search is described as Timap, the fuel injection amount Tout to be actually output is determined by the following equation. Tout = Timap × RATIO-A Furthermore, when the behavior of the intake air was verified through simulation, the behavior was different when the chamber filling air amount Gb increased and decreased. This state is shown in FIG. In FIG. 12, focusing on the movement of the throttle valve, which is the main factor in the case where the chamber filling air amount Gb fluctuates, the intake air amount (throttle) when the throttle valve moves in the opening direction and in the closing direction is changed. (Passing air amount, cylinder intake air amount, chamber filling air amount)
The change behavior of is shown. Further, FIG. 13 shows the pressure fluctuation in the chamber with respect to the fluctuation of the throttle valve. In this case as well, the behavior of the pressure change in the chamber is different when the throttle valve changes in the opening direction and when it changes in the closing direction. It is considered that one of the factors that the behavior of the intake air changes in the opening direction and the closing direction of the throttle valve is that the intake air is a compressible fluid.

Therefore, in the intake air amount estimating apparatus for the internal combustion engine according to the present embodiment, in order to more accurately estimate the cylinder intake air amount, the amount of throttle change depending on whether the chamber filling air amount Gb increases or decreases. The correction coefficient B for the primary delay is set individually.

The operation of the intake air amount estimating apparatus will be described below with reference to the block diagram of FIG. 14 and the main flowchart of FIG. It should be noted that this flowchart is activated at each TDC position.

First, the engine speed N detected by each sensor
e, intake pressure Pb, throttle opening θTH, atmospheric pressure Pa, engine cooling water temperature Tw, etc. are read (S10). Further, as the throttle opening θTH, the throttle fully closed opening in the idle operation state is learned and the value is used.

Then, it is judged whether the engine is cranking (starting) or not (S20). If it is judged that the engine is not cranking ("NO" in S20), then it is judged whether or not the fuel is cut. It is determined whether or not (S30). If "NO" is determined in S30, the map (FIG. 6) stored in the ROM 58 including the engine speed Ne and the intake pressure Pb is searched, and the fuel injection amount Timap in the steady operation state (steady operation The intake air amount Gc 'in the state is calculated (S4)
0). Thereafter, the retrieved fuel injection amount Timap is appropriately added with atmospheric pressure correction and the like (not shown).

Next, the first-order delay value θTH-D of the throttle opening θTH read in S10 is calculated (S50). FIG. 16 shows a flowchart of the arithmetic processing performed here. Note that this flowchart is also activated at each TDC position.

First, it is determined whether the operating state is the accelerating state or the decelerating state based on the throttle opening degree θTH obtained from the throttle opening degree sensor 36 (S51). This acceleration / deceleration judgment is based on the throttle opening obtained at this timing by θTH
(K) and the throttle opening obtained at the previous timing is θTH (k-1), θTH (k) and θTH (k-
This is done by comparing with 1). That is, θ
If TH (k) ≧ θTH (k−1), it is judged as an acceleration state,
If θTH (k) <θTH (k-1), it is determined that the vehicle is in the deceleration state.

At this time, if it is determined that the vehicle is in the accelerated state ("YES" in S51), the correction coefficient B ₁ (for example, B ₁ = 0.4) at the time of acceleration is set to the throttle primary delay correction coefficient B.
(S52). On the other hand, when it is determined that the vehicle is in the deceleration state (“NO” in S51), the correction coefficient B during deceleration is set.
₂ (for example, B ₂ = 0.8) is set as the throttle primary delay correction coefficient B (S53).

Next, using the throttle first-order lag correction coefficient B thus set, the first-order lag transfer function "(1-B) / (z-B)" of the throttle opening θTH is set ( S54). Then, a first-order delay value θTH-D of the throttle opening is calculated from the set first-order delay transfer function "(1-B) / (z-B)" and the throttle opening θTH (S55).

Subsequently, returning to the main flow chart of FIG. 15, based on the throttle opening θTH and the intake pressure Pb,
The current effective opening area A of the throttle is calculated by the method described above (S60). Next, throttle opening 1
The primary delay value ADELAY of the effective opening area of the throttle is calculated from the secondary delay value θTH-D and the intake pressure Pb (S70).

Then, "RATIO-A" is calculated from the equation RATIO-A = (A + ABYPASS) / (A + ABYPASS) DELAY (S80). It should be noted that ABYPASS means the amount of air taken into each cylinder combustion chamber (shown as “lift amount” in FIG. 14) via the bypass 32 and the like without passing through the throttle valve, and the intake air is accurately expressed. Since it is necessary to consider this air amount in order to determine the amount, the calculation is performed in consideration of this air amount. Specifically, a value corresponding to this air amount is converted into a throttle opening ABYPASS in accordance with a predetermined characteristic and added to the effective opening area A, and the sum (A + ABYPASS) and its first-order lag are approximated. Find the ratio of the value "(A + ABYPASS) DELAY" and call it RATIO-A.

As described above, as a result of adding to both the numerator and the denominator, even if there is an error in the measurement of the amount of air taken into each cylinder combustion chamber without passing through the throttle valve, The impact is small. Then, RATIO-A is multiplied by the Timap (Gc ') obtained by the search in S40 to calculate the fuel injection amount Tout (Gc) corresponding to the throttle passing air amount (S90).

When it is determined in S20 that cranking is in progress ("YES" in S20), a predetermined table (not shown) is searched from the water temperature Tw to calculate the fuel injection amount Ticr during cranking. (S21), and then, the fuel injection amount Tout is determined based on the equation (the description is omitted) of the start mode (S22).

On the other hand, if the fuel cut is determined in S30 ("YES" in S30), the fuel injection amount Tout is set to zero (S31).

As described above, when the throttle primary delay correction coefficient B is separately provided for acceleration and deceleration, the intake air is more accurate than when the throttle primary delay correction coefficient B is constant. It was evaluated whether the quantity could be estimated. This evaluation was carried out with the engine speed, intake pressure, etc. kept constant.

17 (a) to 17 (c) show the evaluation results. FIG. 17A shows a transition state of the throttle opening θTH, showing a state in which the throttle is rapidly opened to a predetermined opening (acceleration state) and then rapidly closed to a predetermined opening (deceleration state). ing. In the state where the throttle is displaced in this way, when the throttle first-order lag correction coefficient B is kept constant (FIG. 17 (b)), there is a large variation in the behavior of the air-fuel ratio on the closed side compared to the open side of the throttle. Can be confirmed. On the other hand, when the throttle first-order lag correction coefficient B is set to an appropriate value on each of the opening side and the closing side of the throttle (Fig. 17 (c)), the variation in the air-fuel ratio is larger than that in Fig. 17 (b). It can be seen that the air-fuel ratio has remained almost flat over the entire period. Therefore, it has been confirmed that the intake air amount Gc (fuel injection amount Tout) can be more accurately estimated by setting the correction coefficient B to an appropriate value individually on the opening side and the closing side of the throttle. The vertical axes in FIGS. 17B and 17C represent the equivalence ratio, that is, Mst / M (Mst: theoretical air-fuel ratio, M: air consumption / fuel consumption).

Now, another embodiment will be described with reference to FIG. In the above-described embodiment, the chamber filling air amount Gb
The situation in which the increase / decrease is detected by focusing on only the throttle opening, which is the main factor, is detected. However, the chamber filling air amount Gb also increases / decreases due to the following factors. It was decided to detect an increase / decrease in the filled air amount Gb. That is, when the engine speed changes,
The target air-fuel ratio changes when the form of the intake manifold is mechanically changed to increase or decrease its volume, when atmospheric pressure changes, when the intake / exhaust valve opening / closing timing (valve timing) changes. If you do,
The chamber filling air amount Gb changes substantially.

Therefore, in the present embodiment, the increase and decrease in the chamber filling air amount Gb is detected by comprehensively considering these factors, and based on this result, the first-order lag value θTH of the throttle opening is detected.
An example of calculating -D is shown.

FIG. 18 shows the first-order delay value θ of the throttle opening.
The flowchart which performs the calculation process of TH-D is shown. It should be noted that this flowchart shows the arithmetic processing performed in S50 of the main flowchart shown in FIG. 15, and is started at each TDC position.

First, the valve timing V / T is "High".
h ”or“ Low ”(S100), and in any case, the throttle opening θ is set in the same manner as the processing of FIG.
From the change state of TH, it is determined whether the operating state is the acceleration state or the deceleration state (S101, S102).

When it is determined in S101 that the vehicle is in the accelerated state ("YES" in S101), the correction coefficient B during acceleration is set.
₃ (for example, B ₃ = 0.4) is set as the throttle first-order lag correction coefficient B (S103), and when it is determined that the vehicle is in the deceleration state (“NO” in S101), the correction coefficient B ₄ at the time of deceleration is set. (For example, B ₄ = 0.8) is set as the throttle primary delay correction coefficient B (S104).

[0064] Similarly, in S102, the ( "YES" in S102) if it is determined that the acceleration state, the correction coefficient during acceleration B ₅ (e.g., B ₅ = 0.3) the throttle 1
Set the next delay correction coefficient B (S105), when it is determined that the deceleration state ( "NO" in S102), the correction coefficient of deceleration B ₆ (e.g., B ₆ = 0.6), throttle 1 The next delay correction coefficient B is set (S106). As described above, when the valve timing V / T is “High”, the throttle first-order delay correction coefficient B tends to have a smaller value than when the valve timing V / T is “Low”. In any case, the value during acceleration tends to be smaller than the value during deceleration.

Subsequently, the throttle first-order delay correction coefficient B set in S103 to S106 is further corrected according to the engine speed, atmospheric pressure, and the like. In this case, first, as shown in FIGS. 19A to 19D, the correction coefficients KADNe, KADPA, KADATA, and KADAF according to the engine speed Ne, the atmospheric pressure PA, the intake air temperature TA, and the target air-fuel ratio AF. Is calculated in advance, and various correction coefficients KADNe, KADPA, corresponding to the current engine speed, etc. are obtained.
Search KADA and KADAF to obtain (S10
7). Next, with respect to the throttle first-order lag correction coefficient B set in any of S103 to S106, various calculated correction coefficients KADNe, KADPA, KATTA and KA
Multiply each by DAF and set this value as the final throttle primary delay correction coefficient B (S108).

Next, using the throttle first-order lag correction coefficient B thus set, the first-order lag transfer function "(1-B) / (z-B)" of the throttle opening θTH is set (S109). ), The set first-order lag transfer function "(1-
B) / (z−B) ”and the throttle opening θTH, a first-order delay value θTH-D of the throttle opening is calculated (S11).
0).

1 of the throttle opening thus obtained
Using the next delay value θTH-D, the fuel injection amount Tout is calculated according to the main flowchart of FIG.

In the embodiment shown in FIG. 18, it is exemplified that the valve timing V / T is determined to be "High" or "Low" in S100 of the flow chart, but in this S100, the change in the intake manifold volume is determined. It may be detected. In this case, because the control that mechanically changes the form of the intake manifold is involved,
It suffices to detect this control signal. As a result, when the intake manifold volume increases, the response delay increases, so the flow proceeds to S101 in the flowchart of FIG. 18, and the throttle first-order delay correction coefficient B is set to a large value. Further, if it decreases, the response delay becomes small, so the flow proceeds to S102 of the flowchart, and the throttle primary delay correction coefficient B is set to a small value.

Each of the above-described methods for calculating the fuel injection amount Tout can represent from the steady operation state to the transient operation state by a simple algorithm, and the fuel injection amount in the steady operation state can be guaranteed to some extent by map search. At the same time, the fuel injection amount can be optimally determined without requiring complicated calculation. Moreover, since the first-order lag correction coefficient of the throttle opening is set according to the behavior of the intake air that differs between the increase and the decrease, the intake air amount can be estimated more accurately, and controllability and control The system can be further improved.

In the embodiment described above, the fuel injection amount Timap is mapped in advance. Instead of this, the intake air amount Gc 'in the steady operation state is mapped and stored in the ROM 58. You may keep it.

Further, in the illustrated embodiment, the fuel injection amount is determined according to the estimated intake air amount, but the present invention is not limited to this example, and other estimations are made. Other engine control parameters, such as ignition timing and exhaust gas recirculation amount (EGR amount), can be calculated corresponding to the intake air amount.

[0072]

As described above, the intake air amount estimating apparatus for an internal combustion engine according to the first aspect of the invention is provided with the detecting means, so that it is possible to detect the increase or decrease of the filling air amount Gb, and further by the setting means. The first-order delay correction coefficient of the throttle opening can be individually set based on the detection result. Therefore,
It is possible to carry out the intake air amount estimation processing corresponding to the behavior of the intake air that differs when the filled air amount Gb increases and when it decreases. Therefore, it is possible to more accurately estimate the amount of air flowing into the cylinder based on the amount of air passing through the throttle, and it is possible to further improve the controllability of the internal combustion engine.

Further, in the intake air amount estimating apparatus for the internal combustion engine according to the second aspect, the detecting means is connected to the throttle opening θ.
Since it is configured as a means for detecting the increase / decrease of the filling air amount Gb based on the increase / decrease of TH, the filling air amount Gb
The intake air amount estimation processing can be performed based on the movement of the throttle valve, which is the main factor in the case of the fluctuation of the.

Further, in the intake air amount estimating apparatus for the internal combustion engine according to the third aspect, the detecting means also detects other factors contributing to the increase and decrease of the filling air amount Gb such as the change of the atmospheric pressure. It is possible to more accurately estimate the intake air amount.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an arrangement position and the like of an internal combustion engine and various sensors according to this embodiment.

FIG. 2 is a block diagram showing a configuration of a control device in an intake air amount estimation device for an internal combustion engine.

FIG. 3 is an explanatory diagram showing a fluid dynamics model adopted in this embodiment.

FIG. 4 is a block diagram showing a method of calculating an effective opening area of a throttle valve using a flow coefficient and the like using the fluid dynamics model of FIG.

5 is an explanatory diagram showing map characteristics of coefficients used in the calculation of FIG.

FIG. 6 is an explanatory diagram showing map characteristics of a fuel injection amount in a steady operation state.

FIG. 7 is an explanatory diagram showing a map of a target air-fuel ratio.

FIG. 8 is a data diagram showing a simulation result of an effective opening area of a throttle.

FIG. 9 is an explanatory diagram showing a steady operation state and a transient operation state in the present embodiment.

FIG. 10 is an explanatory diagram showing the relationship between the throttle opening and the effective opening area of the throttle.

FIG. 11 is a block diagram showing a process of calculating a fuel injection amount (intake air amount).

FIG. 12 is a data diagram showing the behavior of intake air during acceleration / deceleration.

FIG. 13 is a data diagram showing that the behavior of the pressure in the chamber is different between the opening side and the closing side of the throttle valve.

FIG. 14 is a block diagram showing a calculation process of a fuel injection amount (intake air amount) in the case of individually setting a correction coefficient of the primary delay of the throttle according to an operating state.

FIG. 15 is a main flowchart showing a process of calculating a fuel injection amount (intake air amount).

16 is a flowchart of the main flowchart of FIG.
It is a flow chart which shows only the calculation procedure of the 1st-order lag value THH-D of TH.

FIG. 17A is a data diagram showing a change state of the throttle opening. (B) is the throttle first-order lag correction coefficient B
FIG. 6 is a data diagram showing a transition of the air-fuel ratio corresponding to a state where the throttle has changed as shown in FIG. (C) is a data diagram showing the transition of the air-fuel ratio corresponding to the state where the throttle has changed as shown in (a) when the throttle first-order lag correction coefficient B is separately held on the opening side and the closing side of the throttle. Is.

FIG. 18 is a flowchart showing another embodiment regarding a procedure for calculating the first-order lag value of the throttle opening.

19 (a) is a graph showing the relationship between the engine speed and the correction coefficient KADNe, and FIG. 19 (b) is the atmospheric pressure and the correction coefficient KAD.
6 is a graph showing the relationship with PA, (c) is a graph showing the relationship between the intake air temperature and the correction coefficient KADTA, and (d) is a graph showing the relationship between the target air-fuel ratio and the correction coefficient KADFA.

[Explanation of symbols]

10 ... Internal combustion engine, 12 ... Intake passage, 16 ... Throttle valve,
20 ... Intake manifold, 36 ... Throttle opening sensor.

Claims (3)

[Claims] 1. A first means for detecting an operating state of an internal combustion engine including an engine speed Ne, a throttle opening θTH and a chamber pressure Pb, and at least the engine speed detected by the first means. A second method for obtaining the intake air amount Gc 'into the combustion chamber in the steady operation state based on the number Ne and the chamber pressure Pb
Means for determining the first effective opening area A of the throttle based on at least the throttle opening θTH and the chamber pressure Pb detected by the first means; A fourth means for obtaining a first-order lag value of the first effective opening area A and setting the value as a second effective opening area ADELAY of the throttle; a first effective opening area A and a first effective opening area A obtained by the third means; Four
By correcting the intake air amount Gc 'based on the second effective opening area ADELAY obtained by the means described above, the actual intake air amount G
and a fifth means for obtaining c as Gc = Gc '× (A / ADELAY), and the intake system from the throttle to the combustion chamber is modeled as one chamber, and based on this intake system model, In an intake air amount estimation device for an internal combustion engine for estimating an actual intake air amount Gc to be sucked into a chamber, the fourth means is a detection means for detecting an increase or decrease of a filling air amount Gb filled in the chamber. And receiving the detection result of the detection means, the filling air amount Gb
Based on the setting means for individually setting the first-order lag correction coefficient B of the throttle opening depending on whether it increases or decreases, and the first-order lag correction coefficient B set by the setting means.
An intake air amount estimating apparatus for an internal combustion engine, comprising: a calculating unit that obtains a first-order lag value of the first effective opening area A of the throttle. 2. The intake air for an internal combustion engine according to claim 1, wherein the detecting means detects an increase or a decrease in the filled air amount Gb based on an increase or a decrease in the throttle opening θTH. Quantity estimation device. 3. The charged air is detected based on at least one of a change in intake manifold volume, a change in internal combustion engine valve timing, a change in atmospheric pressure, and a change in target air-fuel ratio. Increase in quantity Gb,
The intake air amount estimating apparatus for an internal combustion engine according to claim 1 or 2, wherein a decrease is detected.