JP2003314347A - Device for detecting cylinder filling air amount of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the calculation accuracy of the amount of cylinder filling air at a transit period. <P>SOLUTION: A response delay compensation element is provided on an input side of an intake system model where a behavior of intake air flowing in an intake passage from a throttle valve to an intake port of an engine is modeled, to compensate a response delay of on output gMAF of an air flow meter by a phase shift compensation. An output g of the element is input to the intake model. The transfer function of the phase shift compensation is g=(1+T 1×s)/(1+T2×s)×gMAF, where T1 and T2 are constants at phase shift compensation; T1 is set based on the engine speed and the output change amount of the air flow meter; and T2 is set as a fixed value. Accordingly, by setting constant T1 based on the engine speed and the output change amount of the air flow meter, the calculation accuracy of the amount of cylinder filling air at a transit period is improved. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder charged air amount detecting device for an internal combustion engine, which detects an intake air flow rate to calculate an in-cylinder charged air amount (cylinder intake air amount).

[0002]

2. Description of the Related Art Generally, a method for measuring the cylinder air filling amount of an engine is to detect the intake air flow rate by an air flow meter (intake air flow rate detecting means) and calculate the cylinder air filling amount from the detected value. Method (hereinafter referred to as "mass flow method") and method to detect the intake pressure with an intake pressure sensor and calculate the cylinder air filling amount from the intake pressure and engine speed (hereinafter referred to as "speed density method") Broadly divided. In the mass flow system, the intake air flow rate =
Since the amount of air charged in the cylinder is the advantage, the accuracy of measurement of the amount of air charged in the cylinder during normal operation is good, but the response delay of the air flow meter during transients (for example, in the case of a thermal air flow meter, the sensor of the air flow meter is used). Since there is a response delay due to the heat mass of the part itself, there is a drawback that the response during transient is poor.

On the other hand, the speed density method is
Compared with the mass flow method, it has the advantage of better response during transients. This is because the intake pressure sensor has a high response.

Therefore, in recent years, a two-sensor combined system having the advantages of both the mass flow system and the speed density system has been developed. In this two-sensor combined system, both an air flow meter and an intake pressure sensor are installed, and in a steady state, the cylinder filling air amount is calculated from the intake air flow rate detected by the air flow meter, and during transition, it is detected by the intake pressure sensor. The in-cylinder filling air amount is calculated from the intake pressure and the engine rotation speed.

[0005]

In the above two-sensor combined system, the cylinder filling air amount is calculated by the conventional mass flow system because the cylinder filling air amount is calculated using the intake pressure detected by the intake pressure sensor at the time of transition. Although it is possible to improve the responsiveness during the transition as compared with the case where the calculation is performed, there is still room for improvement in terms of the calculation accuracy of the cylinder charging air amount during the transition. In recent years, extremely high precision air-fuel ratio control (fuel injection control) is required due to increasingly stringent exhaust gas purification regulations. It is necessary to further improve the calculation accuracy of the quantity.

Further, in the two-sensor combined system, it is necessary to provide an intake pressure sensor in addition to the air flow meter.
Compared with the mass flow method, there is also a drawback that the system configuration becomes complicated and the cost becomes high.

The present invention has been made in consideration of these circumstances. A first object of the present invention is to improve the calculation accuracy of the cylinder air charge amount at the time of transition, and the second object. The purpose of is to be able to accurately calculate the cylinder filling air amount at the time of transition with a simple system configuration similar to the mass flow method, while satisfying the request for improving the calculation accuracy of the cylinder filling air amount at the time of transition, It is to be able to meet the demand for sensor reduction and cost reduction.

[0008]

In order to achieve the above first object, a cylinder air filling amount detecting device for an internal combustion engine according to a first aspect of the present invention is a flow rate of intake air flowing through an intake passage of the internal combustion engine. The response delay of the intake air flow rate detecting means for detecting the above is compensated by the response delay compensating means, and an intake system model simulating the behavior of the intake air until the intake air passing through the throttle valve flows into the cylinder is used. The output of the delay compensation means is input to the intake system model, and the cylinder charging air amount (cylinder intake air amount) that is the output of the intake system model is calculated by the calculating means. Further, the response delay of the intake air flow rate detection means is compensated by phase advance compensation, and the time constant of the phase advance compensation is set based on the engine rotation speed and the output change amount of the intake air flow rate detection means. is there.

In this way, by compensating the response delay of the intake air flow rate detecting means by the phase lead compensation, the problem of the response delay of the intake air flow rate detecting means at the transient time can be improved. Moreover, since the phase lead compensation time constant for compensating the response delay of the intake air flow rate detection means is set based on the engine speed and the output change amount of the intake air flow rate detection means, for example, this phase Compared with the case where the lead compensation time constant is set to a fixed value (see FIG. 10), the compensation accuracy of the phase lead compensation with respect to the response delay of the intake air flow rate detection means can be improved. This makes it possible to accurately calculate the in-cylinder filling air amount from the output of the intake air flow rate detecting means even during a transition.

In order to achieve the above second object,
According to a second aspect of the present invention, there is provided an in-cylinder charging air amount detecting device for an internal combustion engine, wherein a response delay of an intake air flow rate detecting means is compensated by a response delay compensating means, and an output of the response delay compensating means is input to an intake system model. In calculating the cylinder air filling amount which is the output of the intake system model, the model time constant setting means is used to take into account that the response of the intake system model changes depending on the intake air flow rate. The model time constant of the model is set based on the engine speed and the throttle opening, which are parameters that are correlated with the intake air flow rate. With this configuration, the model time constant of the intake system model can be set to an appropriate value according to the intake air flow rate, and the cylinder filling air amount can be accurately calculated from the output of the intake air flow rate detecting means even during a transition. At the same time, the intake pressure sensor is not required, and it is possible to simultaneously satisfy the demands for improving the calculation accuracy of the in-cylinder filling air amount at the time of transition and reducing the sensor and cost.

In this case, since the response of the intake system model also changes depending on the volumetric efficiency, the volumetric efficiency is determined based on the engine speed and the throttle opening which are parameters for changing the volumetric efficiency. The calculation may be performed and the model time constant of the intake system model may be set based on the volume efficiency and the engine speed. By doing so, it is possible to set a highly accurate model time constant in consideration of the volumetric efficiency, and it is possible to further improve the calculation accuracy of the in-cylinder charged air amount during a transition.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION [Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS. 1 to 10. First, the schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 1 is installed in the most upstream part of an intake pipe 12 (intake passage) of an engine 11 which is an internal combustion engine.
3, a thermal type air flow meter 14 (intake air flow rate detecting means) for detecting the amount of intake air is provided on the downstream side of the air cleaner 13. This air flow meter 14 has a built-in heat ray (not shown) arranged in the flow of intake air and an intake air temperature detection element (not shown), and the temperature of the heat ray cooled by the intake air and the temperature of the intake air are cooled. The current supplied to the heating wire is controlled so as to keep the difference constant. As a result, the supply current to the heat wire changes according to the amount of heat radiation of the heat wire that changes according to the intake air flow rate, and the voltage signal corresponding to this supply current is output as the intake air flow rate signal. A throttle valve 1 is provided downstream of the air flow meter 14.
5 and throttle opening sensor 1 for detecting throttle opening
And 6 are provided.

Further, a surge tank 17 is provided on the downstream side of the throttle valve 15.
7, an intake pressure sensor 18 for detecting the intake pressure P is provided. The surge tank 17 has an engine 1
An intake manifold 19 that introduces air into each cylinder of No. 1 is provided, and a fuel injection valve 20 that injects fuel is attached near the intake port of the intake manifold 19 of each cylinder. The intake valve 25 and the exhaust valve 26 of the engine 11 have a variable valve timing mechanism 28,
29, and the intake / exhaust valve timing is adjusted according to the engine operating state. The variable valve timing mechanisms 28 and 29 may be of a hydraulic drive type or an electromagnetic drive type.

On the other hand, in the middle of the exhaust pipe 21 of the engine 11, a catalyst 22 such as a three-way catalyst for purifying exhaust gas is installed. An air-fuel ratio sensor (or oxygen sensor) 23 that detects the air-fuel ratio (or oxygen concentration) of the exhaust gas is provided on the upstream side of the catalyst 22. Further, a cooling water temperature sensor 24 for detecting the cooling water temperature and a crank angle sensor 25 for detecting the engine rotation speed Ne are attached to the cylinder block of the engine 11.

The outputs of these various sensors are input to an engine control circuit (hereinafter referred to as "ECU") 30.
The ECU 30 is mainly composed of a microcomputer, and executes the routines for fuel injection control of FIGS. 4 to 8 stored in a built-in ROM (storage medium), thereby using a cylinder using an intake system model. It functions as a calculation means for calculating the internal charging air amount g _C (cylinder intake air amount), and sets the fuel injection amount according to the cylinder charging air amount g _C.

The intake system model used to calculate the cylinder air charge amount g _C is the throttle valve 15 to the engine 1
It is a model of the behavior of intake air flowing through an intake passage (hereinafter, referred to as “throttle downstream intake passage”) to the first intake port, and is derived from the law of conservation of mass and the equation of state of gas as follows.

When the law of conservation of mass is applied to the flow of intake air in the intake passage downstream of the throttle, the relationship expressed by the following equation (1) is obtained. d / dt · G _IM = g−g _C (1) Here, G _IM is the air mass in the throttle downstream intake passage, d / dt · G _IM is the amount of change in the air mass in the throttle downstream intake passage, g is the amount of air passing through the throttle (the amount of air that passes through the throttle valve 15), and g _C is the amount of air filling the cylinder.

Further, when the gas state equation is applied to the throttle downstream intake passage, the relation expressed by the following equation (2) is obtained. g _C = η · Ne / 2 · V _C · ρ _IM (2) η: Volume efficiency Ne: Engine speed V _C : Cylinder volume ρ _IM : Air density in the intake passage downstream of the throttle

Here, since the volumetric efficiency η changes depending on the intake air flow rate, it is set by a map or the like based on the engine rotation speed Ne and the intake pressure P which are parameters having a correlation with the intake air flow rate. η = f (Ne, P)

Further, the air density ρ _IM in the throttle downstream intake passage is equal to the air mass G in the throttle downstream intake passage.
Obtained by dividing the _IM in the internal volume V _IM throttle downstream intake passage. ρ _IM = G _IM / V _IM ...... (3)

The model time constant τ _IM of the intake system model
Is expressed by the following equation (4). _{τ IM = 2 · V IM /} (V C · η · Ne) ...... (4) above (1) to (4) from the following (5), (6) is derived. g _C = G _IM / τ _IM ...... (5) d / dt · G _IM = g−G _IM / τ _IM ...... (6)

When the above equation (6) is Laplace transformed, the transfer function of the intake system model represented by the following equation (7) is obtained. g _C = 1 / (1 + τ _IM · s) · g (7)

Throttle that is the input of this intake system model
The amount of passing air g is the output g of the air flow meter 14._MAF
The air flow meter 14
Force g _MAFThere is a response delay in the air flow meter
14 output g_MAFAs it is with the input of the intake system model
Output of the intake system model during transient (cylinder filling
Air volume g_C) Calculation error becomes large,
I cannot secure the degree.

Therefore, in the present embodiment, as shown in FIG. 2, on the input side of the intake system model, a response delay compensating element (response delay compensation) for compensating the response delay of the output g _MAF of the air flow meter 14 by phase lead compensation. Means), and the output g of the response delay compensation element is input to the intake system model. The transfer function of the response delay compensation element (phase lead compensation element) is expressed by the following equation (8). g = (1 + T ₁ · s) / (1 + T ₂ · s) · g _MAF …… (8)

Here, T ₁ and T ₂ are time constants for phase lead compensation, and the time constant T ₁ of the numerator term is based on the change amount of the output g _MAF of the air flow meter 14 and the engine rotation speed Ne. The time constant T ₂ of the denominator term is set to a fixed value. The time constant T ₂ of the denominator term is
The map may be set based on at least one of the output g _MAF of the air flow meter 14, the engine rotation speed Ne, the intake pressure P, and the throttle opening.

The model time constant τ _IM of the intake system model represented by the above equation (7) is calculated by the above equation (4) with the volume efficiency η and the engine rotation speed Ne as variables, and the volume efficiency η is It is calculated by a two-dimensional map having the engine speed Ne and the intake pressure P as parameters.

The in-cylinder charged air amount calculation mode of FIG. 2 described above is used.
Cylinder filling air amount g using Dell_CWhen you calculate
Output g of the meter 14_MAFWhen changes rapidly
In addition, the output g of the response delay compensation element vibrates and the intake system model
Output (cylinder filling air amount g_C ) May vibrate
It

[0028] Therefore, in this embodiment, as shown in FIG. 3, a response delay compensation element (phase lead compensation element) the denominator term (1 + T 2 _· s) with the molecules of the term of the transfer function (1 + T ₁
-S) is separated, and the numerator term (1 + T ₁ · s) is incorporated into the numerator term of the transfer function of the inspiration system model. This allows
A compensating element for compensating the output g _MAF of the air flow meter 14 is expressed by the following equation (9). g = 1 / (1 + T ₂ · s) · g _MAF (9)

Since this compensating element is a simple first-order lag element (low-pass filter), the output g of the compensating element does not vibrate (diverge) and is stable even when the output g _MAF of the air flow meter 14 suddenly changes. Sex is secured.

The transfer function of the intake system model is expressed by the following equation (10) by incorporating the numerator term (1 + T ₁ s) of the response delay compensation element. g _C = (1 + T ₁ · s) / (1 + τ _IM · s) · g (10)

The transfer function of the intake system model expressed by the equation (10) has a time constant τ _{I M in} the denominator term that is significantly larger than the time constant T _{1 in} the numerator term. The output of the system model (cylinder filling air amount g _C ) does not vibrate, and stability is secured.

In this embodiment, the cylinder filling air amount g _C is calculated by the above equations (9) and (10) using the cylinder filling air amount calculation model of FIG. However, the above (9), (1
Since the equation (0) is a continuous equation, the equations (9), (1
The continuous equation (0) is discretized by a bilinear transformation and used. As a result, the equation (9) expressing the compensation element is given by the following [Equation 1].
It is converted into a discrete expression expressed by an equation, and the output g of the compensation element (low-pass filter) is calculated using this discrete expression.

[0033]

[Equation 1]

Where g _(i) is the value of g this time, g
_(I-1) is the previous value of g, and Δt is the sampling time. Further, the equation (10) expressing the intake system model is
It is converted into a discrete expression represented by the following [Equation 2], and the cylinder charging air amount g _C which is the output of the intake system model is calculated using this discrete expression.

[0035]

[Equation 2]

Where g _{C (i)} is the current value of g _C ,
g _{C (i-1)} is the value of the last _{g C.} ECU30
4 executes the routines for fuel injection control shown in FIG. 4 to FIG. 8 to calculate the cylinder filling air amount g _C by using the discrete equations of [Equation 1] and [Equation 2], and inject the fuel. Control the amount. The processing contents of each routine will be described below.

[Main Routine] The main routine of FIG. 4 is executed at a predetermined cycle after the ignition switch is turned on. When this routine is started, first, step 10
At 0, the in-cylinder filling air amount calculation routine of FIG. 5 described later is executed, and the in-cylinder filling air amount g _C is calculated based on the output g _MAF of the air flow meter 14. After this, step 2
At 00, a fuel injection amount setting routine (not shown) is executed, a basic injection amount is calculated by a map or the like according to the cylinder charging air amount g _C and the engine rotation speed Ne, and an air-fuel ratio feedback is given to this basic injection amount. A final fuel injection amount is obtained by multiplying various correction coefficients such as a correction coefficient and a water temperature correction coefficient.

[Cylinder Filled Air Amount Calculation Routine] The cylinder filled air amount calculation routine of FIG. 5 is a subroutine executed in step 100 of the main routine of FIG. When this routine is started, first in step 101, the output change amount Δg _MAF of the air flow meter 14 is calculated by the following equation. Δg _MAF = g _MAF (i) −g _MAF (i-2)

Here, g _MAF (i) is the output of the air flow meter 14 read at the time of this calculation, and g _MAF (i)
_MAF (i-2) is the output of the air flow meter 14 read in the calculation two times before. Therefore, this step 10
Output change amount Δg of the air flow meter 14 calculated by 1
_MAF is the amount of change in output from the time before the previous calculation to the time of this time (the amount of change in the output for two calculation cycles), but the amount of change in the output from the time of the previous calculation to the time of this calculation (the calculation cycle The output change amount for one cycle) may be calculated, or the output change amount for three or more calculation cycles may be calculated.

After this, the routine proceeds to step 102, where the air flow is
Output change amount of meter 14 Δg_MAF And engine speed
Time constant T for phase lead compensation based on Ne₁Set
It T₁= F (Δg_MAF, Ne)

At this time, a two-dimensional map of the time constant T ₁ with the output change amount Δg _MAF of the air flow meter 14 and the engine rotation speed Ne as parameters and a table for each engine rotation speed Ne are prepared in advance by experiments or simulations. Created and stored in the ROM of the ECU 30,
Using this two-dimensional map and the table for each engine rotation speed Ne (or each output change amount Δg _MAF ), the time constant T ₁ corresponding to the current output change amount Δg _MAF of the air flow meter 14 and the engine rotation speed Ne is set. To do.

Alternatively, depending on the current engine rotation speed Ne
Set the determined judgment value using a table or formula, and
Output change amount Δg of the afro meter 14_MAFIs the current
Whether or not it is equal to or higher than the judgment value according to the engine rotation speed Ne
Then, the time constant T of the phase lead compensation₁ To switch
Is also good. The time chart of FIG.
Output change amount Δg of the data 14_MAFIs the current engine times
The phase advance depends on whether or not it is equal to or greater than the judgment value according to the rolling speed Ne.
Compensation time constant T₁Shows an example of switching
It

As described above, the air flow meter 14
Output change amount Δg_MAFDepending on the phase lead compensation time constant
T₁After setting, the process proceeds to step 103, which will be described later.
The average processing routine for the cycle of the amount of air passing through the throttle in FIG.
Execute chin and output g of the air flow meter 14_MAF
Average value of the amount of air passing through the throttle for one cycle from
_MAFAVIs calculated. After this, proceed to step 104.
However, the compensation element (low-pass fill
Output)_(I)Is calculated.

[0044]

[Equation 3]

After that, the routine proceeds to step 105, where the model time constant calculation routine of FIG. 7 described later is executed to calculate the model time constant τ _IM of the intake system model. After that, the routine proceeds to step 106, and the cylinder charging air amount g _{CA (i)} which is the output of the intake system model is calculated using the following [Formula 4].

[0046]

[Equation 4]

Since the unit of the cylinder filling air amount g _{CA (i)} calculated by the equation [4] is kg / sec (cylinder filling air amount per unit time), the following step 107
Then, the unit of the cylinder filling air amount g _{CA (i} ) is converted into kg / rev (cylinder filling air amount per engine revolution ₎ by the following equation. g _{CA (i)} = g _{CA (i)} / (Ne / 60) [kg / rev]

[Throttle Passing Air Amount In-Cycle Averaging Processing Routine] The throttle passing air amount in-cycle averaging processing routine is a subroutine executed in step 103 of the cylinder charging air amount calculating routine in FIG. . When this routine is started, first, at step 134, the time t180 for one cycle of the output g _MAF of the air flow meter 14 is fetched. Time t between one cycle
180 is the time required to rotate 180 ° C. A for a 4-cylinder engine.

After that, the routine proceeds to step 135, where the sampling number N180 for one cycle is calculated by the following equation. N180 = t180 / Δt where Δt is the sampling time.

After that, the routine proceeds to step 136, where the average value g of the throttle passing air amount for one cycle is calculated by the following equation.
_MAFAV is calculated by the following equation.

[0051]

[Equation 5]

[Model Time Constant Calculation Routine] The model time constant calculation routine is a subroutine executed in step 105 of the cylinder charging air amount calculation routine of FIG. When this routine is started, first, step 137
Then, the current intake pressure P, atmospheric pressure Pa, intake temperature T, engine speed Ne, valve timing, cooling water temperature THW
The volumetric efficiency η is calculated using After this, step 1
Proceeding to 38, the model time constant τ _IM is calculated by the following equation.

[0053] _{τ IM = 2 · V IM /} (V C · η · Ne / 60) _{where, V IM} the contents of the throttle downstream intake passage product (fixed value), _{V C} is the cylinder volume (fixed value), Ne Is the engine speed (rpm).

The effect of the embodiment (1) described above will be described with reference to FIGS. 9 and 10. FIG. 9 shows a method of calculating the cylinder air charge amount according to the present embodiment (1), that is, the time constant T ₁ for phase lead compensation is set according to the output change amount Δg _MAF of the air flow meter 14 and the engine speed Ne. It is a time chart which shows an example of the behavior of the cylinder filling air amount which was calculated.

On the other hand, FIG. 10 is a time chart showing, as a comparative example, the behavior of the in-cylinder filling air amount calculated by setting the time constant T ₁ for phase lead compensation to a fixed value. Also in this comparative example, since the response delay of the air flow meter 14 is compensated by the phase advance compensation, the problem of the response delay of the air flow meter 14 is improved, and the cylinder filling air amount at the time of the transition from the output of the air flow meter 14 is corrected to some accuracy. However, in this comparative example, since the time constant T ₁ for phase lead compensation is a fixed value, the phase lead compensation may be performed depending on the engine rotation speed Ne or the like during a transition in which the output of the air flow meter 14 suddenly changes. The time constant T _{1 of 1} may deviate from the proper range. Therefore, depending on the engine speed Ne, etc.,
As indicated by the diagonal lines in FIG. 10, during the transition in which the output of the air flow meter 14 suddenly changes, the calculated value and the target value of the in-cylinder filling air amount (the in-cylinder filling air amount calculated by the speed density method)
There will be a slight difference between and. In recent years, extremely high precision air-fuel ratio control (fuel injection control) is required due to increasingly stringent exhaust gas purification regulations. It is necessary to improve the calculation accuracy of the quantity.

On the other hand, in the present embodiment (1), the time constant T ₁ for phase lead compensation is set according to the engine rotation speed Ne and the output change amount Δg _MAF of the air flow meter 14. If the rotation speed Ne or the output change amount Δg _MAF of the air flow meter 14 changes,
Following this, the time constant T ₁ for phase lead compensation can be changed to maintain the time constant T ₁ within an appropriate range. As a result, as shown in FIG.
Even during a transient change in the output of, the difference between the calculated value of the cylinder filling air amount and the target value (cylinder filling air amount calculated by the speed density method) can be reduced, and the cylinder during the transition can be reduced. It is possible to improve the calculation accuracy of the amount of air charged in the interior, to meet the demands for improvement of air-fuel ratio control (fuel injection control) and reduction of exhaust emission.

[Embodiment (2)] In the above embodiment (1), the time constant T for phase lead compensation is determined according to the engine speed Ne and the output variation Δg _MAF of the air flow meter 14.
₁ is set to improve the calculation accuracy of the in-cylinder filling air amount at the time of the transition, but in the embodiment (2) of the present invention shown in FIGS. 11 and 12, the system configuration of FIG. The pressure sensor 18 is omitted, and step 137 in FIG.
Then, when calculating the volume efficiency η used to calculate the model time constant τ _IM of the intake system model, instead of the intake pressure P, a two-dimensional map of the volume efficiency η with the throttle opening and the engine rotation speed Ne as parameters is obtained. The volumetric efficiency η corresponding to the current throttle opening and the engine speed Ne is calculated using a two-dimensional map. Then, using this volume efficiency η, a model time constant τ _IM is calculated by the following equation (step 138).

[0058] _{τ IM = 2 · V IM /} (V C · η · Ne / 60) _{where, V IM} the internal volume (fixed value) of the throttle downstream intake passage, the _{V C} is cylinder volume (fixed value) .

In the embodiment (2) described above, the throttle opening and the engine speed Ne are used instead of the intake pressure P when calculating the volume efficiency η used for the model time constant τ _IM of the intake system model. Since the volumetric efficiency η is calculated by the above, the model time constant τ _IM of the intake system model can be set to an appropriate value according to the intake air flow rate, and the cylinder filling air can be changed from the output of the air flow meter 14 even during a transition. The amount can be calculated accurately. Moreover, since the intake pressure sensor 18 is not required, the cylinder air filling amount during the transition can be accurately calculated with a simple system configuration similar to the mass flow method, and the cylinder air filling amount during the transition can be calculated. It is possible to meet the demands for sensor reduction and cost reduction while satisfying the demands for accuracy improvement.

In the second embodiment (2), the time constant T ₁ for phase lead compensation is set in accordance with the engine speed Ne and the output change amount Δg _MAF of the air flow meter 14 as in the first embodiment (1). Thus, the accuracy of calculating the cylinder air charge amount during the transition is further improved. However, in the present embodiment (2), the phase lead compensation time constant T ₁ may be a fixed value. The second purpose can be achieved.

In addition, the scope of application of the present invention is not limited to an engine with an intake / exhaust variable valve timing mechanism, and an engine having variable valve timing only on the intake side (or exhaust side) or a variable valve timing mechanism is completely excluded. The present invention can be applied to an engine not mounted, and is not limited to the intake port injection engine, and can be applied to a cylinder injection engine. Further, the air flow meter (intake air flow rate detecting means) is not limited to the thermal air flow meter, and it goes without saying that a vane type or Karman vortex type air flow meter may be used.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a block diagram showing an in-cylinder charged air amount calculation model (Part 1) of the embodiment (1).

FIG. 3 is a block diagram showing an in-cylinder filled air amount calculation model (Part 2) of the embodiment (1).

FIG. 4 is a flowchart showing a processing flow of a main routine.

FIG. 5 is a flowchart showing a processing flow of an in-cylinder filled air amount calculation routine.

FIG. 6 is a flowchart showing a processing flow of an inter-cycle average processing routine of the amount of air passing through the throttle.

FIG. 7 is a flowchart showing a processing flow of a model time constant calculation routine.

FIG. 8 is a time chart showing the relationship among the calculated value of the in-cylinder filling air amount, the target value, the air flow meter output, and the air flow meter output change amount of the embodiment (1).

FIG. 9 is a time chart showing the relationship among the calculated value, the target value, and the air flow meter output of the in-cylinder filling air amount during the transition of the comparative example.

FIG. 10 is a block diagram showing an in-cylinder filled air amount calculation model (Part 1) of the embodiment (2).

FIG. 11 is a block diagram showing a cylinder charging air amount calculation model (Part 2) according to the embodiment (2).

[Explanation of symbols]

11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 14 ... Thermal air flow meter (intake air flow rate detecting means), 15 ... Throttle valve, 17 ... Surge tank (intake passage), 18 ... Intake pressure sensor , 19 ... Intake manifold (intake passage), 20 ... Fuel injection valve, 21 ... Exhaust pipe, 28, 29 ... Variable valve timing mechanism, 30 ... E
CU (computing means, response delay compensating means).

Claims (3)

[Claims] 1. An intake air flow rate detecting means for detecting a flow rate of intake air flowing through an intake passage of an internal combustion engine, a response delay compensating means for compensating a response delay of the intake air flow rate detecting means, and an intake air passing through a throttle valve. Using an intake system model that simulates the behavior of intake air until the air flows into the cylinder,
The response delay compensating means inputs the output of the response delay compensating means to the intake system model to calculate the cylinder air filling amount which is the output of the intake system model, and the response delay compensating means detects the intake air flow rate. In the cylinder of the internal combustion engine, the response delay of the means is compensated by phase lead compensation, and the time constant of the phase lead compensation is set based on the engine speed and the output change amount of the intake air flow rate detection means. Filled air amount detector. 2. An intake air flow rate detecting means for detecting a flow rate of intake air flowing through an intake passage of an internal combustion engine, a response delay compensating means for compensating a response delay of the intake air flow rate detecting means, and an intake air passing through a throttle valve. Using an intake system model that simulates the behavior of intake air until the air flows into the cylinder,
A calculating means for inputting the output of the response delay compensating means to the intake system model to calculate a cylinder charging air amount which is an output of the intake system model; and a model time constant of the intake system model for engine speed and throttle. An in-cylinder charged air amount detection device for an internal combustion engine, comprising: a model time constant setting means for setting based on an opening degree. 3. The model time constant setting means calculates the volume efficiency based on the engine speed and the throttle opening, and sets the model time constant of the intake system model based on the volume efficiency and the engine speed. The cylinder air filling amount detecting device for an internal combustion engine according to claim 2, wherein.