JP3119465B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, and more specifically, to simplify a calculation of a fuel injection control over a whole operation state including a transient operation state by using a fluid dynamic model. The present invention relates to a fuel injection amount which is determined optimally and which can eliminate deterioration, variation, aging and the like so that the fuel injection amount can always be optimally determined under all conditions.

[0002]

2. Description of the Related Art In a conventional fuel injection control device, a fuel injection amount is a map which is basically created by an experiment in advance using a parameter having a high correlation with the amount of air flowing into a cylinder and stored in a memory of a microcomputer. Was determined by searching. As a result, it is completely powerless against changes in parameters that were not taken into account when creating the map,
The same was true for deterioration, variation, and aging. Further, since the map is created only for the steady operation state, and the transient operation state is not represented therein, the fuel injection amount during the transition cannot be accurately obtained. Therefore, in recent years, means for applying a fluid dynamics model to an intake system and estimating a correct cylinder inflow air amount using a model formula has been proposed. As an example, the technology described in JP-A-2-157451 or the technology described in U.S. Pat. No. 4,446,523 can be mentioned.

[0003]

Further, the applicant of the present invention has previously disclosed in Japanese Patent Application No. 4-200330 a principle of a throttle type flow meter using a fluid dynamics model, treating a throttle valve as an orifice and measuring the differential pressure across the throttle valve. Although a method of calculating the amount of air flowing into the cylinder by calculating the amount of air passing through the throttle using an equation has been proposed, such a fluid dynamic model is based on an ideal state to the last, and requires various assumptions. Modeling errors cannot be wiped out. In addition, it is difficult to accurately know various constants such as a specific heat ratio used in the model, and there is a disadvantage that errors in the constants are accumulated. Furthermore, the equations of fluid dynamics require calculations of powers, square roots, and the like, and use an approximate value in practical use. Therefore, the applicant of the present application has previously filed Japanese Patent Application No. Hei 4-306086 and its domestic priority claim application (filing date: June 30, 1993, reference number: A
93-0614), while assuming a fluid dynamics model, absorbs errors in the model formulas without requiring complicated calculations, and eliminates transient states, deterioration, variations, and secular changes in engine operation, and performs fuel injection. There is provided a fuel injection control device for an internal combustion engine in which an amount is optimally determined.

An object of the present invention is to improve the technology proposed above, and to provide a fuel injection control device for an internal combustion engine capable of determining a fuel injection amount more optimally.

[0005]

According to the present invention, there is provided a fluid dynamic model for describing a behavior of an amount of air passing through a throttle provided in an engine intake passage. A fuel injection control device for an internal combustion engine that determines a fuel injection amount to be supplied to an engine combustion chamber based on an amount of air drawn into the engine based on the engine speed, including at least an engine speed, an intake pressure, and a throttle opening. A first means for detecting an operating state of the engine, a second means for obtaining a fuel injection amount Timap in a steady operation state from at least the detected engine speed and the intake pressure in accordance with a preset characteristic;
Third means for obtaining a first effective opening area A of the throttle from at least the detected throttle opening and intake pressure; obtaining a first order lag value of the first effective opening area A of the throttle; 2. Effective opening area ADE
A fourth means of setting LAY is to multiply the determined fuel injection amount Timap by the ratio A / ADELAY of the effective opening areas A and ADELAY of the first and second throttles, and to calculate the output fuel injection amount Tou from the product thereof.
A fifth means for obtaining t as Tout = Timap × (A / ADELAY) and a sixth means for driving the injector based on the obtained output fuel injection amount Tout are provided.

[0006]

The characteristics of the fuel injection amount during the steady operation state are set in advance, and the difference between the steady operation state and the transient operation state is due to the difference in the effective opening area of the throttle. The opening area is obtained, the second effective opening area of the throttle is obtained from the first-order lag value, the ratio between the two is obtained, and the output fuel injection amount is obtained by multiplying the set fuel injection amount. , The output fuel injection amount can be optimally determined in all the operating states including the above, and even if there is deterioration, variation, aging, etc., it can be automatically corrected.

[0007]

FIG. 1 is a schematic diagram showing the entire structure. In the figure, reference numeral 10 indicates a four-cylinder internal combustion engine,
The intake air introduced from the air cleaner 14 disposed at the end of the intake passage 12 flows into the first to fourth cylinders via the surge tank (chamber) 18 and the intake manifold 20 while the flow rate is adjusted by the throttle valve 16. . An injector 22 is provided near an intake valve (not shown) of each cylinder to inject fuel. The air-fuel mixture that has been injected and integrated with the intake air is ignited by a spark plug (not shown) in each cylinder, burns, and drives a piston (not shown). The exhaust gas after combustion is discharged to an exhaust manifold 24 via an exhaust valve (not shown), purified through an exhaust pipe 26 by a three-way catalytic converter 28, and discharged outside the engine.

A crank angle sensor 34 for detecting a crank angle position of a piston (not shown) is provided in a distributor (not shown) of the internal combustion engine 10 and a throttle for detecting an opening degree θ TH of the throttle valve 16. The opening degree sensor 36 and the intake pressure P downstream of the throttle valve 16
An intake pressure sensor 38 for detecting b as an absolute pressure is also provided. An atmospheric pressure sensor 40 for detecting the atmospheric pressure Pa, an intake air temperature sensor 42 for detecting the temperature Ta of the intake air, and a humidity sensor 44 for detecting the humidity of the intake air are provided upstream of the throttle valve 16. Further, the three-way catalytic converter 2 is disposed downstream of the exhaust manifold 24 in the exhaust system.
A wide-range air-fuel ratio sensor 46 composed of an oxygen concentration detecting element is provided upstream of 8, and detects the air-fuel ratio of the exhaust gas. Outputs of these sensors 34 and the like are sent to the control unit 50.

FIG. 2 is a block diagram showing details of the control unit 50. The output of the wide-range air-fuel ratio sensor 46 is input to a detection circuit 52 where the air-fuel ratio A / F is detected.
The output of the CPU 2 is output to the CPU 56 and R via the A / D conversion circuit 54.
It is taken into the microcomputer composed of the OM 58 and the RAM 60 and stored in the RAM 60. Similarly, an analog output of the throttle opening sensor 36 and the like is subjected to a level conversion circuit 62, a multiplexer 64 and a second A / D conversion circuit 66, and an output of the crank angle sensor 34 is subjected to a waveform shaping by a waveform shaping circuit 68. Thereafter, 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 according to a command stored in the ROM 58 as described later, and drives the injector 22 of each cylinder via the drive circuit 72.

FIG. 3 is a block diagram functionally showing the control device shown in FIG. 2, and FIG. 4 is a flowchart showing the operation thereof. Before describing the operation with reference to FIG. A method for estimating the amount of air flowing into a cylinder by using a fluid dynamic model will be described. The details are described in the technology proposed above, and will be briefly described below.

First, as shown in the intake system model of FIG. 5, when the throttle (valve) is regarded as an orifice, the relationship between Bernoulli's equation shown in equation (1), continuous equation shown in equation (2), and adiabatic change shown in equation (3) From the formula, a formula for calculating the flow rate of the compressible fluid used in the throttle type flow meter shown in Equation 4 can be derived.
Rewriting equation (4) gives equation (5), which can be used to determine the throttle passing air amount Gth per unit time.

[0012]

(Equation 1)

[0013]

(Equation 2)

[0014]

(Equation 3)

[0015]

(Equation 4)

[0016]

(Equation 5)

That is, as shown in FIG. 6, the throttle opening θ
From TH, a projection area of the throttle (a projection area of the throttle in the longitudinal direction of the intake pipe) S is obtained according to a preset characteristic. On the other hand, as shown in FIG. 7, a coefficient C according to another characteristic set in advance for the throttle opening θTH and the intake pressure Pb.
(The product of the flow coefficient α and the gas expansion correction coefficient ε) is obtained, and the two are multiplied to obtain the effective opening area A of the throttle. As shown in the equation (5), the air density ρ
₁ and throttle upstream and downstream pressures P ₁ , P ₂ (atmospheric pressure Pa
And the intake pressure Pb), the throttle-passing air amount Gth can be obtained. Since the throttle does not function as a throttle in the so-called fully open region of the throttle, the fully open region of the throttle is determined as a critical value for each engine speed.
When the detected throttle opening exceeds that, the critical value is set as the throttle opening.

Next, the amount of air Gb in the chamber is determined from the equation shown in Equation 6 based on the equation of state of gas, and the amount of air ΔGb filled in the chamber this time is determined from the change in chamber pressure ΔP according to Equation 7. If it is assumed that the amount of air filled in the chamber this time is not taken into the cylinder combustion chamber, the cylinder intake air amount Gc per unit time ΔT becomes
Can be represented as shown in the following equation. Here, the “chamber” means not only a part corresponding to a so-called surge tank, but also all parts from the downstream of the throttle to the intake port. “Chamber” means an effective volume that actually serves as a chamber.

[0019]

(Equation 6)

[0020]

(Equation 7)

[0021]

(Equation 8)

On the other hand, as shown in FIG. 8, the ROM 58 stores the fuel injection amount Timap in the steady operation state.
Is set in advance so as to be searched from the engine speed Ne and the intake pressure Pb based on the so-called speed density method, and is stored in a map. Further, since the fuel injection amount Timap is set according to the target air-fuel ratio A / F determined according to the engine speed Ne and the intake pressure Pb,
In order to calculate the corrected fuel injection amount ΔTi described later, FIG.
The target air-fuel ratio A / F is also changed to the engine speed N as shown in FIG.
e and the intake pressure Pb are preliminarily mapped and stored in a searchable manner. The fuel injection amount Timap is set so as to satisfy the above-mentioned fluid dynamic model in a steady operation state, and is directly set in units of the valve opening time of the injector 22.

Here, focusing on the relationship between the fuel injection amount Timap obtained by searching the map and the above-mentioned throttle passing air amount Gth, under certain conditions (the engine speed Ne1 and the intake pressure Pb1) in the steady operation state. The fuel injection amount Timap1 determined by the map search is as shown in Expression 9.

[0024]

(Equation 9)

At this time, the fuel injection amount Timap1 dash determined based on the fluid dynamics model is as shown in Expression 10 when the target air-fuel ratio is set to the stoichiometric air-fuel ratio (14.7: 1). In this specification, "dash" indicates a theoretical value obtained based on a fluid dynamics model formula. The suffix 1 of each parameter indicates a specific numerical value in a steady operation state, and the suffix 2 used later indicates a specific numerical value in a transient operation state.

[0026]

(Equation 10)

Here, if the map values are prepared so as to satisfy the model equation as described above, the fuel injection amount Timap1 obtained by the map search and the fuel determined based on the fluid dynamics model The injection amount Timap1 matches the dash.
Next, when the map search value is obtained under the same conditions (Ne1, Pb1) in the transient operation state, it becomes the same as that in the steady operation state as shown in Expression 11. In this specification, the "transient operation state" refers to a transitional operation state from a steady operation state to a steady operation state as shown in FIG.

[0028]

[Equation 11]

At this time, the fuel injection amount Timap2 dash determined based on the fluid dynamics model is as shown in Expression 12, and does not match the value Timap1 obtained by map search. Therefore, in order to eliminate the mismatch, a complicated calculation based on a fluid dynamic model is required.

[0030]

(Equation 12)

However, when comparing the throttle passing air amount Gth1 in the steady operation state shown in Equation 10 with the throttle passing air amount Gth2 in the transient operation state shown in Equation 12, only the effective opening area A of the throttle differs. Notice that. Therefore, the throttle-passing air amount Gth2 in the transient operation state can be expressed as in Expression 13. That is, the throttle passing air amount Gth2 in the transient operation state can be obtained from the ratio of the throttle passing air amount Gth1 in the steady operation state to the effective opening areas A1 and A2 of the throttle.

[0032]

(Equation 13)

On the other hand, since Gth1 in the steady operation state can be obtained from the map search value Timap1 as shown in Expression 14, the throttle passing air amount Gth2 in the transient operation state is obtained.
Can be obtained as shown in Expression 15. Therefore, Equation 12
From Equation 15 and Equation 15, the fuel injection amount Ti2 dash in the transient operation state is, as shown in Equation 16, the corrected fuel injection corresponding to the map search value Timap1, the ratio A2 / A1 of the effective opening area of the throttle, and the chamber filling air amount ΔGb2. It can be obtained from the quantity ΔTi.

[0034]

[Equation 14]

[0035]

(Equation 15)

[0036]

(Equation 16)

Therefore, the fuel injection amount Tim in the steady operation state
In addition to ap, the effective opening area A1 of the throttle in the steady operation state is mapped in advance so that it can be retrieved from the engine speed Ne and the intake pressure Pb as shown in FIG. As shown in FIG. 12, the amount ΔTi is based on the intake pressure change ΔPb (difference between the previous detection value and the present detection value of the intake pressure Pb) and the target air-fuel ratio A / F (based on the fuel injection amount Timap). (It is searched from the map of FIG. 9 and associated).

Then, the current throttle effective opening area A
2 and throttle effective opening area A obtained by map search
The ratio A2 / A1 to 1 is obtained and multiplied by the fuel injection amount Timap,
Next, the output fuel injection amount Tout can be obtained by subtracting the corrected fuel injection amount ΔTi. In a steady operation state in which the intake pressure does not change, the output fuel injection amount Tout is as shown in Expression 17, and the map search value Timap is used as it is as an output value. In a transient operation state, it is determined as Expression 18 Will be done. Thus, the output fuel injection amount can be determined from the same equation in the transient operation state and the steady operation state, and the continuity of control should be ensured. Further, when the effective opening area A1 of the throttle obtained by the map search and the current effective opening area A2 of the throttle do not coincide with each other even in the steady operation state,
Since the output fuel injection amount Tout is determined as shown in Expression 19, it is possible to automatically correct a map variation or a secular change which causes the mismatch.

[0039]

[Equation 17]

[0040]

(Equation 18)

[0041]

[Equation 19]

However, as a result of verification through a simulation, the effective opening areas A2 and A1 are not actually equal to each other in a steady operation state, and the ratio A2 / A1 is "1".
Did not become. Further, although the chamber filling air amount ΔGb is of a nature that is generated with an increase in the amount of air passing through the throttle, when the behavior of the chamber filling air amount ΔGb is measured, it is delayed that it is reflected in the intake air amount. It turns out that there is. These factors include the intake pressure Pb
And the detection timing of the sensors 36 and 38 for detecting the throttle opening θTH are not the same,
38, in particular, there may be a detection delay in the intake pressure sensor 38.

Therefore, the throttle opening θTH and the intake pressure P
Focusing on the relationship with b, if the engine speed is constant,
In the steady operation state, the throttle opening θTH and the intake pressure Pb
Is in a one-to-one relationship, and even in the transient operation state, the intake pressure Pb has a first-order lag with respect to the change in the throttle opening θTH. Therefore, seeking first-order lag value of the throttle opening .theta.TH (hereinafter referred to as ".theta.TH-D"), the value and the engine rotational
A value obtained according to a predetermined characteristic from the number of inversions is pseudo-intake pressure (hereinafter referred to as “pseudo intake pressure Pb hat”). Thus, it is possible to eliminate a deviation in detection timing and a detection delay of the intake pressure sensor. Specifically, as shown in FIG. 3, the pseudo intake pressure Pb hat is obtained from the primary delay value θTH-D of the throttle opening and the engine speed Ne according to predetermined characteristics.

Further, when the behavior of the effective opening area of the throttle was examined, it was estimated that the set effective opening area A1 could be grasped as a first-order lag of the current effective opening area A2. As shown in FIG. 13, it could be confirmed.
That is, if the primary delay of A2 is called "ADELAY", A2 /
If A2 is the same in A1 and A2 / ADELAY, A1
As shown in the enlarged portion M of FIG. 13, the rise of A1 is delayed due to the detection delay of the intake pressure sensor 38, whereas the ADELAY relatively closely follows A2. You can see that Therefore, instead of the ratio A2 / A1, the ratio A2 // "the first-order lag" is used. As a result, as shown in the lower part of FIG. 14, in the steady operation state, A2 and its first-order lag value (the previous A1) match, and the ratio between the two becomes 1. Hereinafter, this ratio is referred to as "RATIO-
A ".

Further, focusing on the relationship between the effective opening area of the throttle and the throttle opening θTH, the effective opening area greatly depends on the throttle opening as shown in Expression 5, and as shown in FIG. The effective opening area should change substantially following the change in the throttle opening. If so, the above-mentioned first-order lag value of the throttle opening should correspond approximately equivalently to the first-order lag of the effective opening area. Therefore, as shown in FIG. 3, the effective opening area (primary delay value) ADELAY is calculated from the primary delay value of the throttle opening (in FIG. 3, (1-B) / (z−
B) is a discrete transfer function and means a first-order lag). That is, FIG from with determining the throttle projection area S in accordance with characteristics set or we advance throttle opening .theta.TH, a throttle opening primary delay value .theta.TH-D and the pseudo manifold pressure Pb hat 7
The coefficient C is obtained in accordance with the characteristics as shown in (1) and then the product of the two is obtained to calculate the effective opening area (first-order lag value) ADELAY. Thus, in FIG. 3, the first order delay value θTH-D of the throttle opening is used to determine the effective opening area (first order delay value) ADELAY in one part and the pseudo value Pb hat of the intake pressure in two parts. use.

Further, in order to eliminate the delay in reflecting the chamber filling air amount ΔGb on the intake air amount, a first order delay of the value ΔGb is used. That is, FIG. 15 is a block diagram showing details of the block 100 at the end of FIG. 3. As shown in FIG. 15, a primary delay value (hereinafter, referred to as “ΔGb-D”) of the chamber filling air amount ΔGb is obtained. Then, the corrected fuel injection amount ΔTi was determined. Specifically, the characteristics are similar to those shown in FIG. 12, and the target air-fuel ratio A / F and the chamber filling air amount Δ
A searchable characteristic is prepared in advance from the primary delay value ΔGb-D of Gb. In FIG. 15, the time constant of the delay is appropriately set through a test.

Based on the above, the operation of the control device will be described with reference to the flowchart of FIG.

First, at S10, the crank angle sensor 34
Is read, the intake pressure Pb, the throttle opening θTH, etc. are also read. Then, the program proceeds to S12, in which it is determined whether or not the engine is cranking (starting). If not, the program proceeds to S14, in which it is determined whether or not fuel cut is being performed. The map shown in FIG. 8 stored in the ROM 58 is retrieved from the rotational speed Ne and the intake pressure Pb to obtain the fuel injection amount Timap in the steady operation state. An atmospheric pressure correction or the like is then appropriately added to the obtained fuel injection amount Timap as necessary. However, since the correction itself is not the gist of the present invention, a detailed description thereof will be omitted.

Next, proceeding to S18, a primary delay value θTH-D of the detected throttle opening is calculated, and proceeding to S20, a pseudo intake pressure Pb hat is retrieved from the engine speed Ne and the throttle opening primary delay value θTH-D. Then, the program proceeds to S22, in which the current effective opening area A2 of the throttle is calculated from the throttle opening θTH and the pseudo intake pressure Pb hat. Then, the program proceeds to S24, in which the throttle opening primary delay value θTH-D and the pseudo intake pressure P
First order delay value A of effective opening area of throttle from b hat
Then, the process proceeds to S26 to calculate RATIO-A as shown, and then proceeds to S28 to multiply the fuel injection amount Timap by RATIO-A to obtain a fuel injection amount TTH corresponding to the throttle passing air amount.
Is calculated.

Then, the program proceeds to S30, in which a difference between the current calculated value (Pb hat (n)) and the previous calculated value (Pb hat (n-1)) is calculated for the pseudo intake pressure Pb hat, and the change ΔPb hat is obtained. obtains a chamber charged air amount ΔGb based on the state equation of the gas proceeds to S32, the smoothed value proceeds to S34, i.e., to calculate the first-order lag value delta Gb-D, a first-order lag proceeds to S36 A characteristic similar to that of FIG. 12 is retrieved from Gb-D and the target air-fuel ratio to retrieve a corrected fuel injection amount ΔTi.

Then, the program proceeds to S38, in which the search value is multiplied by a coefficient kta to perform intake air temperature correction. This is performed by preparing a table whose characteristics are shown in FIG. 16 in advance, searching for the correction coefficient kta from the detected intake air temperature Ta, and multiplying the corrected fuel injection amount ΔTi by the corrected fuel injection amount ΔTi. It goes without saying that the intake air temperature is corrected here,
This is because the state equation of gas (Equation 6) is used. continue,
Proceeding to S40, the fuel injection amount T corresponding to the throttle passing air amount
The output fuel injection amount Tout is calculated by subtracting the corrected fuel injection amount ΔTi from TH, and the process proceeds to S42 to drive the injector 22 based on the calculated value. The output fuel injection amount T
Although voltage correction and the like are appropriately added to out, this also has no direct relation to the gist of the present invention, and therefore the description thereof is omitted.

When it is determined in step S12 that cranking is being performed, the process proceeds to step S44, where a predetermined table (not shown) is searched from the water temperature Tw, and the fuel injection amount Ticr during cranking is obtained.
The output fuel injection amount Tout is determined on the basis of the start mode equation (description omitted) in S46, and when it is determined in S14 that the fuel cut is performed, the process proceeds to S48, where the output fuel injection amount Tout is set to zero. I do.

In this embodiment, since the configuration is as described above, it is possible to express from a steady operation state to a transient operation state by a simple algorithm, and the fuel injection amount in the steady operation state is guaranteed to some extent by a map search. At the same time, the fuel injection amount can be optimally determined without requiring complicated calculations. Moreover, since it is not necessary to switch the model formula between the steady operating condition and the transient operating condition, the entire operating condition can be expressed by one formula, so that the control discontinuity generally occurs near the switching point occurs. Nothing.

More specifically, the fuel injection amount Timap in the steady operation state is obtained from the engine speed and the intake pressure, and the correction in the transient operation state is basically performed using only the throttle opening as an input. With this configuration, the configuration becomes simple and extremely simple, and the fuel injection amount can be properly calculated without errors of the sensor system adversely affecting each other.
In addition, since the behavior of air can be well expressed, controllability and control accuracy can be improved.

Further, since the output fuel injection amount is determined by obtaining the ratio between the current effective opening area of the throttle and its first-order lag value, even if there is aging, variation, deterioration, etc. It can be corrected automatically.

FIGS. 17 to 19 are explanatory views showing a second embodiment of the present invention. As shown in FIG.
In an engine which is provided with a bypass 120 for controlling the idling speed and is opened and closed by a valve 122, the air taken into the combustion chamber is not limited to the air having passed through the throttle 16.
Further, even in the case of an engine without the bypass 120 shown in FIG. 1, when an air-assisted injector (a technique for introducing intake air to promote atomization of the injector) that is recently proposed is used, Air that does not pass through the throttle enters the combustion chamber. Furthermore, the throttle 16 has a slight gap even in the fully closed state, and strictly speaking, minute air enters the combustion chamber.

Therefore, in the second embodiment, the amount of air taken into the combustion chamber without passing through such a throttle 16 is measured, and the sum is added to determine the fuel injection amount. Specifically, as shown on the right side of FIG. 18, the amount of air that does not pass through the throttle (shown as “lift amount” in the figure) is measured, and the throttle opening θTH
Is added to. As a result, as shown in FIG. 19, in S260 corresponding to S26 in the flow chart of FIG.
A hand upon calculation of, while adding a value corresponding to the addition throttle opening to the molecule (the "ABYPASS"), the value ABY
Calculate the primary delay value of PASS (referred to as “ABYPASS-D”).
This was added to the numerator . Thus, even if there is an error in the measured value of the air amount that does not pass through the throttle, the measured value is added to the denominator and the numerator, so that the influence on the determined fuel injection amount is relatively small. In addition, RATIO-
Although only the case of A is shown, it goes without saying that the added throttle opening is also reflected on the pseudo intake pressure Pb hat and the like. The remaining configuration is not different from the first embodiment.

In the first and second embodiments, to obtain the first-order lag characteristic of the corrected fuel injection amount ΔTi, the first-order lag of the amount of air charged into the chamber is obtained, and then the corrected fuel injection amount is calculated according to a characteristic similar to FIG. Although the amount ΔTi is calculated, the present invention is not limited to this. The primary delay value of the pseudo intake pressure change ΔPb hat may be obtained, or the primary delay value of the corrected fuel injection amount ΔTi may be obtained.
Although the corrected fuel injection amount ΔTi is mapped, all or a part thereof may be calculated. Further, the pseudo intake pressure change is obtained by the difference between the previous detection value and the present detection value, but may be obtained from the difference between the differential value or the integral value.

In the above description, the output fuel injection amount Tout is obtained by subtracting the correction fuel injection amount ΔTi corresponding to the air amount filling the chamber from the fuel injection amount Timap in the steady operation state. When the chamber portion is sufficiently small to be negligible, such as in the case of a cylinder internal combustion engine, the fuel injection amount Timap is calculated without obtaining the corrected fuel injection amount ΔTi.
From this, the output fuel injection amount Tout may be obtained immediately.

In the above description, the fuel injection amount Timap is mapped in advance. Alternatively, if the throttle passage air amount Gth is mapped, the fluctuation of the intake air amount due to the pulsation of the intake passage and the injector The same purpose can be achieved to some extent except that the error when the characteristics lack linearity cannot be absorbed.

[0061]

According to the first aspect of the present invention, the fuel injection amount can be optimally determined in all operation states including the transient operation state, and deterioration, variation, and aging can be automatically corrected.

According to the second aspect, in addition to the above-described effects, the effective opening area of the throttle can be easily obtained, and as a result, the fuel injection amount can be easily determined.

According to the third aspect of the present invention, it is possible to eliminate the deviation of the detection timing between the sensors and the detection delay of the sensor for detecting the intake pressure, and to obtain the fuel injection amount in the transient operation state with higher accuracy. Therefore, the fuel injection amount can be optimally determined in all the operating states including the above.

According to the fourth aspect of the present invention, it is possible to eliminate the delay in reflecting the change in the air filling the chamber to the actual intake air amount, and to optimize the fuel more optimally in all operation states including the transient operation state. The injection amount can be determined.

According to the fifth aspect, the amount of intake air can be determined with high accuracy, and as a result, the amount of fuel injection can be determined with high accuracy.

According to the present invention, it is possible to eliminate the detection timing deviation between the sensors and the detection delay of the sensor for detecting the intake pressure, so that the fuel injection amount can be more optimally determined.

[Brief description of the drawings]

FIG. 1 is a schematic diagram generally showing a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a block diagram showing a configuration of a control device of FIG. 1 in detail.

FIG. 3 is a block diagram functionally showing the configuration of FIG. 2 in more detail;

FIG. 4 is a flowchart showing the operation of the block diagram of FIG. 3;

FIG. 5 is an explanatory diagram showing a fluid dynamic model planned in the block diagram of FIG. 3;

6 is a block diagram showing a method of calculating an effective opening area of a throttle valve in the fluid dynamic model of FIG. 5 using a flow coefficient or the like.

FIG. 7 is an explanatory diagram showing map characteristics of coefficients used in the calculation in FIG. 6;

8 is an explanatory diagram showing a map characteristic of a fuel injection amount in a steady operation state used in the block diagram of FIG. 3 and the flowchart of FIG. 4;

9 is an explanatory diagram showing a map of a target air-fuel ratio used in the block diagram of FIG. 3 and the flowchart of FIG. 4;

FIG. 10 is an explanatory diagram showing a steady operation state and a transient operation state in the present invention.

FIG. 11 is an explanatory diagram showing map characteristics of an effective opening area of a throttle scheduled in fuel injection control according to the present invention.

FIG. 12 is an explanatory diagram showing a map characteristic of a corrected fuel injection amount scheduled for fuel injection according to the present invention.

FIG. 13 is a data diagram showing a simulation result of an effective opening area of a throttle.

FIG. 14 is an explanatory diagram showing the relationship between the throttle opening and the effective opening area of the throttle.

FIG. 15 is a partially enlarged block diagram of the block diagram of FIG. 3;

FIG. 16 is an explanatory diagram showing an intake air temperature correction table characteristic of a corrected fuel injection amount.

FIG. 17 is a partial view of an internal combustion engine similar to FIG. 1, showing a second embodiment of the present invention.

FIG. 18 is a block diagram illustrating a configuration of a control device according to a second embodiment.

FIG. 19 is a partial view of the flow chart of FIG. 4, illustrating features of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake path 16 Throttle valve 18 Surge tank 20 Intake manifold 22 Injector 34 Crank angle sensor 36 Throttle opening degree sensor 38 Intake pressure sensor 50 Control unit

Continued on the front page (72) Inventor Hidetaka Maki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Toshiaki Hirota 1-4-1 Chuo Wako-shi, Saitama Honda Co., Ltd. (56) References JP-A-62-280839 (JP, A) JP-A-2-286851 (JP, A) JP-A-3-210051 (JP, A) (58) Fields investigated (Int. . ^7, DB name) F02D 41/18 F02D 41/34 F02D 45/00 366

Claims (6)

(57) [Claims] An amount of air to be taken into an engine is determined based on a fluid dynamic model describing a behavior of an amount of air passing through a throttle provided in an engine intake passage, and a fuel injection amount to be supplied to an engine combustion chamber is determined. A fuel injection control device for an internal combustion engine, comprising: a. First means for detecting an operating state of the engine including at least an engine speed, an intake pressure, and a throttle opening; b. Second means for obtaining a fuel injection amount Timap in a steady operation state from at least the detected engine speed and intake pressure according to a preset characteristic; c. Third means for obtaining a first effective opening area A of the throttle from at least the detected throttle opening and the intake pressure; d. A first-order lag value of the first effective opening area A of the throttle is obtained, and the first-order lag value is obtained.
A fourth means to be LAY, e. The obtained fuel injection amount Timap is multiplied by the ratio A / ADELAY of the effective opening areas A and ADELAY of the first and second throttles, and the output fuel injection amount Tout is obtained from the product as Tout = Timap × (A / ADELAY). Fifth means, and f. A sixth means for driving the injector based on the determined output fuel injection amount Tout; and a fuel injection control device for an internal combustion engine. 2. The apparatus according to claim 1, wherein said fourth means obtains a second effective opening area of the throttle, ADELAY, from at least a primary delay value of the detected throttle opening in accordance with a preset characteristic. A fuel injection control device for an internal combustion engine according to claim 1. 3. The fifth means determines the amount of air ΔGb filling the chamber from the downstream of the throttle to the front of the engine combustion chamber based on a gas state equation from a change in pressure in the chamber, and a correction corresponding thereto. The fuel injection amount .DELTA.Ti is obtained and subtracted from the product of the fuel injection amount Timap and the ratio A / ADELAY to obtain the output fuel injection amount Tout as Tout = Timap.times. (A / ADELAY)-. DELTA.Ti, and at least the detected engine speed. A pseudo intake pressure Pb hat is obtained from the number and the primary delay value of the throttle opening according to a preset characteristic, and a change Δ
3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the chamber filling air amount .DELTA.Gb is obtained from the Pb hat based on the state equation of the gas. 4. The fifth means includes a correction fuel injection amount ΔT.
4. The fuel injection for an internal combustion engine according to claim 3, wherein a first order delay value .DELTA.Ti-D of i is obtained, and an output fuel injection amount Tout is obtained as Tout = Timap.times. (A / ADELAY)-. DELTA.Ti-D. Control device. 5. The fifth means calculates the amount of air taken into the engine combustion chamber without passing through the throttle, converts the amount of air into a value corresponding to the effective opening area of the throttle, and converts the converted value ABYPASS to the ratio A / P. The ratio is corrected by adding to the denominator and numerator of ADELAY, and then the output fuel injection amount Tout is calculated as follows: Tout = Timap × (A + ABYPASS) / (ADELAY + ABY
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein PASS- D ) is obtained. 6. The third means obtains a throttle projection area S from at least the detected throttle opening in accordance with a preset characteristic, and multiplies it by a coefficient C to obtain a first effective opening area A of the throttle. At the same time, the coefficient C is determined from the pseudo engine intake pressure Pb hat at least from the detected engine speed and the primary delay value of the throttle opening in accordance with a preset characteristic from at least the detected engine speed and the primary opening value of the throttle opening. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, wherein the fuel injection control device is obtained according to a set characteristic.