JPH0742600A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Structure] The fuel injection amount is determined based on the fluid dynamics model, and the fuel injection amount in the steady operation state obtained by the map search is added to the current effective opening area of the throttle valve. ,
The output value is determined by multiplying the ratio with the primary delay value and subtracting the corrected fuel injection amount corresponding to the chamber filling air amount from the product. [Effect] The fuel injection amount can be optimally determined through all operating states including the transient operating state, and deterioration, variation, aging, etc. are automatically corrected.

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, it uses a fluid dynamics model and simplifies its calculation to determine the fuel injection amount over all operating states including transient operating states. The present invention relates to an optimal fuel injection amount that can be determined optimally and under any condition by eliminating deterioration, variation, and secular change.

[0002]

2. Description of the Related Art In a conventional fuel injection control device, a fuel injection amount is a map which is created in advance by experiments using a parameter having a high correlation with the cylinder inflow air amount and stored in a memory of a microcomputer. It was decided by searching. As a result, it is completely helpless against changes in parameters that were not considered when creating the map,
The same was true for deterioration, variation, and secular change. Further, since the map is created only for the steady operation state and the transient operation state is not expressed therein, the fuel injection amount during the transition could not be accurately obtained. Therefore, in recent years, a means for applying a hydrodynamic model to the intake system and estimating the correct cylinder inflow air amount by a model formula has been proposed. As an example thereof, the technique described in JP-A-2-157451 or the technique described in US Pat. No. 4,446,523 can be mentioned.

[0003]

The applicant of the present invention has also previously used a fluid dynamic model in Japanese Patent Application No. 4-200330, and the throttle valve is regarded as an orifice, and the principle of a throttle type flow meter is determined from the differential pressure before and after the throttle valve. We have proposed a method of calculating the cylinder inflow air amount by obtaining the throttle passing air amount using a formula, but such a fluid dynamic model is based on the ideal state only and requires various assumptions. The modeling error cannot be wiped out. Further, it is difficult to accurately know various constants such as the specific heat ratio used in the model, and there is a disadvantage that errors of these constants accumulate. Furthermore, the equation of fluid dynamics requires calculation such as exponentiation and square root, and practically uses an approximate value, so that there is a problem that an error also occurs. Therefore, the present applicant previously filed Japanese Patent Application No. 4-306086 and its domestic priority claim application (filing date: June 30, 1993, reference number: A
93-0614), the assumption is made on the fluid dynamics model, but the error of the model formula is absorbed without requiring complicated calculation, and the transient state of engine operation, deterioration, variation, secular change, etc. are eliminated and fuel injection is performed. Provided is a fuel injection control device for an internal combustion engine which determines the amount of fuel optimally.

An object of the present invention is to improve the previously proposed technique, and it is an object of the present invention to provide a fuel injection control device for an internal combustion engine which can determine the fuel injection amount more optimally.

[0005]

In order to solve the above-mentioned problems, the present invention provides a fluid dynamic model that describes the behavior of the amount of air passing through a throttle provided in an engine intake passage, as set forth in claim 1. A fuel injection control device for an internal combustion engine, which determines an amount of air to be sucked into the engine based on the above, and determines a fuel injection amount to be supplied to an engine combustion chamber. A first means for detecting an operating state of the engine; a second means for obtaining a fuel injection amount Timap in a steady operating state according to a preset characteristic from at least the detected engine speed and intake pressure;
Third means for obtaining the first effective opening area A of the throttle from at least the detected throttle opening and intake pressure, first-order lag value of the first effective opening area A of the throttle, 2 effective opening area ADE
The fourth means for LAY, 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 Tou is calculated from the product.
A fifth means for determining 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]

Operation: The characteristics of the fuel injection amount in the steady operation state are set in advance, and it is noted that the effective throttle area at present is different from the difference between the steady operation state and the transient operation state due to the difference in the effective opening area of the throttle. The opening area is calculated, the second effective opening area of the throttle is calculated from the first-order lag value, the ratio of the two is calculated, and the output fuel injection quantity is calculated by multiplying the set fuel injection quantity. It is possible to optimally determine the output fuel injection amount in all operating states including, and it is possible to automatically correct the deterioration, variation, and secular change.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing it as a whole. In the figure, reference numeral 10 indicates a four-cylinder internal combustion engine,
The intake air introduced from the air cleaner 14 arranged at the tip of the intake passage 12 flows into the first to fourth cylinders through 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 the intake valve (not shown) of each cylinder to inject fuel. The air-fuel mixture injected and integrated with the intake air is ignited by a spark plug (not shown) in each cylinder and burned to drive a piston (not shown). The exhaust gas after combustion is discharged to the exhaust manifold 24 via an exhaust valve (not shown), is purified by the three-way catalytic converter 28 via the exhaust pipe 26, and is discharged to the outside of 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 θTH of a throttle valve 16. Intake pressure P downstream of the opening sensor 36 and the throttle valve 16
An intake pressure sensor 38 for detecting b in absolute pressure is also provided. Further, on the upstream side of the throttle valve 16, an atmospheric pressure sensor 40 for detecting the atmospheric pressure Pa, an intake 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. Further, in the exhaust system, the three-way catalytic converter 2 is provided downstream of the exhaust manifold 24.
A wide-range air-fuel ratio sensor 46 including an oxygen concentration detection element is provided on the upstream side of 8 to detect the air-fuel ratio of the exhaust gas. The 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 the detection circuit 52 to detect the air-fuel ratio A / F, and the detection circuit 5
The output of 2 is sent to the CPU 56, 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, the analog output of the throttle opening sensor 36 and the like is subjected to waveform shaping through the level conversion circuit 62, the multiplexer 64 and the second A / D conversion circuit 66, and the output of the crank angle sensor 34 is subjected to waveform shaping by the waveform shaping circuit 68. After that, 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 as 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.

FIG. 3 is a block diagram functionally showing the control device of FIG. 2, and FIG. 4 is a flow chart showing the operation thereof. The method of estimating the cylinder inflow air amount by the fluid dynamics model is described. The details are described in the previously proposed technique, and will be briefly described below.

First, as shown in the intake system model of FIG. 5, assuming that the throttle (valve) is 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 is given. From the formula, the formula for calculating the flow rate of the compressive fluid used in the throttle flow meter shown in Formula 4 can be derived.
The equation 4 is rewritten to obtain the equation 5, which can be used to obtain 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, the projected area of the throttle (projected area of the throttle in the longitudinal direction of the intake pipe) S is calculated according to the preset characteristics. On the other hand, as shown in FIG. 7, the coefficient C is set according to another preset characteristic for the throttle opening θTH and the intake pressure Pb.
The product of the flow rate coefficient α and the expansion coefficient of gas ε is calculated and multiplied by both to calculate the effective opening area A of the throttle. To that value, as shown in Equation 5, the throttle upstream side air density ρ
₁ and throttle upstream and downstream pressures P ₁ and P ₂ (atmospheric pressure Pa
And the intake pressure Pb are used instead) and the value of the square root in the equation is multiplied to obtain the throttle passing air amount Gth. Since the throttle does not function as a throttle in the so-called throttle fully open region, the throttle fully open region is determined as a critical value for each engine speed,
When the detected throttle opening exceeds it, the critical value is taken as the throttle opening.

Next, the amount of air in the chamber Gb is obtained 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 obtained from the equation of equation 7 from the chamber pressure change ΔP. Assuming that the amount of air filled in the chamber this time is not sucked into the cylinder combustion chamber, of course, the cylinder intake air amount Gc per unit time ΔT is
It can be expressed as the formula shown in. Here, the "chamber" means not only a so-called surge tank-corresponding portion but also all portions from the throttle downstream side to the intake port. Further, the “chamber” means an effective volume actually acting as a chamber.

[0019]

[Equation 6]

[0020]

[Equation 7]

[0021]

[Equation 8]

On the other hand, in the ROM 58, as shown in the characteristic of FIG.
Is preset and stored as a map so that it can be retrieved from the engine speed Ne and the intake pressure Pb based on the so-called speed density method. Further, the fuel injection amount Timap is set there according to the target air-fuel ratio A / F which is 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 also shows the engine speed N
A map is stored in advance so as to be searchable from e and the intake pressure Pb. The fuel injection amount Timap is set so as to satisfy the above-mentioned hydrodynamic model in the steady operation state, and is directly set in the unit of the valve opening time of the injector 22.

Here, focusing on the relationship between the fuel injection amount Timap obtained by retrieving the map and the throttle passing air amount Gth described above, under certain conditions (engine speed Ne1 and intake pressure Pb1) during a steady operation state. Defined by the above), 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 on the basis of the fluid dynamics model is as shown in Formula 10 when the target air-fuel ratio is the theoretical air-fuel ratio (14.7: 1). In this specification, “dash” indicates a theoretical value obtained based on the fluid dynamics model equation. The subscript 1 of each parameter means a concrete value in the steady operation state, and the subscript 2 used later means a concrete value in the transient operation state.

[0026]

[Equation 10]

Assuming that the map value is created so as to satisfy the model formula as described above, the fuel injection amount Timap1 obtained by the map search and the fuel determined based on the fluid dynamics model. It matches the injection amount Timap1 dash.
Next, when the map search value is obtained under the same condition (Ne1, Pb1) in the transient operation state, it becomes the same as that in the steady operation state as shown in Formula 11. In this specification, the "transient operation state" means 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 on the basis of the fluid dynamics model becomes as shown in Expression 12, and it does not match the value Timap1 obtained by the map search. Therefore, in order to eliminate the inconsistency, a complicated calculation based on the hydrodynamic model is required.

[0030]

[Equation 12]

However, comparing the throttle passing air amount Gth1 in the steady operation state shown in Formula 10 and the throttle passing air amount Gth2 in the transient operation state shown in Formula 12, only the effective opening area A of the throttle is different. Notice that. Therefore, the throttle-passing air amount Gth2 in the transient operation state can be expressed as in Eq. That is, the throttle passing air amount Gth2 in the transient operating state can be obtained from the ratio of the throttle passing air amount Gth1 in the steady operating state and the throttle effective opening areas A1, A2.

[0032]

[Equation 13]

On the other hand, since Gth1 in the steady operation state can be obtained from the map retrieval value Timap1 as shown in the equation (14), the throttle passing air amount Gth2 in the transient operation state is obtained.
Can be obtained as in Expression 15. Therefore, the number 12
From equation (15) and equation (15), the fuel injection amount Ti2 dash during the transient operation state is as shown in equation (16), the corrected fuel injection corresponding to the map search value Timap1 and the effective opening area ratio A2 / A1 and the chamber filling air amount ΔGb2. It can be determined by the amount 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 also mapped in advance so that it can be searched from the engine speed Ne and the intake pressure Pb as shown in FIG. The amount ΔTi is also based on the intake pressure change ΔPb (difference between the previous detected value and the present detected value of the intake pressure Pb) and the target air-fuel ratio A / F (fuel injection amount Timap as shown in FIG. 12). A map is created so that the search can be performed from (searching and associating with the map of FIG. 9).

The current throttle effective opening area A
2. Effective throttle area A obtained by map search
Calculate the ratio A2 / A1 with 1 and multiply 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 the steady operation state where the intake pressure does not change, the output fuel injection amount Tout is expressed by the equation 17 and the map search value Timap is directly used as the output value. In the transient operation state, it is determined by the equation 18 Will be done. Thereby, the output fuel injection amount can be determined from the same formula in both 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 effective opening area A2 of the current throttle do not match 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 the variation of the map and the secular change which are the causes of the inconsistency.

[0039]

[Equation 17]

[0040]

[Equation 18]

[0041]

[Formula 19]

However, when verified through simulation, the effective opening areas A2 and A1 are not actually equal to each other in the steady operation state, and the ratio A2 / A1 is "1".
It didn't. Further, the chamber filling air amount ΔGb has a property of being generated as the amount of air passing through the throttle increases, but when the behavior of the chamber filling air amount ΔGb is measured, it is delayed in being reflected in the intake air amount. It turned out that there is. These factors include the intake pressure Pb.
And that the detection timings of the sensors 36 and 38 for detecting the throttle opening θTH are not the same, and
38, especially the intake pressure sensor 38 may have a detection delay.

Therefore, the throttle opening θTH and the intake pressure P
Focusing on the relationship with b, if the engine speed is constant,
During steady operation, throttle opening θTH and intake pressure Pb
And the intake pressure Pb has a first-order lag with respect to the change of the throttle opening θTH even in the transient operation state. Therefore, the first-order delay value of the throttle opening θTH is obtained (hereinafter referred to as “θTH-D”), and the value is pseudo-intake pressure (hereinafter referred to as “pseudo-intake pressure Pb hat”).
And As a result, the deviation of the detection timing and the detection delay of the intake pressure sensor can be eliminated. Specifically, as shown in FIG. 3, the pseudo intake pressure Pb hat is obtained from the first-order delay value θTH-D of the throttle opening and the engine speed Ne according to a predetermined characteristic.

Further, considering the behavior of the effective opening area of the throttle, it is presumed that the set effective opening area A1 can be grasped as the first-order lag of the current effective opening area A2. As shown in 13, it could be confirmed.
That is, if the first-order delay of A2 is called "ADELAY", A2 /
If A2 is the same in A1 and A2 / A DELAY, A1
As compared with ADELAY, as shown in the enlarged portion M of FIG. 13, although the rising of A1 is delayed due to the detection delay of the intake pressure sensor 38, ADELAY follows A2 relatively faithfully. You can see it. 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 (previous A1) match, and the ratio of both becomes 1. Below, 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 the equation (5). The effective opening area should change almost according to the change in throttle opening. If so, the above-mentioned first-order lag value of the throttle opening should theoretically correspond approximately equivalently to the first-order lag of the effective opening area. Therefore, as shown in FIG. 3, the effective opening area (first-order lag value) ADELAY is calculated from the first-order lag value of the throttle opening ((1-B) / (z- in FIG. 3).
B) is a transfer function of a discrete system and means first-order lag). That is, the throttle projection area S is obtained from the throttle opening first-order delay value θTH-D according to a preset characteristic, and the throttle opening first-order delay value θTH-D and the pseudo intake pressure Pb hat are obtained according to the characteristics shown in FIG. Find the coefficient C,
Next, the product of the two is calculated and the effective opening area (first-order lag value) A
DELAY was calculated. Thus, in FIG.
The first-order lag value θTH-D of the throttle opening is used to obtain the effective opening area (first-order lag value) ADELAY for one and the pseudo value Pb hat of the intake pressure for the second.

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

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

First, in S10, the crank angle sensor 34
In addition to reading the engine speed Ne obtained by counting the detected value of, the intake pressure Pb, the throttle opening θTH, etc. are also read. Next, in S12, it is determined whether the engine is cranking (starting). When the result is negative, the process proceeds to S14, in which it is determined whether the fuel cut is in progress. When it is negative, similarly, the process proceeds to S16. The map of FIG. 8 stored in the ROM 58 is searched from the rotational speed Ne and the intake pressure Pb to obtain the fuel injection amount Timap in the steady operation state. It should be noted that the calculated fuel injection amount Timap is then appropriately corrected by atmospheric pressure and the like, but since the correction itself is not the gist of the present invention, detailed description thereof will be omitted.

Next, in S18, the detected primary delay value θTH-D of the throttle opening is calculated, and in S20, the pseudo intake pressure Pb hat is retrieved from the engine speed Ne and the throttle opening primary delay value θTH-D. Then, in S22, the current effective opening area A2 of the throttle is calculated from the throttle opening θTH and the pseudo intake pressure Pb hat. Next, in S24, the throttle opening first-order delay value θTH-D and the pseudo intake pressure P
First-order delay value A of the effective opening area of the throttle from the hat
The delay is calculated, the routine proceeds to S26 to calculate RATIO-A as shown in the figure, and the routine proceeds to S28 where the fuel injection amount Timap is multiplied by RATIO-A to calculate the fuel injection amount TTH corresponding to the throttle passage air amount.
To calculate.

Next, in S30, the 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 amount ΔPb hat is obtained. , S32 to obtain the chamber filling air amount ΔGb based on the gas state equation, to advance to S34 to calculate its smoothed value, that is, its first-order lag value Gb-D, and to proceed to S36, the first-order lag Gb. A characteristic similar to that shown in FIG. 12 is retrieved from -D to retrieve the corrected fuel injection amount ΔTi.

Next, in S38, the retrieved value is multiplied by the coefficient kta to correct the intake air temperature. This is done by preparing a table whose characteristics are shown in FIG. 16, searching for the correction coefficient kta from the detected intake air temperature Ta, and multiplying it by the corrected fuel injection amount ΔTi. Needless to say, the intake air temperature is corrected here.
This is because the gas state equation (Equation 6) is used. continue,
In S40, the fuel injection amount T corresponding to the amount of air passing through the throttle T
The output fuel injection amount Tout is calculated by subtracting the corrected fuel injection amount ΔTi from TH, and the injector 22 is driven based on the calculated value in S42. The output fuel injection amount T
Voltage correction or the like is appropriately added to out, but this does not have a direct relationship with the gist of the present invention, and therefore description thereof will be omitted.

If it is determined in S12 that cranking is in progress, the process proceeds to S44, in which a predetermined table (not shown) is searched from the water temperature Tw to search the fuel injection amount Ticr during cranking.
Is calculated, and the output fuel injection amount Tout is determined based on the formula (explanation omitted) of the starting mode in S46, and when it is determined that the fuel cut is in S14, the process proceeds to S48 and the output fuel injection amount Tout is set to zero. To do.

Since the present embodiment is configured as described above, it is possible to express from the steady operating state to the transient operating state by a simple algorithm, and to guarantee the fuel injection amount in the steady operating state to some extent by map search. At the same time, it is possible to optimally determine the fuel injection amount without requiring complicated calculation. Moreover, it is not necessary to switch the model formula between the steady operating state and the transient operating state, and the entire operating state can be expressed by one equation, so that the control discontinuity generally seen near the switching point occurs. Never.

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 by inputting only the throttle opening. Since it is configured, the configuration is simple and extremely simple, and the fuel injection amount can be appropriately calculated without the errors of the sensor system adversely affecting each other.
Moreover, since the behavior of the air can be expressed well, controllability and control accuracy can be improved.

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

17 to 19 are explanatory views showing a second embodiment of the present invention. As shown in FIG. 17, the intake passage 12
In an engine in which a bypass 120 for idle speed control is provided and opened / closed by a valve 122, the air taken into the combustion chamber is not limited to the one that has passed through the throttle 16.
Further, even in an engine that does not include the bypass 120 shown in FIG. 1, an air-assisted injector that has been proposed recently (a technique of introducing intake air to cool the injector).
When not using, the air that does not pass through the throttle is mixed in the combustion chamber. Further, the throttle 16 has a slight gap even in the fully closed state, and strictly speaking, a minute amount of air penetrates into the combustion chamber through it.

Therefore, in the second embodiment, the amount of air taken into the combustion chamber without passing through such a throttle 16 is measured, and it 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 set according to an appropriately set characteristic.
Add to. As a result, as shown in FIG. 19, RATIO- is executed in S260 corresponding to S26 in the flow chart of FIG.
When calculating A, the denominator and numerator are added with the value corresponding to the addition throttle opening (referred to as "ABYPASS").
As a result, even if there is an error in the measured value of the air amount that does not pass through the throttle, since it is added to the denominator and the numerator, the degree of influence on the determined fuel injection amount becomes relatively small. Although it is shown only in the case of RATIO-A, it goes without saying that the added throttle opening degree is also reflected in the pseudo intake pressure Pb hat and the like. The rest of the configuration is the same as in the first embodiment.

In the first and second embodiments, when obtaining the first-order lag characteristic of the corrected fuel injection amount ΔTi, the first-order lag of the chamber filling air amount is obtained, and then the corrected fuel injection is performed according to a characteristic similar to FIG. Although the amount ΔTi is calculated, the invention is not limited to this, and the first-order lag value of the pseudo intake pressure change ΔPb hat may be obtained, or the first-order lag value of the corrected fuel injection amount ΔTi may be obtained.
Although the corrected fuel injection amount ΔTi is mapped, it may be calculated in whole or in part. Further, although the pseudo intake pressure change is obtained by the difference value between the previous detection value and the current detection value, it may be obtained from the differential value of the differential value or the integral value.

Further, in the above, the output fuel injection amount Tout is obtained by subtracting the corrected fuel injection amount ΔTi corresponding to the air amount filling the chamber portion from the fuel injection amount Timap in the steady operation state. When the chamber is small enough to be ignored, such as in a cylinder internal combustion engine, the fuel injection amount Timap is calculated without obtaining the corrected fuel injection amount ΔTi.
The output fuel injection amount Tout may be immediately obtained from the above.

Although the fuel injection amount Timap is mapped in advance in the above description, the intake air amount fluctuation and the injector due to the pulsation of the intake passage may be mapped instead of the throttle passing air amount Gth. 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 operating states including the transient operating state, and deterioration, variation, and secular change can be automatically corrected.

In addition to the above 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, the deviation of the detection timing between the sensors and the detection delay of the sensor for detecting the intake pressure can be eliminated, and the fuel injection amount in the transient operation state can be obtained with higher accuracy. Therefore, the fuel injection amount can be optimally determined in all operating states including it.

According to the fourth aspect of the present invention, it is possible to eliminate the delay of reflection in the actual intake air amount when the chamber filling air changes, and to optimize the fuel consumption in all operating states including the transient operating state. The injection quantity can be determined.

According to the fifth aspect, the intake air amount can be accurately obtained, and as a result, the fuel injection amount can be accurately determined.

According to the sixth aspect, it is possible to eliminate the detection timing shift between the sensors and the detection delay of the sensor that detects the intake pressure, and it is possible to determine the fuel injection amount more optimally.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a fuel injection control device for an internal combustion engine according to the present invention.

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

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

4 is a flow chart showing the operation of the block diagram of FIG.

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

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

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

FIG. 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 flow chart 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 flow chart of FIG. 4.

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

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

FIG. 12 is an explanatory diagram showing map characteristics of a corrected fuel injection amount planned 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.

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

FIG. 16 is an explanatory diagram showing an intake 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 showing a configuration of a control device according to a second embodiment.

FIG. 19 is a partial view of the flow chart of FIG. 4 showing the characteristics of the second embodiment.

[Explanation of symbols]

 10 Internal Combustion Engine 12 Intake Channel 16 Throttle Valve 18 Surge Tank 20 Intake Manifold 22 Injector 34 Crank Angle Sensor 36 Throttle Opening Sensor 38 Intake Pressure Sensor 50 Control Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidetaka Maki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda R & D Co., Ltd. (72) Toshiaki Hirota 1-4-1 Chuo, Wako-shi, Saitama Stock Company Honda Technical Research Institute

Claims (6)

[Claims] 1. A fuel injection amount to be supplied to an engine combustion chamber by obtaining an air amount sucked into an engine based on a fluid dynamics model describing a behavior of an air amount passing through a throttle provided in an engine intake passage. A fuel injection control device for an internal combustion engine for determining, comprising: a. First means for detecting an engine operating condition including at least engine speed, intake pressure, and throttle opening degree; b. Second means for obtaining the fuel injection amount Timap in the steady operation state according to a preset characteristic from at least the detected engine speed and intake pressure, c. Third means for determining the first effective opening area A of the throttle from at least the detected throttle opening and intake pressure, d. The first-order lag value of the first effective opening area A of the throttle is obtained, and the first-order lag value is calculated as the second effective opening area ADE of the throttle.
Fourth means for 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 calculated from the product as Tout = Timap × (A / ADELAY) Fifth means, and f. Sixth means for driving an injector based on the obtained output fuel injection amount Tout, and a fuel injection control device for an internal combustion engine. 2. The fourth means obtains the second effective opening area ADELAY of the throttle according to a preset characteristic from at least the detected first-order lag value of the throttle opening. A fuel injection control device for an internal combustion engine as described above. 3. The fifth means obtains the amount of air .DELTA.Gb filling the chamber part from the downstream of the throttle to the front of the engine combustion chamber from the pressure change of the chamber part based on the gas state equation, and corrects it accordingly. The fuel injection amount ΔTi is calculated 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 × (A / ADELAY) −ΔTi, and at least the detected engine speed is detected. The pseudo intake pressure Pb hat is obtained from the number and the throttle opening according to a preset characteristic, and the chamber filling air amount ΔG is calculated from the change ΔPb hat of the value based on the gas state equation.
The fuel injection control device for an internal combustion engine according to claim 1 or 2, wherein b is obtained. 4. The corrected fuel injection amount ΔT is provided by the fifth means.
4. The fuel injection for an internal combustion engine according to claim 3, wherein a first-order lag value ΔTi-D of i is calculated, and then the output fuel injection amount Tout is calculated as Tout = Timap × (A / ADELAY) −ΔTi-D. Control device. 5. The fifth means obtains the amount of air taken into the engine combustion chamber without passing through the throttle and converts it into a value corresponding to the effective opening area of the throttle, and the converted value ABYPASS is the ratio A / PASS. The denominator and the numerator of ADELAY are added to correct the ratio, and then the output fuel injection amount Tout is calculated as 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, characterized in that PASS) is obtained. 6. The third means obtains a throttle projected area S from at least the detected throttle opening according to a preset characteristic, and multiplies it by a coefficient C to obtain a first effective opening area A of the throttle. In addition to obtaining the coefficient C, the pseudo intake pressure Pb is calculated based on at least the detected engine speed and throttle opening according to a preset characteristic.
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, characterized in that the hat is obtained and at least the value Pb hat and the engine speed are obtained in accordance with a preset characteristic.