JPH02252933A - Fuel feed controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress the variation of the air-fuel ratio during the transient operation by setting the operation quantity of the feedback correction value on the basis of each proper degree of the control cycle and transient correction of the air-fuel ration feedback correction value and the variation width of the engine load. CONSTITUTION:The feedback correction value for correcting the fundamental fuel feed quantity which is set by a means C on the basis of the engine operation state detected by a means B is set by a means D, in order to make the air-fuel ratio detected by a means A nearly equal to an aimed air-fuel ratio. Further, the transient correction quantity for correcting the fundamental fuel feed quantity is set by a means F on the basis of the engine transient operation state detected by a means E. In this case, the control cycle of the feedback correction value and the proper degree of the transient correction quantity are set by a means G. Further, the variation width of the engine load during the engine transient operation is detected by a means H. The operation quantity of the feedback correction quantity is set by a means I on the basis of the outputs of the means G and H.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly, to an improvement in feedback correction control for bringing the air-fuel ratio of an engine intake air-fuel mixture closer to a target air-fuel ratio.

<Prior Art> The following is known as a fuel supply control device for an internal combustion engine having an air-fuel ratio feedback control function.

The intake air flow rate Q and intake pressure PB are detected as state quantities related to the intake air, and the basic fuel supply amount Tp is calculated based on these and the detected value of the engine rotation speed N. Various correction coefficients C0EF are set for this basic fuel supply amount Tp based on various operating conditions such as engine temperature represented by cooling water temperature.

an air-fuel ratio feedback correction coefficient LAMBDA that is set based on the air-fuel ratio of the intake air-fuel mixture obtained through detection of the oxygen concentration in the exhaust; a correction numerator s based on the battery voltage;
Transient correction amount PRE set according to engine transient operating status
The final fuel supply amount Ti is calculated by correcting it by Tp, etc. Ti = Tp (Unexamined Japanese Patent Publication No. 6
0-240840, etc.).

The air-fuel ratio feedback correction coefficient LAMBI)A is
For example, the actual air-fuel ratio is set by proportional-integral control and is richer (leaner) than the target air-fuel ratio (theoretical air-fuel ratio) based on the oxygen concentration in the exhaust gas detected by the oxygen sensor.
When , the air-fuel ratio feedback correction coefficient LAM
BDA is first decreased (increased) by a proportionality constant P, then gradually decreased (increased) by an integral constant of 1 minute in time synchronization or engine rotation synchronization, and the actual air-fuel ratio repeats reversals near the target air-fuel ratio. This is how it is controlled.

<Problems to be Solved by the Invention> By the way, the air-fuel ratio feedback correction coefficient LAMB
For example, when controlling DA proportionally and integrally as described above, increasing the manipulated variables, proportional constant P and integral constant ■, improves the responsiveness of feedback control, but increasing the manipulated variables will cause problems during steady operation. Since the fluctuation in the air-fuel ratio becomes large and a surge occurs, it has been common practice to set the manipulated variable relatively small so that the level of the surge during steady operation falls within an allowable range.

However, during transient engine operation, changes in the adhesion rate of liquid fuel that adheres to the inner wall of the intake passage and is supplied into the cylinder (hereinafter referred to as wall flow), and changes in the engine load condition detected when setting the fuel supply amount and the supply The air-fuel ratio fluctuates greatly due to differences from the true engine load state when fuel is drawn into the cylinder, and such air-fuel ratio fluctuations during transient operation are
If the various fuel transient correction controls based on transient operating conditions are matched accurately, it can be reduced sufficiently, but if the transient correction control is incorrectly set from the initial state or becomes inappropriate due to changes in the engine over time, the transient Air-fuel ratio fluctuations during operation become large.

In conventional air-fuel ratio feedback correction control, the operation amount of the feedback correction value is determined from the surge level during steady operation as described above, and as shown in Figure 7, transient correction control is well matched and Sometimes, when fluctuations in the air-fuel ratio are small, problem-free air-fuel ratio control can be performed with the manipulated variable adjusted during steady operation, but if there is a defect in the matching of the transient correction control, the feedback correction control can be performed using the manipulated variable adjusted during steady operation. Since responsiveness could not be ensured, large air-fuel ratio fluctuations could not be avoided during transient operation, resulting in an increase in the concentrations of CO, HC, and Nox in the exhaust gas during transient operation.

The present invention has been made in view of the above problems, and it is possible to avoid large fluctuations in the air-fuel ratio even when the fuel correction control during transient operation is not in the best state, and to reduce the surge level during steady operation. It is an object of the present invention to provide a fLLN fuel supply control system.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. basic fuel supply amount setting means for setting the basic fuel supply amount based on the detected engine operating state; air-fuel ratio detection means for detecting engine exhaust components and thereby detecting the air-fuel ratio of the air-fuel mixture taken into the engine; Feedback correction value setting means for setting a feedback correction value for feedback correction of the basic fuel supply amount so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio; and a feedback correction value setting means for detecting the transient operating state of the engine. a transient operating state detecting means for detecting a transient operating state; a transient correction amount setting means for setting a transient correction amount for correcting the basic fuel supply amount based on the transient operating state detected by the transient operating state detecting means; and each of the setting means. a fuel supply amount setting means for setting the fuel supply amount based on the basic fuel supply amount, feedback correction value, and transient correction amount set by the fuel supply amount setting means; A fuel supply control device for an internal combustion engine comprising: a fuel supply control means for controlling fuel supply; An engine load change range detection means for detecting a change range of the engine load during engine transient operation, a control period of the feedback correction value set by the appropriateness degree setting means, appropriate degrees of each of the transient correction amounts, and the engine load change. Feedback correction value operation amount setting means is provided for setting the operation amount of the feedback correction value in the feedback correction value setting means based on the range of change in the engine load detected by the width detection means.

Here, the appropriate degree of the transient correction amount set by the appropriate degree setting means is determined based on the control cycle of the feedback correction value and the increase/decrease control amount by the feedback correction value. It is preferable to

Further, it is preferable that the degree of appropriateness of the transient correction amount set by the appropriateness degree setting means is set for each of the plurality of engine temperature jJ regions.

Furthermore, as shown by the dotted line in FIG. 1, there is provided a transient correction amount correction means for correcting the transient correction amount set by the transient correction amount setting means based on the degree of appropriateness of the transient correction amount set by the appropriateness degree setting means. You can do it like this.

<Operation> In this configuration, the basic fuel supply amount setting means sets the basic fuel supply amount commensurate with the intake air amount based on the engine operating state related to the engine intake air amount detected by the engine operating state detection means. do.

Further, the air-fuel ratio detecting means detects an engine exhaust component, and uses this engine exhaust component to detect the air-fuel ratio of the air-fuel mixture taken into the engine. The feedback correction value setting means sets a feedback correction value for feedback correction of the basic fuel supply amount so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio, and the feedback correction value is used to The actual air-fuel ratio detected through the components is feedback-controlled to be around the target air-fuel ratio.

Further, the transient correction amount setting means sets a transient correction amount for correcting the basic fuel supply amount based on the transient operating state detected by the transient operating state detecting means.

The fuel supply amount setting means includes the basic fuel supply amount;
The fuel supply amount is set based on the feedback correction value and the transient correction amount, and the fuel supply control means controls the fuel supply to the engine based on this fuel supply amount.

On the other hand, the appropriateness level setting means includes a control cycle of the feedback correction value set by the feedback correction value setting means;
and the appropriate degree of each of the transient correction amounts set by the transient correction amount setting means, and determine the appropriate level of the air-fuel ratio feedback correction control and the fuel transient correction control.

Further, the engine load change range detection means detects when the engine load is changing during transient operation of the engine. The feedback correction value manipulated variable setting means determines the feedback correction value in the feedback correction value setting means based on the control cycle of the feedback correction value, the appropriateness of each transient correction amount, and changes in engine load during engine transient operation. Set the amount of operation. Therefore, the operation amount of the feedback correction value is not fixed, but is variably set according to the three conditions: the degree of appropriateness of the feedback correction control described above, the degree of appropriateness of the transient correction control, and the change in engine load during transient operation. This allows the feedback correction value to be set with the manipulated variable according to the air-fuel ratio control state during transient operation.

Here, if the degree of appropriateness of the transient correction amount is determined based on at least one of the control period of the feedback correction value and the increase/decrease control amount by the feedback correction value, the air-fuel ratio controllability during transient operation by the transient correction amount will be improved. The suitability level is set based on this.

Further, by setting the appropriateness degree of the transient correction amount set by the appropriateness degree setting means for each of a plurality of engine temperature regions, it is possible to accurately determine the appropriateness degree of the transient correction amount that is influenced by the engine temperature.

Further, the transient correction amount modification means corrects the transient correction amount set by the transient correction amount setting means based on the appropriateness degree of the transient correction amount set by the appropriateness degree setting means, and adjusts the appropriateness degree of the transient correction amount, i.e. , the air-fuel ratio controllability during transient operation is improved by the amount of transient correction.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing the system configuration of one embodiment, an internal combustion engine l includes an air cleaner 2. Air is taken in through the intake duct 3, the throttle chamber 4, and the intake manifold 5. The air cleaner 2 has an intake air (atmospheric) temperature TA (C).
) is provided with an intake temperature sensor 6 that detects the temperature. The throttle chamber 4 is provided with a throttle valve 7 that operates in conjunction with an accelerator pedal (not shown), and controls the intake air flow rate Q.
control. The throttle valve 7 has its opening TVO.
A throttle sensor 8 including an idle switch 8A that is turned on at its fully closed position W (idle position) is attached along with a potentiometer that detects the position.

The intake manifold 5 downstream of the throttle valve 7 is provided with an intake pressure sensor 9 that detects the intake pressure PB.
An electromagnetic fuel injection valve IO is provided for each cylinder.

The fuel injection valve 10 is driven to open by a drive pulse signal output from a control unit 11 containing a microcomputer, which will be described later, in synchronization with, for example, ignition timing, and is fed under pressure from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator. The fuel is injected and supplied into the intake manifold 5. That is, the amount of fuel supplied by the fuel injection valve 10 is controlled by the valve opening driving time of the fuel injection valve 10.

Furthermore, a water temperature sensor 12 is provided to detect the cooling water temperature Tw in the cooling jacket, which is representative of the engine temperature.
An oxygen sensor 14 is provided as an air-fuel ratio detection means for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas in the exhaust passage 13. The oxygen sensor 14 is a rich/lean sensor that detects whether the actual air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio as the target air-fuel ratio.

The control unit 11 counts the crank unit angle signal PO8 output from the crank angle sensor 15 in synchronization with engine rotation for a certain period of time, or outputs a crank reference angle signal REF at every predetermined crank angle position (in the case of a 4-cylinder engine). The engine rotation speed N is detected by measuring the period (every 180 degrees).

The control unit 11 calculates a basic fuel injection amount (basic fuel supply amount) TpPB based on the intake pressure PB detected by the intake pressure sensor 9 and the engine rotational speed N, and also calculates this basic fuel injection amount TpPB based on the engine speed N. The final fuel injection amount (fuel supply lid) Ti is corrected based on the detected various engine operating conditions, and a drive pulse signal with a pulse width corresponding to the set fuel injection amount T+ is sent to the fuel injection valve 10. output at predetermined timing to control fuel injection supply.

Next, various calculation processes related to fuel supply control performed by the control unit 11 will be explained according to the routines shown in the flowcharts of FIGS. 3 to 6, respectively.

In this embodiment, basic fuel supply amount setting means.

Feedback correction value setting means, transient correction amount setting means,
Fuel supply amount setting means, fuel supply control means.

The functions of the appropriate degree setting means, the feedback correction value manipulated variable setting means 1, the engine load change range detection means, the transient operating state detection means, and the transient correction amount correction means are as shown in the flowcharts of FIGS. 3 to 6. It is equipped with software. Further, in this embodiment, the engine operating state detection means includes the crank angle sensor 15 and the intake pressure sensor 9.
corresponds to

The routine shown in the flowchart of FIG. 3 is based on the proportional/integral calculation of the air-fuel ratio feedback correction coefficient (feedback correction value) LAMBDA for correcting the basic fuel injection amount 'rpPB, which will be described later, so that the actual air-fuel ratio approaches the target air-fuel ratio. This routine is set by control, and is executed every one revolution (1 rev) of the engine based on the reference angle signal REF output from the crank angle sensor 15.

First, step 1 (indicated as Sl in the figure).

The same applies hereafter), the engine rotational speed N and the basic fuel injection amount 'r
For each of a plurality of operating regions divided by
The three data of Rφ, integral ■φ are stored as a set, and from the map in ROM, the proportional and integral control constants (operated amount) corresponding to the current operating condition are calculated based on N and TPPB. Search and ask.

The engine rotational speed N is calculated by measuring the cycle of the reference angle signal REF output from the crank angle sensor 15, for example, as described above, and the engine rotation speed N is calculated by measuring the period of the reference angle signal REF output from the crank angle sensor 15.
B reads what is set in the fuel injection amount setting routine shown in the flowchart of FIG. 5, which will be described later.

In step 2, the detection signal output from the oxygen sensor (0□/5) 14 according to the oxygen concentration in the exhaust gas is input,
In the next step 3, this detected value is compared with a predetermined value equivalent to the stoichiometric air-fuel ratio (500 mV in this example), which is the target air-fuel ratio, and the air-fuel mixture in the engine intake mixture detected through the oxygen concentration in the exhaust gas is The fuel ratio is rich (fi) relative to the stoichiometric air-fuel ratio
or lean.

In step 3, when it is determined that the output of the oxygen sensor 14 is thicker than a predetermined value (the air-fuel ratio is richer than the target), the process proceeds to step 4, where the rich initial determination flag fR is determined.

The rich initial determination flag fR is set to zero when the air-fuel ratio is lean, as will be described later.
When the rich determination in step 3 is made for the first time, the flag fR is determined to be zero.

When it is determined in step 4 that the flag fR is zero and the process proceeds to step 5, the rich first determination flag fR is set to 1, and the lean first determination flag fL is similarly used to determine the first lean detection. set to zero. Therefore, when the rich detection state continues,
In step 4, it is determined that the flag fR is 1.

Rich initial determination is made and flags fR and fL are set in step 5.
After setting, in the next step 6, a membership value mTM indicating the appropriateness of the period time TMO□F of the air-fuel ratio feedback correction coefficient LAMBDA is set in advance as a membership function corresponding to the period time TMO□F. Find it by searching from the map. The period time T
The MOF is reset to zero at the first rich/lean detection of the air-fuel ratio, as will be described later, and is counted up by 1 every 10IIS according to step 51 of the routine executed every 10m5 shown in the flowchart of FIG. It is something that will be done.

Since this is the first time of rich detection, the cycle time TMO□F used in step 6 indicates the duration of the previous air-fuel ratio lean state.
When F is too short, the amount of operation of the air-fuel ratio feedback correction coefficient LAMBDA is too large, causing air-fuel ratio hunting and a surge.
When MO and F are long, the response time to eliminate the lean state of the air-fuel ratio is too long, so the time T
M.O.

The membership value mTM is set near l when F is as short a time as possible within the allowable surge range.

It should be noted that the function giving the membership value mTM is corrected by a skilled and experienced person for a time of this extent TM02F without any problem, and for a time of this extent TMOzF, some correction is performed. The map is set in advance to reflect empirical judgments (rules of thumb) such as:

In the next step 7, the transient flag Ftr is determined.

The transient flag Ftr is set to zero when the wall flow correction amount PRETp as a transient correction amount for correcting the basic fuel injection amount 'rPPB during transient operation of the engine is zero, according to the routine shown in the flowchart of FIG. 5, which will be described later. set,
1 is set when the wall flow correction amount PRETp is not zero and transient correction is being performed.

When it is determined in step 7 that the transient flag Ftr is zero, the fuel supply amount is not corrected by the wall flow correction fiPRETp, and the wall flow correction amount is determined from the cycle time TMO□F of the air-fuel ratio feedback correction coefficient LAMBDA. Since the appropriateness of PRETP cannot be determined, steps 8 to 10 are skipped and the process proceeds to step 11.

On the other hand, when it is determined in step 7 that the transient flag Ftr is 1, it means that the transient correction of the fuel supply amount is being performed by the wall flow correction 1PRETp, so the process proceeds to step 8 and thereafter, and the wall flow correction that is currently added is performed. The appropriateness of the amount PRETp is determined based on the periodic time TMO□F.

In step 8, similarly to the membership 4a m TM indicating the appropriateness of the periodic time TMO,F, the membership value mtr indicating the appropriateness of the wall flow correction amount PRETp based on the periodic time TMO,F is set in advance in the periodicity. Time TM
This is determined by searching from the map of membership functions set corresponding to O and F.

If the air-fuel ratio controllability during transient operation is ensured by the transient correction of fuel using the wall flow correction amount PRETp, the time TMOzF should be sufficiently short. If the increase correction is insufficient, the air-fuel ratio will become lean to a large extent, and it will take time to perform feedback correction to eliminate this lean state. Therefore, when the time TMO
is set to a value close to zero. It should be noted that the empirical rules of experts are also reflected in the membership function that provides this membership value mtr.

In step 8, the membership value mtr is searched from the map, and in the next step 9, the minimum (JM
INmtr is compared with the membership value mtr obtained in step 8 this time, and if the current set value mtr is smaller, the process proceeds to step 10, where the minimum value MINmtr is updated to the current set value mtr, and the wall flow correction amount is PRETf)
Find the data with the lowest degree of appropriateness.

In step 11, the lean control ratio PL by which the air-fuel ratio feedback correction coefficient LAMBDA is reduced by proportional control at the first time of rich detection of the air-fuel ratio is calculated according to the following formula.

PL4-PLφ+PTRX (Mdtp(1-MTR)+mTM) Here, PLφ is the basic value retrieved from the map based on the basic fuel injection amount TpPB and engine rotational speed N in step 1, and PTR is the basic value retrieved from the map in FIG. 5 described later. In the routine shown in the flowchart, the change in engine load during engine transient operation is small ΣDA
A proportional bone for transient operation is set to increase as NTp increases, and Mdtp is a correction coefficient that is set to increase as the engine load change rate DANTp increases during engine transient operation in the routine shown in the flowchart of FIG. M
TR is the membership value m set as described above.
The minimum value MINmtr of tr is updated and recorded as a value corresponding to the cooling water temperature Tw in the flowchart of FIG. 5, and mTM is the periodic time TM0 set in step 6 above.
1 This is a membership value indicating the appropriateness of F.

Therefore, the lean control ratio PL set according to the above calculation formula is determined by the change in engine load during transient operation of the engine Σ
The wall flow correction amount PR is set to increase as DANTp increases, and is stored in accordance with the cooling water temperature Tw.
When the membership value MTR, which indicates the appropriateness of the ETP, becomes smaller, it is set to increase, and the engine load change rate D is set to increase.
It is set to be increased during sudden acceleration/deceleration where ANTp increases, and in addition, it is set to be increased when the cycle time TMO, F of the air-fuel ratio feedback correction coefficient LAMBDA becomes longer.

Therefore, the lean control ratio draw PL is determined when the fuel correction control using the wall flow correction amount PRETp is not performed well during transient engine operation, and the air-fuel ratio tends to deviate greatly from the target air-fuel ratio. In addition, when the sudden acceleration/deceleration state or acceleration/deceleration is continued for a long time, it is set to be increased further, and the air-fuel ratio feedback correction is performed to correct inappropriate fuel correction control by the wall flow correction amount PRETP according to the transient operating state. This is compensated by the coefficient LAMBDA so that the air-fuel ratio quickly converges around the target air-fuel ratio.

In the next step 12, the cycle time TMO,F that measured the lean duration time is reset to zero, and this time the cycle time TM
The rich duration time is measured by O and F.

In step 13, the lean control ratio draw PL set in step 11 is changed to the current air-fuel ratio feedback correction coefficient LA? By subtracting from IBDA, the fuel injection amount Ti calculated using the air-fuel ratio feedback correction coefficient LAMBDA is reduced and the rich state of the air-fuel ratio is eliminated.

On the other hand, when it is determined in step 4 that the rich initial discrimination flag fR is 1, this means that the air-fuel ratio continues to be in a rich state, and in this case, the process advances to step 14 to The membership value mTM is set in the same manner as in step 6 above based on the elapsed time since the fuel ratio became rich. However, step 6
The period time TMO, F in step 14 is a fixed time in the previous lean continuous state of the air-fuel ratio, whereas the period time TMO, F in this step 14 is an undetermined time that changes every moment in the rich continuous state of the air-fuel ratio. .

In the next step 15, an integral {circle around (2)} for integrally controlling the air-fuel ratio feedback correction coefficient LAMBDA is calculated according to the following formula.

14-Tφ+ITRX (Mdtp<1-MTR)+mTM) Here, Iφ is the basic value retrieved from the map based on the basic fuel injection amount TpPB and engine rotational speed N in step 1,
ITR is a small change in engine load during engine transient operation in the routine shown in the flowchart of FIG. 5, which will be described later.
The integral for transient operation, Mdtp, which is set to increase as Tp increases, is determined by the engine load change rate DANT during engine transient operation in the routine shown in the flowchart of FIG.
The correction coefficient MTR is set to increase as p increases, and the minimum value MINmtr of the membership value mtr set as described above is updated and recorded as a value corresponding to the cooling water temperature Tw in the flowchart of FIG. value, also mT
M is a membership value indicating the appropriateness of the periodic time TMO□F set in step 14 above.

Therefore, the integral I set according to the above calculation formula is set to increase as ΣDANTp increases during engine load change during engine transient operation, similar to the lean control ratio PL, and the cooling water temperature Tw When the membership value MTR indicating the appropriateness of the wall flow correction amount PRETp stored in accordance with becomes smaller, the membership value MTR is set to increase, and further,
It is set to be increased during sudden acceleration/deceleration where the rate of change in engine load DANTp increases, and in addition, it is set to be increased when the cycle time TMO□F of the air-fuel ratio feedback correction coefficient LAMBDA becomes longer.

Therefore, the integral control portion I increases when the fuel correction control by the wall flow correction amount PRETp is not performed well during transient engine operation and the air-fuel ratio tends to deviate greatly from the target air-fuel ratio. In addition to being set, it is also set to be increased when there is a sudden acceleration/deceleration state or when acceleration/deceleration continues for a long time.
Inappropriate fuel correction control by the wall flow correction amount PRETp is compensated for so that the air-fuel ratio quickly converges around the target air-fuel ratio.

After setting the integral I in step 15, in the next step, step 16, the current air-fuel ratio feedback correction coefficient LAMB is calculated.
By subtracting the integral (2) from DA, the fuel injection amount Ti is corrected to decrease. This step 15
The integral I is subtracted at every execution cycle of this routine (every engine revolution) while the rich state continues, and when the rich state is eliminated and the air-fuel ratio turns to lean, this time it becomes lean. In order to resolve the situation, control to increase the air-fuel ratio feedback correction coefficient LAMBD^ is performed as described later.

That is, when it is determined in step 3 that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the lean initial determination flag fL is determined in step 17, and when it is the first lean detection, the flag fL is set in the same manner as the first rich detection. , fR are set (step 18), a membership value mTM is set based on the cycle time TMO, F indicating the rich duration time, and then the transient flag Ftr is determined (step 20).
).

When the transient flag Ftr is 1 and fuel transient correction is in progress by the wall flow correction amount PRETP, the wall flow correction amount PR
Update control of the minimum value MINmtr of the membership value mtr indicating the appropriateness of ETp is performed (steps 21 to 2).
3) Next, the rich control proportion PR is calculated according to the following formula (step 24).

PR4-PRφ+PTRX(Mdtp(I MTR)+mTMlThe above calculation formula is based on the lean control ratio P in step 11 above.
The basic value PLφ in the formula for L is simply replaced with the basic value PRφ, and the other calculation elements are the same as the calculation formula for PL, and the change characteristics of the rich control proportional portion PR are the lean control ratio pull portion PL
is the same as

Then, the cycle time TMO□F which measured the rich duration time
While resetting to zero (step 25), the calculated rich control proportion PR is set to the air-fuel ratio feedback correction coefficient L.
It is added to AMBDA and set to increase (step 26).

In addition, when it is determined that the lean initial determination flag fL is 1 in step 17 and the air-fuel ratio lean state continues, the cycle time T indicating the elapsed time from the first lean detection
The membership value mTM is set based on MO□F (step 27), and then the integral ■ is calculated according to the following formula (step 28).

■←Iφ+ITRX (Mdtp(1-MTR)0mTM) The above equation is the same as the equation for the integral I in step 15 above.

Once the integral I is calculated, this integral I is added to the air-fuel ratio feedback correction coefficient LAMBDA to correct the increase in fuel (step 29), and the addition of this integral I is continued until the lean state of the air-fuel ratio is resolved. Continue.

In addition, in the routine shown in the flowchart of FIG. 3 above,
The membership value mtr, which indicates the appropriateness of the wall flow correction amount PRETp, which is the transient correction amount, was set based on the period time TMO However, the degree of appropriateness of the wall flow correction amount PRETp may be set based on the total operation amount (increase/decrease control amount) of the air-fuel ratio feedback correction coefficient LAMBDA, and the degree of appropriateness of the wall flow correction amount PRETp may be set based on the total operation amount (increase/decrease control amount) of the air-fuel ratio feedback correction coefficient LAMBDA. It may be configured such that the degree of appropriateness is set according to each of the amounts and the appropriate degree of wall flow correction amount PRETp is finally set based on both of the appropriate degrees.

As described above, the air-fuel ratio feedback correction coefficient LAMB
The proportional component P and integral component ■ used in proportional and integral control of DA are based on the current air-fuel ratio deviation state, the appropriateness of the wall flow correction amount PRETp confirmed in past transient correction control, and the current state. Since it is variably controlled according to the changing state of the engine load (transient operating state), the wall flow correction amount PRETp during transient operation can be reduced while avoiding the occurrence of surge during steady state.
The deviation in the air-fuel ratio due to the inappropriateness of
, an air-fuel ratio feedback correction coefficient LAMBDA can be set. Therefore, even when the desired air-fuel ratio controllability cannot be obtained with the wall flow correction amount PRETp as the transient correction amount, the air-fuel ratio controllability during transient operation can be ensured and large air-fuel ratio fluctuations can be avoided. This can prevent deterioration of exhaust properties at times.

Next, the routine shown in the flowchart of FIG. 5 is a fuel injection amount setting routine including setting of the wall flow correction amount (transient correction amount) PRETp, and is configured to be executed every 101115 times.

First, in step 61, the opening degree TVO of the throttle valve 7 detected by the throttle sensor 8 is input.

In the next step 62, the opening area A of the engine intake system, which is variably controlled by the throttle valve 7, is searched from the map based on the opening degree TVO input in the step 61.

Then, in step 63, the basic volumetric efficiency QHφ (%) of the internal combustion engine is searched from the map based on the value obtained by dividing the opening area A obtained in step 62 by the engine rotational speed N.

In step 64, '2' is searched for the weighting weight from the map based on the value obtained by multiplying the intake pressure PB detected by the intake pressure sensor 9 and the engine rotational speed N (value equivalent to the intake air flow rate Q). demand. This weighted weight 2 is used to calculate the weighted average of the basic volumetric efficiency QHφ, and by this weighted average calculation, the basic volumetric efficiency QHφ
Volumetric efficiency QCY that follows true engine load changes based on
Let L be set.

In step 65, the volumetric efficiency QCYL is calculated by weighted averaging the basic volumetric efficiencies QHφ obtained in step 63 using 2 as the weighting weight according to the following formula.

°QCYL-2xQHφ+(1-2)QCYLHere, the volumetric efficiency QC weighted with the basic volumetric efficiency QHφ
YL is calculated in step 65 during the previous execution of this routine.

Then, in the next step 66, the basic fuel injection amount ANTp based on the opening area A and the engine rotational speed N is calculated using the volumetric efficiency QCYL calculated in step 65 and the constant XC0NA based on the injection characteristics of the fuel injection valve lO. (engine load parameter) is calculated according to the following formula.

ANTp=KCONAXQCYL The basic fuel injection amount ANTP mentioned above is a value set to obtain the wall flow correction amount PRETp taking into consideration excellent responsiveness, and is different from the basic fuel injection amount in actual fuel supply control. Furthermore, the basic fuel injection 1ANTp corresponds to the ANTp corresponding to each operating state divided by the throttle valve opening TVO and the engine rotational speed N.
It may be configured to search and obtain from a stored map so that the setting can be made more easily.

In step 67, the basic fuel injection amount MANTp calculated in step 66 during the previous execution of this routine is subtracted from the basic fuel injection amount ANTp calculated in step 66 this time.
Change rate DA of basic fuel injection amount AN'rp per s)
Compute NTp (←ANTp−MANTp).

In step 68, the basic fuel injection amount ANTP calculated in step 66 this time is set to the previous value MANTp for use in calculating the change rate DANTp in next step 67.

In step 69, a wall flow correction amount (transient correction amount) PRETp is calculated according to the following equation.

PRETp =PRETp-+ (1-DECKN)
+WEPRTp X DANTp where PRETp-
I is the wall flow correction amount PRETp calculated in step 69 during the previous execution of this routine, and DECKN is the constant DE (J is the engine rotation It is the damping characteristic value obtained by multiplying the speed N,
This damping characteristic value DECKN allows for the wall flow correction amount PRE to be taken away from the wall flow and sucked into the cylinder.
This is so that Tp is integrated and set during transient operation of the engine.

In addition, WEPRTp is determined based on the wall flow correction learning value KLWF that is set based on the membership value MINmtr that indicates the appropriateness of the wall flow correction i1 P RE T p obtained as described above, and the operating conditions such as the cooling water temperature Tw. This is a wall flow correction approximation coefficient calculated in step 93 of the background job in FIG. 6, which will be described later, based on various correction coefficients set depending on the state. Furthermore, DANTp is 10+ of the basic fuel injection amount ANTp calculated in step 67.
It is the rate of change per ns. The wall flow correction amount PRETp calculated by the above formula is set in consideration of changes in the adhesion rate of the injected fuel to the wall surface of the intake passage, and the rate of change is determined by eliminating the change in the basic fuel injection amount ANTp. When DANTp becomes zero, the attenuation characteristic value DEC
It is gradually attenuated by KN.

In the next step 70, it is determined whether or not the wall flow correction amount PRETp calculated in step 69 is zero. If the wall flow correction amount PRETp is not zero, the process proceeds to step 71 and the transient flag Ftr is set to 1. .

On the other hand, when the wall flow correction amount PRETP is zero, the process proceeds to step 72 where the integrated value ΣDAN indicating that the basic fuel injection amount ANTp (engine load) is changing during transient operation is calculated.
Reset Tp to zero.

When the integrated value ΣDANTp is reset to zero, the transient flag Ftr is determined in the next step 73, but if the wall flow correction amount PRETp is not zero, the transient flag Ftr is set to 1 in step 71, so the wall flow correction amount is The first time PRETP becomes zero, this step 73
It is determined that the transient flag Ftr is 1.

When it is determined in step 73 that the transient flag Ftr is 1, the process proceeds to step 74, where the membership value MINmtr up to the previous transient operation set in the routine shown in the flowchart of FIG. The corresponding cooling water temperature T of the map stored in correspondence with
It is updated and stored as the value in w. Incidentally, here, the membership value MI stored in correspondence with the cooling water temperature Tw is
Nmtr is set as MTR to distinguish it from the value before storage, and this MTR is used to set the proportional component P and integral component I in the routine shown in the flowchart of FIG. 3 (step 11.
15.24.28).

That is, each time the air-fuel ratio detected by the oxygen sensor 14 reverses from rich to lean, if the wall flow correction amount PRETp is added at that time, the membership value mtr is set, and the set value and the previous setting are set. Minimum value MINmt
r, and select the smaller mtr as the minimum value MINmt.
r, and when the wall flow correction 11PRETp becomes zero, the minimum value MINmtr is updated and recorded as data corresponding to the cooling water temperature Tw.

By storing the minimum membership value mtr according to the cooling water temperature Tw in this way, it is possible to make a determination corresponding to the appropriateness of the wall flow correction amount PRETp that changes depending on the cooling water temperature Tw. ℃, the air-fuel ratio controllability using the wall flow correction amount PRETp is at an acceptable level, but when the cooling water temperature Tw is 30°C, the desired correction control cannot be performed using the wall flow correction amount PRETp. This can be done based on the map with Tw.

When the latest minimum value MINmtr is stored in the map in the above step 74, this minimum value MINmtr is stored in the next step 75.
mtr is set to 1, and the minimum value MINmtr is set based on the newly set membership value mtr.

Then, in step 76, the transient flag Ftr is set to zero, and if the wall flow correction fiPRETp is approximately zero next time, steps 73 to 74
.about.76 and proceed to step 77.

Further, even after setting the transient flag Ftr to 1 in step 71, the process proceeds to step 77.

In step 77, the change rate DANTp of the basic fuel injection amount ANTp calculated in step 67 is added to the previous integrated value ΣDANTp to update the integrated value ΣDANTp. The integrated value ΣDANTp is the wall flow correction amount PRE.
Since it is reset to zero when Tp is zero, this ΣDANTp is the basic fuel injection 11ANTp during transient operation of the engine where the wall flow correction amount PRETp is not zero.
This indicates a small change in (engine load).

Then, in step 78, based on the integrated value ΣDANTp calculated in step 77, the proportional part PTR and the integral part ITR, which are operation amounts for transient operation, are respectively searched from a preset map. Said proportional portion PTR
and the integral ITR are set to increase as the integrated value ΣDANTp increases, and as a result, according to the routine shown in Figure 3, a larger proportional component P is generated during large transients during changes in engine load.
, the air-fuel ratio feedback correction coefficient LA is determined by the integral ■
N0DA is now controlled.

Further, in step 79, a correction coefficient Mdtp is set in advance based on the rate of change DANTp calculated in step 67, and is set by searching from a map. The change rate DANT9 is the change rate of the basic fuel injection amount ANTP per IQa+s, and this change rate DANT9 is the change rate of the basic fuel injection amount ANTP per IQa+s.
During sudden acceleration/deceleration when p is large, the correction coefficient Mdtp is set to a large value, and the proportional component P and integral component I are increased and corrected in the routine shown in FIG.

In step 80, the basic fuel injection amount TpPB is calculated based on the intake pressure PB according to the following equation.

T p P B 4-K COND X PBAVE X
KQCYL KQCY
L is the volumetric efficiency correction coefficient obtained by correcting the basic volumetric efficiency correction coefficient set based on the intake pressure PB with a minute correction coefficient set based on the intake pressure PB and the engine rotation speed N;
TA is an intake air temperature (air density) correction coefficient set based on the intake air temperature TA detected by the intake air temperature sensor 6.

The intake pressure PB detected by the intake pressure sensor 9 is subjected to weighted average processing as described above, and then the basic fuel injection amount 'r is determined.
The reason used for calculating pPB is that the suction pressure sensor 9 picks up the pressure pulsations that occur in the intake passage during steady engine operation.
The pulsation is attenuated by weighted averaging of the detection results of the intake pressure sensor 9.

After calculating the basic fuel injection amount 'rpPB in step 80, in the next step 81, various corrections are made to this TpPB according to the engine operating state according to the following formula, and the final fuel injection is performed! (Fuel supply amount) Ti is calculated.

T i 4-2 XTpPBXLAMBDAXCOEF
+Ts+PRETpX 2 Here, LAMBDA is the air-fuel ratio feedback correction coefficient set by proportional/integral control in the routine shown in the flowchart of FIG.
C0EF is various correction coefficients that are mainly set based on the cooling water temperature Tw detected by the water temperature sensor 12, and Ts is a correction amount for correcting changes in the effective injection time due to the battery voltage that is the driving power source for the fuel injection valve 10. . Also, P
RETp is the basic fuel injection amount A in step 69.
This is the wall flow correction amount (transient correction amount) set based on the change rate DANTp of NTp.

The fuel injection amount Ti calculated in step 81 is set in the output register of the control unit 11, and at a predetermined injection start timing, a drive pulse signal in the pulse corresponding to the fuel injection amount Ti set in this output register is sent. is output to the fuel injection valve IO, the fuel injection valve 10 is driven to open for a predetermined period of time, and fuel is injected and supplied to the engine.

Next, according to the routine shown in the flowchart of FIG. 6, the wall flow correction amount PRETp is automatically corrected based on the setting control of the wall flow correction learned value KLWF, and the wall flow correction approximation coefficient WEPRT is adjusted.
The setting of p will be explained.

The routine shown in the flowchart of FIG. 6 is executed as a background job (BGJ).
First, in step 91, a membership value M I corresponding to the cooling water temperature Tw updated in step 74 is determined.
From the map of Nm tr (MTR), a value corresponding to the current cooling water temperature Tw detected by the water temperature sensor 12 is searched and obtained.

Then, in the next step 92, the membership value MTR obtained by searching based on the cooling water temperature Tw in the above step 91 is used, and the wall flow correction learning value KL is used according to the following formula.
Calculate WF.

KLWF←1+(1-MTR) MTR indicates the appropriateness of the wall flow correction amount PRETp, and when this membership value MTR is close to zero, it indicates that the desired transient correction control is not being implemented. For example, in a common case where the appropriateness of the wall flow correction amount PRETp decreases due to changes over time such as gum buildup on the intake valve, the air-fuel ratio tends to lean during acceleration, and the air-fuel ratio tends to lean during deceleration. Shows a tendency towards enrichment.

For this reason, the wall flow correction learning value KL calculated using the above calculation formula
WF is multiplied by the wall flow correction approximation coefficient WEPRTp, which will be described later, and -EPRTp is calculated according to the increase in the wall flow correction learned value KLWF.
By increasing the correction amount, when the air-fuel ratio becomes lean during acceleration as described above, the wall flow correction amount PRET is adjusted according to the degree of leanness (decrease in membership value MTR).
In addition, when the air-fuel ratio becomes rich during deceleration, the reduction correction is expanded according to the degree of enrichment (decrease in membership value MTR), and as a result, the initial setting is When sufficient air-fuel ratio controllability cannot be obtained with the fuel correction using the wall flow correction amount PRETp, the wall flow correction amount PRETp is changed using the wall flow correction learning value KLWF.
Transient correction by ETp is automatically corrected to a more appropriate ratio.

After calculating the wall flow correction learning value KLWF in step 92, in the next step 93, the wall flow correction learning value KLWF is multiplied by a correction coefficient corresponding to each of the cooling water temperature Tw, intake pressure PB, and engine speed N. A wall flow correction approximation coefficient WEPRTp is calculated.

Here, the correction coefficient according to the cooling water temperature Tw is set to a larger value as the cooling water temperature Tw is lower. At times, the amount of correction (increase during acceleration, decrease during deceleration) is increased. Further, the correction coefficient according to the intake pressure PB is set in advance based on a change in the adhesion rate of fuel to the intake passage wall, which changes depending on the intake pressure PB. Furthermore, the correction coefficient corresponding to the engine rotational speed N is for minute correction, and is normally set to 100% over the entire range.

Further, in the next step 94, a preset constant DE
By multiplying CK by the engine rotational speed N, a damping characteristic value DECKN of the wall flow correction amount TRETP is set.

The wall flow correction approximation coefficient WEPRTp and the damping characteristic value DECKN set in steps 83 and 84 are used in step 69 to calculate the wall flow correction 1PRETp.

In this embodiment, the wall flow correction amount PRETp is set as the transient correction amount based on the change rate DANTp of the basic fuel injection amount ANTp obtained from the opening area A and the engine rotational speed N. It is clear that the method for setting the correction amount is not limited to this embodiment.

Furthermore, an air flow meter that detects the intake air flow rate Q is provided in place of the intake pressure sensor 9, and the basic fuel injection amount Tp is set based on the intake air flow rate Q and the engine rotational speed N detected by this air flow meter. It is clear that the same effects as in this embodiment can be obtained also in the fuel supply control device having the above configuration.

<Effects of the Invention> As explained above, according to the present invention, the manipulated variable of the feedback correction value is set based on the appropriateness of each of the control period and transient correction amount of the air-fuel ratio feedback correction value, and the state during engine load change. As a result, even when good air-fuel ratio control cannot be obtained with fuel correction control using the transient correction amount, the operating amount can be set by accurately capturing the situation, and the air-fuel ratio can be quickly brought around the target air-fuel ratio. This allows the air-fuel ratio to converge, and avoids the occurrence of large air-fuel ratio fluctuations during transient operation.

Furthermore, by determining the appropriateness of the transient correction amount based on at least one of the control period of the feedback correction value and the increase/decrease control ml, the appropriateness of the transient correction amount, that is, the air-fuel ratio controllability can be confirmed with high accuracy. .

Further, if the degree of appropriateness of the transient correction amount is set for each engine temperature represented by the cooling water temperature, etc., it is possible to accurately determine the degree of appropriateness even when the degree of appropriateness varies depending on the engine temperature.

Furthermore, if the set amount of the transient correction amount is corrected based on the appropriateness of the transient correction amount, the deviation of the air-fuel ratio can be quickly converged by variable control of the manipulated variable of the feedback correction value, and the variable of the manipulated variable can be adjusted. The air-fuel ratio can be controlled to around the target without being affected by the

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing the configuration of an embodiment of the present invention, and FIGS. 3 to 6 are flowcharts showing control details in the above embodiment, respectively. FIG. 7 is a time chart for explaining the conventional problems. 1...i control 7...throttle valve 8...throttle sensor 9...intake pressure sensor 10...
・Fuel injection valve 11...control unit
14...Oxygen sensor 15...Crank angle sensor Patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney

Claims (4)

[Claims] (1) Engine operating state detection means for detecting the engine operating state related to the intake air amount of the engine; and a basic fuel supply amount for setting the basic fuel supply amount based on the engine operating state detected by the engine operating state detection means. a setting means; an air-fuel ratio detecting means for detecting engine exhaust components and thereby detecting an air-fuel ratio of an air-fuel mixture taken into the engine; a feedback correction value setting means for setting a feedback correction value for feedback correction of the basic fuel supply amount; a transient operating state detection means for detecting a transient operating state of the engine; and a transient operating state detection means for detecting a transient operating state of the engine. transient correction amount setting means for setting a transient correction amount for correcting the basic fuel supply amount based on the operating state; and a fuel supply amount based on the set basic fuel supply amount, feedback correction value, and transient correction amount. a fuel supply amount setting means for setting the fuel supply amount setting means; and a fuel supply control means for controlling the fuel supply to the engine based on the fuel supply amount set by the fuel supply amount setting means. In the control device, an appropriate degree setting means for setting the appropriate degree of each of the control cycle and the transient correction amount of the feedback correction value; an engine load change range detecting means for detecting the change range of the engine load during transient engine operation; Feedback correction that sets the operation amount of the feedback correction value in the feedback correction value setting means based on the control cycle of the set feedback correction value, the appropriateness of each transient correction amount, and the range of change in the detected engine load. A fuel supply control device for an internal combustion engine, comprising: a value operation amount setting means; (2) The appropriateness degree of the transient correction amount set by the appropriateness degree setting means is determined based on at least one of a control cycle of the feedback correction value and an increase/decrease control amount by the feedback correction value. The fuel supply control device for an internal combustion engine according to claim 1. (3) The fuel for an internal combustion engine according to claim 1 or 2, wherein the appropriateness degree of the transient correction amount set by the appropriateness degree setting means is set for each of a plurality of engine temperature regions. Supply control device. (4) A transient correction amount correction means is provided for correcting the transient correction amount set by the transient correction amount setting means based on the appropriateness of the transient correction amount set by the appropriateness degree setting means. A fuel supply control device for an internal combustion engine according to claim 1, 2, or 3.