JP3092441B2 - Air-fuel ratio control device for an internal combustion engine equipped with an evaporative fuel processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine having a fuel vapor treatment device.

[0002]

2. Description of the Related Art In an internal combustion engine for automobiles, as a measure to regulate the amount of evaporative fuel generated from a fuel tank, the evaporative fuel is temporarily adsorbed to a canister, and the adsorbed fuel adsorbed to the canister is removed by a predetermined amount. An evaporative fuel processing apparatus has been adopted in which the engine is purged and burned by the suction negative pressure downstream of the throttle valve in the intake passage together with the purging air under the engine operating conditions (see Japanese Utility Model Laid-Open No. 1-58760).

[0003]

On the other hand, in an air-fuel ratio control device for an internal combustion engine, an air flow meter disposed upstream of a throttle valve in an intake passage detects the flow rate of air taken into the engine, and fuel injection is performed based on the detected flow rate. Since the air-fuel ratio of the air-fuel mixture sucked into the engine is controlled by controlling the fuel injection amount from the valve, the provision of the evaporative fuel processing device allows the evaporative fuel generated in the fuel tank from the canister to be provided. Is supplied to the engine, extra fuel is supplied into the cylinder only to that extent, and the air-fuel ratio becomes over-rich.

[0004] For this reason, the conventional apparatus provided with an evaporative fuel treatment apparatus having a constant purge rate does not sufficiently satisfy the demand for reducing the influence of the purge and securing the purge amount. Was. Here, as a technique for securing a larger purge amount, the present applicant has filed an application in which over-rich is prevented by gradually increasing the purge rate (Japanese Patent Application No. 5-51744). reference).

On the other hand, in a control device for an internal combustion engine having an air-fuel ratio feedback control function, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 2-139941, there is a method in which the air-fuel ratio is converged to a stoichiometric condition at an early stage by changing the proportional / integral constant in the enrichment accompanying the canister purge. However, in this case, it is assumed that the evaporative fuel processing apparatus is purging at a constant purge rate, and the control constants such as the proportional and integral constants in the air-fuel ratio feedback control are changed. In the case of a device having an evaporative fuel treatment device that increases the purge rate, the air-fuel ratio cannot be quickly converged to stoichiometry, so that CO, HC, etc. in the exhaust cannot be reduced. There is.

When the air-fuel ratio learning control function is provided, the required correction level is learned in accordance with the canister purge. However, the canister purge is always performed in the operation region where the learning is performed. Not necessarily,
Further, even if the canister purge is performed, the amount of fuel supplied by the purge fluctuates, so that the next time the engine is operated in the same operation region, it is affected by the condition of the canister purge and the air-fuel ratio learning correction value is used. Excess or deficiency occurs in the correction level. Then, the exhaust property deteriorates until the air-fuel ratio deviation caused by the excess or deficiency of the correction level is compensated by the air-fuel ratio feedback control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and even when the purge rate of the fuel vapor to the engine by the fuel vapor processing apparatus changes, the air-fuel ratio of the air-fuel mixture sucked into the engine can be accurately determined. The purpose is to be able to control well.

[0008]

As a means according to the first aspect of the present invention, as shown in FIG. 1, an evaporative fuel generated from a fuel tank is adsorbed and collected, and the adsorbed and collected evaporative fuel is used. An evaporative fuel processing device that purges and combusts the air into the intake passage of the engine, and uses an air-fuel ratio detecting unit that detects the air-fuel ratio of the engine intake air-fuel mixture, and a control constant based on the detection value of the air-fuel ratio detecting unit. Air-fuel ratio feedback correction coefficient setting means for setting the air-fuel ratio feedback correction coefficient; and air-fuel ratio feedback for feedback-controlling the air-fuel ratio to near the target air-fuel ratio based on the air-fuel ratio feedback correction coefficient set by the air-fuel ratio feedback correction coefficient setting means. Control means for controlling the air-fuel ratio of the internal combustion engine, comprising: A fuel vapor purge rate changing means for changing the operating conditions over di rate, the evaporative fuel purge rate varying
When confirming the change of the purge rate by means, on the basis of the purge rate to the engine of the evaporative fuel changes due to the fuel vapor purge rate changing means, for a predetermined time correction control constants in the air-fuel ratio feedback correction coefficient setting means configuration and comprising air-fuel ratio feedback correction coefficient correcting means,
And the air-fuel ratio feedback correction coefficient correction means.
Has the following configuration.

[0009]

[0010] That is, the air-fuel ratio feedback correction coefficient correcting means, wherein the purge rate change vector calculation means for calculating a change vector of the purge rate in the fuel vapor purge rate changing means, the evaporative fuel purge rate change means <br / After the change in the purge rate is confirmed, based on the amount of change in the purge rate calculated by the purge rate change vector calculation means for each change direction of the purge rate calculated by the purge rate change vector calculation means , A control constant in the air-fuel ratio feedback correction coefficient setting means, and a change vector-dependent correction means for correcting the control constant for a predetermined time after the change occurs.
Constitute.

[0011]

According to the first aspect of the present invention, the air-fuel ratio feedback correction coefficient correction unit sets the air-fuel ratio feedback correction coefficient based on the purge rate of the evaporated fuel to the engine changed by the evaporated fuel purge rate change unit. Are corrected for a predetermined time. Then, the air-fuel ratio feedback correction coefficient setting means sets an air-fuel ratio feedback correction coefficient for feedback-correcting the basic control value of the air-fuel ratio,
The air-fuel ratio feedback control means corrects and controls the basic control value of the air-fuel ratio, such as the amount of fuel supplied to the engine, based on the set air-fuel ratio feedback correction coefficient.

When the purge rate of the fuel vapor to the engine changes (for example, when the fuel vapor is purged to the engine, when the purge to the engine ends, or when the purge rate changes). Is a control constant (proportional or integral) corrected to a different value according to each condition
Is corrected and set for a predetermined time as a control constant in the air-fuel ratio feedback correction coefficient setting means, and the air-fuel ratio feedback control is performed, so that the air-fuel ratio feedback control can work effectively as soon as possible.

Further, the correction of the control constant in the air-fuel ratio feedback correction coefficient setting means based on the change in the purge rate of the evaporated fuel to the engine is continued for a predetermined time after the change occurs, for example. As a result, the air-fuel ratio feedback correction coefficient is corrected during the influence of the purge, and after the influence of the purge is reduced, the correction is not performed, and the air-fuel ratio feedback control works effectively. .

Further, the change vector dependent correction means
The control constant in the air-fuel ratio feedback correction coefficient setting means is determined based on the change vector calculated from the change in the purge rate in the evaporative fuel purge rate change means and based on the amount of change in the purge rate for each change direction of the purge rate. Is corrected for a predetermined period of time after the occurrence of the correction, and when the purge rate increases or the purge rate decreases, the control constant in the feedback correction coefficient setting means can be corrected finely, and the control of the air-fuel ratio feedback control can be performed. Performance is improved.

[0015]

Embodiments of the present invention will be described below. In FIG. 2 showing one embodiment, air is sucked into an internal combustion engine 1 through a throttle chamber 2 and an intake manifold 3. The throttle chamber 2 is provided with a throttle valve 4 interlocked with an accelerator pedal (not shown), and controls the intake air flow rate of the engine 1.

The branch portion of the intake manifold 3 is provided with an electromagnetic fuel injection valve 5 for each cylinder. The fuel is fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator.
Inject into and supply. The fuel injection valve 5 is opened intermittently in response to an injection pulse signal sent from a control unit 6 containing a microcomputer, and supplies fuel in accordance with the pulse width of the injection pulse signal calculated by the control unit 6. The amount is controlled.

Each cylinder of the internal combustion engine 1 is provided with an ignition plug 7 to which a high voltage generated by an ignition coil 8 is sequentially applied via a distributor 9, thereby spark ignition. The mixture is ignited and burned. Here, the timing at which the ignition coil 8 generates a high voltage is controlled via a power transistor 10 attached thereto.

The throttle valve 4 has an opening TVO.
Sensor that detects the pressure with a potentiometer
11 is attached. A detection signal is output from the crank angle sensor 12 built in the distributor 9 at every predetermined crank angle, and the engine speed Ne can be calculated based on the detection signal.

The cooling water jacket of the engine 1 has a water temperature sensor for detecting a cooling water temperature Tw representing the engine temperature.
The exhaust manifold 14 is provided with an oxygen sensor 15 (air-fuel ratio detecting means) for detecting the oxygen concentration in the exhaust gas which is closely related to the air-fuel ratio of the intake air-fuel mixture of the engine 1.
Moreover, the the intake duct of the throttle chamber 2 upstream an air flow meter 33 for detecting an intake air flow rate Q _A of the engine 1 is provided.

On the other hand, the engine 1 is provided with an evaporative fuel processing device 21 for a fuel tank 20. The evaporative fuel treatment device 21 causes the adsorbent 23 such as activated carbon filled in the canister 22 to adsorb and collect the evaporative fuel of the fuel generated in the fuel tank 20, and removes the fuel adsorbed by the adsorbent 23. Purging is performed, and the purge air is supplied to an intake passage downstream of the throttle valve 4 via a purge passage 24.

The evaporative fuel in the fuel tank 20 is introduced into the canister 22 through an evaporative fuel passage 26 provided with a check valve 25 which opens when the positive pressure in the fuel tank 20 exceeds a predetermined value. The purge passage 24 is provided with a purge control solenoid 29 for opening and closing the communication between the fuel vapor treatment device 21 and the intake passage downstream of the throttle valve 4.

Therefore, by stepwise controlling the opening and closing of the purge control solenoid 29, the stepwise opening and closing of the purge passage 24 can be electronically controlled by the control unit 6. As the purge control solenoid 29, a proportional solenoid or a step motor valve may be used.

That is, the purge control solenoid 29 and the control unit 6 have the function of evaporative fuel purge rate changing means. The control unit 6 includes a cooling water temperature Tw detected by the water temperature sensor 13, a vehicle speed sensor
Based on operating conditions such as the running speed VSP of the vehicle detected at 32, the elapsed time from the start of the engine, and the tank capacity, etc., canister purge conditions as to whether or not to perform canister purging, and purging when performing the canister purging. The ratio condition is determined, and the valve opening duty ratio of the purge control solenoid 29 is controlled in accordance with the determination result.

Further, the control unit 6 also performs air-fuel ratio feedback control, and the air-fuel ratio feedback control routine will be described with reference to the flowcharts of FIGS. FIG. 3 shows a fuel injection amount setting routine, which is performed at predetermined intervals (for example, 10 msec).
In this embodiment, the function as the air-fuel ratio feedback control means is provided by software in the control unit 6 as shown in the flowchart of FIG.

[0025] At step 51 (in the figure referred to as S51. Hereinafter the same) based on the engine rotational speed Ne that is calculated on the basis of a signal from the intake air flow rate Q _A and the crank angle sensor 12 detected by the air flow meter 33, The basic fuel injection amount Tp corresponding to the intake air flow rate per unit rotation is calculated by the following equation. Tp = K × Q _A / Ne (K is a constant) In step 52, various correction coefficients COEF are set based on the cooling water temperature Tw detected by the water temperature sensor 13.

In step 53, the air-fuel ratio feedback correction coefficient α set by the air-fuel ratio feedback correction coefficient setting routine described later is read. In step 54, a voltage correction Ts is set based on the battery voltage value. This is for correcting a change in the injection flow rate of the fuel injection valve 5 due to a change in the battery voltage.

In step 55, the final fuel injection amount (fuel supply amount) Ti is calculated according to the following equation. Ti = Tp × COEF × α + Ts In step 56, the calculated fuel injection amount Ti is set in an output register. Thus, at a predetermined fuel injection timing synchronized with the engine rotation, a drive pulse signal having a pulse width of the calculated fuel injection amount Ti is given to the fuel injection valve 5, and fuel injection is performed.

Next, an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment of the present invention will be described with reference to FIGS. This routine is executed in synchronization with the engine rotation. The air-fuel ratio feedback correction coefficient setting means,
Evaporative fuel purge rate changing means and air-fuel ratio feedback correction coefficient correcting means (purge rate change vector calculating means and variable
The control unit 6 is provided with a function as a function of a modified vector dependence correction means) as shown in the flowchart of FIG.

In the flowchart, in step 1, it is determined whether or not the operating condition is such that the air-fuel ratio feedback control is performed. If the above operating conditions are not satisfied, the routine proceeds to step 2, where the air-fuel ratio feedback correction coefficient α is clamped to α = 1, and the routine ends. In this case, the air-fuel ratio feedback control is stopped. If it is determined that the operating condition is such that the air-fuel ratio feedback control is performed, the process proceeds to step 3, where the oxygen sensor
The signal voltage OSR1 from 15 is AD-converted and taken in.

In step 4, the signal voltage OSR1 is compared with a reference value SL corresponding to a target air-fuel ratio (stoichiometric air-fuel ratio). If it is determined that the air-fuel ratio is rich (OSR1> SL), the process proceeds to step 5, where the sensor flag F1
(F1 = 1) and the air-fuel ratio is lean (OSR1 <
If it is determined to be SL), the process proceeds to step 6, where the sensor flag F1 is reset (F1 = 0).

In step 7, it is determined whether or not the sensor flag F1 has been inverted during the execution of this routine. If the sensor flag F1 is inverted from F1 = 0 to 1 or from F1 = 1 to 0, the routine proceeds to step 8, where the valve opening duty EVPTR of the purge control solenoid 29 indicating the purge rate has changed. It is determined by comparing the valve opening duty EVPTR1 in the previous routine execution with the valve opening duty EVPTR in the current routine execution.

If it is determined that EVPTR ≠ EVPTR1, it is determined that a change has occurred in the purge rate, and a time EVPTMR of an EVP timer for measuring an elapsed time from the start of the change is set to a predetermined time. Then, in step 10, a change amount X relating to a change in the purge rate is calculated. X = | EVPTR-EVPTR1 | In step 51, it is determined whether the air-fuel ratio changes in the rich direction or the lean direction according to the change in the valve opening duty EVPTR of the purge control solenoid 29. That is, it is determined whether or not (EVPTR−EVPTR1) ≧ 0. If it is determined that (EVPTR−EVPTR1) ≧ 0, the valve opening duty EVPTR1 in the previous execution of the routine is determined.
The valve opening duty EVPTR in this routine execution
Is higher in the direction in which a larger amount of purge fuel is supplied to the intake passage, and the air-fuel ratio is likely to change in the rich direction.

In step 52, the valve opening duty EVPTR in the current routine execution is executed for the next routine execution.
Is set to the previous value EVPTR1. Then, the process proceeds to a step 12, wherein it is determined whether or not the current sensor flag F1 is F1 = 0 or F1 = 1. If it is determined that F1 = 0, it is determined that the air-fuel ratio has changed from rich to lean and the process proceeds to step S13.

At the time of the reversal, the air-fuel ratio should be corrected in the rich direction as soon as possible. However, the change in the air-fuel ratio is larger as the change amount X of the purge rate is larger (see FIG. 7), and the change in the air-fuel ratio is larger. A large deviation occurs, and it is necessary to make a large correction (see FIG. 8). Therefore, in step 13, in order to make a large correction, the larger the amount of change X in the purge rate, the larger the value of the purge correction FPL that becomes larger as the amount of change X in the purge rate is calculated based on the amount of change X in the purge rate obtained in step 10.

[0035] Then, in step 14, the air-fuel ratio is inverted changes from rich to lean, but updates the air-fuel ratio feedback correction value alpha, this time, since the air-fuel ratio is in the case of changes in the rich direction The air-fuel ratio feedback control correction value α is corrected accordingly to the lean side. The air-fuel ratio feedback correction value α is
The proportional value PL in the increasing direction provided at the time of lean reversal for setting the air-fuel ratio feedback correction value is added to the current value α, and updated with a value obtained by subtracting the purge correction amount FPL calculated in step 13.

If it is determined that F1 = 1, it is determined that the air-fuel ratio has been reversed and the air-fuel ratio has changed from lean to rich, and the routine proceeds to step 15. At the time of the reversal, the air-fuel ratio should be corrected quickly in the lean direction. However, the change in the air-fuel ratio is larger as the change amount X of the purge rate is larger (see FIG. 7), and is larger as the change in the air-fuel ratio is larger. Occurs, and it is necessary to make a large correction (see FIG. 8). Therefore, in step 15, in order to make a large correction, the larger the change amount X of the purge rate, the larger the purge correction amount FPR, which becomes a larger value.
It is calculated based on the change amount X of the purge rate obtained in 10.

[0037] Then, in step 16, the air-fuel ratio is inverted changes from lean to rich, but updates the air-fuel ratio feedback correction value alpha, this time, since the air-fuel ratio is in the case of changes in the rich direction The air-fuel ratio feedback control correction value α is corrected accordingly to the lean side. The air-fuel ratio feedback correction value α is
The current value α is updated with a value obtained by subtracting the proportional amount PR in the decreasing direction given at the time of rich inversion for setting the air-fuel ratio feedback correction value and the purge correction amount FPR calculated in step 15.

That is, steps 10 , 51 , and 13 to 16 are claimed in claim 1.
It has the function of the air-fuel ratio feedback correction coefficient correction means according to the described invention. On the other hand, in step 51,
If it is determined that (EVPTR-EVPTR1) <0,
The valve opening duty EVPTR in this routine execution is lower than the valve opening duty EVPTR1 in the previous routine execution, and the purge fuel supplied to the intake passage changes in a direction to decrease, so that the air-fuel ratio becomes lean. The process proceeds to step 61 assuming that there is a possibility of change.

In step 61, the valve opening duty EVPTR in this routine execution is executed for the next routine execution.
Is set to the previous value EVPTR1. Then, the process proceeds to a step 62, wherein it is determined whether or not the current sensor flag F1 is F1 = 0 or F1 = 1. If it is determined that F1 = 0, it is determined that the air-fuel ratio has changed from rich to lean and the process proceeds to step 63.

At the time of the reversal, the air-fuel ratio should be corrected in the rich direction as soon as possible. However, the change in the air-fuel ratio is larger as the change amount X of the purge rate is larger (see FIG. 7), and the change in the air-fuel ratio is larger. A large deviation occurs, and it is necessary to make a large correction (see FIG. 8). Therefore, in step 63, in order to make a large correction, the purge correction amount FPL which becomes larger as the variation X of the purge rate becomes larger is calculated based on the variation X of the purge rate obtained in the step 10.

Then, in step 64, the air-fuel ratio is changed from rich to lean, and the air-fuel ratio feedback correction value α is updated. In this case, the air-fuel ratio changes in the lean direction. The air-fuel ratio feedback control correction value α is corrected to the rich side accordingly. The air-fuel ratio feedback correction value α is
The proportional value PL in the increasing direction given at the time of lean reversal for setting the air-fuel ratio feedback correction value is added to the current value α, and the purge correction amount FPL calculated in step 63 is updated with the added value.

If it is determined that F1 = 1, it is determined that the air-fuel ratio has changed from lean to rich, and the routine proceeds to step 65. At the time of the reversal, the air-fuel ratio should be corrected quickly in the lean direction. However, the change in the air-fuel ratio is larger as the change amount X of the purge rate is larger (see FIG. 7), and is larger as the change in the air-fuel ratio is larger. Occurs, and it is necessary to make a large correction (see FIG. 8). Therefore, in step 65, in order to make a large correction, the purge correction amount FPR, which becomes larger as the variation X of the purge rate becomes larger, is set in the aforementioned step.
It is calculated based on the change amount X of the purge rate obtained in 10.

Then, in step 66, the air-fuel ratio is changed from lean to rich, and the air-fuel ratio feedback correction value α is updated. In this case, the air-fuel ratio changes in the lean direction. The air-fuel ratio feedback control correction value α is corrected to the rich side accordingly. The air-fuel ratio feedback correction value α is
The proportional value PR in the decreasing direction given at the time of rich inversion for setting the air-fuel ratio feedback correction value is subtracted from the current value α, and the current value α is updated with a value obtained by adding the purge correction amount FPR calculated in step 15.

That is, steps 10 , 51 , 62 to 66 are also claimed in claim 1.
It has the function of the air-fuel ratio feedback correction coefficient correction means according to the described invention. On the other hand, in step 8, the EV
PTR = EVPTR1, that is, if it is determined that the valve opening duty EVPTR of the purge control solenoid 29 indicating the purge rate has not changed, and thus it has been determined that the purge rate has not changed, the routine proceeds to step 17 and proceeds to step 9 It is determined whether or not the remaining time EVPTMR of the EVP timer set in step 4 is 0. After decrementing, step
Proceeding to 51 , the air-fuel ratio feedback correction value α is corrected in consideration of the purge correction amount.

On the other hand, if it is determined in step 17 that the remaining time EVPTMR of the EVP timer has become 0 (EVPTMR = 0), the elapsed time from the start of the change has elapsed a predetermined time, and the purge rate Increase / decrease of the air-fuel ratio feedback correction coefficient due to the change (purge correction FP
L, FPR). Therefore, the process proceeds to step 19, where it is determined whether the current sensor flag F1 is F1 = 0 or F1 = 1.

If it is determined that F1 = 0, it is determined that the air-fuel ratio has changed from rich to lean, and the routine proceeds to step 20, where the air-fuel ratio feedback correction value α
Is updated from the present value to a value obtained by adding only the proportional component PL in the increasing direction given at the time of lean inversion for setting the air-fuel ratio feedback correction value. When it is determined that F1 = 1, it is determined that the air-fuel ratio has been changed from lean to rich, and the process proceeds to step 21, where the air-fuel ratio feedback correction value α is changed from the current value to the air-fuel ratio feedback correction value. It is updated with a value obtained by subtracting only the proportional component PR in the decreasing direction given at the time of rich inversion for setting.

On the other hand, if it is determined in step 7 that the sensor flag F1 has not been inverted,
Proceeding to 22, it is determined whether the current sensor flag F1 is F1 = 0 or F1 = 1. If it is determined that F1 = 0, it is determined that the air-fuel ratio remains lean, and the process proceeds to step 23, where the air-fuel ratio feedback correction coefficient α is updated with a value obtained by adding the integral IL to the current value. And return as it is.

If it is determined that F1 = 1, it is determined that the air-fuel ratio remains rich, and the routine proceeds to step 24, where the air-fuel ratio feedback correction coefficient α is obtained by subtracting the integral IR from the current value. And return as it is. Therefore, according to the first embodiment described above, when the fuel vapor from the canister 22 is purged to the internal combustion engine 1 or when the purge ends, or the opening and closing of the purge control solenoid 29 is duty-controlled. When the purge rate changes, depending on the respective conditions,
The air-fuel ratio feedback correction value α is set in consideration of the purge correction amount (FPL, FPR) calculated based on the purge rate change amount X for each purge rate change direction , and the feedback control is performed. As a result, the air-fuel ratio feedback control can act effectively.

Then, the purge correction amount (FPL, FPR)
The air-fuel ratio feedback correction value α in consideration of the above is set for a predetermined time after the change in the purge rate (in the first embodiment,
The air-fuel ratio feedback correction coefficient α is corrected by the purge correction amount (FPL, FPR) during the influence of the purge, and the controllability of the air-fuel ratio feedback control is maintained. Is improving.

Further, after a lapse of a predetermined time from the occurrence of a change in the purge rate, the influence of the purge becomes smaller.
The setting of the air-fuel ratio feedback correction value α in consideration of the above is stopped, and normal air-fuel ratio feedback control is performed. Therefore, in the first embodiment, even if the purge rate when the fuel vapor from the canister 22 is purged to the internal combustion engine 1 changes, the purge rate changes in each direction of the purge rate change. Of the purge correction calculated based on the variation X of the
L, FPR) in consideration of the air-fuel ratio feedback correction value α
Is set, and the feedback control is performed, so that the air-fuel ratio can be promptly converged to stoichiometric ratio, which has the effect of reducing CO, HC, and the like in the exhaust gas.

Next, a second embodiment of the present invention will be described with reference to the drawings. 9 and 10 show an air-fuel ratio feedback correction coefficient setting routine according to the second embodiment.
This routine is also executed in synchronization with the engine rotation.

Steps having functions similar to those of the air-fuel ratio feedback correction coefficient setting routine according to the first embodiment shown in FIGS. 4 to 6 are denoted by the same step numbers, and description thereof is omitted. In step 31, a change vector Y relating to a change in the purge rate is calculated. Y = EVPTR-EVPTR1 In step 32, the direction of the change vector Y calculated in step 31 is determined. When Y> 0, that is, when it is determined that the purge rate increases, the process proceeds to step 12 and subsequent steps.

Then, the process proceeds to a step 12, wherein it is determined whether or not the current sensor flag F1 is F1 = 0 or F1 = 1. When it is determined that F1 = 0,
It is determined that the air-fuel ratio has changed from rich to lean and the process proceeds to step 33. At the time of the reversal, the air-fuel ratio should be corrected in the rich direction promptly. However, the change in the air-fuel ratio increases as the absolute amount Y ′ of the purge rate change vector Y increases (see FIG. 11). The larger the change, the greater the deviation and the greater the need for correction. Therefore, in step 33, in order to make a large correction, the larger the absolute value Y 'of the vector is, the larger the purge correction amount FP becomes.
L is the purge rate change vector Y obtained in step 31.
Is calculated based on the absolute value of the vector Y ′ in the following equation.

FPL = f ₁ (Y ′) That is, steps 31, 32 and 33 are steps for changing vector dependent correction.
It has steps . Then, in step 34, assuming that the air-fuel ratio has changed from rich to lean, the air-fuel ratio feedback correction value α is increased from the current value by a proportional component PL in the increasing direction given at the time of lean inversion for setting the air-fuel ratio feedback correction value. It is updated with a value obtained by subtracting the purge correction FPL calculated in step 33.

When it is determined that F1 = 1, it is determined that the air-fuel ratio has been changed from lean to rich, and the routine proceeds to step 35. At the time of the reversal, the air-fuel ratio should be corrected promptly in the lean direction. However, the change in the air-fuel ratio increases as the absolute amount Y ′ of the purge rate change vector Y increases (see FIG. 11). The larger the change, the greater the deviation and the greater the need for correction. Accordingly, in step 35, in order to make a large correction, the larger the absolute value Y 'of the vector, the larger the purge correction amount FPR, which is larger, based on the absolute amount Y' of the vector of the change vector Y of the purge rate obtained in step 31. Then, it is calculated as in the following equation.

FPL = f ₂ (Y ′) Steps 31, 32 and 35 are also used as the change vector dependent correction means.
It has steps . In step 36, assuming that the air-fuel ratio has changed from lean to rich due to inversion, the air-fuel ratio feedback correction value α is reduced from the current value by a proportional component PR in the decreasing direction given at the time of rich inversion for setting the air-fuel ratio feedback correction value, The purge correction amount FP calculated in step 35
Update with the value obtained by subtracting R.

On the other hand, if it is determined in step 32 that Y <0, that is, the purge rate is decreasing,
Proceed to 37 or less. In step 37, the current sensor flag F
It is determined whether 1 is F1 = 0 or F1 = 1.

When it is determined that F1 = 0, it is determined that the air-fuel ratio has changed from rich to lean and the process proceeds to step 38. At the time of the reversal, the air-fuel ratio should be corrected in the rich direction promptly. However, the change in the air-fuel ratio increases as the absolute amount Y ′ of the purge rate change vector Y increases (see FIG. 11). The larger the change, the greater the deviation and the greater the need for correction. Therefore, in step 38, in order to make a large correction, the larger the absolute value Y 'of the vector is, the larger the purge correction amount FPL becomes, based on the absolute value Y' of the vector of the change vector Y of the purge rate obtained in step 31. Then, it is calculated as in the following equation.

FPL = f ₃ (Y ′) That is, steps 31, 32, and 38 also perform the change vector dependent correction procedure.
It has steps . Then, in step 39, assuming that the air-fuel ratio has changed from rich to lean, the air-fuel ratio feedback correction value α is increased from the current value by a proportional amount PL in the increasing direction given at the time of lean inversion for setting the air-fuel ratio feedback correction value. , The purge correction amount F calculated in step 38
Update with the value obtained by adding PL.

If it is determined that F1 = 1, it is determined that the air-fuel ratio has been reversed and the air-fuel ratio has changed from lean to rich, and the routine proceeds to step 40. At the time of the reversal, the air-fuel ratio should be corrected promptly in the lean direction. However, the change in the air-fuel ratio increases as the absolute amount Y ′ of the purge rate change vector Y increases (see FIG. 11). The larger the change, the greater the deviation and the greater the need for correction. Therefore, in step 40, in order to make a large correction, the larger the absolute value Y 'of the vector is, the larger the purge correction amount FPR becomes, based on the absolute value Y' of the vector of the change vector Y of the purge rate obtained in step 31. Then, it is calculated as in the following equation.

FPL = f ₄ (Y ′) Steps 31, 32 and 40 are also used as the change vector dependent correction means.
It has steps . Then, in step 41, assuming that the air-fuel ratio has been changed from lean to rich by inversion, the air-fuel ratio feedback correction value α is reduced from the current value by a proportional component PR in the decreasing direction given at the time of rich inversion for setting the air-fuel ratio feedback correction value. The value is subtracted and updated with the value obtained by adding the purge correction amount FPR calculated in step 40.

Therefore, according to the second embodiment described above, when the fuel vapor from the canister 22 is purged to the internal combustion engine 1 or when the purge is completed,
Alternatively, when the opening / closing of the purge control solenoid 29 is duty-controlled to change the purge rate, the purge correction amount (FP) calculated based on the absolute value Y ′ of the vector of the change rate Y of the purge rate according to the respective conditions.
L, FPR) in consideration of the air-fuel ratio feedback correction value α
Is set, and the feedback control is performed, so that the air-fuel ratio feedback control can work effectively as soon as possible. Also in the second embodiment, the air-fuel ratio feedback correction value α is set for a predetermined time after the change in the purge rate in consideration of the purge correction, and the controllability of the air-fuel ratio feedback control is improved. I have.

Therefore, also in the second embodiment, even if the purge rate when the fuel vapor from the canister 22 is purged to the internal combustion engine 1 changes, the absolute value of the vector in the purge rate change vector Y is changed. The air-fuel ratio feedback correction value α is set in consideration of the purge correction amount (FPL, FPR) calculated based on the amount Y ′, and the feedback control is performed, so that the air-fuel ratio can quickly converge to stoichiometry. This makes it possible to reduce CO, HC and the like in the exhaust gas.

In the second embodiment, when the purge correction amount (FPL, FPR) is calculated, the purge rate change vector Y is used. The purge correction amount (FPL, FP) differs between when the purge rate increases and when the purge rate decreases.
R) is set, and finer control becomes possible, and controllability is remarkably improved.

[0065]

As described above, in the air-fuel ratio control device for an internal combustion engine provided with the evaporative fuel processing device according to the first aspect of the present invention, the value is corrected to a different value according to the purge rate of the evaporative fuel to the engine. The control constant is set as a control constant in the air-fuel ratio feedback correction coefficient setting means, and the feedback control is performed, so that the air-fuel ratio feedback control can work effectively earlier and a larger purge amount is secured. Therefore, even when the purge amount is increased in a stepwise manner, the air-fuel ratio becomes over-rich due to the change in the purge rate, so that the air-fuel ratio is quickly controlled to an appropriate air-fuel ratio. Alternatively, even at the time of termination, it is possible to stabilize the base air-fuel ratio near the target air-fuel ratio. The air-fuel ratio of the mixture sucked becomes precisely controllable, the effect is obtained of avoiding the deterioration of exhaust emission due to the canister purge.

Further, by calculating the change vector calculated from the change in the purge rate, there is an effect that fine control including the direction of the change in the purge rate can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration according to the first embodiment;

FIG. 2 is a system diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing a fuel injection amount calculation routine of the embodiment.

FIG. 4 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment of the present invention;

FIG. 5 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment of the present invention;

FIG. 6 is a flowchart showing an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a relationship between a change in an air-fuel ratio and a change amount X in a purge rate in the first embodiment.

FIG. 8 is a characteristic diagram showing the relationship between the air-fuel ratio feedback correction amount and the change in the air-fuel ratio in the first embodiment.

FIG. 9 is a flowchart illustrating an air-fuel ratio feedback correction coefficient setting routine according to a second embodiment of the present invention.

FIG. 10 is a flowchart illustrating an air-fuel ratio feedback correction coefficient setting routine according to a second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a relationship between a change in air-fuel ratio and a change vector Y of a purge rate in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Control unit 12 Crank angle sensor 13 Water temperature sensor 20 Fuel tank 21 Evaporative fuel processor 24 Purge passage 29 Purge control solenoid 33 Air flow meter

Continuation of front page (56) References JP-A-62-131962 (JP, A) JP-A-6-25991 (JP, A) JP-A-5-202780 (JP, A) JP-A-2-130240 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/14 310 F02D 41/02 301 F02M 25/08 301

Claims (1)

(57) [Claims] An evaporative fuel processing device is provided for adsorbing and collecting the evaporative fuel generated from a fuel tank, purging the adsorbed and collected evaporative fuel into an intake passage of the engine and burning the evaporative fuel. Air-fuel ratio detection means for detecting an air-fuel ratio; air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient using a control constant based on a detection value of the air-fuel ratio detection means; and air-fuel ratio feedback correction coefficient setting means Air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio to the vicinity of the target air-fuel ratio based on the air-fuel ratio feedback correction coefficient set by: Evaporative fuel purge rate changing means for changing a purge rate to the engine according to operating conditions; When confirming the change of the purge rate by over-di ratio changing means, based on the purge rate to the engine of the evaporative fuel changes due to the fuel vapor purge rate changing means, a predetermined control constant in the air-fuel ratio feedback correction coefficient setting means Air-fuel ratio feedback correction coefficient correction means for correcting time , wherein the air-fuel ratio feedback correction coefficient correction means
Purge rate change vector in fuel generation purge rate change means
Purge rate change vector calculating means for calculating the
A change in purge rate was confirmed by the fuel generation purge rate change means.
Is calculated by the purge rate change vector calculating means.
The purge rate change vector for each change direction of the purge rate
Based on the amount of change in the purge rate calculated by the calculation means
In the air-fuel ratio feedback correction coefficient setting means,
The control constant is corrected for a predetermined time after the change occurs.
An air-fuel ratio control device for an internal combustion engine, comprising an evaporative fuel processing device, comprising: a vector-dependent correction unit .