JPH05223021A - Evaporated fuel disposal device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an evaporated fuel disposal device for an internal combustion engine which can carry out an early purge without disturbing the air-fuel ratio. CONSTITUTION:Evaporated fuel accumulated in a canister M1 is controlled, in its purge volume, by a purge control valve M3 controlled by a purge control valve control means M2, and is discharged into an disposed in an intake passage downstream of a throttle valve in an internal combustion engine M4. Upon fuel cut by a fuel injection control means M5, the purge control valve control means M2 stops the purge of evaporated fuel. A restart purge volume setting means 7 sets the purge volume to a value which is based upon the concentration of evaporated fuel before the fuel cut which is calculated by a vapor concentration calculating means M6 when the purge is restarted after completion of the fuel cut, and a purge value at that time. Further, a fuel injection volume compensating means M8 compensates the fuel injection volume in accordance with a compensated value which is calculated based upon the purge volume and the concentration of evaporated fuel at that time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, which stores evaporated fuel (vapor) in a canister and discharges it to an intake system according to engine operating conditions to process it.

[0002]

2. Description of the Related Art As a conventional device, Japanese Patent Application No. 2-1840
As described in No. 84, when performing purging, the purge valve opening is gradually increased from the start of purging to prevent a sudden change in the air-fuel ratio.

Further, as described in JP-A-61-38153, purging is stopped in conjunction with fuel cut, and purging is performed during deceleration where fuel cut is not performed to prevent catalyst overheating during deceleration and the effectiveness of the canister. There is something that can be utilized.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since the device for stopping the purge in conjunction with the fuel cut described in 8153 does not have a means for gradually increasing the purge amount when the purge is restarted after the cut, the paper is released from the canister at one time when the purge is restarted, and the air-fuel ratio becomes There is a problem of large fluctuations. In addition, the aforementioned Japanese Patent Application No. 2-184
In the device described in 084, which gradually increases the purge valve opening degree from the start of the purge, the purge valve opening degree gradually increases from zero when the fuel cut is ended and the purge is restarted. It may take a long time to complete the purge, and the purge may be delayed.If the fuel cut on / off is repeated in a short cycle before the purge amount is sufficiently increased, the overall purge amount may be very small. Be done.

The present invention has been made in view of the above points,
The purge amount at the time of restarting the purge after the fuel cut is set based on the evaporated fuel concentration before the fuel cut, and the fuel injection amount is corrected by the correction amount calculated based on the set purge amount and the evaporated fuel concentration. Accordingly, it is an object of the present invention to provide an evaporated fuel processing device for an internal combustion engine, which can execute an early purge without causing a disturbance in the air-fuel ratio.

[0006]

As shown in the principle diagram of FIG. 1A, the vaporized fuel processing apparatus for an internal combustion engine of the present invention controls the purge amount of the vaporized fuel stored in the canister M1 by a purge control valve M3. In the evaporative fuel processing apparatus of the internal combustion engine, which purges the intake passage downstream of the throttle valve to process the fuel, and stops the evaporative fuel purging at the time of fuel cut, the vapor concentration detecting means M6 for detecting the evaporative fuel concentration at the time of purging.
And a fuel injection amount correction means M8 for correcting the fuel injection amount based on the vapor concentration and the purge amount at the time of purging and correcting the fuel injection amount by the correction amount, and the above fuel cut is completed. When the purge is restarted, a restart purge amount setting means M7 for setting the purge amount based on the evaporated fuel concentration before the fuel cut is provided.

Further, as shown in FIG. 1B, there is provided a delay means M9 for delaying the correction of the fuel injection quantity by the injection quantity correction means M8 by a predetermined time after the fuel cut is completed and the purging is restarted.

[0008]

In the present invention, the evaporated fuel stored in the canister M1 is purged in the intake passage downstream of the throttle valve of the internal combustion engine M4 by controlling the purge amount by the purge control valve M3 controlled by the purge control valve control means M2. It is processed. At the time of fuel cut by the fuel injection control means M5, the purge control valve control means M2 stops the purge of the evaporated fuel.

The restart purge amount setting means M7 sets the purge amount based on the evaporated fuel concentration before the fuel cut detected by the vapor concentration detecting means M6 when the fuel cut is ended and the purge is restarted.

Further, the injection amount correction means M8 corrects the fuel injection amount injected from the fuel injection valve based on the amount of fuel purged into the intake passage.

The delay means M9 is the injection amount correction means M8.
The correction of the fuel injection amount by is delayed by a predetermined time after the fuel cut is completed and the purging is restarted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram of an embodiment of the device of the present invention. In the figure, 1 is an engine body, 2 is an intake branch pipe, 3 is an exhaust manifold, and 4 is a fuel injection valve attached to each intake branch pipe 2. Each intake branch pipe 2 is connected to a common surge tank 5, and this surge tank 5 is connected to an air cleaner 8 via an intake duct 6 and an air flow meter 7. A throttle valve 9 is arranged in the intake duct 6. Also,
As shown in FIG. 3, the internal combustion engine includes a canister 11 containing an activated carbon 10. This canister 11 has a fuel vapor chamber 12 and an atmosphere chamber 13 on both sides of the activated carbon 10, respectively. The fuel vapor chamber 12 is connected on the one hand to the fuel tank 15 via a conduit 14 and on the other hand to the surge tank 5 via a conduit 16. In the conduit 16, a purge control valve 1 controlled by an output signal of the electronic control unit 20
7 is placed. The fuel vapor generated in the fuel tank 15 is sent into the canister 11 via the conduit 14 and adsorbed on the activated carbon 10. When the purge control valve 17 is opened, air is sent from the atmospheric chamber 13 into the conduit 16 through the activated carbon 10. When the air passes through the activated carbon 10, the fuel vapor adsorbed on the activated carbon 10 is desorbed from the activated carbon 10, and thus the air containing the fuel vapor, that is, vapor, enters the surge tank 5 through the conduit 16. Purged.

The electronic control unit 20 is composed of a digital computer and has a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, and an input port 25 which are mutually connected by a bidirectional bus 21. And an output port 26. The air flow meter 7 generates an output voltage proportional to the intake air amount, and this output voltage is input to the input port 25 via the AD converter 27. A throttle switch 28, which is turned on when the throttle valve 9 is at the idling opening degree, is attached to the throttle valve 9, and an output signal of the throttle switch 28 is input to the input port 25. A water temperature sensor 29 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine body 1, and the output voltage of the water temperature sensor 29 is input to the input port 25 via the AD converter 30. An O ₂ sensor 31 is attached to the exhaust manifold 3, and the output signal of this O ₂ sensor 31 is used as the AD converter 3
It is input to the input port 25 via 2. Further, the input port 25 is connected to a crank angle sensor 33 that generates an output pulse each time the crankshaft rotates, for example, 30 degrees. The CPU 24 calculates the engine speed based on this output pulse. On the other hand, the output port 26 is connected to the fuel injection valve 4 and the purge control valve 17 via the corresponding drive circuits 34 and 35.

In the internal combustion engine shown in FIG. 3, the fuel injection time TAU is basically calculated based on the following equation.

TAU = TP · {1 + K + (FAF-1) + FPG} Here, each coefficient represents the following.

TP: Basic fuel injection time K: Correction coefficient FAF: Feedback correction coefficient FPG: Purge A / F correction coefficient The basic fuel injection time TP is an injection obtained by an experiment necessary to make the air-fuel ratio the target air-fuel ratio. This basic fuel injection time TP, which is a time, is stored in advance as a function of the engine load Q / N (intake air amount Q / engine speed N) and the engine speed N.
It is stored in 22.

The correction coefficient K is a collective expression of the warm-up increase coefficient and the acceleration increase coefficient, and K = 0 when it is not necessary to correct the increase.

The purge A / F correction coefficient FPG is for correcting the injection amount when purging is performed, and therefore FPG = 0 when the purging is not performed.

The feedback correction coefficient FAF is for controlling the air-fuel ratio to the target air-fuel ratio based on the output signal of the O ₂ sensor 31. Although any air-fuel ratio may be used as the target air-fuel ratio, the target air-fuel ratio is the stoichiometric air-fuel ratio in this embodiment. Therefore, the case where the target air-fuel ratio is the stoichiometric air-fuel ratio will be described below. When the target air-fuel ratio is the theoretical air-fuel ratio, a sensor whose output voltage changes according to the oxygen concentration in the exhaust gas is used as the O ₂ sensor 31. This O ₂ sensor 31 produces an output voltage of about 0.9 (V) when the air-fuel ratio is on the rich side, that is, when it is rich, and outputs about 0.1 (V) when the air-fuel ratio is on the lean side, that is, when it is lean. Generate voltage. First of all, this O ₂ sensor 31
Feedback correction coefficient F performed based on the output signal of
The AF control will be described.

FIG. 3 shows a routine for calculating the feedback correction coefficient FAF. This routine is executed, for example, in the main routine.

In the figure, first, at step 40, it is judged if the output voltage V of the O ₂ sensor 31 is higher than 0.45 (V), that is, if it is rich. V ≧ 0.45
In the case of (V), that is, in the case of rich, the routine proceeds to step 41, where it is judged if it was lean in the previous processing cycle. When lean in the previous processing cycle, that is, when changing from lean to rich, the routine proceeds to step 42, where the feedback correction coefficient FAF is set to FAFL,
Go to step 43. At step 43, the skip value S is subtracted from the feedback correction coefficient FAF, so that the feedback correction coefficient FAF is rapidly reduced by the skip value S as shown in FIG. Next, at step 44, the average value FAFAV of FAFL and FAFR is calculated. On the other hand, if it is determined in step 41 that the fuel was rich in the previous processing cycle, the routine proceeds to step 45, where the integral value K (K << S) is subtracted from the feedback correction coefficient FAF. Therefore, as shown in FIG. 4, the feedback correction coefficient FAF is gradually decreased.

On the other hand, in step 40, V <0.45
When it is judged to be (V), that is, when it is lean, the routine proceeds to step 46, where it is judged if it was rich in the previous processing cycle. When rich in the previous processing cycle, that is, when changing from rich to lean, the routine proceeds to step 47, where the feedback correction coefficient FAF is set to FAFR, and the routine proceeds to step 48. At step 48, the skip value S is added to the feedback correction coefficient FAF, so that the feedback correction coefficient FAF is rapidly increased by the skip value S as shown in FIG. Next, at step 44, the average value FAFAV of FAFL and FAFR is calculated. On the other hand, when it is determined in step 46 that the engine was lean in the previous processing cycle, the routine proceeds to step 49, where the integral value K is added to the feedback correction coefficient FAF. Therefore, as shown in FIG. 4, the feedback correction coefficient FAF is gradually increased.

When the fuel injection time TAU becomes rich and the FAF becomes small, the fuel injection time TAU becomes short, and when the fuel injection becomes lean and the FAF becomes large, the fuel injection time TAU becomes long, so that the air-fuel ratio is maintained at the stoichiometric air-fuel ratio. When the purge action is not performed, the feedback correction coefficient FAF fluctuates around 1.0 as shown in FIG. Also, the average value FAFAV calculated in step 44
Indicates the average value of the feedback correction coefficient FAF.

As can be seen from FIG. 4, the feedback correction coefficient FAF is changed relatively slowly with the integration constant K, so that a large amount of purge vapor is suddenly purged into the surge tank 5 and the air-fuel ratio changes abruptly. The fuel ratio cannot be maintained at the stoichiometric air-fuel ratio, and thus the air-fuel ratio fluctuates. Therefore, in this embodiment, in order to prevent the air-fuel ratio from fluctuating, the purge rate is gradually increased when purging. When the purge rate is gradually increased in this way, the air-fuel ratio is maintained at the stoichiometric air-fuel ratio by the feedback control using the feedback correction coefficient FAF even when the purge amount is increasing.
Thus, it is possible to prevent the air-fuel ratio from changing.

However, for example, when the acceleration operation is performed during purging, the purge vapor concentration in the intake air fluctuates greatly as described at the beginning, and therefore the air-fuel ratio fluctuates greatly, so that the purge amount is simply gradually increased. Even if it does, the air-fuel ratio will change. Therefore, in order to prevent the fluctuation of the air-fuel ratio during such an excessive operation, the purge amount is controlled by using the maximum purge rate which is the reference purge rate determined by the engine operating state. Next, a method of controlling the purge amount will be described.

The maximum purge rate MAXPG is the purge control valve 1
7 shows the ratio between the purge amount and the intake air amount when 7 is fully opened. An example of this maximum purge rate MAXPG is shown in Table 1 below.

[0027]

[Table 1]

As can be seen from Table 1, this maximum purge rate M
AXPG is a function of the engine load Q / N and the engine speed N, and the maximum purge rate MAXPG increases as the engine load Q / N decreases and increases as the engine speed N decreases. When performing the purge, first, the target purge rate TGTPG is slowly increased at a constant rate and then, when the target purge rate reaches a constant value, the target purge rate is maintained constant and the target purge rate T with respect to the maximum purge rate MAXPG.
The opening ratio of the purge control valve 17 is controlled according to the ratio of GTPG. In this embodiment, since the duty ratio of the opening time of the purge control valve 17 is controlled, in this case, the opening time of the purge control valve 17 is changed according to the ratio of the target purge rate TGTPG to the maximum purge rate MAXPG. The duty ratio is controlled.

That is, since the amount of evaporated fuel in the purge gas is not known, it is not known what the concentration of purge vapor in the intake air will be when the purge control valve 17 is fully opened.
However, when the adsorption amount of the fuel vapor on the activated carbon 10 of the canister 11 is the same, the purge vapor concentration in the intake air is proportional to the maximum purge rate MAXPG. Therefore, in order to keep the purge vapor concentration in the intake air constant, it is necessary to increase the opening degree of the purge control valve 17 and increase the purge amount as the maximum purge rate MAXPG decreases. In other words, when the target purge rate TGTPG is maintained constant, the opening rate of the purge control valve 17 is controlled according to the ratio of the target purge rate TGTPG to the maximum purge rate MAXPG, that is, the maximum purge rate MAXPG is The smaller the opening, the larger the opening of the purge control valve 17, so that the purge vapor concentration in the intake air becomes constant regardless of the engine operating state, so that the air-fuel ratio does not change even during transient operation. On the other hand, while the target purge rate TGTPG is gradually increased, the purge vapor concentration in the intake air increases in proportion to the target purge rate TGTPG,
At this time, the purge vapor concentration in the intake air is proportional to the target purge rate TGTPG even if the excessive operation is performed. That is, if the target purge rates TGTPG are the same, the purge vapor concentration is not affected by the engine operating state. Therefore, even if the acceleration operation is performed while the target purge rate TGTPG is being increased, the air-fuel ratio does not change, and the air-fuel ratio is maintained at the stoichiometric air-fuel ratio by the feedback control by the feedback correction coefficient FAF.

When the purge action is started, the actual purge rate PRG which normally increases together with the target purge rate TGTPG is gradually increased. Next, when the intake air amount Q increases due to the acceleration operation, the maximum purge rate MAXPG decreases, and the duty ratio PG for the purge control valve 17 decreases.
DUTY is increased. As a result, as described above, the purge vapor concentration in the intake air increases in proportion to the increase in the purge rate PGR, and thus the air-fuel ratio does not change.

On the other hand, when the purge action is started, the feedback correction coefficient FAF is set in order to maintain the air-fuel ratio at the stoichiometric air-fuel ratio.
Becomes smaller, and the average value FAFAV of the feedback correction coefficient FAF gradually becomes smaller when the purge action is started. In this case, the higher the purge vapor concentration in the intake air, the greater the reduction amount of the feedback correction coefficient FAF. At this time, the reduction amount of the feedback correction coefficient FAF is proportional to the purge vapor concentration in the intake air. From this, the purge vapor concentration in the intake air can be known. In this case, as described above, the purge vapor concentration is not affected by the excessive operation, and even during the excessive operation, the purge vapor concentration in the intake air is proportional to the target purge rate TGTPG, and the purge vapor concentration per unit target purge rate and the target The product of the purge rate is proportional to the target purge rate TGTPG even if the excessive operation is performed. Therefore, when the feedback correction coefficient FAF decreases, if the fuel injection amount is corrected based on the purge vapor concentration or the product of the purge vapor concentration per unit purge rate and the target purge rate, the air-fuel ratio can be calculated theoretically regardless of whether the engine is in an excessive operation or not. The air-fuel ratio can be maintained.

Here, if the target purge rate is gradually increased from zero when the fuel cut is ended and the purge is restarted after the purge is stopped at the time of the fuel cut, the purge will be delayed. Therefore, in this embodiment, when the purge is restarted, the target purge rate TGT corresponding to the purge vapor concentration before the fuel cut is executed.
PG is set, purging is performed at this target purge rate TGTPG for a predetermined time after the restart of purging, and then the purge rate is increased to perform early purging.

Next, the correction of the injection amount based on the purge vapor concentration will be described in more detail.

When purging is performed, the feedback correction coefficient FAF decreases to a value corresponding to the concentration of purge vapor in the intake air. However, the feedback correction coefficient FAF also decreases due to other causes such as a measurement error due to the air flow meter 7. Therefore, it is necessary to judge whether the variation of the feedback correction coefficient FAF is due to the purge. However, the reduction amount of the feedback correction coefficient FAF due to the purge becomes larger than the reduction amount of the feedback correction coefficient FAF due to other causes. However, considering the case where the feedback correction coefficient FAF is fixed and the open loop control is performed, the feedback correction coefficient FAF cannot be greatly reduced. Therefore, the average value FAFAV of the feedback correction coefficient FAF
Is reduced to some extent, the feedback correction coefficient F
Reduction of AF is suppressed, and feedback correction coefficient F
After the decrease in AF is suppressed, the purge vapor concentration is calculated using the coefficient FPGA representing the purge vapor concentration per unit target purge rate.

The coefficient FPGA will be described below.
In this embodiment, the feedback correction coefficient FAF is set to be as small as possible below the lower limit threshold value (FBA-X). When the feedback correction coefficient FAF is smaller than the lower limit threshold value (FBA-X) and is rich, the purge vapor concentration coefficient F per unit target purge rate is F.
Increases PGA. The above-mentioned purge A / F correction coefficient FPG is expressed in the form of a negative product of the purge vapor concentration coefficient FPGA per unit target purge rate and the purge rate PRG corresponding to the target purge rate TGTPG (FPG = -FPGA.PRG). Therefore, when the purge vapor concentration coefficient FPGA per unit target purge rate increases, the fuel injection amount is decreased, as can be seen from the above formula for calculating the fuel injection time TAU. In other words, when the purge vapor concentration coefficient FPGA per unit target purge rate becomes large, the fuel injection amount is reduced, so that the reducing action of the feedback correction coefficient FAF is suppressed.

In the internal combustion engine shown in FIG. 2, fuel injection from the fuel injection valve 4 is stopped during engine deceleration operation. If the evaporated fuel is purged when the fuel injection is stopped, the evaporated fuel is discharged into the exhaust manifold 3 without burning. Therefore, the purge action must be stopped when the fuel injection is stopped. When the fuel injection should be stopped, the cut flag is set, and when the cut flag is set, the purge action is stopped.

The cut flag processing routine shown in FIG. 5 is executed, for example, in the main routine.

First, at step 50, it is judged if the cut flag is set or not. When the cut flag is not set, the routine proceeds to step 51, where it is judged if the throttle switch 28 is on, that is, if the throttle valve 9 is at the idling opening degree. When the throttle valve 9 is at the idling opening degree, the routine proceeds to step 52, where the engine speed N is a constant value, for example,
It is determined whether it is 1200r.pm or higher. N ≧ 1200r.
When it is pm, the routine proceeds to step 53, where the cut flag is set. That is, when the throttle valve 9 is at the idling opening and N ≧ 1200 rpm, it is determined that the deceleration operation is being performed, and the cut flag is set.

When the cut flag is set, step 5
From 0, the routine proceeds to step 54, where it is judged if the throttle switch 28 is on, that is, if the throttle valve 9 is at the idling opening degree. When the throttle valve 9 is at the idling opening, the routine proceeds to step 56, where it is judged if the engine speed N is lower than 1000 rpm.
When N ≦ 1000 rpm, the routine proceeds to step 57, where the cut flag is reset. On the other hand, even if N> 1000 rpm, if the throttle valve 9 is opened, the routine jumps from step 54 to step 57 to reset the cut flag. When the cut flag is set, fuel injection is stopped.

FIG. 6 shows an initialization processing routine of purge control which is executed when an ignition switch (not shown) is turned on.

First, at step 60, the purge count value PGC is cleared, and then at step 61, the timer count value T is cleared. Then step 6
2, the drive duty ratio P for the purge control valve 17
GDUTY is set to zero, and then in step 63, the purge rate PGR is set to zero. Next, at step 64, the purge vapor concentration coefficient FPGA is made zero, and at step 65, the vapor concentration calculation count CFPGA is made zero. Next, at step 66, the purge control valve 17 is closed, and then the processing cycle is completed.

7 to 10 show a purge control routine, which is executed by interruption every 1 msec.

In FIG. 7, first, at step 70, the timer count value T is incremented by 1. Next, at step 71, the timer count value T is 100 corresponding to 100 msec which is the opening / closing cycle of the purge control valve 17.
Is determined. When T = 100, the process proceeds to step 72. Therefore, the process proceeds to step 72 every 100 msec. In step 72, the timer count value T is cleared, and then the process proceeds to step 73. Step 73
Then, it is determined whether or not the purge count value PGC is larger than 1. When the routine proceeds to step 73 for the first time after the ignition is turned on, the purge count value PGC is zero, so the routine proceeds to step 74 shown in FIG.

At step 74, it is judged if the condition for starting the purge control is satisfied. Engine cooling water temperature 70
When the temperature is 0 ° C., the air-fuel ratio feedback control is started, and the feedback correction coefficient FAF is skipped five times or more, it is determined that the condition for starting the purge control is satisfied. When the condition for starting the purge control is not satisfied, the processing cycle is completed. On the other hand, when the condition for starting the purge control is satisfied, the routine proceeds to step 75, where the purge count value PGC is set to 1. Next, at step 76, the average value FAFAV of the feedback correction coefficient FAF calculated in the routine shown in FIG. 3 is made FBA. Therefore, FBA represents the average value FAFAV of the feedback correction coefficient FAF when the condition for starting the purge control is satisfied. The processing cycle is then completed.

When it is judged that the condition for starting the purge control is satisfied, it is judged at step 73 of FIG. 7 that the purge count value PGC ≧ 1, so the routine proceeds to step 77. At step 77, it is judged if the cut flag is set, that is, if the fuel injection is stopped. When the cut flag is not set, the routine proceeds to step 78, where it is judged if the air-fuel ratio feedback control is being performed. If feedback control is in progress, the purge count value PGC is incremented by 1 in step 79, and then, in step 80, it is judged if the purge count value PGC is 6 or more. If it is determined that the purge count value PGC ≧ 6, that is, 500 msec has elapsed after the condition for starting the purge control is satisfied, the routine proceeds to step 83 in FIG.

Steps 83 to 93 are portions for calculating the purge vapor concentration, and this portion will be described later. Next, at step 95, the target purge rate TGTPG is calculated by adding a predetermined constant purge change rate PGA to the purge rate PGR. Therefore, the target purge rate TGTPG is increased by PGA every 100 msec. Then, the process proceeds to step 99 in FIG.

On the other hand, if it is judged at step 80 in FIG. 7 that the purge count value PGC <6, the routine proceeds to step 96 in FIG. 9, where it is judged if the vapor concentration calculation number CFPGA is 4 or more. When CPGGA <4 and the purge vapor concentration is not sufficiently calculated, the routine proceeds to step 95, where control is performed so that the purge rate is gradually increased from zero as in the conventional case, and the air-fuel ratio at the restart of purge from fuel cut is not disturbed. To do so.

After the purge vapor concentration is correctly calculated when CFPGA ≧ 4, the routine proceeds to step 97, where the target purge rate TGTPG at the restart of purge is calculated by the following equation.

TGTPG = 0.2 / FPGA That is, the target purge rate TGTPG is set so that the purge A / F correction coefficient FPG becomes -20%. As a result, the disturbance of the air-fuel ratio when restarting the purge from the fuel cut is small and the emission is prevented from deteriorating, and the purge can be executed early. When the fuel cut period is long, the vapor generated during that period is stored in the canister 11 and the vapor concentration at the time of restart of purging may change somewhat, so FAF correction can be used even in the worst case.
The purge is restarted from the purge A / F correction coefficient FPG of about 20%. Therefore, the purge rate at the time of restarting the purge can be set smaller as the vapor concentration is richer, and can be set larger as the leaner the leaner concentration, and the prevention of the air-fuel ratio disturbance and the early purge can be realized.

After executing step 97, the routine proceeds to step 99 of FIG. 10, guards the target purge rate TGTPG so as not to exceed 0.04, and executes the subsequent steps 101 to 109 to end the processing cycle. The control for keeping the purge rate constant at the above step 97 is executed for 500 msec until the purge counter PGC reaches 6 after restarting the purge, and during this period, the evaporation vapor passing through the conduit 16 and the purge control valve 17 is stabilized. And wait to enter the institution.

If it is determined in step 78 of FIG. 7 that the feedback control is not being performed, the process proceeds to step 101 of FIG. 10 to calculate the maximum purge rate MAXPG, and the subsequent steps 102 to 109 are executed to execute the processing cycle. To finish. That is, when feedback control is not performed by fully opening the throttle (WOT), steps 83 to 9 in FIG.
By bypassing 5, the previous purge rate PGR and the purge A / F correction coefficient FPG are maintained.

At step 99, the target purge rate TGTPG is set.
Is 0.04, that is, is greater than 4%. T
When GTPG <0.04, jump to step 101, T
When GTPG ≧ 0.04, the process proceeds to step 100 and TGTP
After G is set to 0.04, the process proceeds to step 101. That is, if the target purge rate TGTPG becomes too large and the purge amount becomes too large, it becomes difficult to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. Therefore, the target purge rate TGTPG is prevented from increasing by 4% or more.

In the following step 101, the engine load Q / N and the engine speed N from the above-mentioned Table 1 stored in the ROM 22 are stored.
The maximum purge rate MAXPG corresponding to is calculated.

Next, at step 102, the drive duty ratio PGDUTY of the purge control valve 17 is calculated based on the following equation.

Duty ratio PGDUTY = (target purge rate TGTPG / maximum purge rate MAXPG) .100 Next, at step 103, the duty ratio PGDUTY is
It is determined whether it is 100 or more, that is, 100% or more. PGD
When UTY <100, jump to step 105, PG
When DUTY ≧ 100, the routine proceeds to step 104, where the duty ratio PGDUTY is set to 100, and then the routine proceeds to step 105. At step 105, the timer count value Ta when the purge control valve 17 is closed is set to the duty ratio PGDUTY.
It is said that. Next, at step 106, the actual purge rate PRG is calculated based on the following equation. Actual purge rate PRG = (maximum purge rate MAXPG / duty ratio PGDUTY) / 100 That is, the duty ratio PGDUT in step 102
In the calculation of Y, when the maximum purge rate MAXPG becomes small (TGTPG / MAXPG) · 100 exceeds 100, the duty ratio PGDUTY is fixed at 100. In this case, the actual purge rate PGR is the target purge rate TGT.
It is smaller than PG. That is, when the purge control valve 17 is fully open and the maximum purge rate MAXPG decreases, the actual purge rate PGR decreases accordingly. In addition, (TGTPG / MAXPG) · 100 is 100
Unless the actual purge rate PRG exceeds the target purge rate T,
Matches GTPG.

Next, at step 107, the duty ratio P
It is determined whether GDUTY is greater than 1. PG
When DUTY <1, the routine proceeds to step 108, where the purge control valve 17 is closed, and then the processing cycle is completed. On the other hand, if PGDUTY ≧ 1, step
Proceeding to 109, the purge control valve 17 is opened, and then the processing cycle is completed.

In the next processing cycle, step 71 in FIG.
Then, the routine proceeds to step 111, where it is judged if the purge count value is 2 or more. If the purge count value is 1, the routine proceeds to step 112, where the purge rate is made zero, and the purge control valve 17 is closed at step 113 for processing. End the cycle. If the purge count value is 2 or more, it is determined in step 114 whether the cut flag is set. When the cut flag is not set, the routine proceeds to step 115, where it is judged if the timer count value T is larger than Ta. When T <Ta, the processing cycle is completed, and T ≧ T
When it becomes a, the purge control valve 17 is closed. Therefore, when PGC becomes larger than 2, that is, when 100 msec has elapsed from the start of the purge control, the purge control valve 17 is opened and the supply of the purge gas is started. At this time, the open period of the purge control valve 17 is the duty cycle. Matches the ratio PGDUTY. Next, as the purge count value PGC increases, the target purge rate TGTPG increases, so that the duty ratio PGDUTY increases, and thus the amount of purge vapor gradually increases. During this period, when the intake air amount Q increases, the duty ratio PGDUTY is increased as described above, and the actual purge rate PRG is increased at a constant rate.

Next, step 83 to step 93 in FIG.
Will be described. In step 83, the purge counter P
It is determined whether or not the GC is 156. When the process proceeds to step 83 for the first time after the purge control is started, PG
Since C = 6, the routine proceeds to step 84. At step 84, the feedback correction coefficient FAF is set to the upper threshold (FB
It is determined whether it is larger than (A + X). FB here
As described above, X is the average value FAFAV of the feedback correction coefficient FAF at the start of purge control, and X is a small constant value. When FAF <(FBA + X), the routine proceeds to step 87.

At step 87, it is judged if the feedback correction coefficient FAF is smaller than the lower limit threshold value (FBA-X). If FAF> (FBA-X), the routine proceeds to step 95. On the other hand, when FAF ≦ (FBA−X), the routine proceeds to step 88, where it is judged if the output voltage V of the O ₂ sensor 31 is higher than 0.45 (V), that is, if it is rich. .. If lean, proceed to step 95. On the other hand, when rich, the routine proceeds to step 89, where the constant value Y is added to the purge vapor concentration coefficient FPGA,
Then, it proceeds to step 95. Therefore FAF ≤ (FBA-
X) and rich, the purge vapor concentration coefficient FPGA is increased by a constant value Y.

On the other hand, in step 84, FAF ≧ (F
If it is BA + X), the process proceeds to step 85 and the O ₂ sensor 3
It is determined whether the output voltage V of 1 is lower than 0.45 (V), that is, whether the output voltage V is lean. If rich, proceed to step 95. On the other hand, when lean, the routine proceeds to step 86, where the constant value Y is subtracted from the purge vapor concentration coefficient FPGA, and the routine proceeds to step 95. Therefore, when the feedback correction coefficient FAF is larger than the upper limit threshold value (FBA + X) and is lean, the purge vapor concentration coefficient FPGA is decreased by a constant value Y. In this way, the air-fuel ratio does not fluctuate after FAF exceeds the upper threshold (FBA + X).

On the other hand, in step 83, PGC = 156
If, for example, 15 seconds elapse after the process proceeds to step 83 for the first time, the process proceeds to step 90 and the purge vapor concentration coefficient FPGA is calculated based on the following equation.

FPGA = FPGA- (FAFAV-FB
A) / (purge rate PRG · 2), that is, half of the deviation between the current feedback correction coefficient average value FAFAV and the feedback correction coefficient average value FBA at the start of purge per unit purge rate PRG is subtracted from the purge vapor concentration coefficient FPGA. .. In other words, half the amount of change in FAF per unit purge rate PRG is subtracted from the FPGA. When FAFAV becomes smaller than FBA, the purge vapor concentration coefficient FPGA is increased. Next, at step 91, the purge count PGC is set to 6. Therefore, it is understood that the process proceeds to step 90 every 15 seconds. Next, at step 92, a calculation flag PGF indicating that the FPGA calculation at step 90 is completed is set to 1, and then at step 93, the vapor concentration calculation count CFP is set.
GA is incremented by 1 and the routine proceeds to step 95.

On the other hand, step 77 or step 11 in FIG.
When it is determined in 4 that the cut flag is set, the routine proceeds to step 117, where the purge count PGC is set to 1. Next, at step 112, the purge rate PRG is made zero, and then at step 113, the purge control valve 1
7 is closed. That is, when the cut flag is set, the purging action is stopped, and the purging action is restarted after waiting until the purge counter PGC reaches 2.

FIG. 11 shows a routine for calculating the fuel injection time, and this routine is executed by interruption every constant crank angle.

In step 200, the purge counter PGC is set to 6
If PGC ≧ 6, the routine proceeds to step 201, where it is judged if the calculation flag PGF is set. When the calculation flag PGF is not set, the routine jumps to step 205. When the calculation flag PGF is set, the routine proceeds to step 202, where half of the deviation between the current feedback correction coefficient average value FAFAV and the feedback correction coefficient average value FBA at the start of the purge control is subtracted from the feedback correction coefficient FAF. The calculation flag PGF is set every 15 seconds, so 1
This process is executed every 5 seconds. FAFAV is FBA
If it becomes smaller than this, the FAF is increased by half the reduction amount of the feedback correction coefficient FAF. That is, FAF
Is increased by half of the decrease amount of FAF every 15 seconds, and at this time, the purge vapor concentration coefficient FPGA is increased by the amount corresponding to the increase amount of FAF.

Next, at step 203, (FAFAV-FBA) / 2 is subtracted from FAFAV in order to change FAFAV by the amount corresponding to the change in FAF. Next, at step 204, the calculation flag PGF is reset and the routine proceeds to step 205. In step 205, the purge A / F correction coefficient FPG is calculated based on the following equation.

Purge A / F correction coefficient FPG =-(purge vapor concentration coefficient FPGA / purge rate PRG) Next, at step 206, the basic fuel injection time TP is calculated, and then at step 207, the correction coefficient K is calculated. Next, at step 208, the fuel injection time TAU is calculated based on the following equation.

TAU = TP · {1 + K + (FAF-1) + FPG} Fuel is injected from the fuel injection valve 4 based on the fuel injection time TAU.

On the other hand, in step 200, the purge counter PG
If C <6, the routine proceeds to step 209, where the purge A / F correction coefficient FPG is set to zero and the routine proceeds to step 206. That is, the purge control is performed to the target purge rate until 500 msec immediately after the restart of the purge, but the A / F correction is not performed in consideration of the delay until the vapor reaches the intake system. Since the above-mentioned delay changes depending on the intake pipe volume and the like, it is adapted for each engine.

Here, when the number of vapor concentration calculations is 4 or more, as shown in FIG. 12, the cut flag is set to ₁ at the time t ₁ when the fuel cut condition occurs, and the purge and A
/ F correction is interrupted and the purge A / F correction coefficient FPG is 1.
At 0, the purge rate is 0% and the duty ratio PGDUTY is 0.
%, And the purge count value PGC is 1.

Next, at time t ₂ when the fuel cut condition disappears, the cut flag is reset to 0, and the target purge rate is set so that the purge A / F correction coefficient FPG becomes -20%, that is, 0.8. PGDUTY is set. Thereafter, the purge count value PGC is incremented every duty cycle (100 msec).

From time t ₃ when the purge count value becomes 6 after 500 msec has passed, the conventional purge rate increase control and purge A / F correction are executed. Compared to the conventional purge rate control shown by the one-dot chain line in FIG. 12, in this embodiment, the purge rate at the time of restarting the purge due to the end of the fuel cut is significantly increased, and the early purge is realized.

[0073]

As described above, according to the evaporated fuel processing apparatus for an internal combustion engine of the present invention, early purging can be executed without causing disturbance of the air-fuel ratio, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an overall view of the device of the present invention.

FIG. 3 is a flowchart for calculating a feedback correction coefficient.

FIG. 4 is a diagram showing a change in a feedback correction coefficient.

FIG. 5 is a flowchart for controlling a cut flag.

FIG. 6 is a flowchart for performing an initialization process of purge control.

FIG. 7 is a flowchart for performing purge control.

FIG. 8 is a flowchart for performing purge control.

FIG. 9 is a flowchart for performing purge control.

FIG. 10 is a flowchart for performing purge control.

FIG. 11 is a flowchart for calculating a fuel injection time.

FIG. 12 is a time chart during purge control.

[Explanation of symbols]

4 Fuel injection valve 9 Throttle valve 11, M1 canister 17, M3 Purge control valve 31 O ₂ sensor M2 Purge control valve control means M4 Internal combustion engine M5 Fuel injection amount control means M6 Vapor concentration detection means M7 Restart purge amount setting means M8 Injection amount Correction means M9 delay means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Kisho 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (2)

[Claims] 1. Evaporation of an internal combustion engine in which the evaporated fuel stored in a canister is purged into an intake passage downstream of a throttle valve while being processed while the purge amount is controlled by a purge control valve, and when the fuel is cut off, the purge of the evaporated fuel is stopped. In the fuel processor, a vapor concentration detecting means for detecting the evaporated fuel concentration at the time of purging, and at the time of purging, a correction amount of the fuel injection amount is calculated based on the detected evaporated fuel concentration and the purge amount at that time, and the correction is performed. An injection amount correction means for correcting the fuel injection amount according to the amount, and a restart purge amount setting means for setting the purge amount based on the evaporated fuel concentration before the fuel cut when the fuel cut is finished and the purge is restarted. An evaporated fuel processing device for an internal combustion engine, comprising: 2. An evaporative fuel treatment system for an internal combustion engine according to claim 1, further comprising delay means for delaying correction of the fuel injection quantity by said injection quantity correction means for a predetermined time after fuel cut is completed and purging is restarted. An evaporated fuel processing apparatus for an internal combustion engine, comprising: