JP2789908B2 - Evaporative fuel treatment system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing system for an internal combustion engine that stores evaporative fuel (vapor) in a canister and discharges the evaporative fuel to an intake system according to the operating state of the engine.

[0002]

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

As described in Japanese Patent Application Laid-Open No. 61-38153, purging is stopped in conjunction with fuel cut, purge is performed during deceleration when fuel cut is not performed, catalyst overheating is prevented during deceleration, and the canister is effectively used. There are things that can be used.

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-61-3
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, so that the paper is discharged from the canister at once when the purge is restarted, and the air-fuel ratio is reduced. There is a problem that it fluctuates greatly. In addition, the aforementioned Japanese Patent Application No. 2-184
The apparatus for gradually increasing the purge valve opening from the start of purging described in 084, since the purge valve opening gradually increases from zero when the fuel cut is terminated and the purge is restarted, the desired purge valve opening and the desired purge valve opening are gradually increased. In some cases, it may take a long time for the purge to be delayed, and if the on / off of the fuel cut is repeated in a short cycle before the purge amount is sufficiently increased, the purge amount as a whole may be very small. Can be

[0005] 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 completed 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 evaporative fuel processing apparatus for an internal combustion engine that 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 evaporated fuel processing apparatus for an internal combustion engine according to the present invention controls the purge amount of the evaporated fuel stored in the canister M1 by a purge control valve M3. A vapor concentration detecting means M6 for detecting the vaporized fuel concentration at the time of purging, in the vaporized fuel processing device for the internal combustion engine, which purges the vaporized fuel into the intake passage of the internal combustion engine while processing and stops the purge of the vaporized fuel when the fuel is cut off; An injection amount correction means M8 for calculating a correction amount of the fuel injection amount based on the vapor concentration at the time of purging and the purge amount at that time, and correcting the fuel injection amount based on the correction amount; When restarting, the purge amount is set to a purge amount based on the evaporated fuel concentration before the fuel cut.

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

[0008]

[Action] In the present invention, evaporated fuel stored in the canister M1 is purged with processed air intake passage of a controlled amount of purge by the internal combustion engine M4 purge control valve M3 which has been controlled to the purge control valve control means M2 . At the time of fuel cut by the fuel injection control means M5, the purge control valve control means M2 stops purging of the evaporated fuel.

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

The injection amount correcting means M8 corrects the amount of fuel injected from the fuel injection valve based on the amount of fuel purged into the intake passage.

The delay means M9 is provided with the injection amount correcting means M8.
The fuel injection amount is delayed by a predetermined time after the fuel cut is completed and the purge is restarted.

[0012]

FIG. 2 is a block diagram showing an embodiment of the apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes an engine main body, 2 denotes an intake branch pipe, 3 denotes an exhaust manifold, and 4 denotes a fuel injection valve attached to each intake branch pipe 2 respectively. 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 in which activated carbon 10 is built. The 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 a fuel tank 15 via a conduit 14 and on the other hand to the surge tank 5 via a conduit 16. A purge control valve 1 controlled by an output signal of an electronic control unit 20 is provided in a conduit 16.
7 are arranged. The fuel vapor generated in the fuel tank 15 is sent into the canister 11 via the conduit 14 and is adsorbed on the activated carbon 10. When the purge control valve 17 is opened, air is sent from the atmosphere chamber 13 through the activated carbon 10 and into the conduit 16. 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, so that the air containing the fuel vapor, that is, the vapor, enters the surge tank 5 through the conduit 16. Purged.

The electronic control unit 20 is composed of a digital computer, and a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, and an input port 25 interconnected by a bidirectional bus 21. And an output port 26. The air flow meter 7 generates an output voltage proportional to the amount of intake air, and the output voltage is input to the input port 25 via the AD converter 27. A throttle switch 28 that is turned on when the throttle valve 9 is at the idling opening is attached to the throttle valve 9, and an output signal of the throttle switch 28 is input to an 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 an input port 25 via an AD converter 30. The exhaust manifold 3 is attached O ₂ sensor 31, the O ₂ output signals AD converter 3 of the sensor 31
2 and input to the input port 25. Further, the input port 25 is connected to a crank angle sensor 33 that generates an output pulse every time the crankshaft rotates, for example, 30 degrees. The CPU 24 calculates the engine speed based on the 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 for setting the air-fuel ratio to the target air-fuel ratio. The basic fuel injection time TP is a function of the engine load Q / N (intake air amount Q / engine speed N) and the engine speed N.
22.

The correction coefficient K is a collective representation of the warm-up increase coefficient and the acceleration increase coefficient. When no increase correction is required, K = 0.

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

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, in this embodiment, the target air-fuel ratio is set to the stoichiometric air-fuel ratio. Therefore, a case where the target air-fuel ratio is set to the stoichiometric air-fuel ratio will be described below. When the target air-fuel ratio is the stoichiometric 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. The O ₂ sensor 31 generates an output voltage of about 0.9 (V) when the air-fuel ratio is rich, that is, when the air-fuel ratio is rich, and outputs about 0.1 (V) when the air-fuel ratio is lean, that is, when the air-fuel ratio is lean. Generates voltage. First, this O ₂ sensor 31
Feedback correction coefficient F 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 a main routine.

In FIG. 3, first, at step 40, it is determined whether or not the output voltage V of the O ₂ sensor 31 is higher than 0.45 (V), that is, whether or not the output voltage 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 determined whether or not the engine was lean in the previous processing cycle. At the time of lean operation in the previous processing cycle, that is, when the air condition changes from lean to rich, the routine proceeds to step 42, where the feedback correction coefficient FAF is set to FAFL.
Proceed to step 43. In step 43, the skip value S is subtracted from the feedback correction coefficient FAF. Therefore, 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 air conditioner was rich in the previous processing cycle, the process 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 reduced.

On the other hand, in step 40, V <0.45
When it is determined that (V), that is, when it is lean, the routine proceeds to step 46, where it is determined whether or not it was rich in the previous processing cycle. When rich in the previous processing cycle, that is, when the state changes 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. In step 48, the skip value S is added to the feedback correction coefficient FAF. Therefore, 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, if it is determined in step 46 that the engine was lean in the previous processing cycle, the process 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 becomes rich and the FAF becomes smaller, the fuel injection time TAU becomes shorter. When the fuel becomes lean and the FAF becomes larger, the fuel injection time TAU becomes longer, so that the air-fuel ratio is maintained at the stoichiometric air-fuel ratio. When the purging operation is not performed, the feedback correction coefficient FAF fluctuates around 1.0 as shown in FIG. 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 by the integration constant K. Therefore, when a large amount of purge vapor is suddenly purged into the surge tank 5 and the air-fuel ratio fluctuates suddenly, it becomes empty. The fuel ratio cannot be maintained at the stoichiometric air-fuel ratio, and the air-fuel ratio will fluctuate. Therefore, in this embodiment, the purge rate is gradually increased when purging is performed to prevent the air-fuel ratio from fluctuating. 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 fluctuating.

However, for example, when the acceleration operation is performed during the purge, as described at the beginning, the purge vapor concentration in the intake air fluctuates greatly, and therefore the air-fuel ratio fluctuates greatly. Even if it does, the air-fuel ratio will fluctuate. Therefore, in order to prevent such a change in the air-fuel ratio during the excessive operation, the purge amount is controlled using a maximum purge rate which is a reference purge rate determined according to an 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 the valve 7 is fully opened. An example of the 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. 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 gradually 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 is set.
The opening ratio of the purge control valve 17 is controlled according to the GTPG ratio. In this embodiment, the duty ratio of the valve opening time of the purge control valve 17 is controlled. In this case, the valve opening time of the purge control valve 17 is set in accordance with 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 fuel vapor in the purge gas is not known, it is not known what the concentration of the purge vapor in the intake air will be when the purge control valve 17 is fully opened.
However, when the amount of fuel vapor adsorbed on the activated carbon 10 by the canister 11 is the same, the concentration of the purge vapor 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 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 kept constant, if the opening ratio 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 becomes If the opening degree of the purge control valve 17 is increased as the value becomes smaller, the concentration of the purge vapor in the intake air becomes constant irrespective of the operating state of the engine, so that the air-fuel ratio does not change even during the 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, even if the transient operation is performed, the purge vapor concentration in the intake air is proportional to the target purge rate TGTPG. That is, if the target purge rate TGTPG is the same, the purge vapor concentration is not affected at all by the operating state of the engine. Therefore, even if the acceleration operation is performed while the target purge rate TGTPG is increased, the air-fuel ratio does not fluctuate, and the air-fuel ratio is maintained at the stoichiometric air-fuel ratio by the feedback control using 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 operation is performed and the intake air amount Q increases, the maximum purge rate MAXPG decreases, and the duty ratio PG for the purge control valve 17 is increased.
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 fluctuate.

On the other hand, when the purge action is started, the feedback correction coefficient FAF is set 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 concentration of the purge vapor in the intake air, the greater the decrease in the feedback correction coefficient FAF. At this time, the decrease in the feedback correction coefficient FAF is proportional to the concentration of the purge vapor in the intake air. From this, the concentration of the purge vapor in the intake air can be determined. 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. The product with the purge rate is proportional to the target purge rate TGTPG even if the transient operation is performed. Therefore, 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 when the feedback correction coefficient FAF decreases, the air-fuel ratio can be theoretically determined whether or not the engine is in an excessive operation. The air-fuel ratio can be maintained.

If the target purge rate is gradually increased from zero when the fuel cut is stopped and the purge is restarted after the purge is stopped at the time of the fuel cut, the purge is delayed. Therefore, in this embodiment, when the purge is restarted, the target purge rate TGT according to the purge vapor concentration before the fuel cut is performed.
The PG is set, the purge is performed at the target purge rate TGTPG for a predetermined time from the restart of the purge, and then the purge rate is increased to perform the early purge.

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

When the purge is performed, the feedback correction coefficient FAF decreases to a value corresponding to the concentration of the purge vapor in the intake air. However, the feedback correction coefficient FAF also decreases due to other causes, for example, a measurement error caused by the air flow meter 7. Therefore, it is necessary to determine whether the fluctuation of the feedback correction coefficient FAF is caused by the purge. However, the amount of decrease in the feedback correction coefficient FAF due to the purge is greater than the amount of decrease in the feedback correction coefficient FAF due to other causes. However, considering the case where open-loop control is performed with the feedback correction coefficient FAF fixed, the feedback correction coefficient FAF cannot be significantly reduced. Therefore, the average value FAFAV of the feedback correction coefficient FAF
Is reduced to some extent, the feedback correction coefficient F
AF is suppressed from decreasing, and the feedback correction coefficient F
After the decrease in AF is suppressed, the purge vapor concentration is obtained using a coefficient FPGA representing the purge vapor concentration per unit target purge rate.

Next, the coefficient FPGA will be described.
In the present embodiment, the feedback correction coefficient FAF is not reduced as much as possible from 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 F
Increase PGA. The above-mentioned purge A / F correction coefficient FPG is expressed in the form of a negative value (FPG = -FPGA.PRG) of a product of a purge vapor concentration coefficient FPGA per unit target purge rate and a purge rate PRG corresponding to the target purge rate TGTPG. Therefore, when the purge vapor concentration coefficient FPGA per unit target purge rate increases, the fuel injection amount is reduced as can be seen from the above-described equation for calculating the fuel injection time TAU. In other words, when the purge vapor concentration coefficient FPGA per unit target purge rate is increased, the fuel injection amount is reduced, so that the effect of decreasing 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. When the fuel vapor is purged when the fuel injection is stopped, the fuel vapor is discharged into the exhaust manifold 3 without burning. Therefore, when the fuel injection is stopped, the purging operation must be stopped. When the fuel injection is to be stopped, the cut flag is set, and when the cut flag is set, the purging operation is stopped.

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

First, at step 50, it is determined whether or not the cut flag is set. When the cut flag is not set, the routine proceeds to step 51, where it is determined whether or not the throttle switch 28 is on, that is, whether or not the throttle valve 9 is at the idling opening. When the throttle valve 9 is at the idling opening, the routine proceeds to step 52, where the engine speed N is a constant value, for example,
It is determined whether the speed is 1200 rpm or more. N ≧ 1200r.
At pm, the routine proceeds to step 53, where the cut flag is set. That is, when the throttle valve 9 has an idling opening degree and N ≧ 1200 rpm, it is determined that a 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 determined whether or not the throttle switch 28 is on, that is, whether or not the throttle valve 9 is at the idling opening. When the throttle valve 9 is at the idling opening, the routine proceeds to step 56, where it is determined whether or not the engine speed N is lower than 1000 rpm.
If 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 process jumps from step 54 to step 57 to reset the cut flag. When the cut flag is set, the fuel injection is stopped.

FIG. 6 shows a purge control initialization routine 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
At 2, the drive duty ratio P for the purge control valve 17
GDUTY is made zero, and then in step 63, the purge rate PGR is made zero. Next, at step 64, the purge vapor concentration coefficient FPGA is made zero, and at step 65, the vapor concentration calculation number CFPGA is made zero. Next, at step 66, the purge control valve 17 is closed, and then the processing cycle is completed.

FIGS. 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 one. Next, at step 71, the timer count value T becomes 100 corresponding to 100 msec which is the opening / closing cycle of the purge control valve 17.
Is determined. When T = 100, the routine proceeds to step 72. Therefore, the process proceeds to step 72 every 100 msec. At step 72, the timer count value T is cleared, and then the routine proceeds to step 73. Step 73
In, it is determined whether the purge count value PGC is greater than one. When the routine proceeds to step 73 for the first time after the ignition is turned on, the purge count value PGC is zero, and the routine proceeds to step 74 shown in FIG.

In step 74, it is determined whether or not a condition for starting the purge control is satisfied. Engine cooling water temperature 70
It is determined that the condition for starting the purge control has been satisfied when the temperature is 0 ° C., the feedback control of the air-fuel ratio has been started, and the skip processing of the feedback correction coefficient FAF has been performed five times or more. 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. Therefore, FBA represents the average value FAFAV of the feedback correction coefficient FAF when the condition for starting the purge control is satisfied. Then the processing cycle is completed.

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

Steps 83 to 93 are for calculating the purge vapor concentration, which 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. Next, the routine proceeds to step 99 in FIG.

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

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 time of restarting the 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, it is possible to prevent the disturbance of the air-fuel ratio when the purge is restarted from the fuel cut and to prevent the deterioration of the emission, and to execute the purge at an early stage. If 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 restarting the purge may change slightly. Therefore, the worst case can be dealt with by the FAF correction.
The purge is restarted from the purge A / F correction coefficient FPG of about 20%. For this reason, the purge rate at the time of restarting the purge can be set smaller as the vapor concentration becomes richer and larger as the vapor concentration becomes leaner, thereby realizing prevention of air-fuel ratio turbulence and early purging.

After executing step 97, the process proceeds to step 99 in FIG. 10, where the target purge rate TGTPG is guarded so as not to exceed 0.04, and the subsequent steps 101 to 109 are executed to terminate the processing cycle. In step 97, the control for keeping the purge rate constant is executed only for 500 msec until the purge counter PGC becomes 6 after the purge is restarted. During this time, the evaporative vapor passing through the conduit 16 and the purge control valve 17 is stabilized. Wait for the institution.

If it is determined in step 78 in FIG. 7 that the feedback control is not being performed, the flow advances to step 101 in FIG. 10 to calculate the maximum purge rate MAXPG and execute the subsequent steps 102 to 109 to execute the processing cycle. To end. In other words, when the feedback control is not performed when the throttle is fully opened (WOT) or the like, steps 83 to 9 in FIG.
5, the previous purge rate PGR and the purge A / F correction coefficient FPG are maintained.

In step 99, the target purge rate TGTPG
Is greater than 0.04, that is, 4%. T
If GTPG <0.04, jump to step 101,
If GTPG ≧ 0.04, proceed to step 100 to execute TGTP
After G is set to 0.04, the routine 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 are obtained from the above-mentioned Table 1 stored in the ROM 22.
Is calculated according to the maximum purge rate MAXPG.

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

Duty ratio PGUDUTY = (target purge rate TGTPG / maximum purge rate MAXPG) · 100 Next, at step 103, the duty ratio PGUDUTY is
It is determined whether it is 100 or more, that is, 100% or more. PGD
If UTY <100, jump to step 105 and select PG
If DUTY ≧ 100, the routine proceeds to step 104, where the duty ratio PGDUTY is set to 100, and then to step 105. In step 105, the timer count value Ta for closing the purge control valve 17 is changed to the duty ratio PGDUTY.
It is said. 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 PGUDUTY) / 100, that is, 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 PGUDUTY is fixed at 100. In this case, the actual purge rate PGR is the target purge rate TGT.
It becomes smaller than PG. That is, if the maximum purge rate MAXPG decreases when the purge control valve 17 is in the fully opened state, the actual purge rate PGR decreases accordingly. (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 one. 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 determined whether or not 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 in step 113, the purge control valve 17 is closed and the processing is performed. End the cycle. If the purge count value is 2 or more, it is determined in step 114 whether the cut flag is set. If the cut flag has not been set, the routine proceeds to step 115, where it is determined whether or not the timer count value T is greater 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 elapses from the start of the purge control, the purge control valve 17 is opened and the supply of the purge gas is started. It matches the ratio PGDUTY. Next, as the purge count value PGC increases, the target purge rate TGTPG increases, and accordingly, the duty ratio PGUDUTY increases, and thus the purge vapor amount is gradually increased. During this time, when the intake air amount Q increases, the duty ratio PGUDUTY is increased as described above, and the actual purge rate PRG is increased at a constant rate.

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

At step 87, it is determined whether or not 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, if FAF ≦ (FBA-X), the routine proceeds to step 88, where it is determined whether or not the output voltage V of the O ₂ sensor 31 is higher than 0.45 (V), that is, whether or not it is rich. . If it is lean, the process proceeds to step 95. On the other hand, if rich, the routine proceeds to step 89, where a constant value Y is added to the purge vapor concentration coefficient FPGA,
Next, the routine 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 (BA + X), the routine proceeds to step 85, where the O ₂ sensor 3
It is determined whether the output voltage V is lower than 0.45 (V), that is, it is lean. If it is rich, go 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 threshold (FBA + X) and lean, the purge vapor concentration coefficient FPGA is decreased by a constant value Y. In this way, the air-fuel ratio does not change after the FAF exceeds the upper threshold (FBA + X).

On the other hand, in step 83, PGC = 156
Is determined, that is, 15 seconds after the process first proceeds to step 83, the process proceeds to step 90, where 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 per unit purge rate PRG between the current feedback correction coefficient average value FAFAV and the feedback correction coefficient average value FBA at the start of purge is subtracted from the purge vapor concentration coefficient FPGA. . In other words, half of 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 can be seen that the process proceeds to step 90 every 15 seconds. Next, at step 92, a calculation flag PGF indicating that the calculation of the FPGA at step 90 has been completed is set to 1, and then at step 93, the number of times of calculating the vapor concentration CFP
GA is incremented by one and the routine proceeds to step 95.

On the other hand, step 77 or step 11 in FIG.
If it is determined in step 4 that the cut flag has been 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 purge action is stopped, and the purge action is started again after waiting until the purge counter PGC becomes 2.

FIG. 11 shows a routine for calculating the fuel injection time. This routine is executed by interruption every fixed 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 determined whether the calculation flag PGF is set. If 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 difference 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. Since the calculation flag PGF is set every 15 seconds, 1
This process is performed every 5 seconds. FAFAV is FBA
When it becomes smaller, the FAF is increased by half of the decrease amount of the feedback correction coefficient FAF. That is, FAF
Is increased by half of the decrease amount of the FAF every 15 seconds. At this time, the purge vapor concentration coefficient FPGA is increased by an amount corresponding to the increase amount of the FAF.

Next, at step 203, (FAFAV-FBA) / 2 is subtracted from FAFAV in order to change FAFAV by an 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, at 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 varies depending on the intake pipe volume and the like, it is adjusted for each engine.

Here, when the number of times of vapor concentration calculation is four or more, as shown in FIG. 12, the cut flag is set to ₁ at 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 becomes 1.
At 0, the purge rate is 0% and the duty ratio PGDTY is 0
% And the purge count value PGC are set to 1.

[0071] Next cut flag at time t ₂ to the fuel cut-off condition has disappeared is reset to 0, the target purge rate is set to the purge A / F correction coefficient FPG is -20%, i.e. 0.8, from which a duty ratio PGDUTY is set. Thereafter, the purge count value PGC is counted up every duty cycle (100 msec).

From time point t ₃ when the purge count value reaches 6 after 500 msec has elapsed, the control of increasing the purge rate and the purge A / F correction as in the prior art are executed. Compared with the conventional purge rate control indicated by the dashed line in FIG. 12, in the present embodiment, the purge rate at the time of restarting the purge after the end of the fuel cut is greatly increased, and the early purge is realized.

[0073]

As described above, according to the evaporative fuel treatment system for an internal combustion engine of the present invention, an early purge can be executed without causing a disturbance in the air-fuel ratio, which is extremely useful in practice.

[Brief description of the 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 a purge control initialization process.

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 the 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 detecting means M7 restart purge amount setting means M8 injection quantity Correction means M9 Delay means

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Kisokoro 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-2-95746 (JP, A) JP-A-63- 189665 (JP, A) JP-A-63-255559 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 25/08 301 F02D 41/00-45/00

Claims (2)

(57) [Claims] An evaporative fuel of an internal combustion engine that purges evaporative fuel stored in a canister into an intake passage of an internal combustion engine while controlling a purge amount with a purge control valve, and stops purging of the evaporative fuel during fuel cut. A vapor concentration detecting means for detecting a vaporized fuel concentration at the time of purging; and a correction amount of the fuel injection amount is calculated at the time of purging based on the detected vaporized fuel concentration and the purge amount at the time. And a resumption purge amount setting means for setting the purge amount based on the evaporated fuel concentration before the fuel cut when resuming the purge after terminating the fuel cut. A fuel vapor treatment device for an internal combustion engine, characterized by: 2. An evaporative fuel processing apparatus for an internal combustion engine according to claim 1, wherein the correction of the fuel injection amount by the injection amount correction unit is delayed by a predetermined time after the fuel cut is completed and the purge is restarted. An evaporative fuel treatment system for an internal combustion engine, comprising: