JP2861369B2 - Evaporative fuel processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus for purging evaporative fuel gas adsorbed by an adsorber by sucking it into an intake system of an internal combustion engine.

[Conventional technology]

Since the fuel gas evaporated in the fuel tank cannot be released to the outside, it is adsorbed by the adsorber and purged into the intake system through a connecting pipe connecting the vicinity of the cylinder inlet of the intake system of the internal combustion engine of the adsorber. Is widely used.

However, in the state where the air-fuel ratio control of the internal combustion engine is being executed, the purged fuel gas acts as a disturbance, and deteriorates the properties of the exhaust gas.

In order to solve this problem, a method is provided in which a purge control valve is provided in a communication pipe, and an opening degree of the purge control valve is equivalently controlled by changing a duty ratio of opening and closing of the purge control valve according to an operation state of the internal combustion engine. Has been proposed (Japanese Unexamined Patent Publication
62-26357, JP-A-63-85249).

[Problems to be solved by the invention]

 However, the purge amount Qp is determined by equation (1).

Qp = k · α · ΔP (1) where α = opening of the purge control valve ΔP = differential pressure between atmospheric pressure and intake system pressure k = constant That is, even if only the opening of the purge control valve is controlled, the differential pressure is If different, the purge amount will be different.

Further, since the purged fuel gas is added to the fuel injection amount based on the output of the air-fuel ratio control device, the controllability of the air-fuel ratio control is affected by the amount of the fuel gas adsorbed in the adsorber. For example, when the amount of fuel gas contained in the purge gas is very large, it is impossible to control the air-fuel ratio normally even if the air-fuel ratio correction amount is minimized.

Conversely, when the fuel gas in the purge gas is small and the purge amount is large, the air-fuel ratio cannot be controlled normally even if the air-fuel ratio correction amount is maximized.

That is, even if the opening degree of the purge control valve is simply controlled in accordance with the operation state of the internal combustion engine, for example, the rotation speed, depending on the intake pipe pressure and the amount of fuel gas adsorbed in the adsorber, depending on the air-fuel ratio control device, This causes a problem that disturbance cannot be corrected.

Therefore, in view of the above problems, the present invention limits the opening of the purge control valve according to the internal combustion engine load proportional to the intake pipe pressure, and also controls the opening of the purge control valve by the air-fuel ratio correction amount of the air-fuel ratio control device. It is an object of the present invention to provide an evaporative fuel treatment apparatus which can suppress the influence of the purge on the air-fuel ratio control by changing the fuel cell.

[Means for solving the problem]

FIG. 1 shows the configuration of an evaporative fuel treatment apparatus for solving the above-mentioned problems.

That is, the air-fuel ratio sensor A installed in the exhaust system of the internal combustion engine
An air-fuel ratio correction amount calculating means B for providing an air-fuel ratio correction amount for controlling the exhaust gas of the internal combustion engine to a predetermined air-fuel ratio in accordance with the output of the air-fuel ratio sensor A; Air-fuel ratio adjusting means C for adjusting the amount of fuel supplied to the internal combustion engine based on the result to adjust the exhaust gas of the internal combustion engine to a predetermined air-fuel ratio, and operating state determining means D for determining the load state of the internal combustion engine And a purge control valve E installed in the middle of a connecting pipe connecting the fuel gas adsorber for adsorbing the fuel gas evaporated from the fuel tank and the intake passage of the internal combustion engine.
When the operating state determining means D detects the light load operating state, the purge control sets a valve opening area narrower than the valve opening area of the purge control valve E set when it is determined that the operating state is not the light load operating state. If the calculation results of the valve opening area setting means F and the air-fuel ratio correction amount calculating means B are within the purge control valve opening area set by the purge control valve opening area setting means F, the operating state determination means D The purge control valve E adjusts the opening degree of the purge control valve E to a smaller opening degree as the load detected by the purge control valve E becomes smaller, and the purge control valve opening degree adjusting means G fully closes the purge control valve when it is out of the valve opening range. Be composed.

(Operation)

In the evaporative fuel treatment device configured as described above, the opening degree of the purge control valve is limited by using the load of the internal combustion engine, which is a parameter proportional to the intake pipe pressure, and is also determined by the air-fuel ratio correction amount. By changing the opening of the purge control valve, the effect of the purge of the fuel gas from the fuel adsorber on the air-fuel ratio control can be suppressed.

〔Example〕

FIG. 2 shows an air-fuel ratio control apparatus 1 for an internal combustion engine according to the present invention.
And FIG. In FIG. 2, the internal combustion engine 1
An air flow meter 3 is installed in the intake passage 2 of the air conditioner. The air flow meter 3 is a device for measuring the amount of air taken in by the internal combustion engine, and outputs an electric signal proportional to the mass flow rate of the intake air. This electric signal is
It is supplied to the A / D converter 101.

The distributor 4 is provided with, for example, a crank angle sensor 5 that outputs a pulse signal every 720 ° converted to a crank angle and a crank angle sensor 6 that outputs a pulse every 30 ° converted to a crank angle.
The pulse output of the crank angle sensor is supplied to the input / output interface 102 of the control circuit 10.

Further, a fuel injection valve 7 for supplying fuel to each cylinder in accordance with a command from the control device 10 is provided in the intake passage 2 of the internal combustion engine.

The water jacket 8 of the internal combustion engine 1 is provided with a water temperature sensor 9 for detecting the temperature of the cooling water.
It is supplied to the A / D converter 101.

The exhaust system downstream of the exhaust manifold 11, HC in the exhaust gas, CO, three-way catalyst 12 simultaneously purifies NO _X is arranged.

An air-fuel ratio sensor 13 is provided in the exhaust pipe 11 upstream of the three-way catalyst, and the output thereof is supplied to the A / D converter 101.

The control circuit 10 is composed of, for example, a microcomputer system, and includes an A / D converter 101, an input / output interface
10, CPU1203, ROM104, RAM105, backup RAM106,
It includes a clock generation circuit 107 and the like.

The throttle valve 16 installed in the intake passage 2 is provided with an idle switch 17 for detecting whether or not the throttle valve 16 is fully opened. This output is input to the control circuit 10 via the input / output interface 102. You.

In the control circuit 10, the down counter 108, the flip-flop 109, and the drive circuit 110 are for controlling the fuel injection valve 7. That is, when the fuel injection amount TAU is calculated in the fuel injection amount calculation routine, the calculation result is set in the down counter 108, and at the same time, the flip-flop 109 is also set. As a result, the drive circuit 110 energizes the fuel injection valve 7. The down counter 108 starts counting clock pulses (not shown). When the value of the down counter 108 becomes zero, the flip-flop 109 is reset, and the drive circuit 110 stops energizing the fuel injection valve. That is, the fuel injection valve 7 is energized for a period calculated by the fuel injection amount calculation routine, and fuel according to the calculation result is supplied to each cylinder of the internal combustion engine 1.

The fuel evaporated in the fuel tank 25 is guided to the adsorber 20 via the connecting pipe 23 and is adsorbed. The adsorber 20 is connected to a purge port 22 provided in a surge tank in an intake passage by a connection pipe 24 equipped with a purge control valve 21.

The opening of the purge control valve is controlled by an opening command signal supplied from the control circuit 10 via an input / output interface.

In the first embodiment of the evaporative fuel treatment apparatus configured as described above, control is performed as follows.

FIG. 3 shows a routine for controlling the opening of the purge control valve, which is executed at regular intervals.

Cooling temperature THW detected by water temperature sensor 9 in step 301
Is determined to be not less than a predetermined value, for example, 60 ° C. If a negative determination is made, the purge control valve opening command VSV = 0 is set in step 311, in order to prevent deterioration of drivability, assuming that the internal combustion engine is not fully warmed up.

If a positive determination is made in step 301, the process proceeds to step 302,
It is determined whether or not the fuel is being cut. Fuel cut is performed for the purpose of suppressing unnecessary fuel consumption, for example, when the accelerator is released during high-speed operation.If purging is performed in such a case, abnormal combustion occurs in the three-way catalyst installed in the exhaust system. Flag during fuel cut because it may happen
FC = 1, and an affirmative determination is made in step 302, step 311
Proceed to.

If the fuel is not being cut, a negative determination is made in step 302 and the routine proceeds to step 303, where it is determined whether air-fuel ratio control is permitted. For example, if the air-fuel ratio sensor is not activated after the start of the internal combustion engine, the flag FB = 0 is reset because the air-fuel ratio control cannot be executed. In this case, a negative determination is made in step 303 and the process proceeds to step 311.

If a positive determination is made in step 303, the process proceeds to step 304,
The parameter Q / N is a value proportional to the pressure of the intake system and representing the load on the internal combustion engine. Here, the value of Q = intake air flow rate N = internal combustion engine speed is determined, and the purge control valve is opened according to this value. The area is switched.

If the value of Q / N is equal to or greater than a predetermined value, for example, 0.5 or more, the internal combustion engine is operated at a relatively heavy load, and even if fuel is purged, it is determined that the effect on air-fuel ratio control is small. And the process proceeds to step 305.

In step 305, the air-fuel ratio sensor 13 installed in the exhaust system
Is determined by the air-fuel ratio correction amount calculation means based on the output of the air-fuel ratio correction amount FAF outputted to the air-fuel ratio adjustment means.

The air-fuel ratio correction amount FAF fluctuates with reference to 1.0, but there are also restrictions on the operating speed, injection speed, and the like of the injector, and it is impossible to control the air-fuel ratio if the air-fuel ratio deviates extremely from the reference value. Therefore, it is determined whether or not 0.85 <air-fuel ratio correction amount FAF <1.15 is satisfied.

If a negative determination is made in step 305, it is considered that proper air-fuel ratio control cannot be performed if disturbance is applied by the purge, and the flow proceeds to step 311.

 If an affirmative determination is made in step 305, the process proceeds to step 306, where it is determined whether or not 0.90 <air-fuel ratio correction amount FAF <1.10.

If an affirmative determination is made in step 306, it is assumed that the correction amount of the air-fuel ratio control is small and disturbance due to purge can be sufficiently corrected, and the routine proceeds to step 307, where the purge control valve valve opening command VSV = 1.

If a negative determination is made in step 306, it is considered that the margin of the air-fuel ratio control is small, and the routine proceeds to step 310, where the purge control valve valve opening command VSV = 0.5.

If a negative determination is made in step 304, it is assumed that the internal combustion engine is operating at a light load, and in step 308 it is determined whether the vehicle speed is equal to or higher than a predetermined value, for example, 15 km / h.

If the pressure is equal to or less than the specified value, the purge becomes a large disturbance, so a negative determination is made in step 308 and the routine proceeds to step 312, where the purge control valve valve opening command VSV = 0 is set. If the value is equal to or larger than the specified value, an affirmative determination is made in step 308 and the process proceeds to step 309.

 In step 309, it is determined whether or not 0.90 <FAF <1.10.

When the internal combustion engine is operated at a light load, the influence of the purge is greater than when the internal combustion engine is operated at a high load. Therefore, the determination range of the air-fuel ratio correction amount FAF is set small.

If an affirmative determination is made in step 309, the process proceeds to step 310, where the purge control valve valve opening command VSV = 0.5. Step 30
If a negative determination is made in step 9, the routine proceeds to step 312, where the purge control valve valve opening command VSV = 0 is set.

Based on the purge control valve valve opening command determined in this way, the control circuit 10 generates a pulse whose on-time occupies in one period of the pulse, that is, a pulse whose duty ratio is equal to the purge control valve valve opening command VSV. The purge control valve is generated and supplied to the purge control valve via the input / output interface 102, and the purge control valve is controlled to a specified opening.

According to the above method, when the operating state of the internal combustion engine changes, the opening degree of the purge control valve changes greatly. At that time, the rotation speed and torque of the internal combustion engine also change, which affects drivability.

A method for improving this point is shown in the flowchart of FIG.

That is, by executing the routine shown in FIG. 4 together with the routine shown in FIG. 3, the opening degree of the purge control valve can be gradually changed.

In step 401, a counter for counting the number of times this routine is executed is incremented by one, and the routine proceeds to step 402. In step 402, it is determined whether the value of the counter CVCS is equal to or greater than a predetermined value KCV. That is, the routine proceeds to step 403 each time the routine is executed KCV times.

After the counter CVCS is reset to 1 in step 403, a flag FC indicating that the fuel is being cut off is determined in step 404. If the fuel is being cut off, FC = 1, and the affirmative determination is made in step 404, and the flow proceeds to step 405.

In step 405, during the fuel cut, the purge control valve is quickly fully closed to prevent the occurrence of abnormal combustion due to the purge.
0 and the duty ratio counter CDUTY are reset to 0, and the routine proceeds to step 411. In step 411, it is determined whether the purge control valve opening target value TDUTY is equal to the value of the duty ratio counter CDUTY. If both values are zero, a positive determination is made in step 411 and the process proceeds to step 415.

In step 415, the counter CVCS and the duty ratio counter C
DUTY values are compared. Duty ratio counter CDUTY =
If it is 0, the process proceeds to step 416, where the purge control valve opening command V
SVON = 0. The purge control valve open command VSVON is directly applied to the purge control valve via the input / output interface 102, and in this case, the purge control valve is fully closed.

If the fuel is not being cut, a negative determination is made in step 404 and the process proceeds to step 406. In step 406, the value of the purge control valve valve opening command VSV determined in the routine of FIG. 3 is determined.

If the purge control valve opening command VSV = 0, step 4
At 06, an affirmative determination is made and the routine proceeds to step 407, where the purge control valve opening target value TDUTY = 0 is set.

Then, the process proceeds to step 411, where the purge control valve valve opening target TDU is set.
It is determined whether or not TY is equal to the value of the duty ratio counter CDUTY. In this case, as the value of the duty ratio counter CDUTY, the value at the time of the previous execution of this routine is used as it is. For example, if the previous duty ratio counter CDUTY was 5, a negative determination is made in step 411, and
Proceed to 12.

Then, a negative determination is made in step 412, and the duty ratio counter CDUTY is decremented by 1 in step 414, and the routine proceeds to step 415.

In step 415, the counter CVCS and the duty ratio counter C
The values of DUTY are compared, but the duty ratio counter = 4,
If the counter CVCS = 1, a negative determination is made in step 415, and in step 417, the purge control valve opening command VSVON = 1.

The next time this routine is executed, a negative determination is made in step 402 and the routine proceeds to step 415.

In step 415, the counter CVCS and the duty ratio counter C
The values of DUTY are compared. If the value of the counter CVCS is equal to or greater than the duty ratio counter CDUTY, an affirmative determination is made in step 415, and the purge control valve open command VSVON = 0.

For example, if KCV = 10, the purge control valve opening command VSVON = 1 for the first four execution cycles of this routine,
Since VSVON = 0 in the remaining six cycles, the actual opening of the purge control valve is controlled to 40%.

When the value of the counter CVCS reaches the specified value, an affirmative determination is made in step 402 and the processing of step 403 and subsequent steps is executed.If the value of the purge control valve opening command VSV does not change, the duty ratio counter CDUTY is decremented by 1 in step 414, As a result, in the processing after step 415, the first three cycles VSVON =
1. The remaining seven cycles VSVON = 0, and the actual opening of the purge control valve is controlled to 30%.

FIG. 5 is a timing chart of the above-described purge control valve opening control. The horizontal axis represents time, and the vertical axis represents the purge control valve opening command VSVON.
Take.

That is, in the first calculation, a pulse with a duty ratio of 40% is output, in the next calculation, a pulse with a duty ratio of 30% is output, and then a pulse with a duty ratio of 20% and 10% is output.
Finally, a duty ratio of 0%, that is, a fully closed command is issued.

As described above, the actual opening of the purge control valve is 10% for each KCV
It gradually decreases and finally becomes fully closed.

When the purge control valve opening command calculated in the routine of FIG. 3 is 0.5 or 1.0, only the process of setting the purge control valve opening target value TDUTY = 5, 10 in steps 409 and 410 is different. , Previous duty ratio counter CDUTY
, The purge control valve opening changes like a ramp toward the purge control valve valve opening target value TDUTY.

However, in the first embodiment, the change in the amount of fuel injected by the air-fuel ratio control and the cycle of the increase and decrease in the amount of fuel injected into the cylinder by opening and closing the purge control valve coincide with each other, so that the fluctuation of the torque becomes large. Performance may be degraded.

That is, when the air-fuel ratio correction amount FAF calculated this time is, for example, near the lower limit boundary in the valve opening region of the purge control valve (for example, when FAF = 0.91), the calculation result of the air-fuel ratio correction amount is If the correction amount is reduced, the air-fuel ratio correction amount becomes equal to or lower than the lower limit (for example, FAF = 0.88), the fuel injection amount by the air-fuel ratio control decreases, the purge control valve closes at the same time, and the fuel by the purge disappears. The amount of fuel injected into the inside will be excessively reduced.

Conversely, when the air-fuel ratio correction amount FAF is, for example, near the lower limit boundary outside the valve opening range of the purge control valve (for example, when FAF = 0.88), the calculation result of the air-fuel ratio correction amount indicates that the air-fuel ratio correction amount is If it increases, the air-fuel ratio correction amount becomes equal to or greater than the lower limit (for example, FAF = 0.91), and at the same time the fuel injection amount by air-fuel ratio control increases, the purge control valve opens to add fuel by purging and inject into the cylinder. The amount of fuel to be used will increase excessively.

In order to prevent this phenomenon from occurring, the second embodiment using the moving average value FAFAV of the air-fuel ratio correction amount can be used.

FIG. 6 is a routine for executing the control of the second embodiment, and the same reference numerals as those in FIG. 3 denote the same processes. Therefore, only the differences will be described below.

That is, when the internal combustion engine is operated with the comparatively heavy load, an affirmative determination is made in step 304 and the process proceeds to step 601.

 Then, in step 601, it is determined whether or not 0.90 <FAFAV <1.10 is satisfied.

If a negative determination is made in step 601, it is considered that proper air-fuel ratio control cannot be executed if the amount of fuel injected into the cylinder by the purge fluctuates, and step 31 is considered.
Proceeding to 1, the purge control valve 21 is closed.

When an affirmative determination is made in step 601, the process proceeds to step 602, where it is determined whether or not 0.95 <FAFAV <1.05 is satisfied.

If a positive determination is made in step 602, step 6
Proceeding to 03, it is determined based on the following equation whether or not the amount of change in the air-fuel ratio correction amount is within a first predetermined width.

| FAFAV−FAF | <ε1 where ε1 = first predetermined allowable width (eg, ε1
(1 = 0.05) When a negative determination is made in step 603, the process proceeds to step 311 as in the case where a negative determination is made in step 601, and the purge control valve 21 is closed.

If an affirmative determination is made in step 603, it is assumed that the air-fuel ratio correction amount by the air-fuel ratio control is small and the effect of the purge can be sufficiently corrected by the air-fuel ratio control. In step 307, the purge control valve valve opening command value VSV = 1.0 And

On the other hand, if a negative determination is made in step 602, the process proceeds to step 604, where it is determined whether the amount of change in the air-fuel ratio correction amount is equal to or less than a second predetermined value ε2.

Note that the second predetermined value ε2 is a value smaller than the first predetermined value ε1 (for example, ε2 = 0.0) because the air-fuel ratio correction amount is large.
Set to 3).

If a negative determination is made in step 604, step 6
The process proceeds to step 311 as in the case where a negative determination is made in 03.

If an affirmative determination is made in step 604, the process proceeds to step 310, where the purge control valve valve opening command value V is set to 0.5.

If a negative determination is made in step 304, it is assumed that the internal combustion engine is operating at a light load, and in step 308 it is determined whether the vehicle speed is equal to or higher than a predetermined value, for example, 15 km / h.

If the speed is equal to or lower than the specified speed, the purge becomes a large disturbance, so that a negative determination is made in step 308 and the process proceeds to step 312 where the purge control valve opening command VSV = 0. If the speed is equal to or higher than the specified speed, an affirmative determination is made in step 308 and the process proceeds to step 605.

 In step 605, it is determined whether or not 0.95 <FAFAV <1.05.

When the internal combustion engine is operated at a light load, the influence of the purge is greater than when the internal combustion engine is operated at a high load.Therefore, the judgment range of the moving average value FAFAV of the air-fuel ratio correction amount is set to be small. I do.

If an affirmative determination is made in step 605, it is determined in step 606 whether or not the amount of change in the air-fuel ratio correction amount is within a second predetermined range based on the following equation.

| FAFAV-FAF | <ε2 If a negative determination is made in step 606, the purge control valve 21 is closed in step 312 as in the case where a negative determination is made in step 605.

If an affirmative determination is made in step 606, the process proceeds to step 310, where the purge control valve opening command value VSV is set to 0.5.

FIG. 7 is a routine for calculating a moving average value FAFAV of the air-fuel ratio correction amount used in steps 601 to 602 in FIG. 6, and is executed together with the routine shown in FIG.

In step 701, it is determined whether the air-fuel ratio sensor 13 is active.

If the air-fuel ratio sensor 13 is not active, step 701
This routine ends without changing the air-fuel ratio correction amount FAF.

On the other hand, if the air-fuel ratio sensor 13 is active, step 70
An affirmative determination is made at 1 and the routine proceeds to step 702, where it is determined whether the air-fuel ratio feedback control condition is satisfied.

During the fuel increase after the start of the internal combustion engine, during the warm-up operation or during the output increase, the air-fuel ratio feedback control condition is not satisfied.In this case, a negative determination is made in step 702 and the air-fuel ratio correction amount FAF is not changed. This routine ends.

Otherwise, a positive determination is made in step 702 and step 7
Go to 03.

In step 703, it is determined whether the air-fuel ratio is lean or rich based on the output read value of the air-fuel ratio sensor 13.

In the case of lean, a positive determination is made in step 703 and step 7
Proceeding to 04, it is determined whether or not it is immediately after the inversion from rich to lean.

Step 704 if immediately after the inversion from rich to lean
In step 707, after the value of the air-fuel ratio correction amount FAF is stored as the air-fuel ratio correction amount FAF _S immediately before skipping,
In step 708, the air-fuel ratio correction amount is increased by "A" in a skip manner.

If the lean state continues, a negative determination is made in step 704, and in step 706, the air-fuel ratio correction amount FAF is integratedly increased by "a".

On the other hand, if a negative determination is made in step 703 as rich, the process proceeds to step 705, and it is determined whether or not it is immediately after the inversion from lean to rich.

Immediately after the inversion from lean to rich, step 705
In step 709, after the value of the air-fuel ratio correction amount FAF is stored as the air-fuel ratio correction amount FAF _S immediately before skipping,
In step 710, the air-fuel ratio correction amount is skipped and reduced by "B".

If the rich state continues, a negative determination is made in step 705, and in step 711, the air-fuel ratio correction amount FAF is integratedly reduced by "b".

Here, the skip amounts A and B are set sufficiently larger than the integral amounts a and b.

If the air-fuel ratio correction amount FAF changes in a skipping manner in steps 708 and 710, the process proceeds to step 712, and the air-fuel ratio correction amount FAF _S calculated immediately before skipping in this calculation and immediately before skipping in the previous skipping change. Air-fuel ratio correction amount FAF
Calculate the average FAFAV with _S-1 .

Then, in step 713, the air-fuel ratio correction amount FAF _S-1 immediately before the previous skip is replaced with the air-fuel ratio correction amount FAF _S immediately before the current skip.

As described above, according to the second embodiment, it is possible to prevent the increase / decrease cycle of the injected fuel amount due to the air-fuel ratio control from being coincident with the increase / decrease cycle of the fuel amount due to the opening / closing of the purge control valve, thereby preventing the deterioration of drivability. it can.

In the embodiment shown here, the switching of the internal combustion engine load is performed in two stages of the light load and the heavy load. However, the switching is performed in three or more stages, and the opening range of the purge control valve becomes narrower as the load becomes lighter. You may make it.

Similarly, in the embodiment shown here, the opening degree of the purge control valve is set to three stages of full opening, half opening and full closing, but even with the same air-fuel ratio correction amount, the valve opening degree becomes smaller as the load becomes lighter. It may be.

Although the present embodiment has been described with respect to an internal combustion engine in which fuel injection is performed by an injector, the present invention can be similarly applied to an internal combustion engine in which an air-fuel mixture is generated by a carburetor.

Further, although the above embodiment is configured by a digital circuit using a microcomputer, it can be configured by an analog circuit.

〔The invention's effect〕

As described above, according to the present invention, the fuel adsorbed by the fuel adsorber can be purged within a range in which the load of the internal combustion engine and the control ability of the air-fuel ratio control device are considered, so that the properties of the exhaust gas In addition to preventing deterioration, the purge can be performed in a wide range, so that the adsorption capacity of the adsorber is prevented from being saturated, and the fuel efficiency can be improved.

[Brief description of the drawings]

1 is a basic configuration diagram of the present invention, FIG. 2 is a configuration diagram of an evaporative fuel processing apparatus according to the present invention, and FIGS. 3 and 4 and FIGS. 6 and 7 are control circuit diagrams of FIG. FIG. 5 is a timing chart for supplementarily explaining the control operation according to the flow chart of FIG. In the figure, A: purge control valve, B: purge control valve opening adjusting means, C: air-fuel ratio sensor, D: air-fuel ratio correction amount calculating means, E: air-fuel ratio adjusting means.

Claims (1)

(57) [Claims] An air-fuel ratio sensor (A) installed in an exhaust system of an internal combustion engine, and an air-fuel ratio sensor for controlling an exhaust gas of the internal combustion engine to a predetermined air-fuel ratio in accordance with an output of the air-fuel ratio sensor (A). Air-fuel ratio correction amount calculating means (B) for calculating the fuel-ratio correction amount; and controlling the amount of fuel supplied to the internal combustion engine based on the calculation result of the air-fuel ratio correction amount calculating means (B). Air-fuel ratio adjusting means (C) for adjusting gas to a predetermined air-fuel ratio; and operating state determining means (D) for determining a load state of the internal combustion engine.
A fuel gas adsorber for adsorbing fuel gas evaporating from the fuel tank and a purge control valve (E) installed in the middle of a connecting pipe connecting the intake passage of the internal combustion engine. In the above, when the operating state determining means (D) detects a light load operating state, the opening of the purge control valve (E) is narrower than the opening area of the purge control valve (E) set when it is determined that the operating state is not the light load operating state. A purge control valve opening area setting means (F) for setting an area; and a purge control valve wherein the calculation result of the air-fuel ratio correction amount calculating means (B) is set by the purge control valve opening area setting means (F). When it is within the valve opening range, the opening degree of the purge control valve (E) is adjusted to a smaller opening degree as the load detected by the operating state determination means (D) becomes smaller, Sometimes, fully close the purge control valve Evaporative fuel processing apparatus characterized by having a chromatography di control valve opening adjusting means (G), the.