JPH10231747A - Evaporation fuel supply control device for lean burn internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rich misfire and the like from occurring accompanied by the turbulence of an air-fuel ratio by controlling at least a purge rate in the purge rate of evaporation fuel decided by a purge control means and a fuel rate injected to an internal combustion engine, when it is judged that the air-fuel ratio becomes rich air-fuel ratio at the time of lean burn operation. SOLUTION: This device is provided with a fuel injection valve M for supplying fuel to an internal combustion engine M1, and an evaporation fuel supplying means M5 for supplying evaporation fuel generated in a fuel tank M4 from a purge passage M11 to an intake passage M2, and a supplying evaporation fuel rate is controlled by a purge control valve M6. In the case where it is judged by a judging means M8 during lean burn operation on the basis of a result detected by an operating condition detecting means M7 that an air-fuel ratio of mixture is rich more than an air-fuel ratio of a normal lean burn condition, the purge control valve M6 is controlled by a fuel control means M9 so as to restrict at least a rate of evaporation fuel supplied to the internal combustion engine M1. It is thus possible to before prevent rich misfire according to an excessive rich condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel supply control device for a lean burn internal combustion engine, and more particularly, to an evaporative fuel (vapor) generated from a fuel tank or the like to an intake system according to an operating state of the lean burn internal combustion engine. The present invention relates to an evaporative fuel supply control device for a lean burn internal combustion engine to be supplied.

[0002]

2. Description of the Related Art In a conventionally used engine, fuel from a fuel injection valve is injected into an intake port, and a homogeneous mixture of fuel and air is supplied to a combustion chamber in advance. In such an engine, an intake passage is opened and closed by a throttle valve linked to an accelerator operation, and by this opening and closing, the amount of intake air supplied to a combustion chamber of the engine (consequently, a gas mixture in which fuel and air are homogeneously mixed). ) Is adjusted, thereby controlling the engine output.

[0003] However, in the technique based on the so-called homogeneous combustion described above, a large intake negative pressure is generated in accordance with the throttle operation of the throttle valve, and the pumping loss increases to lower the efficiency. On the other hand, by reducing the throttle of the throttle valve and supplying fuel directly to the combustion chamber, a combustible air-fuel mixture is present near the ignition plug, and the air-fuel ratio of the portion is increased to improve ignitability. A so-called “lean combustion (stratified combustion)” technique is known.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-223017, a fuel injection valve for homogeneous combustion provided in the middle of an intake passage in order to distribute and inject fuel uniformly into a combustion chamber. For stratified charge combustion, injecting fuel directly into the cylinder around the spark plug (for in-cylinder injection)
And a fuel injection valve. When the load of the engine is relatively low, fuel is injected from the fuel injection valve for stratified combustion, is supplied unevenly around the spark plug, and the throttle valve is opened to perform lean combustion. Thereby, the pumping cross is reduced, and the fuel efficiency is improved.

On the other hand, when the load is high, fuel is also injected from the fuel injector for homogeneous combustion. As a result, an optimum air-fuel mixture is formed, and the output is improved. Further, in this technique, a purge control device for supplying the evaporated fuel generated in the fuel tank into the intake passage is provided. This purge control device controls supply of evaporated fuel into an intake passage by opening and closing an electromagnetic on-off valve controlled according to an operation state.

[0006]

However, in a lean combustion (stratified combustion) state, when a NOx storage reduction catalyst is disposed in an exhaust passage to purify NOx in exhaust gas, NOx trapped by the catalyst is reduced. Saturation occurs, or the negative pressure in the brake booster for assisting the braking operation by the negative pressure tends to be insufficient. For this reason, forcibly releasing and purifying the stored NOx, and temporarily closing the throttle valve to secure the brake negative pressure, the air-fuel ratio is reduced to near the stoichiometric or rich state. It needs to be darkened. As described above, if the evaporated fuel is further supplied when the air-fuel ratio is controlled to be rich, there is a possibility that the air-fuel ratio being controlled may be different from the required air-fuel ratio. As a result, the combustion state becomes unstable, and there is a risk that rich misfire may occur.

Further, in a lean combustion (stratified combustion) state, since the air density (intake air density) is low at high altitude, the air-fuel ratio tends to be small and rich as compared with flat ground. Therefore, if purging is performed as it is in such a state,
The state of lean combustion or stratified combustion becomes unstable, and there is a risk of misfiring.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to an evaporative fuel supply control apparatus for a lean burn internal combustion engine that purges an intake system of an internal combustion engine to process evaporative fuel generated from fuel storage means. An evaporative fuel supply control device for a lean-burn internal combustion engine capable of appropriately controlling the air-fuel ratio in a lean-burn (stratified-combustion) state and thereby preventing the occurrence of rich misfire or the like due to the disturbance of the air-fuel ratio. To provide.

[0009]

In order to achieve the above object, the present invention has the following constitution. In the present invention, in the case where the fuel supply suddenly becomes rich during the lean burn operation, the supply of the fuel vapor is reduced in anticipation of the sudden increase. (1) A characteristic of the present invention is that in a fuel vapor supply control device for a lean burn internal combustion engine, a purge passage for purging vapor fuel generated from fuel storage means for storing fuel of the internal combustion engine to an intake system of the internal combustion engine; Purge control means for controlling the amount of evaporative fuel introduced from the purge passage into the intake system in accordance with the operating state of the internal combustion engine; and, during lean-burn operation, an air-fuel ratio corresponding to lean burn to a rich air-fuel ratio. And a purge amount of the evaporated fuel determined by the purge control unit, and a fuel amount injected from a fuel injection valve of the internal combustion engine when the air-fuel ratio is determined to be rich by the air-fuel ratio determination unit. And a fuel limiting means for limiting at least the purge amount.

In the lean burn internal combustion engine according to the present invention, when the lean burn operation is performed, the fuel vapor generated in the fuel tank is supplied to the intake system. In the lean combustion state, a small amount of fuel is supplied to a large amount of air. However, in such a small amount of fuel, the air-fuel ratio of the combustible mixture supplied to the internal combustion engine M1 is low. Then, in an operation state in which the air-fuel ratio is increased from this state, the effect of the evaporated fuel on the air-fuel ratio is enormous.

Therefore, according to the present invention, when it is determined by the determining means that the air-fuel ratio of the combustible mixture is higher than the air-fuel ratio in the steady lean combustion state, at least the supply of fuel is controlled by the fuel limiting means. There is a limit on the amount of fuel vapor to be evaporated. For this reason, the influence of the evaporated fuel on the air-fuel ratio is reduced, and the air-fuel ratio is appropriately controlled, without disturbance, and rich misfire can be prevented.

Here, the air-fuel ratio determining means is a broad concept included in the determination contents, not only when the air-fuel ratio is actually in the rich direction, but also when the air-fuel ratio is predicted to be rich from various conditions. . In the air-fuel ratio determining means, an air-fuel ratio that is richer than the air-fuel ratio corresponding to lean combustion means that the air-fuel ratio becomes relatively rich, for example, from stratified combustion (strong lean) to homogeneous lean combustion (weak lean). ), Changing from lean combustion to combustion at the stoichiometric air-fuel ratio, changing from lean combustion to rich combustion, and the like.

The restriction by the fuel restricting means includes prohibiting purge or fuel injection and reducing the supply amount. (1-1) By the way, in a lean burn internal combustion engine, it is usual to provide a nitrogen oxide reduction catalyst in an exhaust system in order to remove nitrogen oxides from exhaust gas.

In this case, the air-fuel ratio of the combustible air-fuel mixture is temporarily increased by the rich spike control means in the exhaust passage of the internal combustion engine at least when lean combustion such as stratified combustion is performed. The nitrogen oxides stored in the nitrogen oxide reduction catalyst are released and purified.

In such a case, the air-fuel ratio determining means includes
When the amount of nitrogen oxides stored in the nitrogen oxide reduction catalyst exceeds a predetermined amount, it can be determined that the air-fuel ratio is in a rich state.

When the amount of nitrogen oxides stored in the nitrogen oxide storage reduction catalyst becomes larger than a predetermined amount, the air-fuel ratio of the combustible mixture is temporarily increased by the rich spike control means, and the exhaust gas of the internal combustion engine M1 is exhausted. Nitrogen oxides stored in the nitrogen oxide reduction catalyst provided in the passage are released and purified. Conversely, when the amount of nitrogen oxides stored in the nitrogen oxide storage reduction catalyst becomes larger than a predetermined amount, the air-fuel ratio of the combustible mixture becomes a steady lean combustion (stratified combustion) state. It means that it is made richer than the air-fuel ratio. The air-fuel ratio determination means can use the information used by the rich spike control means for the determination condition, so that the configuration can be simplified. Since the purge amount can be reduced before the rich spike, rich misfire can be prevented.

(1-2) Next, the vehicle may be provided with a brake booster for assisting the braking operation of the vehicle by using the negative pressure in the intake passage as an aid to the braking means. A negative pressure generating means for generating a negative pressure for the brake by reducing an air flow rate in the intake passage.

In this case, the air-fuel ratio judging means can be configured to make a judgment based on the operating state of the negative pressure generating means. The brake booster operates based on the negative pressure in the intake passage.However, when the negative pressure generating means operates to secure the negative pressure for the brake booster, the throttle valve is temporarily operated to generate the negative pressure. This is the case where the air-fuel ratio is increased because the amount of intake air decreases because the air-fuel ratio is closed. Therefore, if it is detected that it is necessary to operate the negative pressure generation means, it is determined that the air-fuel ratio of the combustible mixture is higher than the air-fuel ratio in the steady lean combustion (stratified combustion) state. You can.

In this case, in order to secure the negative pressure for the brake,
Since the air-fuel ratio is determined from the amount of negative pressure or directly from the operation of reducing the amount of intake air to increase the intake pipe negative pressure, the purge amount can be reduced before the air-fuel ratio becomes rich, and misfire can be prevented.

(1-3) Further, when a brake booster is provided, a negative pressure amount detecting means for detecting a negative pressure amount in the brake booster can be provided. In this case, the air-fuel ratio determining means comprises: The air-fuel ratio can be determined based on the negative pressure amount detected by the negative pressure amount detecting means.

If the negative pressure amount detected by the negative pressure amount detecting means is less than a predetermined amount, the above-mentioned (1-
This is synonymous with the case where it is necessary to operate the negative pressure generating means described in 2). Therefore, the air-fuel ratio of the combustible air-fuel mixture may be made higher than the air-fuel ratio in the steady lean combustion (stratified combustion) state. Is determined. Also in this case, similarly to (1-2), the purge amount can be reduced before the air-fuel ratio becomes rich, and misfire can be prevented beforehand.

(1-4) In addition, the air-fuel ratio determining means is provided with an intake density detecting means for detecting an intake density.
The determination can be made based on the intake air density detected by the intake air density detecting means. When the intake air density is lower than the reference value, it is determined that the air-fuel ratio of the combustible air-fuel mixture is made richer than the air-fuel ratio in the steady lean combustion (stratified combustion) state.
When traveling at high altitudes or the like, the purge amount is reduced when the intake air density becomes low, so that misfiring due to an increase in the air-fuel ratio under a shortage of oxygen per unit volume can be prevented.

(1-5) When the air-fuel ratio judging means judges that the air-fuel ratio becomes rich, an injection state changing means for changing the fuel injection state in combination with the restriction of the purge amount by the fuel restricting means may be provided. it can. In this case, since the injection amount is corrected together with the decrease in the purge amount, more appropriate combustion can be ensured.

(1-6) It is possible to provide a concentration detecting means for detecting the fuel vapor concentration, and to provide a correcting means for correcting the purge amount or the fuel injection state according to the fuel vapor concentration. Since the purge amount and the fuel injection state are corrected according to the evaporated fuel concentration, appropriate combustion can be obtained.

(1-7) Conventionally, a normal vehicle is provided with a canister for storing fuel vapor generated from fuel storage means for storing fuel for an internal combustion engine. Therefore, in the present invention, the purge passage may be connected so as to communicate the intake system of the internal combustion engine with the canister. (1-8) The above features can be implemented in combination as much as possible.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> A first embodiment of a fuel vapor supply control device for a lean burn internal combustion engine according to the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a basic configuration of the embodiment. As shown in FIG. 1, an intake passage M2 for guiding at least air is provided for the internal combustion engine M1, and a purge for purging evaporated fuel generated from a fuel tank M4 as a fuel storage means is provided in the intake passage M2. A passage M11 is provided.

Further, in order to perform at least lean combustion,
A fuel supply means M3 (fuel injection valve) for supplying fuel to the internal combustion engine M1 is provided.
An evaporative fuel supply means M5 is provided to supply the evaporative fuel generated in the above to the intake passage M2 from the purge passage.

Also, an adjusting means M6 (purge control valve) for adjusting the flow rate of the evaporated fuel supplied to the internal combustion engine M1 through the evaporated fuel supplying means M5, and for detecting an operating state of the internal combustion engine M1. Operating state detecting means M
7 are provided.

Then, at least when the lean burn operation is being performed, the air-fuel ratio of the combustible mixture supplied to the internal combustion engine M1 is set to a steady lean burn state based on the detection result of the operating state detecting means M7. The determination means M8 for determining that the air-fuel ratio is higher than the air-fuel ratio is provided.

Further, when the determining means M8 determines that the air-fuel ratio of the combustible air-fuel mixture is higher than the air-fuel ratio in a steady lean combustion state, the adjusting means M6 is controlled to at least Fuel control means M9 for limiting the flow rate of the evaporated fuel supplied to the internal combustion engine M1 is provided.

The purge control means in the present invention is a concept including an adjusting means M6 (purge control valve) and an operating state detecting means M7, and the fuel limiting means M9 is external to the purge control means or Provided internally.

The adjusting means M6 can be provided in a form inherent in the evaporated fuel supply means M5. In the following description, stratified combustion may be used as an example of lean combustion.

FIG. 2 is a schematic configuration diagram showing an evaporative fuel supply control device for a direct injection engine mounted on a vehicle as a lean burn internal combustion engine in the present embodiment. The engine 1 includes, for example, four cylinders 1a, and the combustion chamber structure of each of the cylinders 1a is shown in FIG. As shown in these drawings, the engine 1 includes a piston in a cylinder block 2, and the piston reciprocates in the cylinder block 2. A cylinder head 4 is provided above the cylinder block 2, and a combustion chamber 5 is formed between the piston and the cylinder head 4.

In this embodiment, four valves are arranged for each cylinder 1a. As shown in FIG.
First intake valve 6a, second intake valve 6b, first intake port 7
a, a second intake port 7b, a pair of exhaust valves 8, and a pair of exhaust ports 9 are provided, respectively.

As shown in FIG. 4, the first intake port 7a
Is composed of a helical intake port, and the second intake port 7
b consists of a straight port extending almost straight.
In addition, an ignition plug 10 is disposed at the center of the inner wall surface of the cylinder head 4. This spark plug 10 includes:
The igniter 12 via a distributor (not shown)
High voltage is applied. And
The ignition timing of the ignition plug 10 is determined by the igniter 1
2 is determined by the output timing of the high voltage. Further, a fuel injection valve 11 for in-cylinder injection as a fuel supply means is disposed around the inner wall surface of the cylinder head 4 near the first intake valve 6a and the second intake valve 6b. That is, in the present embodiment, the fuel from the in-cylinder injection fuel injection valve 11 is directly injected into the cylinder 1a, and performs not only homogeneous combustion but also stratified combustion. Is available.

As shown in FIG. 2, each cylinder 1a
The first intake port 7a and the second intake port 7b of the first intake passage 1 formed in each intake manifold 15 respectively.
It is connected to the inside of the surge tank 16 via the 5a and the second intake path 15b. A swirl control valve 17 is disposed in each of the second intake passages 15b. These swirl control valves 17 are connected to a step motor 19 via a common shaft 18. The step motor 19 is controlled based on an output signal from an electronic control unit (hereinafter simply referred to as “ECU”) 30 described later.

The surge tank 16 includes an intake duct 20
Is connected to the air cleaner 21 through the intake duct 20.
Inside, a throttle valve 23 as negative pressure generating means which is opened and closed by a separate step motor 22 is provided. That is, the throttle valve 23 of the present embodiment is of a so-called electronic control type. Basically, the throttle valve 23 is controlled to open and close by the step motor 22 being driven based on the output signal from the ECU 30. Is done. By opening and closing the throttle valve 23, the amount of intake air introduced into the combustion chamber 5 through the intake duct 20 is adjusted. In the present embodiment,
Intake duct 20, surge tank 16, and first intake path 1
An intake passage is constituted by 5a, the second intake passage 15b, and the like. In the vicinity of the throttle valve 23, a throttle sensor 25 for detecting the opening (throttle opening TA) is provided.

Further, a homogenizing fuel injection valve 41 is provided in the intake duct 20 upstream of the throttle valve 23. That is, in the present embodiment, the fuel from the homogenizing fuel injection valve 41 is injected in a state of being dispersed in the intake duct 20, and is injected into the cylinder 1 through the intake passage.
a.

An exhaust manifold 14 is connected to the exhaust port 9 of each cylinder. Then, the exhaust gas after combustion is discharged to the exhaust duct 13 via the exhaust manifold 14. In the present embodiment, an exhaust passage is constituted by the exhaust manifold 14 and the exhaust duct 13.

Further, in this embodiment, a known exhaust gas circulation (EGR) device 51 is provided. This EG
The R device 51 includes an EGR passage 5 as an exhaust gas circulation passage.
2 and an EGR valve 53 as an exhaust gas circulation valve provided in the middle of the passage 52. EGR passage 5
2 is an intake duct 20 downstream of the throttle valve 23;
It is provided so as to communicate with the exhaust duct 13.
The EGR valve 53 has a built-in valve seat, valve body, and step motor (all not shown). The opening degree of the EGR valve 53 fluctuates when the stepping motor intermittently displaces the valve body with respect to the valve seat. And E
When the GR valve 53 is opened, a part of the exhaust gas discharged to the exhaust duct flows to the EGR passage 52. The exhaust gas is supplied to the intake duct 20 via the EGR valve 53.
Flows to That is, a part of the exhaust gas is
Recirculates into the intake mixture. At this time, EGR
By adjusting the opening of the valve 53, the recirculation amount of the exhaust gas is adjusted.

As shown in FIG. 2, in the present embodiment, a brake booster 71 is provided as a device for assisting a braking operation of the vehicle. The brake booster 71 amplifies the depressing force of a brake pedal (not shown), converts the pressure into a hydraulic pressure, and drives a brake actuator (not shown) for each wheel. The brake booster 71 is connected to the intake duct 20 downstream of the throttle valve 23 via a connection pipe 73, and is configured to use a negative pressure generated in the duct 20 as a driving force. ing. Further, the connection pipe 73 has a check valve 7 that opens into the intake duct 20 by negative pressure.
4 are provided. That is, the brake booster 71
Is provided with a diaphragm as an operating part inside. One side of the diaphragm is open to the atmosphere, and a negative pressure generated in the duct 20 acts on the other side via the connection pipe 73. The connection pipe 73 is provided with a pressure sensor 72 as a negative pressure amount detecting means for detecting the pressure (absolute pressure) in the brake booster.

Further, in the present embodiment, a nitrogen oxide storage reduction catalyst 61 as a nitrogen oxide reduction catalyst is provided in the exhaust duct 13. The catalyst 61 is for purifying NOx which is likely to be generated in a lean air-fuel ratio region. Basically, when the engine is operated at a lean air-fuel ratio, NOx in exhaust gas is stored in the catalyst. Also,
When the air-fuel ratio is controlled to be rich, the stored NOx is released from the catalyst due to an increase in the amount of reducing agents such as HC and CO in the exhaust gas, and at the same time, the NOx is reduced from the NOx to nitrogen gas on the catalyst, thereby reducing the atmospheric pressure. It is to be released inside.

The NOx storage reduction catalyst 61 uses, for example, alumina as a carrier, and on the carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li or cesium Cs, or an alkaline earth such as barium Ba or calcium Ca. , Lanthanum La, at least one selected from rare earths such as yttrium Y, and a noble metal such as platinum Pt.

When the excess air ratio λ of the exhaust gas is greater than 1 (lean), the NOx storage reduction catalyst
(NO ₂ , NO ₂ ) is absorbed in the form of nitrate ions NO ₃ ⁻ .

That is, taking as an example a case where platinum Pt and barium Ba are carried on the carrier, if the oxygen concentration in the exhaust gas flowing into the catalyst increases (ie, the excess air ratio λ of the exhaust gas becomes larger than 1 ( lean) comes to) O ₂ these oxygen on the platinum Pt ^- or attached to O ^2- shape on the surface of the platinum Pt in, NO in the exhaust gas, O on the surface of the platinum Pt
₂ ^- or O ^2- and reacts, becomes _{NO 2 (2NO + O 2 →} 2
NO ₂ ). Further, NO ₂ and NO ₂ produced by the above in the inflowing exhaust gas while being further oxidized on platinum Pt, NOx
It is absorbed into the absorbent and bonded with barium oxide BaO, nitrate ions NO ₃ ^- diffuses in the NOx absorbent in the form of. For this reason, under the condition of λ> 1.0, NOx in the exhaust gas becomes NOx
It is absorbed in the storage reduction catalyst.

When the oxygen concentration in the inflowing exhaust gas is significantly reduced (ie, when the excess air ratio λ of the exhaust gas becomes 1 or less (rich)), the amount of NO ₂ generated on the platinum Pt decreases. the reaction is now proceeds in the reverse direction, the nitrate ions NO in absorbent ₃ ^- is released from the NOx absorbent in the form of NO ₂ or NO. In this case, if reducing components such as HC and CO are present in the exhaust gas, NO ₂ is reduced on the platinum Pt by these components.

In the present embodiment, the rich spike control, which is a well-known technique, is performed using the NOx storage reduction catalyst 61. That is, when the operation at the lean air-fuel ratio is continued, as described above, the catalyst 6
The NOx adsorbed on the fuel cell 1 reaches a saturated state, and surplus NOx
May be discharged while being mixed in the exhaust gas.

For this reason, in the present control, the throttle control of the throttle valve 23 is performed by the ECU 30, and the air-fuel ratio is temporarily forcibly determined at a predetermined timing determined by the count value of the rich spike condition satisfaction counter. Is richly controlled. By such control, the amount of HC in the exhaust gas increases, and NOx is reduced to nitrogen gas and released to the atmosphere.

The count value is incremented by "1" according to the load and the engine speed. When the count value reaches a predetermined value, the rich spike control is executed. After the end of the rich spike control, the count value is cleared to “0”. Then, the same processing is repeated.

FIG. 5 shows an example of a control routine for the NOx release flag. This routine is executed by interruption every predetermined time. First, at step 50, it is determined whether or not the correction coefficient L is smaller than 1.0, that is, whether or not the lean air-fuel mixture is being burned. L
If ≧ 1.0, that is, if the air-fuel mixture supplied into the combustion chamber is in the stoichiometric air-fuel ratio range or rich, step 56
Then, the NOx release flag is reset, and then the count value C is made zero in step 57, and similarly, the count value D is made zero in step 58.

On the other hand, when it is determined at step 50 that L <1.0, that is, when the lean air-fuel mixture is being burned, the routine proceeds to step 51, where the count value C is incremented by one. Then step 5
Count C value in 2 whether exceeds a predetermined value C ₀ is determined. When C> C ₀ , the process proceeds to step 53 and NO
The x release flag is set, and then at step 54 the count value D is incremented by one. Next, at step 55, whether the count value D exceeds the certain value D ₀ is determined, the routine proceeds to step 56 if the D> D ₀ N
The Ox release flag is reset. That is, if the combustion of the lean mixture is maintained for a certain time until C> C ₀ , for example, 5 minutes, the NOx release flag is set, and then NOx for a certain time until D> D ₀ , for example, 5 seconds.
When the NOx release flag is set, the mixture supplied to the combustion chamber of the engine cylinder is enriched.

Next, a description will be given of a purge control device 81 as an evaporative fuel supply means, which is attached to supply the evaporative fuel into the intake duct. As shown in FIG. 2, the purge control device 81 includes a canister 83 having an activated carbon layer 82. The canisters 83 on both sides of the activated carbon layer 82 have an evaporative fuel chamber 84 and an air chamber 85, respectively.
Are formed.

A part of the steam fuel chamber 84 is provided with an electromagnetic on-off valve 87.
A check valve 90 formed in the upper space of the fuel tank 89 through the other, and which can flow only from the steam fuel chamber 84 to the inside of the intake duct 20 in another part, and a purge control valve including an electromagnetic on-off valve as an adjusting means It is connected to the intake duct 20 downstream of the throttle valve 23 via 86.

The air chamber 85 communicates with an air intake 91 which opens in the intake duct 20 upstream of the throttle valve 23 toward the upstream of the intake air flow. Further, the upper space of the fuel tank 89 is connected to an intake duct upstream of the throttle valve 23 and downstream of the air intake 91 via an electromagnetic opening / closing valve 88. A pressure sensor 92 is attached.

As described above, the air inlet 91 opens to the upstream of the intake air flow, and thus the air inlet 9
1 is affected by dynamic pressure. Therefore, during operation of the engine, the pressure in the canister 83 is slightly higher than the atmospheric pressure.
On the other hand, when the solenoid on-off valve 87 opens, the fuel tank 8
9 is higher than the pressure in the canister 83, the evaporative fuel generated in the fuel tank 89 flows into the evaporative fuel chamber 84 via the electromagnetic switching valve 87, and then the evaporative fuel is Adsorbed on activated carbon inside. When the electromagnetic on-off valve 86 opens, the air that has flowed into the air intake 91 is sent into the air chamber 85, and then this air is sent into the activated carbon layer 82.

At this time, the fuel adsorbed on the activated carbon is desorbed, and the air containing the fuel component is thus released from the fuel vapor chamber 84.
Spills into. Next, the air containing the fuel component is supplied into the intake duct 20 via the check valve 90 and the electromagnetic switching valve 86. In the present embodiment, during stratified charge combustion, the throttle valve 23 is held in a fully open state except during extremely low loads. Thus, even when the throttle valve 23 is almost fully opened, the evaporated fuel is kept in the exhaust duct 20. Dynamic pressure acts on the air inlet 91 so that it can be supplied.

On the other hand, if the pressure in the upper space of the fuel tank 89 is higher than the atmospheric pressure at this time, the evaporated fuel generated in the fuel tank 89 will cause the electromagnetic on-off valve 8 to open.
The air is supplied into the intake duct 20 through the air duct 8. In the present embodiment, when the pressure in the upper space of the fuel tank 89 is not the atmospheric pressure but becomes higher than a set pressure slightly higher than the atmospheric pressure, the electromagnetic on-off valve 88 is opened.

As described above, in this embodiment, when the electromagnetic on-off valve 86 is opened, the activated carbon layer 8 of the canister 83 is opened.
The fuel vapor adsorbed in the fuel tank 2 is supplied into the intake duct 20, and when the electromagnetic opening and closing valve 88 is opened, the fuel vapor generated in the fuel tank 89 is supplied into the intake duct 20.
As described above, in the present embodiment, the evaporated fuel can be supplied into the intake duct 20 from both the canister 83 and the fuel tank 89.

As shown in FIGS. 2 and 3, the above-described ECU 30 is formed of a digital computer, and RAMs are connected to each other via a bidirectional bus 31.
(Random access memory) 32, ROM (read only memory) 33, CPU comprising microprocessor
(Central processing unit) 34, an input port 35 and an output port 36. In the present embodiment, the E
The CU 30 constitutes a determining unit and a fuel limiting unit.

The accelerator pedal 24 of the vehicle is connected to an accelerator sensor 26A that generates an output voltage proportional to the amount of depression of the accelerator pedal 24, and the accelerator sensor 26A detects the accelerator opening ACCP. The output voltage of the accelerator sensor 26A is input to the input port 35 via the AD converter. Similarly, the accelerator pedal 24 has a fully-closed switch 26B for detecting that the depression amount of the accelerator pedal 24 is "0".
Is provided. That is, the fully open switch 26B
Generates a signal of "1" as the fully closed signal when the depression amount of the accelerator pedal 24 is "0", and generates a signal of "0" otherwise. And the fully closed switch 26
The output voltage of B is also input to the input port 35.

The top dead center sensor 27 generates an output pulse when the first cylinder 1a reaches the intake top dead center, for example, and this output pulse is input to the input port 35. The crank angle sensor 28 has a crankshaft of 30 °, for example.
An output pulse is generated each time the CA rotates, and this output pulse is input to the input port. The CPU 34 calculates (reads) the engine speed NE from the output pulse of the top dead center sensor 27 and the output pulse of the crank angle sensor 28.

Further, the rotation angle of the shaft 18 is
The swirl control valve sensor 29 detects the opening degree of the swirl control valve 17. The output of the swirl control valve sensor 29 is input to the input port 35 via the A / D converter 37.

At the same time, the throttle sensor 25 detects the throttle opening TA. The output of the throttle sensor 25 is supplied to an input port 3 via an A / D converter.
5 is input.

In addition, in the present embodiment, an intake pressure sensor 46 for detecting the pressure (intake pressure) in the surge tank 16 is provided. Further, a water temperature sensor 47 for detecting the temperature of the cooling water of the engine 1 (cooling water temperature) is provided. The exhaust duct 13 is provided with an oxygen sensor 62. The outputs of these sensors 46, 47 and 62 are also A
The data is input to the input port 35 via the / D converter.

In the present embodiment, the throttle sensor 25, the accelerator sensor 26A,
B, top dead center sensor 27, crank angle sensor 28, swirl control valve sensor 29, intake pressure sensor 46,
Water temperature sensor 47, oxygen sensor 62 and pressure sensor 72,
The operating state detecting means is constituted by 92 and the like.

On the other hand, the output port 36 is connected to each of the fuel injection valves 11 and 41, each of the step motors 19 and 22, the igniter 12, the EGR valve 53 (step motor), and each of the electromagnetic switching valves 86 to 88 via the corresponding drive circuits. Etc. are connected. Then, the ECU 30 controls each sensor 25 to 29,
46, 47, 62, 72, and 92,
In accordance with a control program stored in the OM 33, the fuel injection valves 11, 41, the step motors 19, 22, the igniter 12, the EGR valve 53 (step motor), and the electromagnetic switching valves 86 to 88 are suitably controlled.

A control program according to the first embodiment in the evaporative fuel supply control device for the engine 1 having the above configuration will be described with reference to the flowchart of FIG.

That is, FIG. 6 shows a "evaporative fuel supply control routine" for purge control for controlling the electromagnetic on-off valve 86 in the present embodiment to control the evaporative fuel supplied to the intake duct 20. 5 is a flowchart shown, which is executed by the ECU 30. This example is (1
-1).

The purge is performed under the purge execution conditions, for example, when the warm-up is completed, when a predetermined time has elapsed from the start,
When all of the conditions such as that the fuel injection amount is equal to or more than the minimum injection amount for establishing combustion are satisfied, the purge execution flag is turned on and started.

Then, the solenoid on-off valve 8 for controlling the purge amount
In the case of the duty control type, the duty ratio 6 is gradually increased from 0% (fully closed) to a duty ratio corresponding to the engine operating state (fuel injection amount). Then, when the purge prohibition condition, for example, execution of fuel cut or the like is satisfied, the purge is stopped.

Further, since the fuel vapor is supplied to the internal combustion engine by the purge, the fuel injection amount supplied to the internal combustion engine is:
The correction is performed by the evaporated fuel correction amount FPG corresponding to the supplied evaporated fuel.

That is, final fuel injection amount QALLINJ = basic fuel injection amount QALL-evaporative fuel amount correction amount FPG + K (1) K: warm-up increase coefficient, acceleration increase coefficient, deceleration correction coefficient, reduction described later Various correction coefficients such as a dose coefficient.

The processing of FIG. 6 will be described on the premise of the above points. In the purge control, in the process of FIG.
First, the engine speed NE and the accelerator opening ACA are input (step 90). Next, a basic basic fuel injection amount (QALL) is calculated according to the input engine speed and accelerator opening (step 91).

That is, first, a basic fuel injection amount corresponding to the engine speed and the accelerator opening is interpolated from a map that defines the correlation between the engine speed and the accelerator opening (not shown) and the basic fuel injection amount. To calculate. In addition,
As the injection amount map, a plurality of maps according to the operating conditions or the combustion state are prepared, and are appropriately selected from the maps and used.

At step 92, it is determined whether or not purging is being performed. If the purging is being performed, it is determined at step 101 whether or not rich spike control is currently being executed. If it is determined that the rich spike control is being performed, it is determined that the supply of the evaporated fuel is inappropriate, and in step 106, the duty ratio DPG corresponding to the opening of the electromagnetic switching valve 86 is set to “0”. Then, the subsequent processing is temporarily ended. That is, when it is determined that the rich spike control is being performed, the supply of the evaporated fuel is stopped.

On the other hand, if it is determined in step 101 that the rich spike control is not currently being performed, the process proceeds to step 102. Step 10
In 2, it determines whether the count value of the rich spike conditions are satisfied counter is greater than the predetermined value C ₀ which is set in advance. This rich spike condition satisfaction counter is
As described above, it is counted by the ECU 30 based on predetermined conditions according to the flowchart shown in FIG. 5, and is reset and re-counted after the execution of the rich spike control. If it is determined that the count value of the rich spike condition satisfaction counter is equal to or _smaller than the predetermined value C ₀ , the duty ratio DPG is determined in step 107 based on the pressure difference dp between the atmospheric pressure and the pressure in the intake duct 20. Is calculated.

The function f used in this calculation is
Is conventionally used corresponding to the differential pressure dp, and the flow rate of the evaporated fuel is controlled by the opening degree of the electromagnetic switching valve 86 based on the calculation result. As the atmospheric pressure for calculating the differential pressure dp, for example, the intake pressure obtained by the intake pressure sensor 46 at the time of starting the engine is recorded and used. On the other hand, the pressure in the intake duct 20 utilizes the intake pressure determined by the intake pressure sensor 46 each time.

If it is determined in step 102 that the count value of the rich spike condition satisfaction counter is larger than the predetermined value C _0, it is estimated that rich spike control will be executed soon.
Shift to 03. In step 103, the previous duty ratio DPG _i-1 is reduced by a predetermined value α. That is, the opening degree of the solenoid on-off valve 86 is gradually reduced,
The flow rate of the fuel vapor is reduced. Thereafter, the process proceeds to step 104.

In step 104, it is determined whether the duty ratio DPG is "0". If it is determined that the duty ratio DPG is not “0”, the subsequent processing is temporarily terminated. That is, as long as the supply of the evaporated fuel is not stopped by the process of step 103, the opening of the electromagnetic on-off valve 86 is controlled based on the duty ratio DPG obtained in step 103, and the supply of the evaporated fuel is controlled.

On the other hand, if it is determined in step 104 that the duty ratio DPG is "0", the process proceeds to step 105. In step 105, execution of the rich spike control is permitted. That is, after confirming that the supply of the evaporated fuel has been stopped, the rich spike control is executed.

Thereafter, at step 108, the correction amount of the evaporated fuel amount is converted from the duty ratio. That is, since the purge amount is determined by the opening degree of the purge control valve determined by the duty ratio and the negative pressure of the intake pipe, etc., if the concentration of the fuel vapor amount in the purge gas is known, the fuel vapor amount is known. Since this amount of fuel vapor is supplied to the internal combustion engine, step 10
In equation (9), the formula (1) final fuel injection amount QALLINJ = basic fuel injection amount QAL
L-Evaporated fuel amount correction amount FPG + K0 K0: Evaporated fuel amount is subtracted from the previously obtained basic fuel injection amount as a correction amount in accordance with a reducing agent amount coefficient that determines the amount of reducing agent (HC) necessary for purifying NOx. Thus, the fuel injection amount finally supplied to the internal combustion engine is corrected.

If it is determined in step 92 that purging is not being performed, the correction amount of the evaporated fuel amount is set to 0 in step 93, and the final fuel injection amount (QALLINJ) is set to the basic fuel injection amount (QALL) + K0. Thereafter, fuel injection is performed according to a separately determined fuel injection program. Next, the operation and effect of the present embodiment will be described.

(A) According to the present embodiment, when the NOx trapped by the catalyst 61 becomes saturated in the stratified combustion state, the rich spike control is executed to forcibly release and purify the NOx. . At this time, the throttle valve 23 is temporarily closed, and the air-fuel ratio becomes close to stoichiometric or rich. On the other hand, the ECU 30 reduces the duty ratio DPG, and thereafter reduces it to zero, controls the opening of the electromagnetic on-off valve 86, and reduces and stops the evaporated fuel supplied from the purge control device 81 into the intake duct 20. I made it. Therefore, during the rich spike control, the effect of the evaporated fuel on the air-fuel ratio is reduced. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, it is possible to prevent the occurrence of rich misfire and the like, and to maintain good drivability.

(B) Further, the ECU 30 measures the start timing of the rich spike control based on the count value of the rich spike control establishment counter, and based on the count value, gradually increases the duty ratio DPG before the execution of the rich spike control. It was decided to reduce the weight. Therefore, it is possible to prevent the air-fuel ratio from rapidly changing before and after the start of the rich spike control. Therefore, the operation and effect of the above (a) can be made more reliable.

In the first embodiment, the predetermined value α of the duty ratio DPG reduced in step 103 is a constant, but this may be a variable according to the operating state.

In the first embodiment,
In step 103, the duty ratio DPG repeatedly decreases the predetermined value α, gradually decreases the duty ratio DPG, and eventually reduces it to zero. However, the duty ratio DPG may be set to “0” at one time.

<Second Embodiment> Next, a second embodiment of the present invention will be described. However, the configuration and the like of this embodiment are the same as those of the above-described first embodiment, and thus description thereof will be omitted. In the following, description will be made focusing on differences from the first embodiment. In this example, the features of (1-2) and (1-3) are implemented.

In the first embodiment, the execution status of the rich spike control is determined, and based on the determination result, the electromagnetic switching valve 86 is controlled to control the evaporated fuel supplied to the intake duct 20. did. On the other hand, the present embodiment is characterized in that the above-described evaporated fuel is controlled when the intake air amount is reduced in order to generate and secure the negative pressure in the brake booster 71 by increasing the negative pressure of the intake duct 20. doing.

FIG. 7 is a flowchart showing an “evaporative fuel control routine” for executing the control of the evaporative fuel according to the present embodiment. As a main routine, the EC is used instead of steps 101 to 107 in FIG.
This is executed by U30.

When the process proceeds to this routine, the ECU
30 first determines in step 201 whether or not the brake control is currently being executed. When it is determined that the brake control is being performed, it is determined that the supply of the evaporated fuel is inappropriate, and in step 203,
The duty ratio DPG is set to “0”, and the subsequent processing is temporarily ended. That is, when it is determined that the brake control is being executed, the supply of the evaporated fuel is stopped.

On the other hand, if it is determined in step 201 that the brake control is not currently being performed, the process proceeds to step 202. In step 202, the brake negative pressure is set to a predetermined value BkPa
It is determined whether it is greater than (absolute pressure). Here, the predetermined value BkPa is a value at which the brake negative pressure securing process is executed when the brake negative pressure becomes a value obtained by adding a constant value to the brake negative pressure. If it is determined that the brake negative pressure is greater than the predetermined value BkPa, in step 204, the duty ratio DPG is calculated based on the differential pressure dp, and the subsequent processing is temporarily terminated. That is, the duty ratio DPG is equal to the differential pressure d.
It is calculated as a function g of p. Then, based on the result, the opening of the electromagnetic on-off valve 86 is controlled, and the flow rate of the evaporated fuel is controlled.

If it is determined in step 202 that the brake negative pressure is equal to or less than the predetermined value BkPa, a process for securing the brake negative pressure will be performed soon (temporarily closing the throttle valve 23 to reduce the air-fuel ratio). It is presumed that the process of increasing the density to the vicinity will be executed, and step 203
, The duty ratio DPG is set to “0”, and the subsequent processing is temporarily terminated. That is, when it is determined that the process of securing the brake negative pressure will be executed soon, the supply of the evaporated fuel is stopped.

Next, the operation and effect of this embodiment will be described. (A) According to the present embodiment, in the stratified combustion state,
When the negative pressure in the brake booster 71 for assisting the braking operation by the negative pressure is insufficient, the brake negative pressure is secured. At this time, the throttle valve 23 is temporarily closed, for example, to increase the air-fuel ratio to near stoichiometric. On the other hand, the ECU 30 sets the duty ratio DPG to zero before the negative pressure is secured, closes the electromagnetic on-off valve 86, and stops the evaporated fuel supplied from the purge control device 81 into the intake duct 20. For this reason, the influence of the evaporated fuel on the air-fuel ratio during the process of securing the brake negative pressure is eliminated. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, the occurrence of rich misfire or the like can be prevented, and the drivability can be well maintained.

In particular, in a direct injection type lean burn internal combustion engine, the throttle valve is usually operated with the throttle fully open in many cases. Therefore, when braking by a brake, a negative pressure for the brake booster must be generated each time. No. The negative pressure is generated by temporarily closing the throttle valve. However, the air-fuel ratio becomes temporarily rich, which may cause misfire. Therefore, in such a case, misfire can be prevented by restricting the supply of the evaporated fuel as described above. As described above, this embodiment is an extremely effective means in a direct injection type lean burn internal combustion engine.

In the second embodiment, in step 203, the duty ratio DPG is cut at once and the duty ratio DPG is set to "0". However, the duty ratio DPG may be gradually reduced. Good. If the amount is gradually decreased, a rapid change in combustion at the time of switching can be suppressed.

As a negative pressure generating means, a throttle valve 23 provided in the intake duct 20 and a step motor 2 as an actuator for opening and closing the throttle valve 23 are provided.
The electronic control type throttle mechanism comprises an idle speed control valve provided in a bypass ventilation passage which bypasses the throttle valve 23, and an ISC mechanism comprising an actuator for opening and closing the valve. You may.

Further, the E having the EGR valve 53 and the like
It may be constituted by the GR device 51. Further, a negative pressure generating mechanism (not shown) may be separately provided. In these cases, a mechanical throttle valve linked to an accelerator pedal 24 may be used instead of the so-called electronically controlled throttle valve 23. Furthermore, the negative pressure generating means may be configured by appropriately combining them.

<Third Embodiment> Next, a third embodiment of the present invention will be described. However, the configuration and the like of this embodiment are the same as those of the above-described first embodiment, and thus description thereof will be omitted. The following description focuses on the differences from the first embodiment.

In the first embodiment, the execution status of the rich spike control is determined, and based on the determination result, the electromagnetic switching valve 86 is controlled to control the evaporated fuel supplied to the intake duct 20. did. In contrast, in the present embodiment, the output of the intake pressure sensor 46 detects that the intake density has decreased, for example, at high altitudes.
It is characterized in that the above-mentioned evaporated fuel is controlled. This example is an example of implementing (1-4).

FIG. 8 is a flowchart showing an "evaporative fuel supply control routine" for executing the control of the evaporative fuel according to the present embodiment. As a main routine, the routine shown in FIG. It is executed by the ECU.

When the processing shifts to this routine, the ECU
30 first determines in step 301 whether the atmospheric pressure is larger than a predetermined value CkPa set in advance.
If it is determined that the atmospheric pressure is larger than the predetermined value CkPa, in step 303, the differential pressure d is determined.
The duty ratio DPG is calculated based on p, and the subsequent processing is temporarily terminated. That is, assuming that the intake air density does not decrease, the duty ratio DPG is calculated as a function h of the differential pressure dp as usual. Then, based on the result, the opening of the electromagnetic on-off valve 86 is controlled, and the flow rate of the evaporated fuel is controlled.

If it is determined in step 301 that the atmospheric pressure is equal to or less than the predetermined value CkPa,
Correction coefficient β (0 ≦ β ≦ 1) obtained from the correspondence between the previous duty ratio DPG _i-1 and the atmospheric pressure shown in FIG.
Is set as a new duty ratio DPG. Thereafter, the processing is temporarily terminated. That is, through step 302, the duty ratio DPG is gradually reduced.

Next, the operation and effect of this embodiment will be described. (A) According to the present embodiment, in the stratified combustion state,
At high altitudes, the air density (intake air density) is low, so that the air-fuel ratio tends to be richer than at flat altitudes. In contrast, E
When the atmospheric pressure (corresponding to the air density) is low, the CU 30
The ECU 30 controls the opening of the electromagnetic on-off valve 86 by reducing the duty ratio DPG, and reduces the amount of fuel vapor supplied from the purge control device 81 into the intake duct 20. Therefore, at high altitudes, the influence of the fuel vapor on the air-fuel ratio is reduced. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, it is possible to stabilize the combustion by suppressing the occurrence of rich misfire and the like, and to maintain good drivability.

In the third embodiment, as shown in FIG. 9, a value that changes linearly with the atmospheric pressure is used as the correction coefficient β, but this value corresponds to the atmospheric pressure. As long as the characteristic has a characteristic that gradually increases to a predetermined value CkPa, another arbitrary curve can be adopted.

<Fourth Embodiment> The fourth embodiment is the first embodiment.
In order to correct the basic fuel injection amount in the control of the DPG in the embodiment, the evaporated fuel correction amount FP
The control by G is added.

The purge control valve is controlled by controlling the DPG,
When the purge amount is controlled in the increasing direction, the amount of evaporated fuel added to the basic fuel injection amount increases. Therefore, if left as it is, the air-fuel ratio may become too rich. So D
An abrupt rich state is avoided by obtaining the evaporated fuel amount correction amount FPG corresponding to the increase in PG and reducing the evaporated fuel amount correction amount FPG from the basic fuel injection amount injected from the fuel injection valve. Next, an example of fuel injection control including purge control in the present embodiment will be described with reference to the flowchart of FIG. This is an example in which the evaporated fuel amount is corrected according to the engine speed.

First, the engine speed NE and the accelerator opening ACA are input (step 681). Next, the basic fuel injection amount (QALL) is calculated in an interpolation manner according to the input data (step 682).

That is, a basic fuel injection amount corresponding to the engine speed and the accelerator opening is interpolatively calculated from a map that defines the correlation between the engine speed and the accelerator opening (not shown) and the basic fuel injection amount. I do.

In step 683, it is determined whether or not purging is being performed. If purging is being performed, the throttle opening TA and the engine speed NE are fetched (step 684). Next, an evaporative fuel amount correction amount (FPG) is calculated (step 685). This calculation is performed from the correlation between the throttle opening TA engine speed NE previously stored in the ROM as a map and the evaporated fuel amount correction amount (FPG) (see FIG. 11). In the drawings, high, medium, and small are engine speeds. When the engine speed is low, the amount of fuel vapor correction increases.

If it is determined in step 683 that purging is not being performed, then in step 687, the fuel vapor amount correction amount is set to zero.
In steps 685 and 687, the fuel vapor amount correction amount (FPG)
Is determined, the routine proceeds to step 686, where the final fuel injection amount is determined. Here, the fuel vapor amount correction amount (FPG) is subtracted from the basic fuel injection amount (QALL) calculated in step 682, and the correction coefficient K is added to determine the final fuel injection amount.

Thereafter, fuel injection is performed according to a separately determined fuel injection program. The correction amount of the evaporated fuel amount (FP
As another calculation method of G), as shown in FIG.
A method of obtaining from the purge gas amount Qp and a method of obtaining from the pressure of the intake manifold as shown in FIG. 13 can be exemplified.

The routine shown in FIG. 10 is repeatedly executed at predetermined time intervals. Since the correction amount of the evaporated fuel is detected and corrected in such a correction routine, particularly in steps 684 and 685, a large amount of the evaporated fuel can be processed without affecting the drivability and the emission.

Meanwhile, during the purge control shown in FIG. 10, the air-fuel ratio may suddenly become rich depending on the operating conditions. In such a case as well, if the supply of the evaporated fuel is continued, an air-fuel ratio higher than necessary temporarily occurs, and there is a possibility that a fire may occur.

Therefore, as described below, a state in which the air-fuel ratio suddenly becomes rich is predicted by the judging means, and the supply of the fuel vapor or the restriction of the fuel vapor and the fuel from the fuel injection valve are simultaneously performed. Limit injection volume.

Hereinafter, an example of controlling the FPG will be described with reference to FIG. This implements the feature point (1-1). The control of the FPG is used together with the control of the DPG described above.

When the processing shifts to this routine, the ECU
30 first determines in step 1101 whether or not the rich spike control is currently being executed. If it is determined that the rich spike control is being performed, it is determined that the supply of the fuel vapor is inappropriate, and in step 1106, the fuel vapor correction amount FPG is set to “0”, and the subsequent processing is temporarily terminated. I do. That is, when it is determined that the rich spike control is being performed, the final injected fuel amount = the basic injected fuel amount + K0 from the above equation (1).
(K0: Reducing agent (HC) required to purify NOx
(A reducing agent amount coefficient that defines the amount of the reducing agent).

On the other hand, if it is determined in step 1101 that the rich spike control is not currently being performed, the process proceeds to step 1102. Step 1
In 102, it is determined whether the count value of the rich spike conditions are satisfied counter is greater than the predetermined value C ₀ which is set in advance. The rich spike condition satisfaction counter is counted by the ECU 30 based on predetermined conditions according to the flowchart shown in FIG. 5 as described above, and is reset and re-counted after performing the rich spike control. It is. If it is determined that the count value of the rich spike condition satisfaction counter is equal to or _smaller than the predetermined value C0, the process proceeds to step 1107.
, The differential pressure dp between the atmospheric pressure and the pressure in the intake duct 20
, The FPG is calculated, and the subsequent processing is temporarily terminated.

Note that the function f used in this calculation is
Corresponds to the differential pressure dp. The differential pressure dp
As the atmospheric pressure for calculation, for example, the intake pressure obtained by the intake pressure sensor 46 at the time of starting the engine is recorded and used. On the other hand, the pressure in the intake duct 20 uses the intake pressure obtained by the intake pressure sensor 46 each time. Then, based on the calculated FPG = f (dp), the fuel injection amount is controlled by the evaporated fuel amount correction amount.

If it is determined in step 1102 that the count value of the rich spike condition satisfaction counter is larger than the predetermined value C _0, it is estimated that rich spike control will be executed soon. Move to In step 1103, the previous FPG _i-1 is decreased by a predetermined value α.

The fact that the FPG has decreased from the previous time means that, from the equation (1), the fuel injection amount finally supplied to the engine increases. Then step 11
Move to 04.

During this time, as is apparent from FIG.
As the DPG gradually subtracts toward the lean direction,
Since the FPG is gradually subtracted toward rich, the air-fuel ratio is kept at the required value.

At step 1104, it is determined whether or not the FPG is "0". If it is determined that the FPG is not “0”, the subsequent processing is temporarily terminated. That is, the FPG obtained in step 1103 is obtained until the fuel vapor correction amount becomes 0 by the processing in step 1103.
, The final fuel injection amount increases. That is, the air-fuel ratio is changed to the rich-side air-fuel ratio corresponding to the rich spike.

If it is determined in step 1104 that the FPG is "0", the process proceeds to step 110.
Move to 5. In step 1105, execution of the rich spike control is permitted, and the subsequent processing is temporarily terminated. Next, differences in control between the prior art and this embodiment will be described with reference to FIG.

FIG. 19A shows how the rich spike counter described with reference to FIG. 5 counts up.
FIG. 19D shows a change in the air-fuel ratio before and after the rich spike during the conventional purge. Before the rich spike, the required air-fuel ratio is larger than the required air-fuel ratio due to the effect of the purge on the required air-fuel ratio. It shows that the state shifted to is continued. If the rich spike is executed in a state where the air-fuel ratio deviates from the required air-fuel ratio as it is, the air-fuel ratio becomes richer than the air-fuel ratio corresponding to the rich spike, and eventually a rich misfire may occur.

On the other hand, FIG. 19C shows the DP of the present embodiment.
This is the case where only G is controlled. The DPG gradually changes the air-fuel ratio from a state richer than the required air-fuel ratio to a required air-fuel ratio by gradually subtracting until a rich spike is executed. As a result, when a rich spike is executed, the air-fuel ratio corresponding to the rich spike can be adjusted, so that a rich misfire can be prevented. Further, since the DPG is gradually subtracted, the combustion can be stabilized by suppressing the roughening of the air-fuel ratio. And gradually DPG
, The purge execution time is longer than in the method of rapidly decreasing the DPG to match the required air-fuel ratio,
Therefore, a sufficient purge amount can be secured.

Next, FIG. 19 (2) corresponds to the embodiment of FIG. 14, and is a case where both DPG and FPG are gradually subtracted to approach 0. When the DPG is subtracted, the air-fuel ratio is shifted to the lean side, and when the FPG is subtracted, the air-fuel ratio is shifted to the rich side. Therefore, if the DPG and the FPG are subtracted synchronously, the air-fuel ratio can be made equal to the required air-fuel ratio.

As described above, according to this embodiment,
In conjunction with the DPG control, the air-fuel ratio can be made equal to the required air-fuel ratio until the execution of the rich spike, and the effect of the evaporated fuel on the air-fuel ratio during the rich spike control is reduced. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, it is possible to prevent the occurrence of rich misfire and the like, and to maintain good drivability.

In the fourth embodiment, the predetermined value α of the FPG reduced in step 1103 is a constant, but this may be a variable according to the operating state.

Further, in the fourth embodiment,
In step 1103, the FPG repeatedly decreases the predetermined value α, gradually reduces the FPG, and eventually reduces the FPG to zero. However, the FPG may be set to “0” at one time.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described. However, the configuration of this embodiment is the same as that of the above-described second embodiment, and the control target is simply changed from DPG to FPG. This FPG control has the effect of FIG. 19 (2) in combination with the DPG control according to the second embodiment. This example implements the features of (1-2) and (1-3).

FIG. 15 is a flowchart showing an "evaporative fuel control routine" for executing the control of evaporative fuel in the present embodiment, which is executed by the ECU 30 as a main routine.

When the processing shifts to this routine, the ECU
30 first determines in step 1201 whether or not the brake control is currently being executed. If it is determined that the brake control is being executed, it is determined that the supply of the evaporated fuel is inappropriate, and in step 1203, the evaporated fuel amount correction amount FPG is set to “0”, and the subsequent processing is temporarily terminated. I do. That is, when it is determined that the brake control is being executed, the final injection fuel amount = the basic injection fuel amount + K1 from the equation (1). Here, K1 is a fuel injection amount correction coefficient for making the air-fuel ratio equal to the required air-fuel ratio when the brake negative pressure is secured. When the brake negative pressure is secured, the throttle is driven in a direction to close the throttle, and as a result, the air-fuel ratio changes to the rich side. Therefore, it can be said that K1 is a correction coefficient for making the air-fuel ratio equal to a required air-fuel ratio, for example, a stoichiometric or predetermined lean air-fuel ratio when the purge is stopped.

On the other hand, if it is determined in step 1201 that the brake control is not currently being performed, the process proceeds to step 1202. Step 1202
, The brake negative pressure is set to a predetermined value Bk
It is determined whether it is greater than Pa (absolute pressure). Here, the predetermined value BkPa is a value at which the brake negative pressure securing process is executed when the brake negative pressure becomes a value obtained by adding a constant value to the brake negative pressure. If it is determined that the brake negative pressure is greater than the predetermined value BkPa, in step 1204, the differential pressure d
FPG is calculated based on p, and the subsequent processing is temporarily terminated. That is, FPG is calculated as a function g of the differential pressure dp. Then, based on the calculated FPG = g (dp), the fuel injection amount is controlled by the evaporated fuel amount correction amount.

During this time, as is apparent from FIG.
The value of the DPG control and the value of the FPG control cancel each other,
The air-fuel ratio can be made to match the required air-fuel ratio.

If it is determined in step 1202 that the brake negative pressure is equal to or lower than the predetermined value BkPa, a process for securing the brake negative pressure will be performed soon (temporarily closing the throttle valve 23 to reduce the air-fuel ratio). It is presumed that the process of increasing the density to the vicinity will be executed, and step 12
In 03, the FPG is set to "0", and the subsequent processing is temporarily ended. That is, if it is determined that the process of securing the brake negative pressure will be executed soon, the final injection fuel amount = the basic injection fuel amount + K1 (where K1 is the correction coefficient of the fuel injection amount at the time of securing the brake negative pressure) from equation (1). ), Meaning that the air-fuel ratio is shifted to a richer side than before the braking.

As a result, until the brake negative pressure is required, as shown in FIG.
As the PG control is performed and the FPG approaches 0, that is, the air-fuel ratio fluctuates toward the rich side, the DPG also approaches 0, the air-fuel ratio fluctuates toward the lean side, and the air-fuel ratio relatively increases to the target lean value. State.

According to the present embodiment, in the stratified charge combustion state, when the negative pressure in the brake booster 71 for assisting the braking operation by the negative pressure is secured, the air-fuel ratio tends to be high, but the ECU 30 determines the negative pressure. FPG before securing
Is zero, the air-fuel ratio is kept constant in combination with the DPG control, and the effect of the evaporated fuel on the air-fuel ratio during the process of securing the brake negative pressure is eliminated. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, the occurrence of rich misfire or the like can be prevented, and the drivability can be well maintained.

In particular, in a direct injection type lean burn internal combustion engine, the throttle valve is usually operated with the throttle valve almost fully opened. Therefore, when braking with a brake, a negative pressure for the brake booster must be generated each time. Must. The negative pressure is generated by temporarily closing the throttle valve. However, the air-fuel ratio becomes temporarily rich, which may cause misfire. Therefore, in such a case, misfire can be prevented by restricting the supply of the evaporated fuel as described above. As described above, this embodiment is an extremely effective means in a direct injection type lean burn internal combustion engine.

In the fifth embodiment, the FPG is cut at once in step 1203 to set the FPG to “0”. However, the FPG may be gradually reduced.

<Sixth Embodiment> Next, a sixth embodiment of the present invention will be described. However, the configuration of this embodiment is the same as that of the third embodiment described above. This example is an example of implementing (1-4).

FIG. 16 shows an "evaporative fuel supply control routine" for executing the control of the evaporative fuel in the present embodiment.
Is a flowchart showing a main routine executed by the ECU. This processing is performed in the third
The embodiment is used together with the DPG control of FIG.

When the processing shifts to this routine, the ECU
30 first determines in step 1301 whether the atmospheric pressure is greater than a predetermined value CkPa set in advance. When it is determined that the atmospheric pressure is larger than the predetermined value CkPa, in step 1303, the FPG is calculated based on the differential pressure dp, and the subsequent processing is temporarily terminated. That is, assuming that the intake air density does not decrease, the FPG is calculated as a function h of the differential pressure dp as usual. The final fuel injection amount is adjusted according to the amount of FPG.

If it is determined in step 1301 that the atmospheric pressure is equal to or lower than the predetermined value CkPa, the process proceeds to step 1302 in which the previous FPG _i-1 corresponds to the atmospheric pressure shown in FIG. Correction coefficient β (0
≦ β ≦ 1) is set as a new FPG.
Thereafter, the processing is temporarily terminated. That is, by going through step 1302, the FPG is gradually reduced. As the FPG is gradually subtracted, the air-fuel ratio is shifted to the rich side.

On the other hand, in the control by the DPG, the air-fuel ratio is shifted to the lean side, and the air-fuel ratio is maintained at the required air-fuel ratio by the control of both.

According to the present embodiment, in the stratified combustion state, the air density (intake air density) is low at high altitudes, so that the air-fuel ratio tends to be rich as compared with flat ground. On the other hand, when the atmospheric pressure (corresponding to the air density) is low, the ECU 30 reduces the FPG and increases the final fuel injection amount, but also controls the DPG and at the same time reduces the amount of evaporated fuel. The required air-fuel ratio can be controlled.

Thus, at high altitudes, the effect of the fuel vapor on the air-fuel ratio is reduced. Therefore, the air-fuel ratio is appropriately controlled and is not disturbed. As a result, it is possible to prevent the occurrence of a rich misfire or the like, and to maintain good drivability.

In the sixth embodiment, as shown in FIG. 9, a value that changes linearly with the atmospheric pressure is used as the correction coefficient β, but this value corresponds to the atmospheric pressure. As long as the characteristic has a characteristic that gradually increases to a predetermined value CkPa, another arbitrary curve can be adopted. <Seventh Embodiment> Next, a seventh embodiment of the present invention will be described. This embodiment is an example in which the correction coefficient β is changed to β ′ according to the vapor concentration in the sixth embodiment. Although not shown, the DPG control of FIG.
Is used in combination with the present embodiment.

The present embodiment is an example of implementing (1-6).

FIG. 17 shows an "evaporative fuel supply control routine" for executing the control of the evaporative fuel in the present embodiment.
Is a flowchart showing a main routine executed by the ECU.

When the processing shifts to this routine, the ECU
30 first determines in step 2301 whether the atmospheric pressure is greater than a predetermined value CkPa set in advance. When it is determined that the atmospheric pressure is larger than the predetermined value CkPa, in step 2305, the FPG is calculated based on the differential pressure dp, and the subsequent processing is temporarily terminated. That is, assuming that the intake air density does not decrease, the FPG is calculated as a function h of the differential pressure dp as usual. Then, the final fuel injection amount is adjusted based on the result.

If it is determined in step 1301 that the atmospheric pressure is equal to or lower than the predetermined value CkPa, an HC sensor (not shown) serving as a concentration detecting means provided in the evaporated fuel chamber 84 in step 2302. In step 2303, a correction coefficient β ′ corresponding to the vapor concentration is calculated from the map shown in FIG.

Next, at step 2304, the previous FP
A value obtained by multiplying G _i−1 by a correction coefficient β ′ (0 ≦ β ′ ≦ 1) obtained from the correspondence between the atmospheric pressure and the vapor concentration shown in FIG. 18 is set as a new FPG. Thereafter, the processing is temporarily terminated. That is, by going through this step 2302, the FPG is gradually reduced. FPG is gradually subtracted, and the air-fuel ratio is shifted to the rich side.

On the other hand, in the control by the DPG, the air-fuel ratio is shifted to the lean side, so that the air-fuel ratio is maintained at the required air-fuel ratio by the control of both.

Next, the operation and effect of this embodiment will be described in the sixth.
However, in this case, finer control is possible in accordance with a change in the vapor concentration. <Eighth Embodiment> A case where the concentration of the fuel vapor is detected and purge control is performed will be described with reference to FIG. This realizes the feature point (1-6). (1-5)
In the brake control, instead of setting the purge amount to “0”, the purge control valve is throttled to reduce the amount of fuel vapor, and the fuel injection amount supplied from the fuel injection valve is also reduced. When the required final fuel injection amount is obtained from the fuel injection from the fuel vapor and the fuel injection valve, the purge amount or the fuel injection state is corrected and controlled according to the concentration in consideration of the concentration of the fuel vapor.

First, a routine for performing purge control for brake control is entered (step 3021). At this time, the vapor concentration is detected by the vapor concentration detecting means (step 3022).

Next, it is determined whether or not the brake negative pressure is equal to or less than a predetermined reference value BKPa (step 30).
23). If it is less than the reference value, the operating state detecting means detects the fuel injection amount, fuel injection timing, throttle opening, purge control valve opening, engine speed, engine load, etc., and takes them into the CPU (step 3024). . Thereafter, the air-fuel ratio determining means at the time of brake control determines the air-fuel ratio (step 3025).

In order to determine the operating state based on the air-fuel ratio determined in step 3025, in step 3026, the operating state correction means during brake control uses the fuel injection amount, fuel injection time, The correction amount of the purge control valve opening is determined.

In consideration of the correction amount, the fuel injection amount supplied from the fuel injection valve and the supply amount of the evaporated fuel based on the opening of the purge control valve are determined so as to achieve the air-fuel ratio determined as described above. . That is, the final fuel injection amount is calculated from a map that defines the correlation between the engine speed and the accelerator opening and the basic fuel injection amount. Add and get the amount.

In determining the fuel injection timing (AINJ), the map shown in FIG. 21 is referred to. In this map, the correlation between the fuel vapor correction amount (FPG) and the change amount of the fuel injection timing (△ AINJ) is determined in advance.
M. In FIG. 21, the intersection between the graph and the horizontal axis indicates the stoichiometric air-fuel ratio. The part to the left of this intersection means that only air is purged. That is, the present fuel injection timing is calculated by subtracting the fuel injection timing change amount (ＪAINJ) corresponding to the evaporated fuel amount correction amount (FPG) from the previous fuel injection timing (AINJO).

In step 3027, the purge control at the time of braking is executed according to the determined conditions. In step 3023, the brake negative pressure is set to a predetermined reference value B.
If not, the process ends. As the vapor concentration detecting means, in addition to the HC sensor, the vapor concentration may be calculated from an oxygen sensor provided on the intake pipe and an air-fuel ratio sensor provided on the exhaust pipe.

In this case, since the purge gas can be supplied even during the brake control, the chance of purging increases and the release of vapor to the atmosphere can be prevented. Further, since the fuel injection amount, fuel injection timing, and the like are determined according to the vapor concentration, an optimal air-fuel ratio can be realized, and good drivability can be maintained. Embodiments of the present invention are not limited to the above, and may be modified as follows.

First, in each of the above-described embodiments, the determination that the air-fuel ratio of the combustible air-fuel mixture in the stratified combustion state is made richer than the air-fuel ratio in the steady stratified combustion state in the stratified fuel supply control routine is made. Independently, it is determined that the amount of NOx stored in the NOx storage reduction catalyst 61 for performing the rich spike control is larger than a predetermined amount, and the amount of negative pressure in the brake booster 71 detected by the pressure sensor 72 is reduced. It was determined that the air volume in the intake duct 20 detected by the intake pressure sensor 46 was lower than the reference value, or that the air density in the intake duct 20 detected by the intake pressure sensor 46 was lower than the predetermined amount. Two or more steps may be performed at the same time to reduce or stop the fuel vapor.

In each of the above embodiments, the present invention is embodied in the in-cylinder injection type engine 1. However, any other type of internal combustion engine that performs so-called stratified combustion or weakly stratified combustion may be used. For example, the intake valves 6 of the intake ports 7a and 7b
a and 6b include those of the type that sprays toward the back side of the umbrella portion. Although the fuel injection valve is provided on the intake valves 6a and 6b side, a type in which the fuel is injected directly into the cylinder bore (combustion chamber 5) is also included.

Further, in each of the above embodiments, the helical type intake port is provided, and so-called swirl can be generated. However, it is not always necessary to generate swirl. Therefore, for example, the swirl control valve 17 and the step motor 1
9 and the like can be omitted.

Further, in each of the above embodiments, the present invention is embodied in the case of the gasoline engine 1 as the internal combustion engine. However, the present invention can also be embodied in the case of a diesel engine or the like.

In each of the above embodiments, the intake pressure sensor 61
Is used to detect the atmospheric pressure PA. However, an atmospheric pressure sensor may be separately provided, thereby providing an atmospheric pressure sensor, and thereby detecting the atmospheric pressure. Also, during the brake control, the purge amount is not always set to “0”.
By narrowing the purge control valve to reduce the amount of fuel vapor,
It is also possible to limit the fuel injection quantity supplied from the fuel injection valve, so that the required final fuel quantity obtained from the fuel injection from the fuel injection valve is reduced as a whole.

[0168]

As described in detail above, according to the present invention,
In the evaporative fuel supply control device for the lean burn internal combustion engine having an adjusting means for adjusting the flow rate of the evaporative fuel, it is possible to appropriately control the air-fuel ratio in the stratified combustion state, so that rich misfire etc. This has an excellent effect that generation of pits can be prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram showing a basic concept of the invention of claim 1;

FIG. 2 is an external force configuration diagram showing an evaporative fuel supply control device of the in-cylinder injection engine according to the first embodiment.

FIG. 3 is a block circuit diagram showing an electrical configuration of an ECU.

FIG. 4 is an enlarged schematic cross-sectional view showing a cylinder portion of the engine.

FIG. 5 is a flowchart illustrating an example of a control routine of a NOx release flag.

FIG. 6 is a flowchart illustrating an “evaporative fuel supply control routine” executed by the ECU.

FIG. 7 is a flowchart illustrating an “evaporative fuel supply control routine” according to the second embodiment.

FIG. 8 is a flowchart illustrating an “evaporative fuel supply control routine” according to a third embodiment.

FIG. 9 is a map showing a relationship between a correction coefficient and an atmospheric pressure.

FIG. 10 is a flowchart illustrating an example of correction control of an evaporated fuel amount.

FIG. 11 shows a throttle opening degree TA and a fuel vapor amount correction amount FP.
5 is a map that defines a correlation between G and an engine speed NA.

FIG. 12 is a diagram illustrating a fuel vapor amount correction amount FPG and a purge gas amount Qp.
It is a map that defines the relationship with.

FIG. 13 is a map that defines a correlation between an evaporated fuel amount correction amount FPG and a differential pressure between the atmospheric pressure and the intake manifold pressure.

FIG. 14 is a flowchart illustrating an “evaporative fuel supply control routine” according to a fourth embodiment.

FIG. 15 is a flowchart illustrating an “evaporative fuel supply control routine” according to the fifth embodiment.

FIG. 16 is a flowchart illustrating an “evaporative fuel supply control routine” according to a sixth embodiment.

FIG. 17 is a flowchart illustrating an “evaporative fuel supply control routine” according to a seventh embodiment.

FIG. 18 is a map showing a relationship between a correction coefficient with respect to an atmospheric pressure and a vapor concentration.

FIG. 19 is a time chart showing the relationship between rich spike control and purge control.

FIG. 20 is a flowchart illustrating an “evaporative fuel supply control routine” according to the eighth embodiment.

FIG. 21 is a map that defines a correlation between an evaporated fuel amount correction amount (FPG) and a change amount of fuel injection timing (ＪAINJ).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine 11 ... In-cylinder fuel injection valve as a fuel supply means 13 ... Exhaust duct as an exhaust passage 20 ... Intake duct forming an intake passage 23 ... Throttle valve as negative pressure generating means 25 ... Throttle sensor 26A constituting the operating state detecting means Accelerator sensor 26B constituting the operating state detecting means 26B Fully-closed switch constituting the operating state detecting means 27 Upper fulcrum sensor constituting the operating state detecting means 28 Operating state detecting means The crank angle sensor 29 that constitutes the operating state detecting means 30 The SCV sensor that constitutes the operating state detecting means 30 The ECU that constitutes the determining means and the fuel limiting means 46 The intake pressure sensor 47 which constitutes the operating state detecting means 47 The operating state detecting means Water temperature sensor 61: NOx storage reduction catalyst constituting rich spike control means 62: Operation state Oxygen sensor 71 constituting a detecting means 71 Brake booster 72 Pressure sensor as a negative pressure amount detecting means constituting an operating state detecting means 81 Purge control device 83 as a fuel supply means 83 Canister 86 Electromagnetic as adjusting means On-off valve 87, 88 ... Electromagnetic on-off valve 89 ... Fuel tank

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Zenichiro Mashiro 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Automobile Co., Ltd. (72) Inventor Tetsuji Nagata 1-1-1 Showa Town, Kariya City, Aichi Prefecture Inside DENSO Corporation

Claims (7)

[Claims] A purge passage for purging evaporative fuel generated from fuel storage means for storing fuel of the internal combustion engine into an intake system of the internal combustion engine; and an evaporative fuel amount introduced from the purge passage into the intake system. Purge control means for controlling in accordance with the operating state of the engine; air-fuel ratio determination means for determining that the air-fuel ratio corresponding to lean combustion shifts to a richer air-fuel ratio during lean-burn operation; and air-fuel ratio determination means. When it is determined that the air-fuel ratio becomes rich, a fuel limiting means for limiting at least the purge amount of the purge amount of the evaporated fuel determined by the purge control means and the fuel amount injected from the fuel injection valve of the internal combustion engine; An evaporative fuel supply control device for a lean burn internal combustion engine, comprising: 2. At least when a lean burn operation is being performed, the air-fuel ratio of the combustible air-fuel mixture is temporarily increased to be stored in a nitrogen oxide reduction catalyst provided in an exhaust passage of the internal combustion engine. A rich spike control unit for releasing and purifying the nitrogen oxides is provided, and the air-fuel ratio determination unit is configured to determine when the amount of nitrogen oxides stored in the nitrogen oxide reduction catalyst is larger than a predetermined amount.
2. The evaporative fuel supply control device for a lean burn internal combustion engine according to claim 1, wherein the controller determines that the air-fuel ratio is in a rich state. 3. A brake booster for assisting a braking operation of a vehicle based on a negative pressure in the intake passage, and a negative pressure for generating a negative pressure for the brake by reducing an air flow rate in the intake passage. 2. The evaporative fuel supply control device for a lean burn internal combustion engine according to claim 1, wherein a generator and a generator are provided, and the air-fuel ratio determiner determines the air-fuel ratio based on an operation state of the negative pressure generator. 4. An air-fuel ratio determining means for detecting a negative pressure amount in the brake booster, wherein the air-fuel ratio determining means determines an air-fuel ratio based on the negative pressure amount detected by the negative pressure amount detecting means. 2. The method according to claim 1, wherein
4. The evaporative fuel supply control device for a lean burn internal combustion engine according to 3 or 3. 5. The lean combustion according to claim 1, further comprising intake density detecting means for detecting an intake density, wherein the air-fuel ratio determining means makes a determination based on the intake density detected by the intake density detecting means. An evaporative fuel supply control device for an internal combustion engine. 6. An injection state changing means for changing a fuel injection state in combination with limiting the purge amount by said fuel limiting means when the air-fuel ratio determining means determines that the air-fuel ratio becomes rich. An evaporative fuel supply control device for a lean burn internal combustion engine according to any one of claims 1 to 5. 7. The apparatus according to claim 1, further comprising a concentration detecting means for detecting the concentration of the evaporated fuel, and a correcting means for correcting the purge amount or the fuel injection state according to the concentration of the evaporated fuel. Fuel supply control device for a lean burn internal combustion engine.