JP3509404B2 - Intake control device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a device for forming a stratified air-fuel mixture in a combustion chamber at least under a predetermined operating condition for combustion and supplying evaporated fuel to an intake system for processing. The present invention relates to a technique for controlling intake air by supplying evaporated fuel in an engine.

[0002]

2. Description of the Related Art In an internal combustion engine, a stratified mixture which forms a mixture layer of combustible mixture in the vicinity of a spark plug in a combustion chamber of the engine in a predetermined operating condition region and an air layer in other regions. Is known, and is burned with a stratified mixture. For example, as a spark ignition type engine in which fuel is directly injected into a combustion chamber, there is disclosed in Japanese Patent Laid-Open No. 4-241.
There is one shown in No. 754.

Further, in order to prevent the fuel evaporated in the fuel tank and the like from being diffused into the atmosphere, it is adsorbed and held by an adsorbent such as activated carbon contained in a container (canister), and released according to the situation. A system is also known in which the evaporated fuel is consumed by being mixed with intake air and supplied to the engine. However, in the case of an internal combustion engine that has operating conditions that generate the stratified mixture, the evaporated fuel that is stored in this canister and is discharged (purged) into the intake system is mixed with the intake, so the stratified mixture is generated. The vaporized fuel is also mixed in the air layer of the air. Since the mixture ratio of the air layer mixed with the vaporized fuel is much higher than the normal combustible mixture ratio and becomes lean, the combustion flame formed in the combustible mixture layer disappears without advancing to this air layer. Therefore, the evaporated fuel contained in the air layer is directly discharged from the combustion chamber.

Therefore, if the purging is performed unnecessarily during the stratified combustion, unnecessary HC components are released into the exhaust gas, which is not always desirable from the viewpoint of exhaust gas purification. For this reason, Japanese Patent Application Laid-Open No. 5-223017 proposes a configuration in which vaporized fuel is not purged in a low / medium load region where stratified charge combustion is performed.

[0005]

However, in the case of adopting the configuration as disclosed in the above-mentioned Japanese Patent Laid-Open No. Hei 5-223017, the evaporative fuel has a chance to be purged under the condition that the operation under a low load is continuously carried out. Without it, it will continue to be stored in the canister. In other words, even if the capacity of the canister is exceeded, the evaporated fuel will continue to be supplied, so a large canister should be installed if possible.
It becomes a problem in terms of weight and layout.

The present invention has been made in view of the above conventional problems, and by appropriately purging the vaporized fuel, the consumption rate of the vaporized fuel can be increased, and the vaporized fuel can be purged by nitrogen oxidation. An object of the present invention is to provide an intake control device for an internal combustion engine, which is also capable of improving the purification performance of substances (NOx).

[0007]

[0008]

[0009]

[0010]

Therefore, according to claim 1,
As shown in FIG. 1, the present invention relates to stratified mixture combustion in which a stratified state of a mixture layer and an air layer is formed in a combustion chamber for combustion, and a homogeneous mixture is formed in the combustion chamber for combustion. A homogeneous air-fuel mixture combustion that performs the above, and a mixture formation switching unit that performs switching by switching in accordance with the operating conditions of the engine; and an evaporated fuel supply unit that supplies the fuel evaporated from the fuel supply system to the intake system of the engine,
Evaporative fuel supply amount control means for controlling the supply amount of the evaporated fuel to the intake system, nitrogen oxide discharge amount calculating means for calculating the amount of nitrogen oxides discharged from the combustion chamber, and the nitrogen oxide discharge amount Demand for reducing agent to calculate the amount of hydrocarbons required to reduce nitrogen oxides with an exhaust purification catalyst installed in the exhaust system of the engine, with respect to the amount of nitrogen oxides calculated by the calculation means And a vaporized fuel supply amount setting means for setting a supply amount so as to supply an amount of vaporized fuel according to the reducing agent required amount to the intake system during stratified mixture combustion. The hydrocarbon component of the evaporated fuel supplied to the intake system during combustion of the stratified mixture is mixed into the air layer of the stratified mixture and discharged to the exhaust system as it is unburned, and is used for the reduction of nitrogen oxides. Supply of evaporated fuel during combustion
Is the set air-fuel ratio of the air-fuel mixture due to deterioration of combustion stability.
The feature is that it is performed during rich correction .

(Operation / Effect) The nitrogen oxide calculating means calculates the emission amount of nitrogen oxides from the combustion chamber, and the reducing agent required amount calculating means calculates the amount of nitrogen oxides in the catalyst. The required amount of hydrocarbon (HC) as a reducing agent necessary for the redox reaction is calculated. The evaporative fuel supply amount setting means sets the supply amount of the evaporative fuel that serves as a reducing agent for nitrogen oxides during stratified mixture combustion based on the reducing agent required amount, and the evaporative fuel supply amount control means sets the set amount. The supply amount of evaporated fuel is controlled so that a large amount of evaporated fuel is supplied to the intake system.

As described above, by supplying the evaporated fuel in an amount corresponding to the discharge amount of the nitrogen oxide, the evaporated fuel and the nitrogen oxide can be effectively treated at the same time. Well
In addition, when the stratified mixture burns, the combustion stability deteriorates.
Therefore, the air-fuel ratio of the air-fuel mixture is rich-corrected with respect to the set value.
Nitrogen oxides emissions tend to increase
One. Therefore, supply of vaporized fuel during combustion of the stratified mixture
The set air-fuel ratio of the air-fuel mixture due to deterioration of combustion stability.
Because you did it while performing rich correction
Can process evaporative fuel by reacting with nitrogen oxides and catalysts
At the same time, nitrogen oxides downstream of the catalyst can be reduced.
It Further, the invention according to claim 2 is characterized in that the nitrogen oxides emission amount calculating means calculates the emission amount of nitrogen oxides based on the operating state of the engine, the air-fuel ratio of the air-fuel mixture, and the fuel injection timing. To do.

(Operation / Effect) The emission amount of nitrogen oxides affects the operating conditions such as the engine speed and load, and the generation of nitrogen oxides such as the air-fuel ratio and fuel injection timing of the air-fuel mixture supplied to the combustion chamber. Can be estimated and calculated with high accuracy on the basis of a large element. Further, in the invention according to claim 3 , as shown by a one-dot chain line in FIG. 1, the vaporized fuel supply means includes a vaporized fuel storage portion for temporarily storing fuel vaporized from a fuel system, and the vaporized fuel storage means Is configured to include an evaporated fuel accumulated amount calculating means for calculating an accumulated amount of evaporated fuel in the section, and the supply of evaporated fuel during the stratified mixture combustion is
It is characterized in that it is carried out when the accumulated amount of the evaporated fuel becomes close to the limit value.

(Operation / effect) By doing so,
In the stratified air-fuel mixture combustion, the conditions for purging the evaporated fuel to the intake system are limited. That is, purging is performed when the amount of evaporated fuel approaches the limit value of the amount that can be accumulated. This has the following two goals and effects.

(1) One is that, if there is a room to store the evaporated fuel in the evaporated fuel storage portion (for example, the activated carbon layer of the canister), the processing of the evaporated fuel is not necessarily required. (2) As another reason, the control of the evaporated fuel amount is actually performed by controlling the amount of the purged air-fuel mixture mixed with the purging air, and not the direct control of the evaporated fuel amount. Absent. Therefore, the amount of evaporated fuel actually introduced into the intake system changes depending on the amount of fuel accumulated in the evaporated fuel accumulation portion. In that case, if the evaporated fuel is sufficiently accumulated and held in the evaporated fuel storage unit, the supply amount of evaporated fuel relative to the operation amount of the supply amount control member (purge control valve, etc.) can be estimated relatively accurately, and the evaporated fuel can be estimated. This is because it is possible to control the mixing amount of the intake air into the intake air with relatively high accuracy.

According to a fourth aspect of the present invention, the supply of the evaporated fuel during the stratified mixture combustion is performed when the nitrogen oxide emission amount calculated by the nitrogen oxide emission amount calculating means is equal to or more than a predetermined value. It is characterized in that it is done. (Operation / Effect) As in the case of the invention according to claim 3 , the conditions for deliberately purging evaporated fuel into the intake system during stratified mixture combustion are limited. That is, when the emission amount of nitrogen oxides obtained by the nitrogen oxide emission amount calculation means is relatively large, purging is performed even during stratified mixture combustion. As a result, as described above, the amount of nitrogen oxides discharged downstream of the catalyst can be reduced even if the amount of nitrogen oxides discharged increases due to some demand.

However, in an ordinary engine, the total emission of nitrogen oxides is designed in consideration of such an increase in the emission by an EGR system or the like, so that the total emission becomes less than a desired amount. Since such an operation is designed as described above, such an operation has more implications for those who have an effect on environmental protection rather than an effect that is highly necessary .

[0018]

Further, as shown by a dotted line in FIG. 1, the invention according to claim 5 comprises a catalyst active state judging means for judging an active state of the exhaust gas purification catalyst, and when the stratified mixture combustion is performed. When it is determined that the catalytic activity of the evaporated fuel is not sufficient for the reduction of nitrogen oxides to proceed,
The feature is that it is prohibited.

(Operation / Effect) The effects of purging the evaporated fuel during the stratified mixture combustion are premised on that the catalyst is functioning normally. Therefore, the evaporative fuel is supplied only when it is judged that the catalyst is sufficiently activated as a necessary condition for surely reducing the nitrogen oxides when the hydrocarbon is supplied by judging the active state of the catalyst. As a result, the effects described above can be exhibited reliably.

Further, in the invention according to claim 6 , the evaporative fuel supply amount setting means reduces the evaporative fuel supply amount with respect to the reducing agent required amount calculated by the reducing agent required amount calculating means. Is set as follows. (Action / Effect) With respect to the required amount calculated by the reducing agent required amount calculating means,
By supplying at least a small amount of evaporated fuel to the intake system, at least part of the nitrogen oxides can be reduced, and even if there is an error in the estimation of the nitrogen oxide emissions, carbonization will occur. It is possible to prevent excessive supply and discharge of hydrogen.

Further, in the invention according to claim 7 , the evaporative fuel supply amount setting means reacts with oxygen in exhaust gas among hydrocarbons in evaporative fuel at the time of stratified mixture combustion with a large lean degree of air-fuel ratio. It is characterized in that the supply amount of the evaporated fuel is set based on the ratio of those that undergo the reduction reaction with the nitrogen oxides.

(Action / Effect) The reducing agent demand amount calculating means does not react with oxygen in the exhaust gas among hydrocarbons in the evaporated fuel supplied to the catalyst in a state where the air-fuel ratio lean degree is large, and the reducing agent is a nitrogen oxide. By calculating from the reaction ratio of reducing, it is possible to calculate the appropriate amount of reducing agent required to react with the discharged nitrogen oxides.

Further, in the invention according to claim 8 , the nitrogen oxide emission amount calculating means obtains the basic emission amount of nitrogen oxides based on the operating state of the engine and the air-fuel ratio of the air-fuel mixture, It is characterized in that the emission amount is calculated by correcting the fuel injection timing. (Operation / Effect) The emission amount of nitrogen oxides can be calculated accurately with a relatively simple configuration.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration of one embodiment. In the figure, an air flow meter 3 for detecting an intake air flow rate Q is provided in an intake passage 2 of an internal combustion engine 1, a throttle valve 4 for adjusting the intake air flow rate Q, and an auxiliary air bypassing the throttle valve 4. Passage 5,
An auxiliary air amount control valve 6 for controlling the flow rate of the auxiliary air flowing through the auxiliary air passage 5 is provided.

Further, the combustion chamber 7 is provided in the cylinder portion of the engine 1.
A fuel injection valve 8 for injecting fuel and a spark plug 9 for spark ignition in the combustion chamber 7 are provided. Further, the exhaust passage 10 of the engine 1 is provided with an air-fuel ratio sensor 11 for detecting the air-fuel ratio of the air-fuel mixture from the oxygen concentration in the exhaust gas and the like, and exhaust gas pollutants such as HC, CO, NOx are provided in the downstream portion. An exhaust gas purification catalyst (three-way catalyst) 21 for purification is provided.

In addition, a crank angle sensor 12 for detecting the crank angle position of the engine and the engine rotation speed Ne, a water temperature sensor (not shown) for detecting the engine cooling water temperature, etc. are provided. Further, an evaporated fuel passage 14 for guiding the fuel evaporated from the fuel tank 13, and an activated carbon layer as an evaporated fuel storage portion for temporarily adsorbing and storing the evaporated fuel guided through the evaporated fuel passage 14.
15, a canister 16 containing the activated carbon layer 15, a purge air introduction passage 17 for introducing air for purifying evaporated fuel from the intake passage 2 upstream of the throttle valve 4 to the activated carbon layer 15 in the canister 16, from the activated carbon layer 15 A purge passage 18 for guiding the discharged vaporized fuel to the intake passage 2 downstream of the throttle valve 4 and a purge control valve 19 for controlling the flow passage area of the purge passage 18 to control the purge amount of the vaporized fuel are provided. The evaporative fuel processing system is constituted by these. In addition,
Evaporative fuel passage 14, canister 16, purge air introduction passage 1
7. The purge passage 18 constitutes evaporative fuel supply means, and the purge control valve 19 and the control unit 20 described later constitute evaporative fuel supply amount control means.

Signals from various sensors for detecting the engine operating state are input to a control unit (ECU) 20, and the control unit 20 responds to these signals by the auxiliary air amount control valve 6 and fuel injection. Drive signals are output to actuators such as the valve 8, the spark plug 9, and the purge control valve 19 to perform various controls of the engine. Next, the operation of the system will be described.

As the air-fuel ratio of the air-fuel mixture in the combustion chamber 7 becomes leaner, the amount of fuel generally required to obtain the same output torque is reduced due to a reduction in intake pumping loss and the like, thus improving fuel efficiency. . Here, in the case of a normal spark ignition type engine of the type in which fuel such as gasoline is injected into the intake port to form an air-fuel mixture with a uniform air-fuel ratio in the combustion chamber and spark ignition is used, in the case of gasoline, the air-fuel ratio is 25
There is a limit to stable combustion around here. On the other hand, as in the present embodiment, the fuel is directly injected into the combustion chamber 7 to form the air-fuel mixture only around the spark plug 9, and the air is distributed in the other regions to form a stratified air-fuel mixture. If the combustion is carried out in this manner, a leaner state can be realized as the average air-fuel ratio in the combustion chamber 7 while there is a combustible air-fuel mixture around the spark plug 9, and the fuel efficiency can be further improved. Can be achieved.

Further, when the engine is operated in the stratified mixture state, the generated torque becomes small because the fuel amount is relatively small even if the intake air is increased to the maximum. Therefore, the stratified mixture combustion is usually used under a relatively small load condition, and when the load is large, the homogeneous mixture is operated while the entire combustion chamber 7 is filled with the mixture.

On the other hand, most of the evaporated fuel is generated after the operation of the engine is stopped, but it is also generated during normal running, and the generated amount increases with the increase of the fuel temperature. In many systems, these vaporized fuels are adsorbed by the activated carbon in the canister.Under certain operating conditions, the purge control valve is opened to release the adsorbed vaporized fuel, which is then introduced from the intake system into the combustion chamber for processing. There is.

At this time, in general, the introduction amount of the evaporated fuel into the intake system is proportionally controlled according to the intake amount and the fuel injection amount so that the air-fuel ratio control and the exhaust component are not adversely affected. However, when the stratified mixture is formed as described above, if the evaporated fuel is mixed in the air layer that is not involved in combustion, it will be discharged from the combustion chamber as an unburned HC component. During the formation of the stratified mixture, the vaporized fuel should not be released.

However, if the engine continues to be operated under the operating conditions such that a stratified mixture is formed, there is a problem that there is no opportunity to release the evaporated fuel. In the embodiment of the present invention, such a problem that the evaporated fuel cannot be sufficiently processed is addressed by performing the following control. The control of this embodiment will be described below with reference to the flowcharts shown in FIG.

FIG. 3 is a flowchart showing the overall control flow. In step 301, it is determined whether to form a stratified mixture or a homogeneous mixture according to the operating conditions of the engine. The details of this determination will be described later. Step
At 302, based on the determination made at step 301, the process proceeds to step 303 when forming a homogeneous mixture, and proceeds to step 304 when forming a stratified mixture.

In step 303, control is performed in the case of homogeneous mixture combustion. Since this is a control that is generally performed at present, the description is omitted. In step 304, it is determined whether or not the purge of the evaporated fuel is to be performed according to the current operating condition, and if the purge is unnecessary, this routine ends. When purging is necessary, the routine proceeds to step 305, and first, the emission amount of nitrogen oxides (hereinafter referred to as NOx) is calculated. Details of the calculation of the NOx emission amount will be described later.

In step 306, the generated NOx is generated.
Calculate the required amount of reducing agent required to reduce. Details of this calculation will be described later. In step 307, the required amount of the evaporated fuel as the reducing agent to be actually purged is calculated with respect to the reducing agent required amount. In step 308, the opening degree of the purge control valve 19 is controlled based on the required amount of evaporated fuel.

FIG. 4 is a flow chart showing a method for judging the mixture formation in step 301 of FIG. The function shown in FIG. 4 constitutes a mixture forming method switching means. In step 401, the engine speed Ne is read, and in step 402, the load of the engine, for example, the basic fuel injection amount and the like are read.

In step 403, the region where the stratified mixture is to be formed or the homogeneous mixture is determined from the stratified / homogeneous mixture formation region determination map, which is set in advance with the engine speed Ne and the engine load as parameters. Determine if it is a region to be formed. Specifically, in the medium / low rotation speed and medium / low load load regions, it is determined that the stratified mixture is to be formed, and the other region is determined to be the homogeneous mixture.

FIG. 5 is a flow chart showing a method for judging whether or not purging of evaporated fuel in step 304 of FIG. 3 is necessary. In step 601,
The accumulated amount of evaporated fuel in the canister 16, that is, the evaporated fuel amount is calculated. This evaporative fuel amount calculation routine will be described with reference to the flowchart of FIG.

In step 110, it is judged whether or not this processing is executed for the first time after the internal combustion engine is started. If it is determined that it is the first time, the routine proceeds to step 120, where the initial amount of evaporated fuel is set to Qevap for the first time. (Qevap = Qevap
int). This initial value is given, for example, as a function of the fuel temperature when the engine was stopped the last time or its estimated value. As one of the estimation methods, there is a method of defining the amount because the engine cooling water temperature when the engine is stopped and the engine operation duration time from the start, the larger the respective amounts, the more evaporated fuel is generated. is there.

In step 130, it is judged whether or not the purge control valve for releasing the evaporated fuel is opened, and if it is closed, ΔQevap is increased, and step 14
At 0, the amount of increase ΔQevap (positive value) is estimated. This estimation method is given, for example, as a function of the fuel temperature or its estimated value. In step 150, conversely, the reduction amount ΔQevap (negative value) resulting from the purging is estimated. As the estimation method, for example, ΔQevap is given as a function of the control valve opening and the intake negative pressure.

In step 160, the variation amount ΔQevap is added to Qevap to obtain the estimated evaporated fuel amount (Q
evap ← Qevap + ΔQevap). From the above, the evaporated fuel amount Qevap, that is, the accumulated evaporated fuel amount in the canister is estimated. Returning to FIG. 5, in step 602,
It is determined whether or not the accumulated amount has reached a predetermined limit value, and if it is a limit, the process proceeds to step 603, and if there is a margin, the process proceeds to step 604.

In step 603, it is judged whether or not the set air-fuel ratio is corrected to rich, and if rich correction is being performed, the routine proceeds to step 604, and if not, the routine proceeds to step 606. For example, when the stability of the engine decreases during operation at a normal set air-fuel ratio, the set air-fuel ratio may be rich-corrected to ensure stability. As described above, when the rich correction is performed, the NOx emission amount becomes larger than the desired value, but the increase amount of the NOx emission amount may be reduced by the fuel vapor supply during the stratified mixture combustion. In this case, the processing amount of the evaporated fuel can be increased and the NOx emission amount can be reduced, and further, the supply of the evaporated fuel can reduce the fuel injection amount for the rich correction by that amount, thereby improving the fuel efficiency. Therefore,
In such a case, even when the amount of accumulated evaporated fuel in the canister 16 has a margin, the process proceeds to step 604 and thereafter, and the evaporated fuel is purged as much as possible. If the rich correction of the set air-fuel ratio is not performed, the evaporated fuel may be supplied more than the amount required to reduce NOx, and the HC emission amount may increase, so the routine proceeds to step 606. Prohibit purging of evaporated fuel.

In step 604, the activity of the exhaust purification catalyst 21 is judged. This is judged from the catalyst temperature, the elapsed time after starting, and the like. When it is determined that the activated carbon has sufficient purification performance, step 605
When it is determined that the fuel vapor has not been activated, the process proceeds to step 606, and the fuel vapor purge is prohibited. It should be noted that the function of this step 604 constitutes a catalyst active state judging means.

FIG. 6 shows NO in step 305 of FIG.
It is a figure for clarifying one method of calculating x emission. The function of this step 305 constitutes NOx emission amount calculating means. This is a characteristic diagram showing the relationship between the NOx emission amount and the air-fuel ratio in the operating state determined by the predetermined engine rotation speed Ne and the load. By storing such information in (the ROM of) the control unit 20, the NOx emission amount is calculated from the operating conditions and the air-fuel ratio of the air-fuel mixture.
Further, this characteristic is data when burning with a stratified mixture, and is different from the data when burning a homogeneous mixture. Also,
In the stratified mixture combustion, the characteristic of the NOx emission amount also changes depending on the fuel injection timing. Therefore, as shown in FIG. 7, the correction coefficient is set according to the fuel injection timing, and the correction coefficient is used for the correction.

Next, in step 306 of FIG.
The basic idea when calculating the required amount of the reducing agent based on the calculated NOx emission amount will be described. This step 30
The six functions constitute the reducing agent demand amount calculation means. When using normal gasoline fuel, when the mass ratio of gasoline to air is 14.7 / 1, it becomes stoichiometric air-fuel ratio combustion,
Hydrogen and carbon contained in gasoline balance the amount of oxygen in the atmosphere. The mass of oxygen in the atmosphere accounts for about 25%, and the amount of oxygen per 1 g of gasoline is about 3.7 g.

From this, the amount of oxygen bound to the nitrogen is calculated on the basis of the above-mentioned NOx emission amount, and the gasoline mass balanced with this oxygen amount is used as the reducing agent gasoline.
Calculated as the required amount of (evaporated fuel). Next, the calculation of the actual purge amount of the evaporated fuel in step 307 of FIG. 3 will be described. The function of this step 307 constitutes evaporative fuel supply amount setting means.

The basic idea of this calculation is step 30.
Calculate the amount of reducing agent actually supplied to be smaller than the required amount of reducing agent calculated in step 6. As a result, it is possible to obtain the effect of reducing at least part of NOx, and it is possible to reliably prevent the emission of the HC component of the evaporated fuel even if there is an error in the estimation of the NOx emission amount. As this method, the method of uniformly multiplying the required amount of reducing agent in step 306 by a correction coefficient smaller than 1 is simple.

Further, among the evaporated fuel mixed in the intake air by the purge, the mixed fuel in the combustible mixture portion of the stratified mixture in the combustion chamber will be burnt. Therefore, the combustion amount is taken into consideration and the correction is reduced. There is also the idea that it may not be necessary. The extent to which these ideas are applied to determine the actual purge amount of the evaporated fuel should be determined for each system in consideration of the control accuracy of the purge flow rate control.

Next, the control of the purge control valve 19 in step 308 of FIG. 3 will be briefly described. The opening of the purge control valve 19 is set to the purge amount of the evaporated fuel calculated in step 307 and the intake negative pressure. And so on. Although details are omitted, for example, when the same purge amount is obtained, when the intake negative pressure estimated based on the engine operating state (rotational speed, load, etc.) is large, the opening is controlled to be smaller than when it is small.

Further, if the wide-range type which can linearly detect the air-fuel ratio is used as the air-fuel ratio sensor 11, the opening degree of the purge control valve 19 is increased little by little, and the air-fuel ratio changed as a result is changed. By detecting the fuel ratio by the air-fuel ratio sensor, the actual purge amount of the evaporated fuel may be estimated and feedback controlled, which improves the control accuracy. In this method, the NOx emission amount can also be estimated with high accuracy based on the actually detected air-fuel ratio.

Further, in the exhaust purification catalyst 20, HC as a reducing agent does not selectively react only with NOx, but also with oxygen in the exhaust. Therefore, NOx
The amount of the reducing agent to be supplied to the catalyst for reducing is calculated by increasing the ratio of the reducing agent that reacts with NOx with respect to the required amount of the reducing agent. Specifically, when a large amount of oxygen is contained in the exhaust gas with an air-fuel ratio of about 40, it is necessary to supply a reducing agent in the order of several times to more than ten times the required amount. Control the amount of fuel purge.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

FIG. 3 is a flowchart showing a main routine of control according to the embodiment.

FIG. 4 is a flowchart showing a routine for switching a mixture forming method.

FIG. 5 is a flowchart showing a routine for determining whether purging of evaporated fuel is necessary.

FIG. 6 is a diagram for clarifying a method of calculating NOx emission amount.

FIG. 7 is a diagram for setting a correction coefficient according to a fuel injection timing which is also used for calculation of NOx emission amount.

FIG. 8 is a flowchart showing a routine for estimating the amount of evaporated fuel accumulated in the canister.

[Explanation of symbols]

1 Internal combustion engine 2 Intake passage 7 Combustion chamber 8 fuel injection valves 10 exhaust passage 13 Fuel tank 14 Evaporative fuel passage 15 Activated carbon bed 16 canister 17 Purge air introduction passage 18 Purge passage 19 Purge control valve 20 Control unit 21 Exhaust purification catalyst

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/02 301 F02D 41/02 301F 301J 41/04 335 41/04 335C 43/00 301 43/00 301E 301J 301T (56) References JP-A-6-173660 (JP, A) JP-A-7-63096 (JP, A) JP-A-4-295150 (JP, A) JP-A-5-113144 (JP, A) (58) Survey Fields (Int.Cl. ⁷ , DB name) F02M 25/08 301 F01N 3/08 ZAB F01N 3/36 ZAB F02D 41/02 301 F02D 41/04 335 F02D 43/00 301

Claims (8)

(57) [Claims] 1. A stratified mixture combustion in which a stratified state of a mixture layer and an air layer is formed in a combustion chamber for combustion, and a homogeneous mixture combustion in which a homogeneous mixture is formed for combustion in the combustion chamber. When,
A fuel-air mixture formation switching means for switching the fuel injection system according to the operating conditions of the engine, an evaporated fuel supply means for supplying the fuel evaporated from the fuel supply system to the intake system of the engine, and a supply of the evaporated fuel to the intake system. Evaporative fuel supply amount control means for controlling the amount, nitrogen oxide discharge amount calculation means for calculating the amount of nitrogen oxides discharged from the combustion chamber, and nitrogen oxide calculated by the nitrogen oxide discharge amount calculation means Reducing agent demand amount calculation means for calculating the amount of hydrocarbons required to reduce nitrogen oxides with an exhaust purification catalyst installed in the exhaust system of the engine against the amount of emissions, and during stratified mixture combustion And evaporative fuel supply amount setting means for setting a supply amount so as to supply an amount of evaporated fuel corresponding to the reducing agent required amount to the intake system, and supply to the intake system during the stratified mixture combustion. The hydrocarbon components of the evaporated fuel Is mixed into the air layer of the stratified air-fuel mixture is discharged to leave the exhaust system unburned subjected to reduction of nitrogen oxides, the supply of the evaporative fuel during the stratified mixture combustion, the combustion stability
Rich correction of the set air-fuel ratio of the air-fuel mixture due to the deterioration of
An intake control device for an internal combustion engine, which is characterized in that it is performed when the engine is in operation. Wherein said nitrogen oxide emission calculating means, claims, characterized in that to calculate the emissions of nitrogen oxides based on the operating state, the air-fuel ratio and fuel injection mixture timing of the engine
1. An intake control device for an internal combustion engine according to 1 . 3. The evaporated fuel supply means comprises an evaporated fuel accumulation part for temporarily accumulating fuel evaporated from a fuel system, and an evaporated fuel accumulation amount calculation for calculating an accumulation amount of evaporated fuel in the evaporated fuel accumulation part. 2. The method according to claim 1 or 2 , wherein the means for supplying the evaporated fuel during the stratified mixture combustion is performed when the accumulated amount of the evaporated fuel approaches a limit value. Item 3. An intake control device for an internal combustion engine according to item 2 . 4. A supply of evaporative fuel during the stratified mixture combustion, and characterized in that nitrogen oxide emissions calculated by the nitrogen oxide emission calculating means when more than a predetermined, and to perform The intake control device for an internal combustion engine according to any one of claims 1 to 3 . 5. A is configured to include a catalytic active state determining means for determining the activity status of the emission control catalyst, the supply of the evaporative fuel during the stratified mixture combustion, the reduction of nitrogen oxides to proceed when the catalyst activity is determined not to be sufficient, according to claim 1 to claim 4, characterized in that so as to prohibit
An intake control device for an internal combustion engine according to any one of 1. Wherein said evaporative fuel supply amount setting means includes a setting means sets to the reducing agent required amount calculated by the reducing agent required amount calculating means, so that fewer supply amount of the fuel vapor The intake control device for an internal combustion engine according to any one of claims 1 to 5 . 7. The vaporized fuel supply amount setting means does not react with oxygen in exhaust gas among hydrocarbons in vaporized fuel during combustion of a stratified mixture having a large lean air-fuel ratio, and reduces with nitrogen oxides. based on the percentage of those carrying out the reaction, claims 1 and sets the supply amount of the fuel vapor 6
An intake control device for an internal combustion engine according to any one of 1. Wherein said nitrogen oxide emission calculating means, operating condition of the engine, based on the air-fuel ratio of the mixture obtains a basic emissions of nitrogen oxides, the correction in the fuel injection timing the basic emissions The intake control device for an internal combustion engine according to any one of claims 1 to 7 , wherein: