JPH11351081A - Evaporative fuel treatment system for internal combustion engines - Google Patents

Abstract

(57) [Problem] To enable purging as much as possible without uniformly prohibiting canister purging during stratified combustion. SOLUTION: An air-fuel ratio AFREVP of an air-fuel mixture formed in a region around a combustion chamber by evaporative fuel purged from a canister during stratified combustion is estimated. Then, the estimated air-fuel ratio AFREVP is determined (S701). When the air-fuel ratio is richer than the first predetermined air-fuel ratio SLEVP1, or when the air-fuel ratio is leaner than the second predetermined air-fuel ratio SLEVP2 (> SLEVP1), the purge is performed. Purge is performed with the valve opening correction coefficient KEVP = 1 (no correction; S703). Also, the first
Of the predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP
When it is between P2 and P2, the purge valve opening correction coefficient KEVP is reduced (S704), and the purge valve opening is restricted before purging. When the catalyst temperature is high (S70
2) Purging is performed regardless of the air-fuel ratio.

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, and more particularly, to a fuel vapor processing apparatus for a direct injection spark ignition type internal combustion engine.

[0002]

2. Description of the Related Art A conventional evaporative fuel processing apparatus for an internal combustion engine is:
The fuel tank includes a canister for adsorbing fuel vapor generated in the fuel tank, and a purge valve interposed in a purge passage for the fuel vapor from the canister to the engine intake passage to control the purge of the fuel vapor. On the other hand, in recent years, a direct-injection spark ignition type internal combustion engine has attracted attention. In this engine, switching control of a combustion method is performed according to engine operating conditions, that is, by injecting fuel in an intake stroke, the fuel is injected into a combustion chamber. Generally, switching control is performed between homogeneous combustion in which a homogeneous combustible mixture is formed and stratified combustion in which the combustible mixture is unevenly distributed in a specific range in a combustion chamber by injecting fuel in a compression stroke. It is a target.

Here, if canister purging is performed during stratified combustion, if supplied to the center of the combustion chamber, combustion occurs, and C
Although purged as O ₂ and H ₂ O, the non-combustible air-fuel ratio purge gas supplied to the periphery of the combustion chamber is discharged without contributing to combustion, and is released into the atmosphere as a large amount of HC. Therefore, for example, in the apparatus described in Japanese Patent Application Laid-Open No. H5-223017, canister purging is prohibited during stratified combustion.

[0004]

However, if the canister purge is uniformly prohibited during stratified charge combustion, the chance of the canister purge is reduced, the canister is likely to be full, the opportunity to discharge the evaporated fuel to the atmosphere is increased, and the air pollution is reduced. ,
Problems such as gasoline odor occur. As a means for solving the above problem, an increase in the capacity of the canister and the like can be considered, but this leads to an increase in cost.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention not to prohibit canister purging during stratified charge combustion, but to enable purging as much as possible.

[0006]

According to the first aspect of the present invention, there is provided a direct-injection spark in which a combustible air-fuel mixture is unevenly distributed in a specific range in a combustion chamber under predetermined operating conditions to perform stratified combustion. An ignition type internal combustion engine, which includes a canister for adsorbing evaporative fuel generated in a fuel tank, a purge valve interposed in a purge passage for evaporative fuel from the canister to an engine intake passage for controlling the purge of evaporative fuel, and As shown in FIG. 1, purge air-fuel ratio estimating means for estimating an air-fuel ratio of an air-fuel mixture formed in a region other than a specific range by evaporative fuel purged from a canister during stratified combustion, A purge determining means for determining whether or not to purge the fuel vapor by the purge valve during stratified charge combustion based on the air-fuel ratio, to provide an evaporative fuel processing device for the internal combustion engine.

[0007] In the invention according to claim 2, the purge determination means permits purging during stratified combustion when the estimated air-fuel ratio is richer than the first predetermined air-fuel ratio. In the invention according to claim 3, the purge determination means is configured to perform the purge during stratified charge combustion when the estimated air-fuel ratio is leaner than the first predetermined air-fuel ratio and is leaner than the second predetermined air-fuel ratio. Allow

In the invention according to a fourth aspect, the purge judging means determines that the estimated air-fuel ratio is leaner than the first predetermined air-fuel ratio and richer than the second predetermined air-fuel ratio (ie, When the air-fuel ratio is between the first predetermined air-fuel ratio and the second predetermined air-fuel ratio), the opening of the purge valve is limited to a value smaller than the normal opening, and the purging during stratified combustion is permitted. In the invention according to claim 5, the air-fuel ratio estimated by the purge air-fuel ratio estimating means is on the lean side of the first predetermined air-fuel ratio,
A means for inhibiting stratified combustion when the air-fuel ratio is richer than the predetermined air-fuel ratio and forming a homogeneous combustible mixture in the combustion chamber to perform homogeneous combustion.

[0009] In the invention according to claim 6, the purge judging means, when the temperature of the exhaust gas purifying catalyst interposed in the exhaust passage of the engine is equal to or higher than a predetermined value, regardless of the estimated air-fuel ratio. Allow time purge. In the invention according to claim 7, the purge air-fuel ratio estimating means includes an air-fuel ratio feedback correction value (for the fuel injection amount) based on a detection value of an air-fuel ratio sensor (generally, an O ₂ sensor) disposed in the engine exhaust passage. In general, an air-fuel ratio feedback correction coefficient is set, and the air-fuel ratio feedback control means for performing feedback control of the average air-fuel ratio in the combustion chamber to the target air-fuel ratio is used. Then, the air-fuel ratio of the air-fuel mixture formed in a region other than the specific range by the evaporated fuel purged from the canister during stratified combustion is estimated.

[0010] In the invention according to claim 8, the direct-injection spark ignition type internal combustion engine forms a homogeneous combustible mixture in the combustion chamber under a condition other than the predetermined operating condition to perform homogeneous combustion. The purge air-fuel ratio estimating means sets an air-fuel ratio feedback correction value for a fuel injection amount based on a detection value of an air-fuel ratio sensor disposed in an engine exhaust passage during homogeneous combustion, and sets an air-fuel ratio in the combustion chamber. The air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio to the target air-fuel ratio is used. The air-fuel ratio of the air-fuel mixture formed in the region other than the above is estimated.

According to the ninth aspect, at the time of stratified combustion,
Means are provided for forcibly performing homogeneous combustion at a predetermined timing. In the invention according to claim 10, the purge air-fuel ratio estimating means is configured to set an area other than a specific range by evaporative fuel purged from the canister at the time of stratified combustion, based on a detection value of the HC sensor disposed in the engine exhaust passage. The air-fuel ratio of the mixture formed is estimated.

[0012]

According to the first aspect of the present invention, the air-fuel ratio (purge air-fuel ratio) of the air-fuel mixture formed in a region other than the specific range by the evaporated fuel purged from the canister during stratified combustion is estimated. It is determined whether or not to purge the fuel vapor by the purge valve during stratified charge combustion, and purging is performed when purging is possible even during stratified charge combustion, resulting in problems such as air pollution and gasoline odor. Can be solved.

According to the second aspect of the present invention, when the purge air-fuel ratio is richer than the first predetermined air-fuel ratio, the flame reaches the vicinity of the combustion chamber and the deterioration of HC is small, so that the stratified charge combustion is performed. By allowing the purge at that time, the chance of purging can be increased. According to the third aspect of the invention, when the purge air-fuel ratio is leaner than the second predetermined air-fuel ratio, the amount of HC increase is small and there is no problem in the exhaust performance, so the purging during stratified combustion is permitted. This can increase the chance of purging.

According to the present invention, when the purge air-fuel ratio is between the first predetermined air-fuel ratio and the second predetermined air-fuel ratio, the opening of the purge valve is set to be smaller than the normal opening. By permitting purging during stratified combustion after restricting, it is possible to increase the chances of purging while suppressing the amount of HC emission as compared with the case where purging is prohibited. According to the fifth aspect of the invention, when the purge air-fuel ratio is between the first predetermined air-fuel ratio and the second predetermined air-fuel ratio, stratified charge combustion is prohibited and homogeneous combustion is performed. Purge can be prioritized over fuel economy.

According to the invention of claim 6, when the catalyst temperature is equal to or higher than the predetermined value, it can be determined that the deterioration of HC is small, so that purging during stratified charge combustion is permitted regardless of the purge air-fuel ratio. Purging opportunities can be increased.
According to the invention according to claim 7, by estimating the purge air-fuel ratio based on the air-fuel ratio feedback correction value when the purge is performed and when the purge is not performed, it is possible to estimate the purge air-fuel ratio without adding a special sensor. become.

According to the eighth aspect of the present invention, on the premise of switching between homogeneous combustion and stratified combustion, purging during stratified combustion is performed based on the air-fuel ratio feedback correction value during execution of the homogeneous combustion and non-execution of the purge. By estimating the air-fuel ratio, accurate estimation can be performed without adding a special sensor.
In particular, during homogeneous combustion, the fuel supplied from the fuel injection valve and the evaporative fuel purged from the canister form an air-fuel mixture of the same quality, and the air-fuel ratio of the air-fuel mixture is accurately reflected in the exhaust air-fuel ratio. The purge air-fuel ratio can be estimated with extremely high accuracy based on the air-fuel ratio feedback correction values when the purge is performed and when the purge is not performed. Further, when the air-fuel ratio during homogeneous combustion is controlled stoichiometrically, the purge air-fuel ratio using the air-fuel ratio feedback correction value can be estimated with an O ₂ sensor that is less expensive than a wide-range air-fuel ratio sensor.

According to the ninth aspect of the present invention, when stratified charge combustion is performed, homogeneous combustion is forcibly performed at a predetermined timing, thereby increasing the chance of estimating the purge air-fuel ratio. According to the tenth aspect of the present invention, by using the HC sensor for estimating the purge air-fuel ratio, the purge air-fuel ratio can be estimated without performing the air-fuel ratio feedback control, and good control becomes possible.

[0018]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention. First, this will be described. Air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from the air cleaner 2 through the intake passage 3 under the control of the throttle valve 4.

An electromagnetic fuel injection valve (injector) 5 is provided so as to directly inject fuel (gasoline) into the combustion chamber. The fuel injection valve 5 is energized by a solenoid in response to an injection pulse signal output in an intake stroke or a compression stroke from the control unit 20 in synchronization with engine rotation, opens the valve, and injects fuel adjusted to a predetermined pressure. It has become. The injected fuel diffuses into the combustion chamber in the case of the intake stroke injection to form a homogeneous mixture, and in the case of the compression stroke injection, forms a stratified mixture around the ignition plug 6. , Control unit 20
Is ignited by the ignition plug 6 based on the ignition signal from
Combustion (homogeneous combustion or stratified combustion). Here, an example is shown in which the air-fuel ratio is controlled to stoichiometric (stoichiometric air-fuel ratio) in the case of homogeneous combustion, and the air-fuel ratio is controlled lean in the case of stratified combustion. Alternatively, control may be performed separately for stoichiometry and lean.

Exhaust gas from the engine 1 is discharged from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7. Further, a canister 10 is provided as an evaporative fuel processing device for processing the evaporative fuel generated from the fuel tank 9. The canister 10 is a sealed container filled with an adsorbent such as activated carbon. An evaporative fuel introduction pipe 11 from the fuel tank 9 is connected via a check valve 12.
Therefore, evaporative fuel generated in the fuel tank 9 while the engine 1 is stopped or the like is guided to the canister 10 through the evaporative fuel introduction pipe 11 and is absorbed therein.

The canister 10 also has a fresh air inlet 13.
Are formed, and the purge passage 14 is led out. The purge passage 14 is connected to the intake passage 3 via a purge valve 15.
Downstream of the throttle valve 4 (intake manifold). The purge valve 15 is opened by a signal output under predetermined conditions from the control unit 20 during operation of the engine 1. Therefore, when the engine 1 is started and the purge permission condition is satisfied, the purge valve 15 is opened, and the suction negative pressure of the engine 1 acts on the canister 10. As a result, the air introduced from the fresh air inlet 13 causes Evaporated fuel adsorbed by the adsorbent is desorbed, and a purge gas containing the desorbed evaporative fuel is drawn into the intake passage 3 downstream of the throttle valve 4 through the purge passage 14, and thereafter, the combustion chamber of the engine 1. Combustion treatment.

The control unit 20 includes a CPU, R
A microcomputer including an OM, a RAM, an A / D converter, an input / output interface, and the like is provided. The microcomputer receives input signals from various sensors, performs arithmetic processing based on the input signals, and executes a fuel injection valve 5, an ignition plug 6, And the operation of the purge valve 15 and the like. As the various sensors, a crank angle sensor 21 for detecting a crankshaft rotation of the engine 1 is provided, and an engine speed Ne can be detected from a signal thereof.

In addition, an air flow meter 22 for detecting an intake air amount (flow rate) Qa upstream of the throttle valve 4 in the intake passage 3, a throttle sensor 23 for detecting an opening TVO of the throttle valve 4 (a fully closed position of the throttle valve 4). in including an idle switch which becomes oN), the water temperature sensor 24 for detecting the cooling water temperature Tw of the engine 1, O ₂ sensor 25 for outputting a signal corresponding to a rich-lean exhaust air-fuel ratio in the exhaust passage 7,
A catalyst temperature sensor 26 for detecting the temperature TCAT of the catalyst 8 is provided. In the case of a third embodiment described later, an HC sensor 27 for detecting the concentration of HC in the exhaust gas in the exhaust passage 7 is provided and used.

Next, the control performed by the microcomputer in the control unit 20 will be described with reference to the control block of FIG. 3 and the flowcharts of FIGS. 4 to 11 (first embodiment). As shown in the control block diagram of FIG. 3, the stratified combustion permission means 100, the homogeneous combustion means 200, the stratified combustion means 300, the evaporative fuel introduction permission means 400, the learning value updating means 500, the evaporative fuel introduction amount measuring means 600, the evaporative fuel It is configured to include an introduction amount changing unit 700 and a purge valve opening calculating unit 800 at the time of homogeneous combustion.

FIG. 4 shows the control contents of the stratified combustion permission means 100. In S101, it is determined whether or not a predetermined stratified combustion condition is established based on the engine speed Ne, the load (basic fuel injection amount Tp), the water temperature Tw, and the like.
Proceed to 102. In S102, the base learning convergence flag F
It is determined whether BSLTD = 1 or not, and if YES, S10
Proceed to 3. That is, unless the air-fuel ratio learning value at the time of no introduction of evaporative fuel by the flow of FIG. 8 (learning value updating means 500) described below converges, the amount of introduced evaporative fuel is not known, so that stratified combustion is not permitted. .

In S103, it is determined whether or not the evaporative concentration determination is being executed, and in the case of YES, the flow proceeds to S105. That is, in order to perform homogeneous combustion at predetermined intervals for measuring the amount of introduced fuel vapor, stratified combustion is prohibited even during the determination of the evaporative concentration. In S105, stratified combustion is permitted. If NO in any of the determinations in S101 to S103, the process proceeds to S106 and stratified combustion is not permitted.

FIG. 5 shows the control contents of the homogeneous combustion means 200, which is executed when stratified combustion is not permitted. In S201, the intake air amount Qa and the engine speed Ne are detected. S
At 202, from the intake air amount Qa and the engine speed Ne,
The basic fuel injection amount Tp corresponding to the stoichiometric (stoichiometric air-fuel ratio) is calculated according to the following equation.

Tp = K × Qa / Ne (where K is a constant) In S203, the air-fuel ratio feedback control is performed.
Based on the signal from the O ₂ sensor, the air-fuel ratio feedback correction coefficient α is set by the well-known proportional integral control (FIG. 12).
reference). That is, rich / lean is determined based on a signal from the O ₂ sensor, and the air-fuel ratio feedback correction coefficient α is increased by a predetermined proportional amount P at the time of rich → lean reversal, and the air-fuel ratio feedback correction coefficient α is predetermined at the subsequent lean. (I << P).
The air-fuel ratio feedback correction coefficient α is reduced by a predetermined proportional amount P when the lean-to-rich reversal is performed, and the air-fuel ratio feedback correction coefficient α is reduced by a predetermined integral amount I when the rich state continues. When the air-fuel ratio is made lean during homogeneous combustion and the air-fuel ratio is feedback-controlled,
The above-mentioned O ₂ sensor may be replaced by a wide-range air-fuel ratio sensor.

In the next step S204, from the basic fuel injection amount Tp and the air-fuel ratio feedback correction coefficient α, the following equation is used.
The fuel injection amount Ti for homogeneous combustion is calculated. Ti = Tp × α When the fuel injection amount Ti is calculated, an injection pulse signal having a pulse width corresponding to the Ti is output to the fuel injection valve at a predetermined timing in the intake stroke, and fuel injection is performed.

FIG. 6 shows the control contents of the stratified combustion means 300, which is executed when stratified combustion is permitted. In S301, the intake air amount Qa and the engine speed Ne are detected. S
At 302, from the intake air amount Qa and the engine speed Ne,
The basic fuel injection amount Tp corresponding to the stoichiometric (stoichiometric air-fuel ratio) is calculated according to the following equation.

Tp = K × Qa / Ne (where K is a constant) In step S303, the fuel for obtaining the target air-fuel ratio for stratified combustion is obtained from the basic fuel injection amount Tp and the air-fuel ratio feedback correction coefficient α according to the following equation. The injection amount Ti is calculated. Ti = (14.7 / target air-fuel ratio) × Tp × α In this case, the air-fuel ratio feedback correction coefficient α is clamped to the previous value or the reference value (1.0). That is,
In this example, the air-fuel ratio feedback control is not performed during stratified combustion, and the air-fuel ratio is controlled to, for example, a lean air-fuel ratio of about 40 by open control.

When the fuel injection amount Ti is calculated, this Ti
Is output to the fuel injection valve at a predetermined timing in the compression stroke to perform fuel injection. FIG. 7 shows the control contents of the evaporative fuel introduction permission means 400, which is executed at the time of homogeneous combustion.

In step S401, it is determined whether or not a predetermined condition for permitting the canister purge is determined based on the water temperature Tw, ON / OFF of the idle switch, and the like.
Proceed to 2. In S402, the base learning convergence flag FBS
It is determined whether LTD = 1 or not, and in the case of YES, the process proceeds to S403. That is, if the air-fuel ratio learning value when no evaporative fuel is introduced by the flow of FIG. 8 (learning value updating means 500) described below does not converge, the amount of evaporative fuel introduced is unknown, so that canister purging is not permitted. .

In step S403, canister purge is permitted. If NO in either of the determinations in S401 and S402, the process proceeds to S404, and the canister purge is not permitted. FIG. 8 shows the control contents of the learning value updating means, which is executed at the time of homogeneous combustion. In S501, the learning value update condition (ie, during the air-fuel ratio feedback control, the water temperature Tw
Is greater than or equal to a predetermined value).
Only in the case of ES, proceed to S502 and subsequent steps.

In S502, the average value Mα of the air-fuel ratio feedback correction coefficient α is calculated by the following equation. Mα = (a1 + a2) / 2, where a1 is the value of the air-fuel ratio feedback correction coefficient α immediately before the latest inversion from lean to rich, and a2 is the air-fuel ratio feedback correction immediately before the latest inversion from rich to lean. This is the value of the coefficient α (see FIG. 12).

In S503, the learning value LALPHA is updated according to the following equation based on the deviation of the average value Mα of the air-fuel ratio feedback correction coefficient α from the reference value (1.0). LALPHA = LALPHA + (Mα−1.0) × GAI
N GAIN is a predetermined value, 0 <GAIN <1, and is used to suppress a sudden change in the learning value.

In S504, the updated LALPHA is stored in the current operating region position of the learning map for each operating region using the engine speed Ne and the load (basic fuel injection amount) Tp as parameters. In S505, the learning convergence counter CBSLTD corresponding to the updated operation region is counted up.

In S506, it is determined whether or not convergence has been made in all areas even once in the past.
07, the predetermined value is set to a predetermined value 1 (a relatively small value), and NO
In this case, the predetermined value is set to the predetermined value 2 (a relatively large value) in S508. In S509, it is determined whether or not the learning convergence counter CBSLTD is equal to or larger than the predetermined value set in S507 or S508 in all of the regions designated in advance.
In the case of S, it is determined that the learning has converged, and the learning convergence flag FBSLTD is set to 1 in S510.

When the convergence has been made in the entire area even once in the past, the predetermined value is equal to the predetermined value 1 (relatively small value). This is for shifting to combustion and permitting purging. FIG. 9 shows the control contents of the evaporative fuel introduction amount measuring means 600, which is executed at the time of homogeneous combustion and at the time of evaporative fuel introduction, and the average value and the learning value of the air-fuel ratio feedback correction coefficient when the purge gas is introduced. From the difference, the air-fuel ratio in the manifold at the time of introducing the evaporated fuel is obtained by calculation.

In step S601, the average value Mα of the air-fuel ratio feedback correction coefficient α is calculated by the following equation. Mα = (a1 + a2) / 2 In S602, the learning value LALPHA of the current operation region is read from the learning map for each operation region using the engine speed Ne and the load (basic fuel injection amount) Tp as parameters.

In step S603, based on the intake air amount Qa, the engine speed Ne, the learned value LALPHA, the air-fuel ratio feedback correction coefficient average value Mα, and the fuel injection amount Ti, the manifold air-fuel ratio (purge air (Fuel ratio) AFREVP is calculated. AFREVP = (Qa × k2 / Ne) / ((LALPH
A−Mα) × Ti) Here, (LALPHA−Mα) × Ti is used to calculate the fuel vapor amount per cylinder, and Qa × K2 / Ne (where k2 is a constant) to calculate the air amount per cylinder. Is calculated, the purge air-fuel ratio is calculated by this equation. Therefore, this part corresponds to the purge air-fuel ratio estimating means.

FIG. 10 shows the control contents of the evaporative fuel introduction amount changing means 700, which is executed at the time of stratified combustion. S7
01, the purge air-fuel ratio AFREVP, the first predetermined air-fuel ratio SLEVP1, and the second predetermined air-fuel ratio SLEVP2 (S
LEVP1 <SLEVP2).
It is determined whether or not <SLEVP1 or AFREVP> SLEVP2.

If YES (AFREVP <SLEVP1 or AFREVP> SLEVP2), the purge valve opening correction coefficient KEVP = 1 (no correction) is set in S703. If NO, it is determined in S702 whether the catalyst temperature TCAT is equal to or higher than a predetermined value (SLTCAT). Where Y
In the case of ES, the purge valve opening correction coefficient KEV is set in S703.
Set P = 1 (no correction). This is because if the catalyst is sufficiently warm, HC is purified and a large amount of purge is permitted.

Also in the case of NO, the purge valve opening correction coefficient KEVP is calculated by the following equation in S704. KEVP = AFREVP / SLEVP2 This is because the purge valve opening is corrected by KEVP, and the purge air-fuel ratio is set to SLEVP2 or less.

In step S705, the basic purge valve opening BSDTY is calculated from the intake air amount Qa with reference to the table. In step S706, the basic purge valve opening degree B is calculated according to the following equation.
The SDTY is corrected by a purge valve opening correction coefficient KEVP to calculate a purge valve opening EVPDTY and control the purge valve.

EVPDTY = BSDTY × KEVP As described above, the evaporative fuel introduction amount changing means 700 permits purging in accordance with the measured purge air-fuel ratio, and the purge air-fuel ratio is changed to the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio. Air-fuel ratio S
If it is determined that it is between LEVP2, the purge valve is throttled to control the purge air-fuel ratio to be lower than the second predetermined air-fuel ratio SLEVP2 (see FIG. 13). If the catalyst temperature is equal to or higher than a predetermined value, it is determined that the deterioration of HC is small,
Normal purging is allowed. Therefore, this part corresponds to a purge determination unit.

FIG. 11 shows the control contents of the homogeneous-combustion purge valve opening calculating means 800, which is executed during homogeneous combustion. In step S801, the purge valve opening EVPDTY is directly calculated from the intake air amount Qa with reference to a table to control the purge valve. Next, a second embodiment will be described.

The control block diagram of the second embodiment is the same as that of the first embodiment (FIG. 3), and only the control content of the stratified combustion permission means 100 is different. FIG. 14 shows the control contents of the stratified combustion permission means of the second embodiment. S101 to S10
3 is the same as in the first embodiment (FIG. 4),
If all of these are YES, the process proceeds to S104.

At S104, the purge air-fuel ratio AFREVP
Is compared with the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2 (SLEVP1 <SLEVP2), and AFREVP <SLEVP1 or AFREVP> S
It is determined whether or not it is LEVP2. YES (AFREVP <
If SLEVP1 or AFREVP> SLEVP2), the process proceeds to S105. That is, the purge air-fuel ratio AFRE
When VP is between the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2 (SLEVP1 <AF
This is because stratified combustion is not permitted when REVP <SLEVP2).

In S105, stratified combustion is permitted. S1
If NO in any of the determinations from 01 to S104,
Proceeding to 106, stratified combustion is not permitted. in this way,
In the present embodiment, the purge air-fuel ratio AFREVP is equal to the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2.
And stratified combustion is prohibited. This is to give priority to purging over fuel economy.

Next, a third embodiment will be described. Third
The control block diagram of the embodiment is shown in FIG. 15, and the stratified combustion permission means 100, the homogeneous combustion means 200, the stratified combustion means 300, the evaporative fuel introduction amount predicting means 650, and the evaporative fuel introduction amount changing means (introduction prohibiting means) 750. It is comprised including. Here, the stratified combustion permission means 100, the homogeneous combustion means 2
00, the control content of the stratified combustion means 300 is as shown in FIG. 4 (or FIG. 14), FIG. 5, and FIG.

FIG. 16 shows the control contents of the evaporative fuel introduction amount predicting means of the third embodiment. In step S651, the purge valve opening EV is determined based on the intake air amount Qa with reference to the table.
Calculate and output PDTY. That is, purging is performed at a predetermined purge rate. In S652, it is determined whether a predetermined time has elapsed, and when the predetermined time has elapsed, the flow proceeds to the next S653.
That is, there is a delay until the effect of the purge appears.

In step S653, the output HCSEN of the HC sensor disposed in the exhaust passage is read and stored as the detection value HCSEN1 = HCSEN when purge is present. S65
In step 4, the purge valve opening degree E is set so that the purge valve is fully closed.
Output as VPDTY = 0. That is, the purge is cut. In S655, it is determined whether a predetermined time has elapsed, and when the predetermined time has elapsed, the flow proceeds to the next S656. That is, there is a delay until the effect of the purge cut appears.

In step S656, the output HCSEN of the HC sensor disposed in the exhaust passage is read and stored as the detection value HCSEN2 = HCSEN when no purge is performed. S56
7, the HC sensor detection value HCSEN1 when purge is present
DHC = HCSEN1-HCSEN2, which is a difference between the HC value and the HC sensor detection value HCSEN2 when no purge is performed.

When the difference DHC is large, the purge concentration is in the NG region, and when it is small, the purge concentration is in the OK region. Therefore, this part corresponds to the purge concentration estimating means. FIG. 17 shows the control contents of the evaporative fuel introduction amount changing means (introduction prohibiting means) of the third embodiment.

In S751, it is determined whether or not the difference DHC is equal to or less than a predetermined value (SLHC). YES (DHC <
In the case of (SLHC), the purge valve opening correction coefficient KEVP is set to 1 (no correction) in S753. If no,
In S752, the catalyst temperature TCAT is set to a predetermined value (SLTCAT).
It is determined whether or not this is the case.

If YES, the purge valve opening correction coefficient KEVP is set to 1 (no correction) in S753. This is because if the catalyst is sufficiently warm, HC is purified and a large amount of purge is permitted. Again, NO
In step S754, the purge valve opening correction coefficient KEVP is set to 0 in step S754.

In S755, the basic purge valve opening degree BSDTY is calculated from the intake air amount Qa with reference to the table. In S756, the basic purge valve opening degree B is calculated by the following equation.
The SDTY is corrected by a purge valve opening correction coefficient KEVP to calculate a purge valve opening EVPDTY and control the purge valve.

EVPDTY = BSDTY × KEVP In this way, when the difference DHC is large according to the difference HC detected by the HC sensor between the presence and absence of the purge, the purge valve is closed and the purging is prohibited. However, if the catalyst temperature is equal to or higher than a predetermined value, it is determined that HC deterioration is small, and normal purging is permitted. Therefore, this part corresponds to a purge determination unit.

As described above, the use of the HC sensor makes it possible to predict the purge air-fuel ratio even when the air-fuel ratio feedback control is not being performed, and the stratified charge combustion is open-controlled to a large lean air-fuel ratio without performing the normal air-fuel ratio feedback control. Can be judged while purging is possible, which leads to further improvement in fuel efficiency.

[Brief description of the drawings]

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

FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a control block diagram of the first and second embodiments.

FIG. 4 is a flowchart showing control contents of a stratified combustion permitting means.

FIG. 5 is a flowchart showing control contents of the homogeneous combustion means.

FIG. 6 is a flowchart showing control contents of a stratified combustion means.

FIG. 7 is a flowchart showing the control content of the evaporative fuel introduction permission means.

FIG. 8 is a flowchart showing control contents of a learning value updating unit.

FIG. 9 is a flowchart showing the control contents of an evaporative fuel introduction amount measuring means.

FIG. 10 is a flowchart showing the control contents of the evaporative fuel introduction amount changing means.

FIG. 11 is a flowchart showing the control contents of a stoichiometric purge valve opening calculating means.

FIG. 12 Supplementary diagram of air-fuel ratio feedback control

FIG. 13 is a diagram showing the operation of the present invention.

FIG. 14 is a flowchart showing the control contents of the stratified combustion permitting means of the second embodiment.

FIG. 15 is a control block diagram according to the third embodiment.

FIG. 16 is a flowchart showing control contents of evaporative fuel introduction amount predicting means of the third embodiment.

FIG. 17 is a flowchart showing the control content of the evaporative fuel introduction amount changing means of the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 2 Air cleaner 3 Intake passage 4 Throttle valve 5 Fuel injection valve 6 Spark plug 7 Exhaust passage 8 Catalyst 9 Fuel tank 10 Canister 11 Evaporated fuel introduction pipe 12 Check valve 13 Fresh air introduction port 14 Purge passage 15 Purge valve 20 Control unit Reference Signs List 21 crank angle sensor 22 air flow meter 23 throttle sensor 24 water temperature sensor 25 O ₂ sensor 26 catalyst temperature sensor 27 HC sensor

Claims (10)

[Claims] 1. A direct-injection spark ignition type internal combustion engine that performs stratified combustion by predisposing a combustible air-fuel mixture to a specific range in a combustion chamber under a predetermined operating condition, wherein evaporation generated in a fuel tank is performed. A canister for adsorbing fuel, and a purge valve interposed in a purge passage for evaporative fuel from the canister to an engine intake passage to control purging of the evaporative fuel, wherein the evaporative fuel purged from the canister during stratified charge combustion Purge air-fuel ratio estimating means for estimating the air-fuel ratio of the air-fuel mixture formed in a region other than the specified range, and determining whether to purge the evaporated fuel by the purge valve during stratified charge combustion based on the estimated air-fuel ratio. An evaporative fuel processing apparatus for an internal combustion engine, comprising: a purge determination means for determining. 2. The internal combustion engine according to claim 1, wherein said purge judging means permits purging during stratified combustion when the estimated air-fuel ratio is richer than a first predetermined air-fuel ratio. Evaporative fuel treatment equipment for engines. 3. The purge judgment means permits purging during stratified charge combustion when the estimated air-fuel ratio is leaner than a first predetermined air-fuel ratio and is leaner than a second predetermined air-fuel ratio. 3. The fuel vapor treatment device for an internal combustion engine according to claim 1, wherein: 4. The purge judging means restricts the opening of the purge valve when the estimated air-fuel ratio is leaner than the first predetermined air-fuel ratio and richer than the second predetermined air-fuel ratio. The fuel vapor processing apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein a purge during stratified combustion is permitted after the operation is performed. 5. An air-fuel ratio estimated by said purge air-fuel ratio estimating means is on a leaner side than a first predetermined air-fuel ratio and a second air-fuel ratio is determined by a second air-fuel ratio.
A means for prohibiting stratified combustion when the air-fuel ratio is richer than a predetermined air-fuel ratio and forming a homogeneous combustible mixture in the combustion chamber to perform homogeneous combustion. An evaporative fuel processing apparatus for an internal combustion engine according to any one of the preceding claims. 6. When the temperature of an exhaust purification catalyst provided in an exhaust passage of an engine is equal to or higher than a predetermined value, the purge determination means permits purging during stratified charge combustion regardless of the estimated air-fuel ratio. An evaporative fuel treatment system for an internal combustion engine according to any one of claims 1 to 5, characterized in that: 7. The purge air-fuel ratio estimating means sets an air-fuel ratio feedback correction value for a fuel injection amount based on a detection value of an air-fuel ratio sensor disposed in an engine exhaust passage, and sets an average air-fuel ratio in the combustion chamber. Using an air-fuel ratio feedback control unit that feedback-controls the fuel ratio to the target air-fuel ratio, based on the air-fuel ratio feedback correction value when purging is performed and when it is not performed, the area outside the specified range due to the evaporated fuel purged from the canister during stratified combustion. The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein an air-fuel ratio of the air-fuel mixture formed in the engine is estimated. 8. The direct injection spark ignition type internal combustion engine forms a homogeneous combustible air-fuel mixture in a combustion chamber under a condition other than the predetermined operating condition to perform homogeneous combustion. The means sets the air-fuel ratio feedback correction value for the fuel injection amount based on the detection value of the air-fuel ratio sensor disposed in the engine exhaust passage during homogeneous combustion, and feeds back the air-fuel ratio in the combustion chamber to the target air-fuel ratio. Using the air-fuel ratio feedback control means for controlling, based on the air-fuel ratio feedback correction value during the execution of the homogeneous combustion and during the non-execution of the purge, the fuel vapor is purged from the canister during the stratified combustion to form an area other than the specific range. The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein an air-fuel ratio of the air-fuel mixture is estimated. 9. An apparatus according to claim 8, further comprising means for forcibly performing homogeneous combustion at a predetermined timing during stratified combustion. 10. The purge air-fuel ratio estimating means is formed in an area other than a specific range by evaporative fuel purged from a canister during stratified combustion, based on a detection value of an HC sensor disposed in an engine exhaust passage. The air-fuel ratio of the air-fuel mixture is estimated.
An evaporative fuel processing apparatus for an internal combustion engine according to any one of the preceding claims.