JP3633283B2 - Evaporative fuel processing device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporative fuel treatment apparatus for an internal combustion engine, particularly a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
A conventional evaporative fuel processing apparatus for an internal combustion engine controls a purge of evaporative fuel by interposing a canister that adsorbs evaporative fuel generated in a fuel tank and a purge path of evaporative fuel from the canister to an engine intake passage. And a purge valve.
On the other hand, in recent years, a direct-injection spark-ignition internal combustion engine has attracted attention. In this engine, the combustion system is switched according to the engine operating conditions, that is, by injecting fuel in the intake stroke, thereby injecting into the combustion chamber. It is common to switch control between homogeneous combustion, which is performed by forming a homogeneous combustible mixture, and stratified combustion, where fuel is injected in a compression stroke and the combustible mixture is unevenly distributed in a specific range in the combustion chamber. Is.
[0003]
Here, when canister purge is performed during stratified combustion, if it is supplied to the center of the combustion chamber, it will burn, and CO ₂ , H ₂ Although the non-combustible air-fuel ratio purge gas supplied to the periphery of the combustion chamber is discharged without contributing to combustion and discharged into the atmosphere as a large amount of HC. In the apparatus described in Japanese Patent No. 5-223017, canister purge is prohibited during stratified combustion.
[0004]
[Problems to be solved by the invention]
However, if canister purge is uniformly prohibited during stratified combustion, the chance of canister purge decreases, the canister tends to fill up, the chance of releasing evaporated fuel to the atmosphere increases, and problems such as air pollution and gasoline odor occur. .
As a means for solving the above problem, it is conceivable to increase the capacity of the canister, but this leads to an increase in cost.
[0005]
In view of such a point, the present invention aims to enable purge as much as possible rather than prohibiting canister purge uniformly during stratified combustion.
[0006]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is a direct-injection spark-ignition internal combustion engine that performs stratified combustion by making a combustible mixture unevenly distributed in a specific range in a combustion chamber under predetermined operating conditions, FIG. 1 shows a canister that adsorbs evaporated fuel generated in a tank and a purge valve that is interposed in the purge passage of evaporated fuel from the canister to the engine intake passage and controls the purge of evaporated fuel. By evaporative fuel purged from the canister during stratified combustion Said Based on the estimated 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, whether or not to purge the fuel vapor by the purge valve during stratified combustion is determined based on the estimated air-fuel ratio And an evaporative fuel processing apparatus for an internal combustion engine.
[0007]
In the invention according to claim 2, the purge determining means permits purging at the time of 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 determining means is configured to perform purge during stratified combustion when the estimated air-fuel ratio is leaner than the second predetermined air-fuel ratio leaner than the first predetermined air-fuel ratio. Allow.
[0008]
According to a fourth aspect of the present invention, the purge determining means is configured such that when the estimated air-fuel ratio is leaner than the first predetermined air-fuel ratio and richer than the second predetermined air-fuel ratio (that is, the first (Between the predetermined air-fuel ratio and the second predetermined air-fuel ratio), the purge valve is allowed to purge at the time of stratified combustion after limiting the opening of the purge valve from the normal opening.
In the invention according to claim 5, when the air-fuel ratio estimated by the purge air-fuel ratio estimating means is leaner than the first predetermined air-fuel ratio and richer than the second predetermined air-fuel ratio, stratified combustion is performed. Prohibiting and providing means for forming a homogeneous combustible air-fuel mixture in the combustion chamber for homogeneous combustion.
[0009]
According to a sixth aspect of the present invention, the purge determining means performs purge during stratified combustion when the temperature of the exhaust gas purification 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.
In the invention according to claim 7, the purge air-fuel ratio estimation means is an air-fuel ratio sensor (generally O ₂ An air-fuel ratio feedback control means for setting an air-fuel ratio feedback correction value (generally an air-fuel ratio feedback correction coefficient) for the fuel injection amount based on a detection value of the sensor) and feedback-controlling the average air-fuel ratio in the combustion chamber to the target air-fuel ratio Based on the air-fuel ratio feedback correction value at the time of purge execution and non-execution, the fuel vapor purged from the canister during stratified combustion Said The air-fuel ratio of the air-fuel mixture formed in a region other than the specific range is estimated.
[0010]
In the invention according to claim 8, the direct-injection spark-ignition internal combustion engine is configured to form a homogeneous combustible air-fuel mixture in a combustion chamber and perform homogeneous combustion under the conditions other than the predetermined operating conditions, and the purge The air-fuel ratio estimation means sets the air-fuel ratio feedback correction value for the fuel injection amount based on the detected value of the air-fuel ratio sensor disposed in the engine exhaust passage during homogeneous combustion, and sets the air-fuel ratio in the combustion chamber to the target air By using air-fuel ratio feedback control means for feedback control to the fuel ratio, the fuel vapor purged from the canister during stratified combustion is based on the air-fuel ratio feedback correction values during purge execution and non-execution during homogeneous combustion. Said The air-fuel ratio of the air-fuel mixture formed in a region other than the specific range is estimated.
[0011]
The invention according to claim 9 includes means for forcibly performing homogeneous combustion at a predetermined timing during stratified combustion.
In the invention according to claim 10, the purge air-fuel ratio estimating means is based on the evaporated fuel purged from the canister during stratified combustion based on the detection value of the HC sensor arranged in the engine exhaust passage. Said The air-fuel ratio of the air-fuel mixture formed in a region other than the specific range is estimated.
[0012]
【The invention's effect】
According to the first aspect of the present invention, the air-fuel ratio (purge air-fuel ratio) of the air-fuel mixture formed in the region other than the specific range by the evaporated fuel purged from the canister during stratified combustion is estimated, and based on this, the stratification is performed. By determining whether or not the evaporated fuel is purged by the purge valve at the time of combustion, purging when purging is possible even at the time of stratified combustion can solve problems such as air pollution and gasoline odor.
[0013]
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. By allowing this, the opportunity for purging can be increased.
According to the third aspect of the present 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 exhaust performance, so purge during stratified combustion is permitted. As a result, the number of purge opportunities can be increased.
[0014]
According to the fourth 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, the opening of the purge valve is limited more than the normal opening. By permitting purge during stratified combustion, the opportunity for purging can be increased while suppressing the amount of HC emission compared to when purging is prohibited.
According to the fifth aspect of the present invention, when the purge air-fuel ratio is between the first predetermined air-fuel ratio and the second predetermined air-fuel ratio, stratified combustion is prohibited and homogeneous combustion is performed. Purge can be prioritized over fuel consumption.
[0015]
According to the sixth aspect of the invention, when the catalyst temperature is equal to or higher than the predetermined value, it can be determined that the deterioration of HC is small. Therefore, the purge opportunity is permitted by allowing the purge during the stratified combustion regardless of the purge air-fuel ratio. Can be increased.
According to the seventh aspect of the present invention, it is possible to estimate the purge air-fuel ratio without adding a special sensor by estimating the purge air-fuel ratio based on the air-fuel ratio feedback correction value at the time of purging and when not performing the purging. become.
[0016]
According to the eighth aspect of the invention, on the premise of switching between homogeneous combustion and stratified combustion, the purge air-fuel ratio at the time of stratified combustion is determined based on the air-fuel ratio feedback correction values at the time of purge execution and non-executed at the time of homogeneous combustion. By estimating, 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 evaporated fuel purged from the canister form a homogeneous mixture, and the air-fuel ratio of the 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 value at the time of purge execution and at the time of non-execution. In addition, when controlling the air-fuel ratio at the time of homogeneous combustion to stoichiometric, the estimation of the purge air-fuel ratio using the air-fuel ratio feedback correction value is less expensive than the wide-range air-fuel ratio sensor. ₂ Can be implemented with sensors.
[0017]
According to the ninth aspect of the present invention, the opportunity for estimating the purge air-fuel ratio can be increased by forcibly performing homogeneous combustion at a predetermined timing during stratified combustion.
According to the invention of claim 10, by using the HC sensor for estimating the purge air-fuel ratio, the purge air-fuel ratio can be estimated even during the air-fuel ratio feedback control, and good control is possible.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
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 under the control of the throttle valve 4 from the air cleaner 2 through the intake passage 3.
[0019]
An electromagnetic fuel injection valve (injector) 5 is provided to inject fuel (gasoline) directly into the combustion chamber.
The fuel injection valve 5 is energized to the solenoid by an injection pulse signal output in the intake stroke or the compression stroke in synchronization with the engine rotation from the control unit 20 to open the valve, and injects fuel adjusted to a predetermined pressure. It is like that. In the case of intake stroke injection, the injected fuel diffuses into the combustion chamber to form a homogeneous mixture, and in the case of compression stroke injection, a stratified mixture is intensively formed around the spark plug 6. Based on the ignition signal from the control unit 20, the ignition plug 6 ignites and burns (homogeneous combustion or stratified combustion). Here, an example is shown in which the air-fuel ratio is controlled to stoichiometric (theoretical air-fuel ratio) in the case of homogeneous combustion, and the air-fuel ratio is controlled to be lean in the case of stratified combustion. Control may be performed separately for stoichiometric and lean.
[0020]
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 in order to process evaporative fuel generated from the fuel tank 9. The canister 10 is a sealed container filled with an adsorbent such as activated carbon, and an evaporated fuel introduction pipe 11 from the fuel tank 9 is connected via a check valve 12. Therefore, the evaporated fuel generated in the fuel tank 9 while the engine 1 is stopped is guided to the canister 10 through the evaporated fuel introduction pipe 11 and adsorbed thereto.
[0021]
The canister 10 is also formed with a fresh air inlet 13 and a purge passage 14 is led out. The purge passage 14 is connected to the downstream side of the throttle valve 4 (intake manifold) of the intake passage 3 via the purge valve 15. The purge valve 15 is opened by a signal output from the control unit 20 under a predetermined condition during the operation of the engine 1. Accordingly, 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 the canister 10 to The evaporated fuel adsorbed by the adsorbent is desorbed, and the purge gas containing the desorbed evaporated fuel is sucked through the purge passage 14 downstream of the throttle valve 4 of the intake passage 3, and then the combustion chamber of the engine 1. Is burned.
[0022]
The control unit 20 includes a microcomputer including a CPU, ROM, RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors, performs arithmetic processing based on the signals, and performs fuel processing. The operation of the injection valve 5, spark plug 6, purge valve 15 and the like is controlled.
As the various sensors, a crank angle sensor 21 for detecting the crankshaft rotation of the engine 1 is provided, and the engine speed Ne can be detected from the signal.
[0023]
In addition, an air flow meter 22 for detecting the intake air amount (flow rate) Qa upstream of the throttle valve 4 in the intake passage 3 and a throttle sensor 23 for detecting the opening TVO of the throttle valve 4 (ON when the throttle valve 4 is fully closed). A temperature sensor 24 for detecting the coolant temperature Tw of the engine 1, and a signal corresponding to the rich / lean exhaust air / fuel ratio at the exhaust passage 7. ₂ A sensor 25, a catalyst temperature sensor 26 for detecting the temperature TCAT of the catalyst 8, and the like are provided. In the case of a third embodiment to be described later, an HC sensor 27 for detecting the HC concentration in the exhaust gas is provided in the exhaust passage 7 and used.
[0024]
Next, 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, stratified combustion permission means 100, homogeneous combustion means 200, stratified combustion means 300, evaporated fuel introduction permission means 400, learned value update means 500, evaporated fuel introduction amount measurement means 600, evaporated fuel It includes an introduction amount changing means 700 and a homogeneous combustion purge valve opening degree calculating means 800.
[0025]
FIG. 4 shows the control contents of the stratified combustion permission means 100.
In S101, based on the engine speed Ne, the load (basic fuel injection amount Tp), the water temperature Tw, etc., it is determined whether or not a predetermined stratified combustion condition is satisfied. If YES, the process proceeds to S102.
In S102, it is determined whether or not the base learning convergence flag FBSLTD = 1. If YES, the process proceeds to S103. That is, if the air-fuel ratio learning value when no evaporative fuel is introduced according to the flow of FIG. 8 (learning value updating means 500) described later does not converge, the amount of evaporative fuel introduced is not known, and stratified combustion is not permitted. .
[0026]
In S103, it is determined whether or not the evaporation concentration determination is being executed. If YES, the process proceeds to S105. That is, because homogeneous combustion is performed at predetermined intervals for measuring the amount of fuel vapor introduced, stratified combustion is not permitted even during evaporation concentration determination.
In S105, stratified combustion is permitted.
If any of the determinations in S101 to S103 is NO, the process proceeds to S106 and stratified combustion is not permitted.
[0027]
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.
In S202, the basic fuel injection amount Tp corresponding to the stoichiometric (theoretical air-fuel ratio) is calculated from the intake air amount Qa and the engine speed Ne according to the following equation.
[0028]
Tp = K × Qa / Ne (where K is a constant)
In S203, the air-fuel ratio feedback control is performed. ₂ Based on the signal from the sensor, the air-fuel ratio feedback correction coefficient α is set by known proportional integral control (see FIG. 12). That is, O ₂ Rich / lean is determined based on the signal from the sensor, and the air-fuel ratio feedback correction coefficient α is increased by a predetermined proportional amount P when rich-to-lean is reversed, and the air-fuel ratio feedback correction coefficient α is increased by a predetermined integral I during subsequent lean. Increase by 1 (I << P). The air-fuel ratio feedback correction coefficient α is decreased by a predetermined proportional amount P when lean → rich is reversed, and the air-fuel ratio feedback correction coefficient α is decreased by a predetermined integral amount I at the subsequent rich time. When the air-fuel ratio is made lean during homogeneous combustion and this air-fuel ratio is feedback controlled, the above-mentioned O ₂ The sensor may be a wide area air-fuel ratio sensor.
[0029]
In next S204, the fuel injection amount Ti for homogeneous combustion is calculated from the basic fuel injection amount Tp and the air-fuel ratio feedback correction coefficient α according to the following equation.
Ti = Tp × α
When the fuel injection amount Ti is calculated, an injection pulse signal having a pulse width corresponding to this Ti is output to the fuel injection valve at a predetermined timing in the intake stroke, and fuel injection is performed.
[0030]
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.
In S302, the basic fuel injection amount Tp corresponding to the stoichiometric (theoretical air-fuel ratio) is calculated from the intake air amount Qa and the engine speed Ne according to the following equation.
[0031]
Tp = K × Qa / Ne (where K is a constant)
In S303, the fuel injection amount Ti for obtaining the target air-fuel ratio for stratified combustion is calculated from the basic fuel injection amount Tp and the air-fuel ratio feedback correction coefficient α according to the following equation.
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, air-fuel ratio feedback control is not performed during stratified combustion, and the air-fuel ratio is controlled to a lean air-fuel ratio of, for example, around 40 by open control.
[0032]
When the fuel injection amount Ti is calculated, an injection pulse signal having a pulse width corresponding to this Ti is output to the fuel injection valve at a predetermined timing in the compression stroke, and fuel injection is performed.
FIG. 7 shows the control contents of the evaporative fuel introduction permission means 400, which is executed during homogeneous combustion.
[0033]
In S401, based on the water temperature Tw, ON / OFF of the idle switch, etc., it is determined whether or not a predetermined canister purge permission condition is satisfied. If YES, the process proceeds to S402.
In S402, it is determined whether or not the base learning convergence flag FBSLTD = 1. If YES, the process proceeds to S403. That is, if the air-fuel ratio learning value when no evaporated fuel is introduced by the flow of FIG. 8 (learned value updating means 500) described later is not converged, the amount of evaporated fuel introduced is not known, and canister purge is not permitted. .
[0034]
In S403, canister purge is permitted.
If any of the determinations in S401 and S402 is NO, the process proceeds to S404 and canister purge is not permitted.
FIG. 8 shows the control contents of the learning value updating means, which is executed during homogeneous combustion.
In S501, it is determined whether or not a learning value update condition (that is, during air-fuel ratio feedback control, the water temperature Tw is equal to or higher than a predetermined value, etc.) is determined.
[0035]
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
Here, 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 value of the air-fuel ratio feedback correction coefficient α immediately before the latest inversion from rich to lean ( (See FIG. 12).
[0036]
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) × GAIN
GAIN is a predetermined value, 0 <GAIN <1, and is used to suppress a sudden change in the learning value.
[0037]
In S504, the updated LALPHA is stored in the current operation region position of the learning map for each operation 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.
[0038]
In S506, it is determined whether or not the entire region has converged even once in the past. If YES, the predetermined value = predetermined value 1 (relatively small value) is set in S507, and if NO, the predetermined value is determined in S508. Value = predetermined value 2 (relatively large value).
In S509, it is determined whether or not the learning convergence counter CBSLTD is greater than or equal to the predetermined value set in S507 or S508 in all the pre-designated areas. If YES, it is determined that learning has converged, and learning convergence is performed in S510. Set the flag FBSLTD = 1.
[0039]
Note that when there has been convergence in the entire region even once in the past, the predetermined value = predetermined value 1 (relatively small value) is set to the predetermined value = 0 in the extreme case, and shifts to stratified combustion quickly. This is to allow purge.
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 evaporative fuel introduction, and the average value and 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 when evaporative fuel is introduced is obtained by calculation.
[0040]
In 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 region-specific learning map using the engine speed Ne and the load (basic fuel injection amount) Tp as parameters.
[0041]
In S603, from 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, according to the following equation, the air-fuel ratio (purge air-fuel ratio) AFREVP in the post-evaporated fuel introduction Is calculated.
AFREVP = (Qa × k2 / Ne) / ((LALPHA−Mα) × Ti)
Here, the vaporized fuel amount per cylinder is calculated by (LALPHA-Mα) × Ti, and the air amount per cylinder is calculated by Qa × K2 / Ne (where k2 is a constant). The purge air-fuel ratio is calculated by the equation. Therefore, this part corresponds to the purge air-fuel ratio estimating means.
[0042]
FIG. 10 shows the control contents of the evaporated fuel introduction amount changing means 700, which is executed during stratified combustion.
In S701, 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) to determine whether AFREVP <SLEVP1 or AFREVP> SLEVP2.
[0043]
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).
If YES, the purge valve opening correction coefficient KEVP = 1 (no correction) is set in S703. This is because if the catalyst is sufficiently warm, HC is purified and a large purge is permitted.
[0044]
Again, 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.
[0045]
In S705, the basic purge valve opening degree BSDTY is calculated from the intake air amount Qa with reference to a table.
In S706, the basic purge valve opening degree BSDTY is corrected by the purge valve opening degree correction coefficient KEVP, the purge valve opening degree EVPDTY is calculated, and the purge valve is controlled as in the following equation.
[0046]
EVPDTY = BSDTY × KEVP
Thus, the evaporated fuel introduction amount changing means 700 permits purging according to the measured purge air-fuel ratio, and the purge air-fuel ratio is between the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2. If it is determined, the purge valve is throttled to control the purge air-fuel ratio to be thinner than the second predetermined air-fuel ratio SLEVP2 (see FIG. 13). Further, if the catalyst temperature is equal to or higher than a predetermined value, it is determined that the deterioration of HC is small, and normal purge is permitted. Therefore, this portion corresponds to the purge determination means.
[0047]
FIG. 11 shows the control contents of the purge valve opening degree calculation means 800 during homogeneous combustion, which is executed during homogeneous combustion.
In S801, the purge valve opening EVPDTY is directly calculated from the intake air amount Qa with reference to the table, and the purge valve is controlled.
Next, a second embodiment will be described.
[0048]
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 S103 are the same as those in the first embodiment (FIG. 4), but if all of these are YES, the process proceeds to S104.
[0049]
In 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) to determine whether AFREVP <SLEVP1 or AFREVP> SLEVP2.
If YES (AFREVP <SLEVP1 or AFREVP> SLEVP2), the process proceeds to S105. That is, when the purge air-fuel ratio AFREVP is between the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2 (when SLEVP1 <AFREVP <SLEVP2), stratified combustion is not permitted.
[0050]
In S105, stratified combustion is permitted.
If any of the determinations in S101 to S104 is NO, the process proceeds to S106 and stratified combustion is not permitted.
Thus, in this embodiment, stratified combustion is prohibited when the purge air-fuel ratio AFREVP is between the first predetermined air-fuel ratio SLEVP1 and the second predetermined air-fuel ratio SLEVP2. This is because purge is prioritized over fuel consumption.
[0051]
Next, a third embodiment will be described.
The control block diagram of the third embodiment is shown in FIG. 15, and the stratified combustion permission means 100, the homogeneous combustion means 200, the stratified combustion means 300, the evaporated fuel introduction amount prediction means 650, the evaporated fuel introduction amount change means (introduction prohibition means) ) 750.
Here, the control contents of the stratified combustion permission means 100, the homogeneous combustion means 200, and the stratified combustion means 300 are as shown in FIG. 4 (or FIG. 14), FIG. 5, and FIG.
[0052]
FIG. 16 shows the control contents of the evaporative fuel introduction amount prediction means of the third embodiment.
In S651, the purge valve opening EVPDTY is calculated from the intake air amount Qa with reference to the table and output. 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 process proceeds to the next S653. In other words, the delay is made until the influence of purging occurs.
[0053]
In S653, the output HCSEN of the HC sensor disposed in the exhaust passage is read and stored as a detection value HCSEN1 = HCSEN when purge is present.
In S654, the purge valve opening EVPDTY = 0 is output so that the purge valve is fully closed. 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 process proceeds to the next S656. That is, the delay is made until the influence of the purge cut occurs.
[0054]
In S656, the output HCSEN of the HC sensor disposed in the exhaust passage is read and stored as a detection value HCSEN2 = HCSEN when there is no purge.
In S567, the difference DHC = HCSEN1-HCSEN2 between the HC sensor detection value HCSEN1 with purge and the HC sensor detection value HCSEN2 without purge is calculated.
[0055]
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 portion corresponds to the purge concentration estimating means.
FIG. 17 shows the control contents of the evaporated fuel introduction amount changing means (introduction prohibiting means) of the third embodiment.
[0056]
In S751, it is determined whether or not the difference DHC is equal to or less than a predetermined value (SLHC).
If YES (DHC <SLHC), the purge valve opening correction coefficient KEVP = 1 (no correction) is set in S753.
If NO, it is determined in S752 whether or not the catalyst temperature TCAT is equal to or higher than a predetermined value (SLTCAT).
[0057]
If YES, the purge valve opening correction coefficient KEVP = 1 (no correction) is set in S753. This is because if the catalyst is sufficiently warm, HC is purified and a large purge is permitted.
Here again, in the case of NO, the purge valve opening correction coefficient KEVP = 0 is set in S754 for purge cut.
[0058]
In S755, the basic purge valve opening degree BSDTY is calculated from the intake air amount Qa with reference to a table.
In S756, the basic purge valve opening BSDTY is corrected by the purge valve opening correction coefficient KEVP as in the following equation, the purge valve opening EVPDTY is calculated, and the purge valve is controlled.
[0059]
EVPDTY = BSDTY × KEVP
In this way, when the difference DHC is large according to the difference DHC between the detected values of the HC sensor with and without the purge, the purge valve is closed and the purge is prohibited. However, if the catalyst temperature is equal to or higher than a predetermined value, it is determined that the deterioration of HC is small, and normal purge is permitted. Therefore, this portion corresponds to the purge determination means.
[0060]
Thus, by using the HC sensor, the purge air-fuel ratio can be predicted even when the air-fuel ratio feedback control is not being performed, and the stratified combustion that is open-controlled to a large lean air-fuel ratio is continued without performing the normal air-fuel ratio feedback control. On the other hand, since it is possible to determine whether or not purge is possible, the fuel efficiency is further improved.
[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 the control contents of the stratified combustion permission means.
FIG. 5 is a flowchart showing the control content of the homogeneous combustion means.
FIG. 6 is a flowchart showing the control contents of the stratified combustion means.
FIG. 7 is a flowchart showing the control contents of the evaporated fuel introduction permission means.
FIG. 8 is a flowchart showing the control content of learning value update means.
FIG. 9 is a flowchart showing the control contents of the 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 degree calculation means;
FIG. 12 is a 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 permission means of the second embodiment.
FIG. 15 is a control block diagram of the third embodiment.
FIG. 16 is a flowchart showing the control contents of the evaporated fuel introduction amount prediction means of the third embodiment.
FIG. 17 is a flowchart showing the control contents of the evaporated fuel introduction amount changing means of the third embodiment.
[Explanation of symbols]
1 organization
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 Evaporative fuel introduction pipe
12 Check valve
13 Fresh air inlet
14 Purge passage
15 Purge valve
20 Control unit
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)

A direct-injection spark ignition type internal combustion engine in which a flammable mixture is unevenly distributed in a specific range in a combustion chamber under a predetermined operating condition to perform stratified combustion,
A canister that adsorbs the evaporated fuel generated in the fuel tank, and a purge valve that is interposed in the purge passage of the evaporated fuel from the canister to the engine intake passage and controls the purge of the evaporated fuel,
A purge air-fuel ratio estimating means for estimating an air-fuel ratio of the mixture formed in a region other than the specific range by the fuel vapor purged from the canister when stratified charge combustion,
A purge determining means for determining whether or not to purge the evaporated fuel by the purge valve during stratified combustion based on the estimated air-fuel ratio;
An evaporative fuel processing apparatus for an internal combustion engine, comprising: 2. The evaporative fuel processing for an internal combustion engine according to claim 1, wherein the purge determining means permits purge during stratified combustion when the estimated air-fuel ratio is richer than the first predetermined air-fuel ratio. apparatus. The purge determination means permits purge during stratified combustion when the estimated air-fuel ratio is leaner than the second predetermined air-fuel ratio leaner than the first predetermined air-fuel ratio. The evaporative fuel processing apparatus of the internal combustion engine according to claim 1 or 2. 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 purge determining means restricts the opening of the purge valve and stratifies combustion. The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein purge at the time is permitted. When the air-fuel ratio estimated by the purge air-fuel ratio estimating means is leaner than the first predetermined air-fuel ratio and richer than the second predetermined air-fuel ratio, stratified combustion is prohibited and homogeneous in the combustion chamber. The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising means for forming a combustible air-fuel mixture to perform homogeneous combustion. The purge determining means permits purge during stratified combustion regardless of the estimated air-fuel ratio when the temperature of the exhaust gas purification catalyst interposed in the exhaust passage of the engine is equal to or higher than a predetermined value. The evaporative fuel processing apparatus of the internal combustion engine according to any one of claims 1 to 5. The purge air-fuel ratio estimating means includes
Air-fuel ratio feedback control for setting the air-fuel ratio feedback correction value for the fuel injection amount based on the detected value of the air-fuel ratio sensor disposed in the engine exhaust passage, and feedback control of the average air-fuel ratio in the combustion chamber to the target air-fuel ratio Using means,
Based on the purge execution time and the air-fuel ratio feedback correction value at the time of non-execution, and characterized by estimating an air-fuel ratio of the mixture formed in a region other than the specific range by the fuel vapor purged from the canister when stratified charge combustion The evaporated fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 6. The direct-injection spark-ignition internal combustion engine is configured to form a homogeneous combustible air-fuel mixture in a combustion chamber and perform homogeneous combustion under conditions other than the predetermined operating conditions,
The purge air-fuel ratio estimating means includes
During homogeneous combustion, an air-fuel ratio feedback correction value for the fuel injection amount is set based on the detected value of the air-fuel ratio sensor disposed in the engine exhaust passage, and the air-fuel ratio in the combustion chamber is feedback-controlled to the target air-fuel ratio. Using the fuel ratio feedback control means,
Based on the air-fuel ratio feedback correction value when the non-runtime purge execution of the homogeneous combustion, to estimate the air-fuel ratio of the mixture formed in a region other than the specific range by the fuel vapor purged from the canister when stratified charge combustion The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 6. 9. The evaporative fuel processing apparatus for an internal combustion engine according to claim 8, further comprising means for forcibly performing homogeneous combustion at a predetermined timing during stratified combustion. The purge air-fuel ratio estimation means, based on the detected value of the HC sensor disposed in the engine exhaust passage, the air of the mixture formed in a region other than the specific range by the fuel vapor purged from the canister when stratified charge combustion The evaporative fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the fuel ratio is estimated.

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