JPH06323179A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To control a fuel injection amount in good responsiveness in accordance with changing air-fuel ratio by a purge by updating a purge concentration correction coefficient, used in controlling a fuel injection valve, based on a direction of changing an air-fuel ratio correction coefficient at the time of operating a purge control valve. CONSTITUTION:A purge control valve 24 is interposed in a purge passage 23 for connecting a canister 21 of adsorbing vaporized fuel in a fuel tank 9 to the downstream of a throttle valve 4 in an intake pipe 2. This purge control valve 24 is controlled by an ECU6 in accordance with an engine operative condition, and also a fuel injection valve 7 is controlled in accordance with an air-fuel ratio correction coefficient and a purge concentration correction coefficient. The air-fuel ratio correction coefficient is calculated in accordance with air-fuel ratio detected by an O2 sensor 16, and the purge concentration correction coefficient is set in accordance with fuel vapor sucked to an engine. Here is updated the purge concentration correction coefficient based on a direction of changing the air-fuel ratio correction coefficient at the time of operating the purge control valve 24, thus to always obtain a proper fuel injection amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine equipped with an evaporated fuel processing device for temporarily adsorbing evaporated fuel generated in a fuel tank and purging the intake system of the internal combustion engine in a timely manner.

[0002]

2. Description of the Related Art The purging of the intake system of an internal combustion engine with evaporated fuel affects the air-fuel ratio control of the air-fuel mixture supplied to the engine.

When the air-fuel ratio feedback correction amount (set according to the output of the O ₂ sensor of the exhaust system) exceeds the set range due to the influence of purge, the basic fuel injection amount is increased or decreased to increase the intake system. Air-fuel ratio control device for correcting the amount of fuel injected into the air-fuel ratio (Japanese Patent Laid-Open No. 63-578)
No. 41).

A control device which obtains the concentration of the evaporated fuel to be purged into the intake system from the air-fuel ratio feedback correction amount and corrects the release amount (purge amount) of the evaporated fuel into the intake system according to this concentration (Kaihei 4-94444).

Even if the air-fuel ratio feedback correction coefficient is outside the predetermined range, if it is determined that the feedback correction coefficient is changing toward the predetermined range, the control device is arranged to prohibit the correction of the purge amount. (JP-A-4-94
No. 445).

In a control device that obtains the concentration of evaporated fuel to be purged into the intake system from the air-fuel ratio feedback correction amount and calculates the purge correction amount that corrects the fuel injection amount according to the concentration, the control device determines the purge correction amount according to the purge correction amount. A device for controlling the purge amount and a device for controlling the purge correction amount for correcting the fuel injection amount according to the purge amount
112959).

[0007]

According to the above control device, when the air-fuel ratio feedback correction amount exceeds the set range due to the influence of the purge, the basic fuel injection amount is increased or decreased, but at this time Since the direction of change of the fuel ratio feedback correction amount is not taken into consideration, the correction by the air-fuel ratio feedback correction amount and the correction of the basic fuel injection amount may overlap and become overcorrection.

Further, according to the above control device, the purge correction amount for correcting the fuel injection amount is calculated based on the air-fuel ratio feedback correction amount, and the purge correction amount is further the purge amount, specifically, the purge control valve It is changed according to the duty ratio. However, since this device also does not consider the changing direction of the air-fuel ratio feedback correction amount, it has the same problem as the above device.

Further, since the above-mentioned control device controls the purge amount based on the air-fuel ratio feedback correction amount, the system delay (delay of the time required to reach the intake system from the purge control valve). However, there is a problem that the control response is poor and the deviation from the desired air-fuel ratio becomes large.

The present invention has been made in view of the above-mentioned points, and the fuel injection amount is controlled with high responsiveness according to the change in the air-fuel ratio due to the purge, and the deviation of the air-fuel ratio due to the purge can be minimized. An object is to provide a control device for an engine.

[0011]

In order to achieve the above object, the present invention provides a canister for adsorbing fuel vapor generated from a fuel tank, the canister being provided between the canister and an intake system of an internal combustion engine. For purging the intake system to the intake system, a purge control valve for controlling the flow rate of the fuel vapor supplied to the intake system via the purge passage, and a fuel for controlling the injection amount of the fuel supplied to the engine. An injection valve, an operating state detecting means for detecting an operating state of the engine, an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine, and an air-fuel ratio correction coefficient based on the detected air-fuel ratio. Air-fuel ratio correction coefficient calculating means for calculating, and a purge concentration correction coefficient for setting a purge concentration correction coefficient according to the concentration of the fuel vapor supplied to the intake system through the purge passage based on the air-fuel ratio correction coefficient. Coefficient setting means, purge flow rate control means for controlling the purge control valve according to the detected engine operating state, and fuel injection for controlling the fuel injection valve according to the air-fuel ratio correction coefficient and the purge concentration correction coefficient. In an internal combustion engine control device having a quantity control means,
The purge concentration correction coefficient setting means updates the purge concentration correction coefficient (KEVAP) based on the changing direction of the air-fuel ratio correction coefficient (KO2) when the purge control valve operates.

Further, it is desirable that the purge concentration correction coefficient setting means decreases the purge concentration correction coefficient (KEVAP) when the air-fuel ratio correction coefficient (KO2) is shifting in a decreasing direction.

It is desirable that the purge concentration correction coefficient setting means increases the purge concentration correction coefficient (KEVAP) when the air-fuel ratio correction coefficient (KO2) is increasing.

Further, in the purge concentration correction coefficient setting means, the air-fuel ratio correction coefficient (KO2) is within a predetermined range (KO2).
It is desirable to update the purge concentration correction coefficient (KEVAP) when it is within EVL to KO2EVH.

[0015]

When the purge control valve is activated, the air-fuel ratio correction coefficient (KO
2) Purging concentration correction coefficient (KEV
AP) is updated.

More specifically, the purge concentration correction coefficient decreases when the air-fuel ratio correction coefficient changes in the decreasing direction, and the purge concentration correction coefficient decreases when the air-fuel ratio correction coefficient changes in the increasing direction. Will increase.

Further, the purge concentration correction coefficient is updated when the air-fuel ratio correction coefficient is within a predetermined range.

[0018]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine and a control system therefor according to one embodiment of the present invention. Reference numeral 1 is, for example, 4
A cylinder internal combustion engine (hereinafter referred to as “engine”) is shown, and a throttle body 3 is provided in the middle of an intake pipe 2 of the engine 1, and a throttle valve 4 is arranged inside the throttle body 3.
The throttle valve 4 has a throttle valve opening (θTH) sensor 5
Are connected, and an electric signal corresponding to the opening degree of the throttle valve 4 is output and supplied to an electronic control unit (hereinafter referred to as “ECU”) 6.

The fuel injection valve 7 is provided for each cylinder between the engine 1 and the throttle valve 4 and slightly upstream of an intake valve (not shown) of the intake pipe 2, and each fuel injection valve 7 is provided with a fuel pump 8. Is connected to the fuel tank 9 and is electrically connected to the ECU 6, and the valve opening time of the fuel injection valve 7 is controlled by a signal from the ECU 6.

An intake pipe absolute pressure (PBA) sensor 11 is provided immediately downstream of the throttle valve 4 via a pipe 10. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 11 is sent to the ECU 6. Supplied.

An intake air temperature (TA) sensor 12 is mounted downstream of the absolute pressure sensor 11, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies it to the ECU 6. Engine water temperature (T
The W) sensor 13 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal, and supplies it to the ECU 6.

The engine speed (NE) sensor 14 is mounted around a cam shaft or a crank shaft (not shown) of the engine 1, and a signal pulse (hereinafter referred to as "hereinafter referred to as" a signal pulse "at a predetermined crank angle position for each 180-degree rotation of the engine 1 crank shaft. (Referred to as “TDC signal pulse”), and this TDC signal pulse is supplied to the ECU 6.

O ₂ sensor 1 as an exhaust gas concentration detector
Reference numeral 6 is attached to the exhaust pipe 15 of the engine 1, detects the oxygen concentration in the exhaust gas, outputs a signal according to the concentration, and supplies the signal to the ECU 6. A vehicle speed sensor 33 that detects the speed of the vehicle equipped with the engine 1 is connected to the ECU 6, and a detection signal thereof is supplied to the ECU 6.

The upper portion of the closed fuel tank 9 has a passage 20.
It communicates with the canister 21 via a, and the canister 21 communicates with the downstream side of the throttle valve 4 of the intake pipe 2 via the purge passage 23. The canister 21 is the fuel tank 9
The adsorbent 22 that adsorbs the evaporated fuel generated inside is built in,
It has an outside air intake 21a. A two-way valve 20 composed of a positive pressure valve and a negative pressure valve is arranged in the middle of the passage 20a, and a purge control valve 24 which is a duty control type solenoid valve is arranged in the middle of the purge passage 23. . The solenoid of the purge control valve 24 is connected to the ECU 6, and the purge control valve 24 is controlled according to a signal from the ECU 6 to linearly change the temporal ratio of the valve opening time. Passage 2
0a, the two-way valve 20, the canister 21, the purge passage 23, and the purge control valve 24 constitute an evaporated fuel discharge suppression device.

According to this evaporative fuel discharge inhibiting device, the evaporative fuel generated in the fuel tank 9 opens the positive pressure valve of the two-way valve 20 when it reaches a predetermined set pressure, and then flows into the canister 21 and the canister. It is adsorbed by the adsorbent 22 in 21 and stored. The purge control valve 24 is an ECU
The evaporated fuel temporarily opened and stored in the canister 21 during the valve opening / closing operation according to the duty control signal from the control valve 6 is discharged to the outside air provided in the canister 21 due to the negative pressure in the intake pipe 2. It is sucked into the intake pipe 2 through the purge control valve 24 together with the outside air sucked from the intake port 21a, and is sent to each cylinder. Also, the fuel tank 9
Is cooled and the negative pressure in the fuel tank increases, the negative pressure valve of the two-way valve 20 opens, and the evaporated fuel temporarily stored in the canister 21 is returned to the fuel tank 9. In this way, the fuel vapor generated in the fuel tank 9 is prevented from being released to the atmosphere.

The downstream side of the throttle valve 4 of the intake pipe 2 is connected to the exhaust pipe 15 via an exhaust gas recirculation passage 30, and an exhaust gas recirculation valve (EGR) for controlling the amount of exhaust gas recirculation is provided in the middle of the exhaust gas recirculation passage 30. Valve) 31 is provided.

The exhaust gas recirculation valve 31 is an electromagnetic valve having a solenoid, and the solenoid is connected to the ECU 6 so that the valve opening can be linearly changed by a control signal from the ECU 6. The exhaust gas recirculation valve 31 is provided with a lift sensor 32 that detects the valve opening degree, and the detection signal is supplied to the ECU 6.

The ECU 5 discriminates the engine operating state based on the engine parameter signals from the above-mentioned various sensors, and the valve opening degree of the exhaust gas recirculation valve 31 set according to the absolute intake pipe pressure PBA and the engine speed NE. Command value LCMD
And exhaust gas recirculation valve 31 detected by the lift sensor 32
A control signal is supplied to the solenoid of the exhaust gas recirculation valve 31 so that the deviation from the actual valve opening value LACT of the above is zero.

The ECU 6 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter, referred to as a "central processing unit"). "CPU"),
It comprises a storage means for storing various calculation programs executed by the CPU and calculation results, an output circuit for supplying drive signals to the fuel injection valve 7, the purge control valve 24 and the exhaust gas recirculation valve 31.

Based on the above-mentioned various engine parameter signals, the CPU determines various engine operating conditions such as the feedback control operating region to the stoichiometric air-fuel ratio by the O ₂ sensor 16 and the open loop control operating region and the engine operating condition. According to the fuel injection time T of the fuel injection valve 7.
OUT, the duty ratio of the purge control valve 24, and the valve opening command value LCMD of the exhaust gas recirculation valve are calculated.

The fuel injection by the fuel injection valve 7 is performed in synchronization with the TDC signal pulse, and the fuel injection time TOUT is calculated by the following equation (1).

TOUT = TI × KO2 × KEVAP × K1 + K2 (1) where TI is the basic fuel amount, specifically, the engine speed N
The TI is a basic fuel injection time determined according to E and the intake pipe absolute pressure PBA, and a TI map for determining this TI value is stored in the storage means.

KO2 is an air-fuel ratio correction coefficient, which is set according to the output value of the O ₂ sensor 16 during the air-fuel ratio feedback control, and is set to a predetermined value according to the engine operating state during the open loop control.

KEVAP is an evaporation correction coefficient for compensating for the influence of evaporated fuel due to purging, and is set to 1.0 when purging is not performed, and 0 to when purging is performed.
Set to a value between 1.0. The smaller the value of this coefficient KEVAP, the greater the effect of purging.

K1 and K2 are other correction coefficients and variables calculated according to various engine parameter signals, respectively, so that various characteristics such as fuel consumption characteristics and engine acceleration characteristics can be optimized according to engine operating conditions. Is set to any value.

The CPU of the ECU 6 controls the fuel injection valve 7 and the purge control valve 24 based on the results calculated as described above.
And a signal for driving the exhaust gas recirculation valve 31 is output via an output circuit.

FIG. 2 shows the operation (opening) of the purge control valve 24.
6 is a flowchart of a process of determining / non-operation (valve closing), and this process is executed in synchronization with each generation of a TDC signal pulse.

In step S1, it is determined from the engine speed NE whether or not the engine 1 is in the starting mode, and in the starting mode, the post-starting purge correction coefficient KFLAST, which is applied immediately after the starting of the engine 1, is set to "0" ( Step S
2), an initial timer t that measures the time after the start mode ends
A predetermined time is set in mFLAST to start it (step S3), and a FB control timer tmFR that measures the time after the start of the air-fuel ratio feedback control is set to a predetermined time and started (step S3).
4) The operation permission flag F-FR of the purge control valve 24 is set to "0" to disable the operation of the purge control valve 24 (purge cut state) (step S5).

Here, the initial timer tmFLAST is set to, for example, 50 seconds when the engine water temperature TW in the starting mode is equal to or higher than a predetermined temperature, and is set to, for example, 200 seconds when it is lower than the predetermined temperature. Also, the FB control timer tmFR
Is set to 0.5 seconds, for example.

When the starting mode is completed, the process proceeds from step S1 to step S6, and it is determined whether or not the value of the initial timer tmFLAST is "0". Since tmFLAST> 0 at the beginning, the process proceeds to steps S4 and S5, and the purge is not permitted.

When the engine water temperature TW is low, the air-fuel ratio is enriched, so the timer set time (tmFLAST) is lengthened to prevent overrich due to purge, and the supply air-fuel ratio at low water temperature is stabilized. The driveability is ensured by making it possible.

After the start mode is finished, a predetermined period of time elapses and tm
When FLAST = 0, the routine proceeds to step S7, where it is judged whether or not the FB control flag F-O2FB indicating "1" that the air-fuel ratio feedback control is being performed is "1". FO
If 2FB = 0 and the feedback control is not in progress, the process proceeds to steps S4 and S5 to prohibit purging, and F-
When O2FB = 1, it is determined whether or not the FC flag F-FC indicating "1" that the fuel cut is in progress is "1" (step S8).

When F-FC = 1 and the fuel is being cut, the procedure advances to steps S4 and S5 to prohibit purging, and when F-FC = 0, the FB control timer started in step S4. It is determined whether or not the value of tmFR is "0" (step S9). Initially, tmFR> 0, so the procedure proceeds to step S5, and the purge is not permitted.
When tmFR = 0 after a lapse of a predetermined time, step S10
Proceed to.

[0045] The step S4, S9, and inhibits the purging until a predetermined time elapses when returning to the O ₂ feedback control, the initialization of the control is performed at the time of return to the O ₂ feedback control, over by the air-fuel ratio correction coefficient KO2 Prevents correction.

In step S10, the exhaust gas recirculation valve 31 is opened, and the exhaust gas recirculation is indicated by "1" EG.
It is determined whether the R flag F-EGR is "1", and F-FG
When R = 1 and exhaust gas recirculation is in progress, the routine proceeds to step S11, where the detected engine speed NE and the intake pipe absolute pressure P are detected.
The KFREGR map is searched according to BA, and the EGR correction coefficient KFREGR corresponding to the EGR amount is determined.

In the KFREGR map, for example, as shown in FIG. 8, a predetermined value is set for each grid point determined by a predetermined engine speed N (1) to N (n) and a predetermined intake pipe absolute pressure 0 to P (n). Is an EGR correction map in which the EGR correction coefficient KFREGR = 0.85 and the surrounding 0.95.
Areas and other 1.0 areas are provided.

Here, the EGR correction coefficient KF during exhaust gas recirculation
A purge duty map value DF, which will be described later, according to REGR
The RMAP is corrected in order to prevent the air-fuel ratio of the air-fuel mixture from becoming excessively rich by reducing the purge supply amount because the ratio of the air-fuel mixture contributing to combustion decreases as the exhaust gas recirculation amount increases.

If the exhaust gas recirculation is not in progress (F-EGR =
0), proceeding to step S12, EGR correction coefficient KFRE
GR is set to 1.0 and purge correction is not performed.

Then, in step S13, a map in which the map value DFRMAP of the purge duty amount DFR that determines the ratio of the valve opening time of the purge control valve 24 is set according to the engine speed NE and the intake pipe absolute pressure PBA is searched. Determined by In the following step S14,
The engine water temperature TW is a predetermined water temperature TWFRIDL (for example, 4
0 ℃), TW ≦ TWFRIDL
When is satisfied, the process immediately proceeds to step S19. On the other hand, when TW> TWFIDL is satisfied, it is further determined whether or not the intake air temperature TA is higher than a predetermined intake air temperature TAFRIDL (for example, 30 ° C.) (step S15). TA ≦ T
If AFRIDL, the process immediately proceeds to step S19, where T
When A> TAFRIDL is satisfied, it is determined whether the engine 1 is in the idle state (step S16).

If the engine 1 is not in the idle state, the routine proceeds to step S19, and when the engine 1 is in the idle state, the purge duty map value DFRMAP is set to the predetermined amount DFRID.
It is determined whether it is smaller than L. And DFRMAP ≧
When DFRIDL is established, the process immediately proceeds to step S19, and when DFRMAP <DFRIDL is established,
This predetermined amount DFRIDL is used as the purge duty map value D
FRMAP is set, the minimum purge amount is secured (step S18), and the process proceeds to step S19. Predetermined amount DFRIDL
This is because, if it is about a degree, there is almost no effect even if purging is performed.

In step S19, it is determined whether the purge duty map value DFRMAP is larger than 0, and D
When FRMAP = 0, the process proceeds to step S5, and purging is not permitted. When DFRMAP> 0, it is determined whether the engine water temperature TW is higher than a predetermined water temperature TWFR (for example, 20 ° C.), and when TW> TWFR is satisfied, the intake air temperature TA is further increased to a predetermined intake air temperature TAFR (for example, 30 ° C.). ) It is determined whether it is higher (step S21). As a result, if TA> TAFR is satisfied, the purge control valve operation permission flag F-FR is set to "1" to permit the purge (step S22), while TW≤TWFR or TA≤TAF.
When R is satisfied, the process proceeds to step S5 and purge is not permitted.

By the process shown in FIG. 2, whether the purge control valve 24 is operated or not is determined, and the EGR correction coefficient KFREGR and the purge duty map value DFRMA are determined.
The value of P is determined.

FIG. 3 is a flow chart of the process for calculating the purge duty amount DFR of the purge control valve 24.
This process is executed every predetermined time (for example, 40 msec).

In step S31, it is determined whether or not the current purge operation permission flag F-FR is "1", and FF is determined.
When R = 0 and purge is not permitted, the routine proceeds to step S32, where the post-startup purge correction coefficient KF applied immediately after the start-up is applied.
RAST current value KFRAST (n) is changed to previous value KFRA
A counter CFRA that holds the same value as ST (n-1) (hereinafter referred to as "previous value hold") and is applied when the vehicle starts.
A predetermined value is set in DD (FIG. 4, step S65) (step S33), and the initial purge amount set value DFRX is set to "0".
(Step S34), the initial flag F-FRADD which indicates "1" immediately after the transition from the non-permission of purging to the permission (hereinafter referred to as "initial purging state") is set to "0" (step S35), and the purge duty is set. The amount DFR is set to "0" (step S36), and this processing ends.

If F-FR = 1 in step S31 and the purge is permitted this time, it is further determined whether or not F-FR = 1 was set last time (step S37). As a result, the initial flag F-FRADD is set to "1" (step S38) when F-FR = 0 last time and the shift to the purge permission is made this time, and the purge permission continues last time as well. If so, the process immediately proceeds to step S39.

At step S39, the evaporation correction coefficient KE
It is determined whether VAP (see the above formula (1)) is larger than a predetermined value KEVAPFR, and KEVAP> KEVAPFR.
If so, the post-start-up purge correction coefficient KFLAST (n) of this time is calculated by the following equation (2) (step S4).
0).

KFRAST (n) = KFLAST (n−1) + DKFLAST (2) Here, DKFRAST is a predetermined addition term, and the addition term DKFLAST is added to the previous post-starting purge correction coefficient KFLAST (n−1). By doing so, the value of the post-startup purge correction coefficient KFLAST is gradually increased, and the purge amount is gradually increased.

On the other hand, when KEVAP≤KEVAPFR is satisfied, the post-startup purge correction coefficient KFRAST is held at the previous value (step S41).

That is, in the initial stage of the start of purge supply, when the evaporation correction coefficient KEVAP is large and the influence of the purge on the fuel injection amount is small, the purge amount is gradually increased, but when the influence is large, the purge amount is increased. I try to suppress the increase in volume.

In subsequent steps S42 and S43, it is judged whether or not the post-start-up purge correction coefficient KFRAST (n) is larger than 1, and when it becomes larger than 1, KFRA.
The maximum value is set to 1.0 with ST (n) = 1.0.

Then, in step S44, the purge duty amount DFR is calculated by the following equation (3).

DFR = DFRMAP × KFRAST × KFREGR × KFRTW × KFRPA (3) Here, the purge duty map values DFRMAP and E
The GR correction coefficient KFREGR is calculated in the process of FIG. 2, KFRTW is a water temperature purge correction coefficient set according to the engine water temperature TW, and KFRPA is the atmospheric pressure PA.
It is an atmospheric pressure correction coefficient set according to. The water temperature purge correction coefficient KFRTW is set to increase as the engine water temperature TW increases, and the atmospheric pressure correction coefficient KFRPA is set.
Is set to increase as the atmospheric pressure PA decreases. This is because purging becomes difficult as the atmospheric pressure PA decreases.

In step S44, the purge duty amount DF
After calculating R, the initial flag F-FRADD is "1".
It is determined whether or not F-FRADD = 0 and the initial purge state is not established, and the process immediately proceeds to step S51. on the other hand,
When F-FRADD = 1 and the initial purge state,
The initial purge amount set value DFRX (n) is calculated by the following equation (4) (step S46).

DFRX (n) = DFRX (n−1) + DFRADD (4) Here, DFRADD is an initial purge addition term, and its value is set in the process of FIG. 4 described later. The value of the initial purge amount set value DFRX gradually increases according to the equation (4).

Then, it is determined whether or not the purge duty amount DFR calculated in step S44 is larger than the initial purge amount set value DFRX (n) calculated in equation (4) (step S47). Initially, DFR> DFRX (n) is established, so the routine proceeds to step S48, where the initial purge amount set value DFRX is set as the purge duty amount DFR, and thereafter D
When FR ≦ DFRX (n), the purge duty amount D
Initial purge amount set value DFRX without correction of FR value
Is set to "0" (step S4
9) The initial flag F-FRADD is set to "0" (step S50), and the process proceeds to step S51.

In steps S51 to S54, a limit check of the purge duty amount DFR is performed. When the value of the purge duty amount DFR exceeds the upper limit value DFRLMTH, DFR = DFRLMTH (step S5
3), the value of the purge duty amount DFR is the lower limit value DFRL
When it is less than MTL, DFR = DFRLMTL is set (step S54), and this processing is ended.

Thus, the purge duty amount DFR is determined, the purge control valve 24 is controlled based on the value of the purge duty amount DFR, and the evaporated fuel is supplied to the intake pipe 2.

Post-start purge correction coefficient KF in this process
The manner in which RAST increases will be briefly described with reference to FIG. 9, which shows the comparison between the evaporation correction coefficient KEVAP and the purge duty amount DFR.

After the engine is started and before the purge is started, the post-start purge correction coefficient KFLAST is 0 and the evaporation correction coefficient K is 0.
EVAP is 1.0, purging is not permitted, and the purge duty amount DFR is 0.

When purging starts, steps S46 and S4
7. The purge duty amount DFR is gradually increased by repeating S and S48, and the purge correction coefficient KEVAP after the start is correspondingly increased.
Decreases from 1.0. And the evaporation correction coefficient KE
Since VAP is initially larger than the predetermined value KEVAPFR, step S40 is repeated and the purge correction coefficient KFRAS after the start.
T gradually increases. That is, the purge amount also gradually increases.

When the purge cut is performed, the purge duty amount DFR becomes 0 and the evaporation correction coefficient KEVAP increases, but the post-starting purge correction coefficient KFRAST is fixed to the previous value in step S32, and again when the purge is restarted. Start increasing.

When the evaporation correction coefficient KEVAP gradually decreases and falls below the predetermined value KEVAPFR and the influence of the purge becomes large, the post-starting purge correction coefficient KFRAST is fixed to the previous value in step S41 and the purge amount is required. If the effect of purge is not so great (KEVAP> KEVAPF,
R), and the purge correction coefficient KFLAST increases again after the engine starts, and finally becomes 1.0.

Therefore, when the purge is stopped, the post-startup purge correction coefficient KFLAST is fixed to the previous value so that when the purge is restarted, the fixed value KFLAST (n-1) is added to the addition term D.
It is increased by KFRAST to prevent a delay in following the purge duty map value DFRMAP depending on the operating state.

Further, in an operating state where the purge concentration is high such that the evaporation correction coefficient KEVAP decreases and falls below the predetermined value KEVAPFR, the purge correction coefficient KFRAST is fixed to the previous value so that the purge duty amount DFR is set during execution of the purge. The sudden change of the supply air-fuel ratio and the overcorrection of the evaporation correction coefficient KEVAP due to the increase of the

Next, the procedure for determining the initial purge addition term DFRADD added to the previous initial purge amount set value DFRX (n-1) in step S46 of FIG. 3 will be described with reference to FIG.

In step S61, the engine speed NE
Is higher than a predetermined speed NFRADD, and N
When E ≦ NFRADD is satisfied, it is determined whether or not the vehicle speed V is higher than a predetermined vehicle speed VFRADD (step S6).
2). And NE> NFRADD or V> VFRAD
If D is satisfied, the process immediately proceeds to step S64, where N
When E ≦ NFRADD and V ≦ VFRADD are satisfied when the vehicle starts, a start time tmFRADD is set to a predetermined time and started (step S6).
3) and proceeds to step S64.

In step S64, the timer tmFRAD is set.
It is determined whether or not the value of D is "0". At the time of starting the vehicle, initially tmFRADD> 0, so step S65.
And the counter C set in step S33 of FIG.
It is determined whether or not the value of FRADD is "0". Initially, CFRADD> 0, so steps S67 and S6 are performed.
In step 8, the counter CFRADD is decremented by "1", the initial purge addition term DFRADD (see FIG. 3, step S46) is set to "0", and this processing ends.

After that, in step S65, CFRADD = 0
Then, a predetermined value is set in the counter CFRADD (step S69), the addition term DFRADD is set to a relatively small predetermined value DFRADD0 (step S70), and the present process is terminated.

At step S69, the counter CFRADD
Is reset, the process proceeds from step S65 to steps S67 and S68 next time, and the purge duty amount DFR is fixed, but when CFRADD = 0, step S6 is performed.
9, the purge duty amount DFR further increases by the addition term DFRADD (= DFRADD0).

The processing of steps S65 and S67 to S70 is repeated until the timer tmFRADD = 0, the purge duty amount DFR is gradually increased with a relatively small width, and when the timer tmFRADD = 0, step S66.
And add the addition term DFRADD to a relatively large predetermined value DF
RADD1 (> DFRADD0) is set to gradually increase the purge duty amount DFR with a relatively large width.

In addition, high engine speed (NE> VFRAD
D) or the high vehicle speed (V> VFRADD), the process immediately proceeds to step S64, and the purge duty amount is gradually increased with a relatively large width from the beginning.

The transition of the purge duty amount DFR calculated as described above will be described with reference to FIG.

Looking at the movement (solid line) of the purge duty amount DFR at the time of starting, the purge duty map value DFRM
Even if AP (two-dot chain line) is calculated, step S3 in FIG.
The addition term DFRADD is 0 until the counter CFRADD set in 3 becomes "0" (step S68),
The purge duty amount DFR is fixed to 0 and purging is not performed. When the counter CFRADD reaches 0, the increment value DFRADD0 is increased by the addition amount DFRADD0 (step 70). Gradually increase.

That is, at the time of starting, a predetermined period (CFRA
DD) By setting the purge duty amount DFR to 0, the intake air amount is small immediately after the purge is restarted and the purge is restarted, and the air-fuel ratio immediately after starting becomes overrich due to the influence of the concentrated fuel vapor concentration accumulated in the canister, resulting in a decrease in output torque. To prevent the startability from deteriorating.

After the lapse of a predetermined period, the purge duty amount DFR corresponding to the operating state of the engine is gradually increased to prevent a sudden change in the supply air-fuel ratio at the start.

When the purge is restarted at the time of a shift change or the like other than when the vehicle is starting, the purge duty amount DFR is stepwise with the addition amount DFRADD1 (step S66), which is relatively large by one step, as indicated by the broken line. However, it increases with a large inclination and reaches the target purge duty calculation value (two-dot chain line).

Next, referring to FIG. 5, the evaporation correction coefficient KE
The VAP calculation process will be described.

In step S81, it is determined whether or not the engine 1 is in the starting mode. In the starting mode, the value of the evaporation correction coefficient KEVAP is set to 1.0 (step S8
2), set the learning value KEVAPREF of the evaporation correction coefficient to 1.
This is set to 0 (step S83), and this processing ends.

If it is not the starting mode, it is judged whether or not the purge permission flag F-FR is "1" this time (step S8).
4) When F-FR = 0 and purge is not permitted, both flags F-KO2EVH and F-KO2EVL used in the process of FIG. 6 described later are set to “0” (step S8).
5) It is determined whether or not the previous purge permission flag F-FR was "1" (step S86).

If the purge is not permitted in the previous time, immediately, and if the purge is permitted in the previous time, the learning value KEVAPR
EF is set to the previous value KEVAP (n-1) of the evaporation correction coefficient (step S87), and the process proceeds to step S88.
In step S88, the purge on transition timer tmEVD
A predetermined time (for example, 0.5 seconds) is set in EC and started, and it is determined whether or not the value of the purge-off transition timer tmEVADD is 0 (step S89).

The purge-on transition timer tmEVDEC is
The value is determined in step S98 which will be described later, and the purge is not permitted (F-FR = 0) to permitted (F-FR).
Measure the predetermined time immediately after the transition to (1). The purge-off transition timer tmEVADD is set in step S93 or S94, which will be described later, and measures the predetermined time immediately after the transition from purge permission (F-FR = 1) to non-permission (F-FR = 0). To do.

Immediately after the shift from purge permission to non-permission, if tmEVADD> 0, the process proceeds from step S89 to S90, the evaporation correction coefficient KEVAP is held at the previous value, and the process proceeds to step S103. After that tmEVAD
When D = 0, the current evaporation correction coefficient KEVAP (n) is calculated by the following equation (5) (step S91), and the process proceeds to step S103.

KEVAP (n) = KEVAP (n-1) + DKEVADD (5) Here, DKEVADD is a predetermined addition term, whereby the evaporation correction coefficient KEVAP is gradually increased.

That is, when the timer tmEVADD is set and the purge is not permitted, the timer tmEVADD is set.
Until D becomes 0, the evaporation correction coefficient KEVAP is fixed at the previous value (step S90), the correction of the fuel injection amount due to the influence of the purge is continuously performed even after the purge cut, and the timer tmEVADD becomes 0. After that, the evaporation correction coefficient KEVAP is increased stepwise (step S9
1), KEVAP = 1, which is not affected by purging, is reached.

This is the purge passage 23 immediately after the purge cut.
This is due to the influence of the evaporated fuel remaining inside. That is, immediately after the purge cut, the air-fuel ratio does not immediately become lean due to the influence of the evaporated fuel remaining in the purge passage 23,
As a result, the evaporation correction coefficient KEVAP, which changes according to the output signal of the O ₂ sensor, does not change. Therefore, the coefficient is set to a fixed value to prevent overcorrection by the coefficient. Thereafter, the coefficient is gradually increased to prevent a sudden change in the air-fuel ratio and to correct the fuel injection amount according to the purge concentration.

On the other hand, if F-FR = 1 at this time and the purge is permitted in step S84, step S92 is performed.
And the evaporation correction coefficient KEVAP is set to the predetermined value KEVAD.
It is determined whether or not it is larger than D. As a result, KEVAP ≦
If KEVADD and the amount of evaporated fuel to be purged is large and the influence of purging is large, the process proceeds to step S93.
The purge off transition timer tmEVADD is set to a predetermined time (for example, 1.0 second) and started, and the process proceeds to step S95. When KEVAP> KEVADD and the influence of the purge is small, the process proceeds to step S94, the timer tmEVADD is set to 0, and the process proceeds to step S95. Therefore, when the influence of the purge is small, step S91 is immediately executed without passing through step S90.

That is, when the influence of the purge is small, the timer tmEVADD is set to 0, and the evaporation correction coefficient KEVAP is gradually increased immediately after the purge cut, whereby the air-fuel ratio followability can be improved.

Then, in step S95, it is determined whether or not the learning value KEVAPREF of the evaporation correction coefficient KEVAP is smaller than 1.0, and if KEVAPREF = 1.0, the process proceeds to step S96 to be described later.
AP is calculated. On the other hand, when KEVAPREF <1.0 is established, the process proceeds to step S97 and the initial flag FF
It is determined whether RADD (FIG. 3, step S38) is "1". If F-FRADD = 0 and the initial purge state is not set, the process immediately proceeds to step S96, and F-FRADD =
If it is 1 and is in the initial purge state, the routine proceeds to step 98.

In step S98, it is determined whether or not the value of the purge-on transition timer tmEVDEC is 0. Initially, tmEVDEC> 0, so the routine proceeds to step S99, where the evaporation correction coefficient KEVAP is held at the previous value and tmEV.
When DEC = 0, the process proceeds to step S100, and the current evaporation correction coefficient KEVAP is calculated by the following equation (6).

KEVAP (n) = KEVAP (n-1) -DKEVDEC (6) Here, DKEVDEC is a predetermined subtraction term, whereby the value of the evaporation correction coefficient KEVAP gradually decreases.

From step S99 or S100, the process proceeds to step S101, where the evaporation correction coefficient KEVAP for this time.
It is determined whether or not (n) is larger than the learning value KEVAPREF. If KEVAP (n)> KEVAPREF is satisfied, the process directly proceeds to step S103. On the other hand, KEV
When AP (n) ≦ KEVAPREF is established, the process proceeds to step S102, and the current evaporation correction coefficient KEVAP
Set (n) to the learning value KEVAPREF and step 1
Go to 03.

That is, immediately after shifting from the purge non-permission to the permission, the evaporation correction coefficient KEVAP (n-) is changed until the value of the purge-on transition timer tmEVDEC set in step S88 becomes 0.
1) (initially 1.0) is maintained (step S9)
9), the fuel injection amount is not corrected. And timer t
After the value of mEVDEC becomes 0, the evaporation correction coefficient KE
The learning value KE that stores the value of the evaporation correction coefficient KEVAP in the previous purge state by gradually reducing the VAP (step S100) to gradually compensate for the influence of the purge.
The value of the evaporation correction coefficient KEVAP is decreased until VAPREF is reached, and the fuel injection amount corresponding to the purge amount is corrected only after an appropriate time has elapsed.

Immediately after the purge is restarted, there is no evaporated fuel in the purge passage 23, and the effect of the purge appears only when the evaporated fuel reaches the intake pipe 2 through the purge pipe 23 by opening the purge control valve 24. , This time delay is taken into consideration.

That is, this time delay (tmEVDE
Even if the purge amount is corrected during the period C), the air-fuel ratio does not follow and does not change to the rich side, and as a result, the evaporation correction coefficient KEVAP that changes according to the output signal of the O ₂ sensor does not change. Is set to prevent overcorrection by the coefficient. After that, the coefficient is gradually subtracted to prevent a sudden change in the air-fuel ratio and to correct the fuel injection amount according to the purge concentration.

The timers tmEVADD and tmEV
The predetermined time period measured by the DEC is preferably set according to the operating state of the engine 1, for example, the engine speed NE and the intake pipe absolute pressure PBA. For example, as the engine speed NE increases, the predetermined time is shortened, so that the air-fuel ratio followability can be further improved.

The transition of the evaporation correction coefficient KEVAP calculated by the processing of FIG. 5 is shown in FIGS. 11 and 12 in comparison with the purge duty amount DFR.

FIG. 11 shows the transition when the purge permission is changed to the purge non-permission.
When the VAP value is smaller than the predetermined value KEVADD and the influence of the purge is large (solid line), the purge off transition timer tmEV
A predetermined time is set in ADD (step S93), and when the purge is not permitted, the KEVAP value is fixed until the value of the timer tmEVADD becomes 0 (step S93).
90).

Therefore, since the evaporated fuel having a high concentration remaining in the purge passage 23 affects the fuel supply amount immediately after the purge control valve is closed, the evaporation correction coefficient KEVAP is fixed to the value immediately after the end of the purge and correction is performed for a predetermined time. To stabilize the air-fuel ratio control during purge cut.

After the elapse of a predetermined time after the influence of the residual evaporated fuel has disappeared, the evaporation correction coefficient KEVAP is gradually increased (step S91) to secure stable followability of the air-fuel ratio control.

When the value of the evaporation correction coefficient KEVAP is larger than the predetermined value KEVADD and the influence of the purge is small (broken line), the set time of the purge-off transition timer tmEVADD is set to 0 (step S94), and when the purge is not permitted, the evaporation is not permitted. The correction coefficient KEVAP is not fixed but is gradually increased (step S91) to improve the followability of the air-fuel ratio control.

FIG. 12 shows the transition when the purge is not permitted and the purge is permitted. When the purge is not permitted, the purge-on transition timer tmEVDEC is set to a predetermined time (step S88), and when the purge is permitted,
The value of the evaporation correction coefficient KEVAP is fixed to the previous value KEVAP (n-1) until the value of the timer tmEVDEC becomes 0 (step S99), and the correction of the fuel injection amount by the purge is not performed for a predetermined time after the restart of the purge.

The fuel injection amount is not corrected by the purge for a predetermined time (tmEVDEC period) until the purge control valve 24 opens and the evaporated fuel reaches the intake pipe 2 through the purge passage 23 and the influence of the purge starts to appear. Stable air-fuel ratio control can be performed when purging is restarted.

Since the influence of the purge appears after the elapse of a predetermined time, the evaporation correction coefficient KEVAP is set to the previous value KEVAP (n
-1) is gradually reduced (step S100), and is also reduced to the KEVAP value (KEVAPREF) in the previous purge state to secure stable followability of the air-fuel ratio control.

Next, the calculation processing of the evaporation correction coefficient KEVAP in step S96 of FIG. 5 will be described with reference to FIG.

First, in step S111, the air-fuel ratio correction coefficient KO2 set in accordance with the oxygen concentration in the exhaust gas,
The upper threshold value KO2EVH and the lower threshold value KO2EVL in consideration of the influence of purging are calculated by the following equations (7) and (8).

KO2EVH = KREF + DKO2EVH (7) KO2EVL = KREF-DKO2EVL (8) where KREF is the learning value of the air-fuel ratio correction coefficient, DKO2
EVH is a predetermined addition term, and DKO2EVL is a predetermined subtraction term. The learning value KREF is calculated based on the value of the air-fuel ratio correction coefficient KO2 during the air-fuel ratio feedback control, and has various values according to the operating state. However, the evaporation correction coefficient KEVAP is the predetermined value KEV.
When it is smaller than APL, it is determined that the influence of the purge is large, and the learning value KREF is prohibited from being calculated.

In the following step S112, the air-fuel ratio correction coefficient K
It is determined whether the value of O2 is larger than the learning value KREF,
When the value of the air-fuel ratio correction coefficient KO2 is large, it is further determined whether or not the value of the air-fuel ratio correction coefficient KO2 is larger than the upper threshold value KO2EVH (step S113). As a result, when the value of the air-fuel ratio correction coefficient KO2 is larger than the upper threshold value KO2EVH, the upper flag F-KO2EVH is set to "1".
Then, the process proceeds to step S119, and the air-fuel ratio correction coefficient KO2
Is smaller than the upper threshold value KO2EVH, step S
Proceed to 117.

When the value of the air-fuel ratio correction coefficient KO2 is smaller than the learning value KREF in step S112, the process proceeds to step S115, and it is further determined whether or not it is larger than the lower threshold value KO2EVL. When the value of the air-fuel ratio correction coefficient KO2 is less than or equal to the lower threshold value KO2EVL, the lower flag F-
Set KO2EVL to "1" and proceed to step S119,
If the value of the air-fuel ratio correction coefficient KO2 is larger than the lower threshold value KO2EVL, the process proceeds to step S117.

The value of the air-fuel ratio correction coefficient KO2 is the upper threshold value KO.
When it is between 2EVH and the lower threshold value KO2EVL, the routine proceeds to step S117, and it is determined whether or not the value of the current air-fuel ratio correction coefficient KO2 is inverted with respect to the learned value KREF (whether the magnitude relationship between them has been inverted). If it is reversed, the process proceeds to step S118, and the upper flag F-KO2EVH and the lower flag F-KO2EVL are both set to "0" and step S118.
119. If not reversed, step S117.
Then, the process directly proceeds from step S119 to the flag F-KO2E.
VH and F-KO2EVL are not changed.

Therefore, once the flag F-KO2EVH or F-KO2EVL becomes "1", the air-fuel ratio correction coefficient K
"0" unless the value of O2 is inverted with respect to the learning value KREF
It does not become.

At steps S119 and S120, the lower flag F-KO2EVL and the upper flag F-KO2EVH are set.
Are both "1", and if both are "0", the process proceeds to step S121, and the current evaporation correction coefficient KEVAP.
Let (n) hold the previous value.

That is, if the value of the air-fuel ratio correction coefficient KO2 is within the upper and lower threshold values after being inverted with respect to the learned value KREF, the value of the evaporation correction coefficient KEVAP (n) is fixed to the previous value.

Then, the value of the air-fuel ratio correction coefficient KO2 falls below the lower threshold value KO2EVL, and the lower flag F-KO2EVL.
Becomes "1", the steps S119 to S12
The routine proceeds to 2 and it is determined whether the purge duty amount DFR is 0 or not. When DFR = 0, the process proceeds to step S121, and the evaporation correction coefficient KEVAP is held at the previous value.
If R> 0 and purging is being executed, step S
In step 123, it is determined whether or not the current air-fuel ratio correction coefficient KO2 (n) is smaller than the previous air-fuel ratio correction coefficient KO2 (n-1). When KO2 (n) ≦ KO2 (n−1) is satisfied, that is, when the value of the air-fuel ratio correction coefficient KO2 decreases and changes in the direction away from the learning value KREF, the process proceeds to step S124, and the previous evaporation correction coefficient KEVAP
The predetermined subtraction term DKEVAPM is subtracted from (n-1) to obtain the current evaporation correction coefficient KEVAP (n), and the correction by the purge is strengthened.

However, when KO2 (n)> KO2 (n-1) is satisfied and the value of the air-fuel ratio correction coefficient KO2 is changing toward the learning value KREF, the process proceeds from step S123 to step S121, and the evaporation correction is performed. The coefficient KEVAP is held at the previous value.

That is, when the value of the air-fuel ratio correction coefficient KO2 is changing toward the learning value KREF (recovery direction), the fuel injection amount is not corrected more than necessary and the air-fuel ratio control is stabilized. I am trying to

Similarly, when the upper flag F-KO2EVH becomes "1", steps S120 to S125.
Then, it is determined whether the purge duty amount DFR is 0 or not. When DFR = 0, the process proceeds to step S121, and DF
When R> 0, the routine proceeds to step S126, where the current air-fuel ratio correction coefficient KO2 (n) is the previous air-fuel ratio correction coefficient KO2.
It is determined whether or not it is larger than (n-1). KO2> KO
When 2 (n-1) is satisfied, that is, when the value of the air-fuel ratio correction coefficient KO2 increases and changes in the direction away from the learning value KREF, the process proceeds to step S127 and the previous value K
The addition term DKEVAPP is added to the EVAP (n-1) value to obtain the current value KEVAP (n) to enhance the correction by the purge. On the other hand, when the value of the air-fuel ratio correction coefficient KO2 is decreasing and is changing toward the learning value KREF, the process proceeds to step S121, and the evaporation correction coefficient KEVAP is held at the previous value to prevent the unnecessary correction. .

FIG. 13 shows an example of the transition of the evaporation correction coefficient KEVAP with respect to the change of the air-fuel ratio correction coefficient KO2. The value of the air-fuel ratio correction coefficient KO2 decreases when the purge disapproval is changed to the purge enable. If the value of the air-fuel ratio correction coefficient KO2 falls below the lower threshold value KO2EVL, the lower flag F-KO2EVL becomes "1" (step S116), and the value of the evaporation correction coefficient KEVAP gradually decreases (step S116). S124).

However, when the value of the air-fuel ratio correction coefficient KO2 increases toward the learning value KREF, the value of the evaporation correction coefficient KEVAP is fixed (step S121) and does not change.

Further, when the value of the air-fuel ratio correction coefficient KO2 increases and exceeds the learning value KREF and is reversed, the lower flag F-KO.
2EVL becomes "0" (step S118), the air-fuel ratio correction coefficient KO2 further increases, and the upper threshold value KO2E is increased.
When it exceeds VH, the upper flag F-KO2EVH becomes "1" (step S114), and the evaporation correction coefficient KEVAP.
The value of is gradually increased this time (step 127).

When the upper flag F-KO2EVH is "1", the value of the air-fuel ratio correction coefficient KO2 decreases and the learned value K
Evaporative correction coefficient KEVAP when heading toward REF
The value of is fixed (step S121) and has not changed.

As described above, when the value of the air-fuel ratio correction coefficient KO2 is in the recovery state toward the learning value KREF, the correction by the purge is not performed more than necessary to stabilize the air-fuel ratio control.

That is, during the purge execution, the air-fuel ratio correction coefficient KO
When 2 is decreasing, the purge concentration is high and the air-fuel ratio is rich, so the evaporation correction coefficient KEVA
By reducing P, overriching of the air-fuel ratio is prevented.

On the other hand, during the purge execution, the air-fuel ratio correction coefficient KO
When 2 shifts to the increasing direction, the purge concentration is low and the air-fuel ratio does not become overrich. Therefore, the evaporation correction coefficient KEVAP is increased to improve the control response of the air-fuel ratio. In step S103 of FIG. 5, the upper / lower limit value setting process of the evaporation correction coefficient KEVAP is performed, and the process will be described with reference to FIG.

It is determined whether or not the current evaporation correction coefficient KEVAP (n) is larger than 1.0 (step 131),
If KEVAP (n)> 1.0, the process proceeds to step S133 to set the evaporation correction coefficient KEVAP (n) to 1.0 (upper limit value), and if KEVAP (n) ≦ 1.0, the evaporation correction coefficient further KEVAP ( n) Value is the lower limit value KEVLMT
It is determined whether it is smaller than L (step S132), and K
If EVAP (n) <KEVLMTL, step S
In step 134, the evaporation correction coefficient KEVAP (n) value is set as the lower limit value KEVLMTL, and the evaporation correction coefficient KEVAP is set.
The value of is within the range from the lower limit value KEVLMTL to the upper limit value 1.0.

In this embodiment, the evaporation correction coefficient KE
Although VAP is obtained according to the KO2 value, a concentration sensor that directly detects the concentration of the evaporated fuel in the purge passage may be provided, and the fuel injection amount may be corrected according to the output thereof.

[0137]

As described above in detail, according to the present invention, the purge concentration correction coefficient (KEVAP) is updated based on the changing direction of the air-fuel ratio correction coefficient (KO2) when the purge control valve is operated. The responsiveness of the fuel injection amount can be controlled well in accordance with the change in the air-fuel ratio due to, and the deviation of the air-fuel ratio due to the purge can be minimized.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an internal combustion engine and a fuel supply control device therefor according to an embodiment of the present invention.

FIG. 2 is a flowchart of a purge control valve opening / closing control routine in the same apparatus.

FIG. 3 is a flowchart showing a purge duty amount DFR determination routine.

FIG. 4 DFRA added to purge duty amount DFR
It is a flowchart which shows the determination routine of DD.

FIG. 5 is a flowchart showing a main routine for determining an evaporation correction coefficient KEVAP.

FIG. 6 is a flowchart showing an evaporation correction coefficient KEVAP calculation subroutine.

FIG. 7 is a flowchart showing a subroutine for determining upper and lower limit values of the evaporation correction coefficient KEVAP.

FIG. 8 is a diagram showing an EGR circulation correction map.

FIG. 9 is a purge correction coefficient KFLAST, an evaporation correction coefficient KEVAP, and a purge duty amount DFR for starting.
It is a figure which shows the change of.

FIG. 10 is a diagram showing changes in the purge duty amount DFR when purging is permitted.

11] An evaporation correction coefficient KEVAP and a purge duty amount DF when shifting from purge permission to purge cut
It is a figure which shows the change of R.

FIG. 12 is an evaporation correction coefficient KEVAP and a purge duty amount DF when shifting from purge cut to purge permission.
It is a figure which shows the change of R.

FIG. 13 is a diagram showing an example of changes in the evaporation correction coefficient KEVAP with respect to changes in the air-fuel ratio feedback correction coefficient KO2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine 2 intake pipe 6 ECU 7 fuel injection valve 9 fuel tank 11 PBA sensor 12 TA sensor 13 TW sensor 14 NE sensor 15 exhaust pipe 16 O ₂ sensor 21 canister 23 purge pipe 24 purge control valve 30 exhaust gas recirculation path 31 EGR valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Sakana 1-4-1 Chuo, Wako-shi, Saitama Stock Research Institute Honda Technical Research Institute

Claims (4)

[Claims] 1. A canister for adsorbing fuel vapor generated from a fuel tank, a purge passage provided between the canister and an intake system of an internal combustion engine for purging the fuel vapor into the intake system, and the purge passage. A purge control valve for controlling the flow rate of the fuel vapor supplied to the intake system via
A fuel injection valve for controlling an injection amount of fuel supplied to the engine, an operating state detecting means for detecting an operating state of the engine, and an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine. An air-fuel ratio correction coefficient calculating means for calculating an air-fuel ratio correction coefficient based on the detected air-fuel ratio, and a concentration of fuel vapor supplied to the intake system via the purge passage based on the air-fuel ratio correction coefficient. Purge concentration correction coefficient setting means for setting a purge concentration correction coefficient according to the purge concentration, purge flow control means for controlling the purge control valve according to the detected engine operating state, the air-fuel ratio correction coefficient and the purge concentration correction coefficient And a fuel injection amount control means for controlling the fuel injection valve according to the above, the purge concentration correction coefficient setting means sets the air-fuel ratio when the purge control valve operates. A control device for an internal combustion engine, wherein the purge concentration correction coefficient is updated based on a changing direction of the ratio correction coefficient. 2. The internal combustion engine according to claim 1, wherein the purge concentration correction coefficient setting means reduces the purge concentration correction coefficient when the air-fuel ratio correction coefficient is decreasing. Control device. 3. The internal combustion engine according to claim 1, wherein the purge concentration correction coefficient setting means increases the purge concentration correction coefficient when the air-fuel ratio correction coefficient is increasing. Control device. 4. The control device for an internal combustion engine according to claim 1, wherein the purge concentration correction coefficient setting means updates the purge concentration correction coefficient when the air-fuel ratio correction coefficient is within a predetermined range. .