JPH0988677A - Evaporated fuel processing device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly correct the air-fuel ratio against the change of operating conditions by learning the deviation of the air-fuel ratio feedback correction quantity against the purge rate, and controlling the correction of the air-fuel ratio based on the learned value and the purge rate. SOLUTION: A purge valve passage area and a purge cut valve area are obtained (B1, B2). Since a purge valve and a purge cut valve are provided in series, the smaller area is selected as the purge passage area AP, and the actual purge rate PRATE is calculated from the purge passage area AP and total passage area AA (B3-4). The average of the air-fuel ratio feedback correction quantity α during the purge and the average of the air-fuel ratio feedback correction quantity α during the purge cut are obtained (B5-6). The deviation eα of the air-fuel ratio feedback correction quantity αis calculated, and the new gain G is calculated from the deviation eα and the actual purge rate PRATE (B7-8). The learned value of the gain G (gain leaned value) is allocated to a learning table for the region (purge gas flow).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion system which adsorbs vaporized fuel generated in a fuel supply system of an engine such as a fuel tank and then purges the vaporized fuel together with air into an intake system such as an intake passage. The present invention relates to an evaporated fuel processing device for an engine.

[0002]

2. Description of the Related Art Conventionally, in order to process evaporated fuel generated in a fuel supply system of an engine such as a fuel tank, the evaporated fuel is discharged into an intake passage and burned. In this case, the evaporated fuel is discharged to the intake passage by the amount determined by the negative pressure applied to the inflow port at the end of the evaporated fuel discharge line regardless of the amount of the evaporated fuel generated.

Therefore, the air-fuel ratio set in accordance with the operating state will fluctuate as the concentration of the evaporated fuel changes.
The combustion state may be unstable. In consideration of such problems, it is possible to supply the evaporated fuel under a predetermined operating condition.
The deviation of the air-fuel ratio feedback control signal with respect to nothing is detected, and based on this detected deviation, the change that affects the air-fuel ratio of the evaporated fuel is detected, and based on this deviation, it corresponds to the time when the evaporated fuel is supplied and the time when it is not supplied. There has been proposed a technique in which the correction of the air-fuel ratio is controlled (Japanese Patent Laid-Open No. 63-4163).
No. 2).

Specifically, by the respective air-fuel ratio feedback correction amounts when the barge valve is opened / closed,
Specifies the deviation. Then, based on this deviation and the evaporated fuel purge (release) amount, the air-fuel ratio correction amount corresponding to each operating state of the evaporated fuel release region, that is, for example, the engine speed is the operating state defined by the load. It is calculated and stored in the storage unit. Based on this air-fuel ratio correction amount, the map data of the correction amount of the evaporated fuel release defined in advance in relation to the engine speed and the load is rewritten over the entire operating region.

[0005]

However, in such a conventional technique, the correction of the air-fuel ratio is controlled simply based on the deviation of the air-fuel ratio feedback control signal with or without the supply of the evaporated fuel. Therefore, it is not possible to cope with the case where the purge rate as the ratio of the purge gas flow rate to the intake air flow rate differs in each operating region (even if the purge valve opening is the same, the intake air flow rate controlled by the throttle valve opening changes. Change the purge rate).

Further, since the deviation of the air-fuel ratio feedback control signal is detected only under a predetermined operating condition, it is not possible to cope with the case where the purge concentration changes due to the progress of purging under other operating conditions. That is, in the configuration that controls the correction of the air-fuel ratio based on the deviation of the air-fuel ratio feedback control signal, the correction amount of the air-fuel ratio does not match the actual request when the purge rate changes or the operating conditions change, and The fluctuation of the fuel ratio will remain.

Therefore, the present invention not only controls the correction of the air-fuel ratio based on the deviation of the air-fuel ratio feedback control signal, but also learns the deviation of the air-fuel ratio feedback correction amount with respect to the purge rate, and learns this learned value and purge. It is an object to optimize the air-fuel ratio correction with respect to changes in operating conditions by controlling the correction of the air-fuel ratio from the ratio.

[0008]

Therefore, the invention according to claim 1 is, as shown in FIG. 1, an operating condition detecting means for detecting an operating condition of the engine, and an operation of the engine output from the detecting means. Evaporative fuel for an internal combustion engine equipped with means for receiving a condition signal to determine a purge ON / OFF condition and a device for opening a purge valve under the purge ON condition to introduce a purge gas from a canister into an engine intake system based on the determination result. In the processing device, the air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine, and the air-fuel ratio feedback correction amount from the output of the air-fuel ratio detection means so that the air-fuel ratio feedback correction amount falls within a predetermined range. An air-fuel ratio feedback correction amount calculating means for calculating, a purge rate calculating means for calculating a purge rate as a ratio of a purge gas flow rate to an intake air flow rate, and the air-fuel ratio variable An air-fuel ratio feedback correction amount deviation calculating means for calculating a deviation of the air-fuel ratio feedback correction amount with or without evaporative fuel purge based on the feedback correction amount; and a gain based on the deviation of the purge rate and the air-fuel ratio feedback correction amount. Gain calculation means for calculating
Gain learning value updating means for updating the learning value of the gain calculated by the gain calculating means, and shift amount calculating means for calculating the shift amount of the air-fuel ratio feedback correction amount based on the gain learning value and the purge rate. A correction means for correcting the air-fuel ratio feedback correction amount based on the shift amount; and a correction means for correcting the air-fuel ratio feedback correction amount and the operating condition under the purge ON condition based on the determination result of the purge ON / OFF condition. An internal combustion engine comprising: a fuel supply amount calculation means for calculating a fuel supply amount using a basic fuel supply amount; and a fuel supply means for supplying the fuel supply amount to an engine intake system. Evaporative fuel processor.

According to the first aspect of the present invention, not only the deviation of the air-fuel ratio feedback control signal but also the correction of the air-fuel ratio is controlled based on the gain learning value and the purge rate. When operating conditions change,
The correction amount of the air-fuel ratio matches the actual requirement, and the fluctuation of the air-fuel ratio is suppressed. According to a second aspect of the present invention, the purge amount is calculated by multiplying the learned value of the gain obtained by dividing the deviation of the air-fuel ratio feedback correction amount by the actual purge rate by the shift amount calculation means by the actual purge rate. It is configured to include a calculating unit and a unit that calculates the integrated value of the purge concentration as a shift amount by integrating the purge concentration while decreasing the purge concentration.

According to the second aspect of the present invention, the shift amount can be optimized and the correction amount of the air-fuel ratio can meet the actual demand. According to a third aspect of the present invention, the shift amount calculation means includes means for performing a weighted average process of the calculated purge concentrations to calculate a purge concentration smoothed value.

According to a fourth aspect of the present invention, the shift amount calculation means uses the calculated purge concentration value several times before in order to shorten the delay of the amount of air filled in the intake system. It was composed including. In the invention according to claim 3 and the invention according to claim 4, the generation of the rich spike at the time of purge cut and the lean spike at the time of recovery are suppressed, and the occurrence of the air-fuel ratio fluctuation at the rapid acceleration / deceleration is suppressed.

According to a fifth aspect of the present invention, the shift amount calculating means includes means for multiplying the calculated purge concentration integrated value by an air-fuel ratio feedback correction amount shift reflecting gain. As a result, overcorrection of the air-fuel ratio feedback correction amount can be prevented.

According to a sixth aspect of the present invention, the purge rate calculating means calculates from the purge passage area and the total passage area determined by the throttle valve opening. Thereby, the purge rate can be accurately obtained.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 2, the engine 1
In the first intake passage 12, the intake air amount Qa is interlocked with an air flow meter (not shown) and an accelerator pedal (not shown) that detect an intake air flow rate Qa introduced through an air cleaner (not shown).
A throttle valve 14 for controlling the above is provided, and a downstream manifold portion 15 is provided with an electromagnetic fuel injection valve 16 as a fuel supply means for each cylinder.

The fuel injection valve 16 is a micro computer.
From the control unit 17 with built-in data
The valve is driven by the loose signal to inject and supply fuel. Exhaustion
In the air passage 18, the exhaust acid
The air-fuel ratio of the intake mixture is detected by detecting the elementary concentration.
Air-fuel ratio sensor (hereinafter referred to as O ₂With sensor
19) is provided.

Further, the distributor 13 has a crank angle sensor 20 built-in, which counts a crank unit angle signal output from the crank angle sensor 20 in synchronization with the engine rotation for a certain period of time or a crank reference. The engine rotation speed Ne is detected by measuring the cycle of the angular signal. Further, a water temperature sensor 21 that detects the cooling water temperature TW is provided.

On the other hand, the evaporated fuel accumulated in the upper space of the fuel tank 26 is guided to the canister 23 through the evaporated fuel passage 22 while the engine 11 is stopped, and is temporarily held by the adsorbent 27 such as activated carbon in the canister 23. Is adsorbed on. The space above the canister 23 communicates with a purge port 12 </ b> A formed downstream of the throttle valve 14 in the intake passage 12 via a purge passage 24. The purge passage 24 is provided with a purge valve 25, which is electrically controlled by the control unit 17, and a purge cut valve 28.

The purge valve 14 is a step motor type valve for controlling the purge amount. That is, the opening and closing of the purge valve 25 is controlled so that the purge amount becomes a purge amount according to the intake air amount of the engine 1. For example, when the engine 1 has a low load and a low rotation, the intake air amount is small, so the opening degree is controlled to a small opening. Since the intake air amount is large at the time of high load and high rotation, it is controlled to a large opening.

The purge cut valve 28 is ON / O.
The FF valve is a valve for cutting purge, and is closed when the throttle valve 14 is fully closed, and is opened when the throttle valve 14 is open. In the above structure, the sensors including the air flow meter and the crank angle sensor 20 for detecting the operating state of the engine 11, the O ₂ sensor 19 for detecting the operating air-fuel ratio of the engine 11, and the fuel injection valve as the fuel supply device 16 and whether or not it is in the air-fuel ratio feedback control range based on signals from the sensors, and when it is determined that it is in this control range, the fuel injection is performed so that the actual air-fuel ratio matches the target air-fuel ratio. An air-fuel ratio feedback control system is composed of an air-fuel ratio feedback control means, which is installed in the control unit 17 by software and controls the fuel injected from the valve 16.

On the other hand, for the air-fuel ratio feedback control system, the canister 23, the purge passage 24, the purge valve 25, the purge cut valve 28, and the opening degree of the purge valve 25 are calculated based on the engine operating condition. , This is the purge valve 2
The evaporative fuel purging device is constituted by the purge control means, which is installed in the control unit 17 by software, and which commands the control unit 5 to command.

Here, the contents of control in the embodiment of the present invention will be described based on the block diagrams of FIGS. In block 1 (abbreviated as B1 in the figure; the same applies hereinafter), the purge valve flow passage area is obtained, and in block 2, the purge cut valve area is obtained. The purge valve passage area is a value obtained by referring to the purge valve passage area table TAPV from the step position monitor value EVSTPM of the step motor.

In the block 3, since the purge valve 25 and the purge cut valve 28 are provided in series, the smaller area is selected and set as the purge flow path area AP. In block 4, the actual purge rate PRATE (inlet purge rate) is calculated from the purge channel area AP and the total channel area AA (PRATE = AP / AA). On the other hand, in block 5, the average of the air-fuel ratio feedback correction amount α during purging is calculated. In this case, the weighted average value EVALPH of α is obtained, but the initial value is 100%, the weighted average is not performed during the open loop and the clamp, and the old data is retained.

Further, in block 6, the average of the air-fuel ratio feedback correction amount α during the purge cut is calculated (1
00% or weighted average). Then, in block 7, a deviation eα of the air-fuel ratio feedback correction amount α is calculated (for example, eα = 100% -EVALPH). In block 8, a new gain G is calculated from the deviation eα of the air-fuel ratio feedback correction amount α calculated in block 7 and the actual purge rate PRATE calculated in block 4 (G
= Eα / PRATE).

Here, the learning value of the gain G (gain learning value) GALPR is assigned to the learning table TGALPR of the block 10 for the region (purge gas flow rate). Then, the gain learning value GA in block 11
LPR search is performed by purging gas flow rate equivalent area QPAGE
(AP / KPB, where KPB is the differential pressure correction rate), and the above table is referred to with interpolation calculation.

In updating the gain learning value GALPR during purging, the learning table TGALPR is backed up by a battery, and when it is not backed up at the time of starting, and when the starting water temperature TWINT <TWGAC.
In the case of (gain learning value initialization water temperature), the gain learning initial value INGALP is stored in all areas. The update condition of the learning value during purging is when all of the following conditions are satisfied. (A) KDUTY (duty correction coefficient) = 1.0 (b) PRATE (actual purge rate) ≥ GPRATE (learning permission calculation purge rate) (c) EVPTR (target purge rate) ≥ GEVPTR (learning permission target purge rate) ( d) It is the first time after P is added by the air-fuel ratio feedback control while (a) to (c) are established.

Gain learning value GALPR during the purge
When the update condition is satisfied, the learning table value GTBL of the region corresponding to the latest purge gas flow rate equivalent area QPAGE determined in the block is updated in block 9 by the following formula. GTBL = GNEW × X + GTBL _n-1 (1-X) where, NEW is a newly calculated gain, GTBL _n-1 is an old learning table value, and X is a weighted average coefficient.

After updating the learning table value GTBL of the above area, the learning value of the learning table TGALPR of the other area determined in block 12 is limited to the upper and lower values calculated by the following equation (estimated learning). Update: see block 13). However, TGALPR ≦ GALMAX (maximum gain learning value). In this case, the upper limit values are C and D in FIG. 12, and are set to C (= new GTBL × ULSUI [estimated learning upper limit limiter gain]) in a region larger than the current region by QPAGE.

In addition, D is set in the area smaller than the current area by QPAGE, and is doubled by C every time the area is lowered by 1 from the current area.
It will be doubled again. The lower limit limit values are B and A in FIG. 12, and are set to A (= new GTBL × LLSUI [estimated learning lower limit limiter gain]) in a region smaller than the current region by QPAGE.

In addition, in the area larger than the current area by QPAGE, it is set to B, and 1/2 is dropped from the current area by one half of A.
Double, and halve again. In block 14, the purge concentration predicted value PFR is calculated from the PRATE calculated in block 4 and the GALPR searched in block 11 (PFR = PRATE × GAL).
PR).

In block 15, a weighted average is calculated in order to perform the smoothing process (approximates the diffusion of purge gas in the intake manifold) to the predicted purge concentration PFR. That is, the purge concentration smoothing value PFRD is calculated by the following equation. PFRD = PFR × PDMANI + PFRD _n-1 (1-
PDMANI) where PDMANI is a weighted average coefficient.

In block 18, the in-cylinder intake purge concentration PFRC is subjected to the anneal processing in block 15 and the block 17 with respect to the purge concentration predicted value PFR.
The dead time for shortening the delay of the filling air amount in the intake manifold at is given. That is, PFRC is PFRD before NDLYPR (the number of purge concentration delay cycles) (PFRC = PF).
RD _n-NDLYPR ) In this case, _n in PFRD _n-NDLYPR is about acceleration / deceleration (Tp per air-fuel ratio feedback control job)
(Basic fuel injection pulse width) rate of change (new Tp / old Tp)
Is determined according to.

Therefore, in block 16, the degree of acceleration / deceleration is determined, in block 17, PFRD _n-NDLYPR is determined, and in block, the cylinder intake purge concentration PFRC.
Is calculated. In block 19, the purge concentration change amount integrated value SPFRC is calculated by the following equation. SPFRC = SPFRC _n-1 + (PFRC-PFRC
_n-1 ) However, SPFRC _n-1 (previously obtained value) is set so as to decrease by 1 bit at every purge concentration integrated value reduction index number, and the purge concentration change amount is integrated while decreasing. To go.

Further, PFRC _n-1 is the value obtained last time. Here, the latest air-fuel ratio feedback correction amount α is
Assuming that the correction calculation value one time before is αO, it can be obtained by the following formula by I minutes, P minutes, and an evaporation α shift correction amount EALSFT described later (see block 22). α = αO ± I ± P + EALSFT In this case, if all of the following additional conditions (a) to (c) are satisfied, the α shift additional condition is satisfied, and α is corrected by the correction formula for α described above. (A) | EALSFT | ≧ ALSON where ALSON is an α shift addition determination α value. (B) The air-fuel ratio feedback control is not in open loop or clamp (except during α change). (C) Neither of the air flow meter and the throttle sensor is under NG determination in fail-safe control.

When the above-mentioned additional condition is determined (see block 21), and when the α-shift additional condition is satisfied, and when the conditions (b) and (c) in the additional condition are not satisfied, the purge after calculating EALSFT is performed. Concentration change integrated value SPF
Set RC = 0 to prepare for the next change in the purge rate. The above-mentioned evaporation α shift correction amount EALSFT is obtained by the following equation (see block 20).

EALSFT = −SPFRC × GALSFT (±) where GALSFT is an α shift reflection gain. still,
The maximum value of | EALSFT | is limited to EALMAX (α shift correction amount upper limit value). When the above additional condition is not satisfied, EALSFT = 0.

Then, in block 23, the upper and lower limits of the air-fuel ratio feedback correction amount α are limited, and the fuel injection pulse width Ti
Leads to the calculation of. Next, the operation based on this configuration will be described. 5 and 6 are flowcharts for explaining the air-fuel ratio feedback control job executed once per engine revolution.

In this flowchart, step 1
(In the figure, abbreviated as S1. The same applies hereinafter), it is determined whether or not the air-fuel ratio feedback control (F / B) condition is satisfied. If it is not the air-fuel ratio feedback control condition, the routine proceeds to step 2, where the air-fuel ratio feedback correction amount α is 1
The previous correction calculation value αO is changed toward 100%, the process proceeds to step 3, and if αO is being changed, the changing flag is set and the process proceeds to step 4.

On the other hand, if it is the air-fuel ratio feedback control condition, the routine proceeds to step 5, where it is judged whether it is the clamp condition of the air-fuel ratio feedback control, and if it is the clamp condition, the routine proceeds to step 2 and thereafter. If it is not the clamp condition, the process proceeds to step 6 and the O ₂ sensor output O ₂ is compared with the slice level S / L. If O ₂ <S / L, it is judged in step 7 that O ₂ ≧ S / L. For example, go to step 8 respectively.

In step 7, it is judged whether or not the O ₂ sensor output O ₂ is the same as the previous value, and if it is changed, in step 9, the correction before the air-fuel ratio feedback correction amount α is performed. The calculated value αO is obtained by adding P to the previous value αO _n-1 (αO = αO _n-1 + P), and the process proceeds to the learning value update routine in step 10, and the α shift amount calculation routine in step 4 is executed. move on.

The learning value update routine and the α shift amount calculation routine will be described later. If it is determined in step 7 that the O ₂ sensor output O ₂ is the same as the previous value, then in step 11, the correction calculation value αO one time before the air-fuel ratio feedback correction amount α is set to the previous value. αO
obtained by adding the I component to _{n-1 (αO = αO n} -1 + I), the process proceeds to α shift amount calculation routine of step 4.

Also in step 8, it is judged whether or not the O ₂ sensor output O ₂ is the same as the previous value, and if it is changed, in step 12, the correction before the air-fuel ratio feedback correction amount α is performed once. Calculated value αO from the previous value αO _n-1 to P
It is obtained by subtracting the amount (αO = αO _{n- 1} −P), and the process proceeds to the learning value updating routine of step 13 and proceeds to the α shift amount calculating routine of step 4.

When it is determined in step 8 that the O ₂ sensor output O ₂ is the same as the previous value, in step 14,
The correction calculation value α one time before the air-fuel ratio feedback correction amount α
O is also obtained by subtracting I from the previous value αO _n-1 (α
O = αO _n-1 −I), and proceed to the α shift amount calculation routine in step 4. The subsequent step 15 and subsequent steps are steps related to the α shift determination, and in step 15, it is determined whether or not the air-fuel ratio feedback control (F / B) condition is satisfied.

If it is not the air-fuel ratio feedback control condition, the routine proceeds to step 16. If it is the air-fuel ratio feedback control condition, the routine proceeds to step 17, where it is judged whether it is the clamp condition of the air-fuel ratio feedback control. If it is not the clamp condition, the routine proceeds to step 18, and if it is the clamp condition, the routine proceeds to step 19. move on. In step 19, αO
Is being changed, that is, whether the αO changing flag is set or not. It is determined that the αO changing flag is set and αO is not 100%. Then, the process proceeds to step 20, and if it is determined that the αO changing flag is not set and αO is 100%, the process proceeds to step 16.

In step 20, the maximum α shift amount (1
00-αO)% is set, and the process proceeds to step 18. In step 18, failsafe control is performed to determine whether the air flow meter and the throttle sensor are OK,
If OK, the process proceeds to step 21, and if NG, the process proceeds to step 16.

At step 21, | EALSFT | ≧ ALSON as an α shift addition condition is judged (however,
EALSFT = -SPFRC * GALSFT). ｜ EA
It is determined that LSFT | ≧ ALSON, and the evaporation α shift correction amount EALSFT is the α shift addition determination α value ALSON.
When the above is reached, the routine proceeds to step 22, where the evaporation α shift correction amount EALSFT is calculated. However, | EALSF
The maximum value of T | is EALMAX (α shift correction amount upper limit value)
Is limited to

In step 23, the upper limit of the α shift amount is set to 1
The value is limited to 00%, and in step 24, the purge concentration change amount integrated value SPFRC after EALSFT calculation is set to 0, and the process proceeds to step 26 in preparation for the next change in the purge rate. On the other hand, in step 16 after step 15 and step 18, E
Purge concentration change amount integrated value SPFRC = after ALSFT calculation
In preparation for the next change in the purge rate, 0 is set in step 25, and then the evaporation α shift correction amount EALSFT is reset to 0, and the process proceeds to step 26.

At step 26, α shift correction is executed. That is, the latest air-fuel ratio feedback correction amount α
Is obtained by adding the evaporation α shift correction amount EALSFT to the correction calculation value αO (= αO _n-1 ± I ± P) obtained one time before (α
= ΑO + EALSFT). In step 27, the deviation eα of the air-fuel ratio feedback correction amount α is calculated (e
α = 100% −EVALPH) weighted average value E of α
Ask for VALPH.

Next, the learning value update routine in steps 10 and 13 of the flowcharts of FIGS. 5 and 6 will be described with reference to the flowchart of FIG. In step 31, it is determined whether or not the update of the learning value is the first after the start, and if it is not the first, the process proceeds to step 32, and if it is the first, the process proceeds to step 33.

In step 33, the learning table TGAL
The PR determines whether or not the battery is backed up. If the battery is backed up, the process proceeds to step 34. If not, the process proceeds to step 35. Step 3
In 4, the start-up water temperature TWINT is compared with the gain learning value initialization water temperature TWGAC. If TWINT <TWGAC, the process proceeds to step 35, and if TWINT ≧ TWGAC, the process proceeds to step 32.

In step 35, the gain learning initial value INGALP is stored in all areas. Step 3
In 2, step 36 and step 37, the update condition of the learning value during purging is determined. That is, in step 32, it is determined whether KDUTY (duty correction coefficient) is 1.0, and in step 36, PRATE
(Actual purge rate) is compared with GPRATE (learning permission calculation purge rate). In step 37, EVPTR (target purge rate) is compared with GEVPTR (learning permission target purge rate), and KDUTY (duty correction coefficient) = 1.
0, PRATE (actual purge rate) ≧ GPRATE (learning permission calculation purge rate), EVPTR (target purge rate) ≧ GE
When all VPTR (learning permission target purge rate) is satisfied,
It is determined that the update condition of the gain learning value GALPR during purging is satisfied, and the process proceeds to step 38. If any of the above conditions is not satisfied, the learning value updating condition is not satisfied and the flow is ended.

In step 38, the deviation eα (= 100% -EVALPH) of the air-fuel ratio feedback correction amount α,
A new gain GNEW is calculated from the actual purge rate PRATE (GNEW = eα / PRATE). Where the gain G
The learning value (gain learning value) GALPR is assigned to the learning table TGALPR for the region (purge gas flow rate), and in step 39, the gain learning value GALPR.
Search for PR. That is, the area equivalent to the purge gas flow rate QP
According to AGE (AP / KPB, where KPB is a differential pressure correction rate), the gain learning value GALPR is referred by referring to the table with interpolation calculation.

Then, in step 40, as shown in FIGS.
As has been clarified in the explanation of the block diagram of the above, the learning table value GTBL of the region corresponding to the latest purge gas flow rate equivalent area QPAGE is updated [GTBL = GNEW ×
X + GTBL _n-1 (1-X)] After updating the learning table value GTBL of the above area, in steps 41 and 42, the learning values of the learning table TGALPR in other areas are limited to upper and lower values.

Regarding the upper and lower limits of the learning value,
This is as described in the description of the block diagrams of FIGS. 3 and 4. Next, the shift amount calculation routine in step 4 of the flowcharts of FIGS. 5 and 6 will be described based on the flowchart of FIG. In step 51, delay processing of the purge cut valve is executed, and step 52
Then, it is determined whether or not the purge cut is being performed by the purge cut valve.

If the purge cut is not in progress, step 53.
Next, select the smaller flow passage area from the purge valve flow passage area (the value obtained by referring to the table from the step position monitor value EVSTPM of the step motor) and the purge cut valve flow passage area, and set this as the purge flow passage. The area is AP. If the purge is being cut, the routine proceeds to step 54, where the purge flow path area AP is set to zero.

In step 55, the actual purge rate PRAT is calculated from the purge channel area AP and the total channel area AA.
Calculate E (inlet purge rate) (PRATE = AP / A
A). In the next step 56, the purge gas flow rate equivalent area QPAGE is calculated (= AP / KPB
KPB is the differential pressure correction rate). It is the value that is compared.

In step 57, the learning table T
Area equivalent to purge gas flow rate QPA with reference to GALPR
The gain learning value GALPR is searched based on GE. In step 58, P calculated in step 55
RATE and GALP retrieved in step 57
The purge concentration predicted value PFR is calculated from R (PFR =
(PRATE × GALPR).

In step 59, a weighted average is calculated in order to perform a smoothing process (approximates the diffusion of purge gas in the intake manifold) to the predicted purge concentration PFR. That is, the purge concentration smoothing value PFRD is calculated by the following equation. PFRD = PFR × PDMANI + PFRD _n-1 (1-
PDMANI) where PDMANI is a weighted average coefficient.

In step 60 and step 61, the dead-time for reducing the delay of the in-cylinder intake purge concentration PFRC with respect to the predicted purge concentration PFR and the delay of the amount of air filled in the intake manifold. And ask. That is, PFRC is PFRD before NDLYPR (number of purge concentration delay cycles) (PFF).
RC = PFRD _n-NDLYPR ) In this case, _n in PFRD _n-NDLYPR is about acceleration / deceleration (Tp per air-fuel ratio feedback control job)
(Basic fuel injection pulse width) rate of change (new Tp / old Tp)
Is determined according to.

In step 62, the purge concentration change amount integrated value SPFRC is calculated by the following equation. SPFRC = SPFRC _n-1 + (PFRC-PFRC
_n-1 ) However, SPFRC _n-1 (previously obtained value) is set so as to decrease by 1 bit at every purge concentration integrated value reduction index number, and the purge concentration change amount is integrated while decreasing. To go.

Further, PFRC _n-1 is the value obtained last time. FIG. 9 is a flowchart for explaining the calculation function of the fuel injection pulse width Ti given to the fuel injection valve 16. In step 71, variables indicating the basic operating state (for example, intake air amount Qa and engine rotation speed Ne) and Basic fuel injection pulse width Tp [= (Qa / Ne) calculated according to the constant K
XK] is a correction amount Coef based on another operation variable, an air-fuel ratio feedback correction amount α obtained by the flowcharts of FIGS. 5 and 6, an air-fuel ratio learning value αm, and an invalid injection pulse width as a voltage correction coefficient Ts. The fuel injection pulse width Ti is obtained according to the following equation by correcting with.

Ti = Tp × Coef × (α + αm) + Ts In step 72, the fuel injection pulse width Ti calculated in step 71 is set in the output register. Next, the operation and effect of the invention according to claims 1 to 6 will be described based on the configuration of the embodiment described above.

First, in the first aspect of the invention, the gain is calculated based on the purge rate and the deviation of the air-fuel ratio feedback correction amount with and without the evaporated fuel purge,
The learning value of this gain is updated, the shift amount of the air-fuel ratio feedback correction amount is calculated based on this gain learning value and the purge rate, and the air-fuel ratio feedback correction amount is corrected based on this shift amount. .

As described above, as a result of correcting the air-fuel ratio feedback correction amount based on the shift amount calculated based on the gain learning value and the purge ratio, the purge ratio as the ratio of the purge gas flow rate to the intake air flow rate becomes It becomes possible to deal with the case where the purge concentration varies depending on the operating region, and it is possible to deal with the case where the purge concentration changes due to the progress of the purge under all the operating conditions.

That is, not only the deviation of the air-fuel ratio feedback control signal but also the correction of the air-fuel ratio is controlled based on the gain learning value and the purge rate, so that the air-fuel ratio changes when the purge rate changes or the operating conditions change. The correction amount can match the actual requirement, and the fluctuation of the air-fuel ratio can be suppressed. According to the second aspect of the present invention, the purge concentration is calculated by multiplying the actual purge rate by the learning value of the gain obtained by dividing the deviation of the air-fuel ratio feedback correction amount by the actual purge rate. Since the purge concentration integrated value that is integrated while decreasing is used as the shift amount and the air-fuel ratio feedback correction amount is corrected based on this shift amount, the shift amount can be optimized and the correction amount of the air-fuel ratio can be made more practical. Can be adapted to your requirements.

Here, the purge gas supplied to the downstream side of the throttle valve is sucked into each cylinder with a delay and diffusion in the intake manifold (see FIG. 14 showing movement of gas in the intake manifold). Therefore, for example, when the air-fuel ratio feedback correction amount is corrected by using the change in the purge rate, the correction becomes too early in real time, and a large lean rich spike occurs momentarily, and the rich spike during purge cut and the lean spike during recovery are generated. appear. The same applies when the purge rate changes.

The above-mentioned delay in the intake manifold changes depending on the change in the boost pressure of the intake manifold, and air-fuel ratio fluctuations occur during rapid acceleration / deceleration (see FIG. 15 showing gas movement and compression during acceleration). Therefore, the invention according to claim 3 is configured to calculate the purge concentration smoothed value by performing a weighted average process of the calculated purge concentration, and according to the invention according to claim 4, the filling in the intake system is performed. In order to shorten the delay of the air component, the dead time process is performed using the calculated purge concentration value several times before.

That is, the block 1 in FIGS. 3 and 4 described above.
5, the purge concentration predicted value PFR is subjected to a smoothing process to obtain a weighted average in order to approximate the diffusion of purge gas in the intake manifold. Further, in block 17 of FIG. 3 and FIG. 4, a dead time for reducing the delay of the filling air in the intake manifold is given and determined.

In this case, the cylinder intake purge concentration PF
RC is the purge concentration smoothing value PFRD before NDLYPR (the number of cycles of delaying the purge concentration). in this case,
_{N in} PFRD _n-NDLYPR is determined according to the acceleration / deceleration degree (change rate [new Tp / old Tp] of Tp [basic fuel injection pulse width] per air-fuel ratio feedback control job), and from the change rate of Tp It is estimated that the dead time is shortened by the gas compression in the figure.

As described above, the weighted average process of the calculated purge concentrations is performed to calculate the purge concentration smoothed value, and the dead time process using the calculated purge concentration values several times before is performed. It is possible to suppress the occurrence of rich spikes during purge cut and lean spikes during recovery, and to suppress the occurrence of air-fuel ratio fluctuations during rapid acceleration / deceleration. According to the fifth aspect of the present invention, the calculated purge concentration integrated value is multiplied by the air-fuel ratio feedback correction amount shift reflection gain to obtain the shift amount. It can be prevented.

Further, in the invention according to claim 6, the purge rate is calculated from the purge channel area and the total channel area determined by the throttle valve opening,
Thereby, the purge rate can be accurately obtained. Here, FIG. 13 is a diagram for explaining the effect of the embodiment of the present invention, and shows the relationship between each variable, the air-fuel ratio feedback correction amount α, and the air-fuel ratio A / F at the time of purge cut and at the time of releasing the purge cut. There is.

As is clear from this figure, in the prior art in which the control of the present invention is not executed, the shift amount of the air-fuel ratio feedback correction amount is not added, so α shown by the dotted line in the figure
However, the air-fuel ratio A / F becomes as shown by the dotted line in the figure, and the air-fuel ratio correction becomes insufficient or excessive. However, according to the control of the present invention, the shift amount of the air-fuel ratio feedback correction amount is appropriately added, The change in α is shown by the solid line in the figure, and
/ F becomes like the solid line in the figure, and the air-fuel ratio controllability can be improved without causing insufficient or excessive air-fuel ratio correction.

[0072]

As described above, according to the invention of claim 1, the gain is calculated based on the purge rate and the deviation of the air-fuel ratio feedback correction amount with and without the evaporated fuel purge. Since the learning value of the gain is updated, the shift amount of the air-fuel ratio feedback correction amount is calculated based on this gain learning value and the purge rate, and the air-fuel ratio feedback correction amount is corrected based on this shift amount.
When the purge rate changes or the operating conditions change, the correction amount of the air-fuel ratio can match the actual requirement, and the fluctuation of the air-fuel ratio can be suppressed.

According to the second aspect of the present invention, the purge concentration is calculated by multiplying the actual purge rate by the learning value of the gain obtained by dividing the deviation of the air-fuel ratio feedback correction amount by the actual purge rate. Since the purge concentration integrated value integrated while decreasing the purge concentration is used as the shift amount and the air-fuel ratio feedback correction amount is corrected based on this shift amount, the shift amount can be optimized and the air-fuel ratio correction amount can be improved. Can be more tailored to your actual requirements.

According to the invention of claim 3, a weighted average process of the calculated purge concentration is performed to calculate the purge concentration smoothing value. According to the invention of claim 4, the calculated purge concentration is calculated several times before. As a result of performing the dead time process using the purge concentration value of, the generation of the rich spike at the time of purge cut and the lean spike at the time of recovery can be suppressed, and the occurrence of the air-fuel ratio fluctuation at the rapid acceleration / deceleration can be suppressed.

According to the fifth aspect of the present invention, the calculated purge concentration integrated value is multiplied by the air-fuel ratio feedback correction amount shift reflection gain to obtain the shift amount. Can be prevented. According to the invention of claim 6, since the purge rate is calculated from the purge flow channel area and the total flow channel area determined by the throttle valve opening, the purge rate can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an invention according to claim 1.

FIG. 2 is a common system diagram of an embodiment of the invention according to claims 1 to 7.

FIG. 3 is a block diagram showing the content of control in the embodiment of the present invention.

FIG. 4 is a block diagram showing the contents of control in the embodiment of the present invention.

FIG. 5 is a flowchart illustrating an air-fuel ratio feedback control job.

FIG. 6 is a flowchart illustrating an air-fuel ratio feedback control job.

FIG. 7 is a flowchart showing a learning value update routine.

FIG. 8 is a flowchart showing a shift amount calculation routine.

FIG. 9 is a flowchart illustrating a fuel injection pulse width calculation function.

FIG. 10 is a diagram showing a table of a memory for explaining the control method of the invention according to claims 1 and 2.

FIG. 11 is a diagram showing a table of a memory for explaining the control method of the invention according to claim 3;

FIG. 12 is a diagram showing a table of a memory for explaining the control method of the invention according to claims 4 to 7.

FIG. 13 is a diagram for explaining the effect of the embodiment of the present invention, and is a diagram showing the relationship between each variable, the air-fuel ratio feedback correction amount α, and the air-fuel ratio A / F at the time of purging cut and its cancellation.

FIG. 14 is a diagram showing gas movement in the intake manifold.

FIG. 15 is a diagram showing gas transfer and compression under acceleration.

[Explanation of symbols]

11 engine 12 intake passage 16 fuel injection valve 17 control unit 18 exhaust passage 19 O ₂ sensor 20 crank angle sensor 23 canister 24 purge passage 25 purge valve

Claims (6)

[Claims] 1. An operating condition detecting means for detecting an operating condition of an engine, a means for judging an ON / OFF condition of a purge in response to an engine operating condition signal outputted from the detecting means, and a purging operation based on the judgment result. In an evaporative fuel treatment system for an internal combustion engine, comprising an apparatus for opening a purge valve under an ON condition and introducing a purge gas from a canister into an engine intake system, 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 feedback correction amount calculation means for calculating an air-fuel ratio feedback correction amount from the output of the air-fuel ratio detection means so that the air-fuel ratio feedback correction amount falls within a predetermined range, and a purge as a ratio of the purge gas flow rate to the intake air flow rate A purge rate calculation means for calculating the rate, and an air-fuel ratio with or without evaporative fuel purge based on the air-fuel ratio feedback correction amount. The air-fuel ratio feedback correction amount deviation calculation means for calculating the deviation of the feedback correction amount, the gain calculation means for calculating a gain based on the deviation of the purge rate and the air-fuel ratio feedback correction amount, and the gain calculation means Gain learning value updating means for updating the learning value of the gain, shift amount calculating means for calculating the shift amount of the air-fuel ratio feedback correction amount based on the gain learning value and the purge rate, and empty based on the shift amount. A correction unit that corrects the fuel ratio feedback correction amount, and a fuel that uses the corrected air-fuel ratio feedback correction amount under the purge ON condition and the basic fuel supply amount according to the operating condition based on the determination result of the purge ON / OFF condition A fuel supply amount calculating means for calculating a supply amount, and a fuel supply device for supplying the fuel supply amount to an engine intake system If, fuel vapor treatment system for an internal combustion engine, characterized in that it is configured to include. 2. The shift amount calculating means calculates the purge concentration by multiplying the actual purge rate by a learning value of a gain obtained by dividing the deviation of the air-fuel ratio feedback correction amount by the actual purge rate. 2. The evaporated fuel processing apparatus for an internal combustion engine according to claim 1, further comprising: a means for calculating the purge concentration integrated value as a shift amount by integrating the purge concentration while decreasing the purge concentration. 3. The internal combustion engine according to claim 2, wherein the shift amount calculating means includes means for performing a weighted average process of the calculated purge concentrations to calculate a purge concentration smoothing value. Evaporative fuel treatment system for engines. 4. The shift amount calculating means is configured to include a dead time processing means that uses the calculated purge concentration value several times before in order to shorten the delay of the filling air amount in the intake system. The evaporated fuel processing apparatus for an internal combustion engine according to claim 2 or 3, characterized in that. 5. The shift amount calculating means is configured to include means for multiplying the calculated purge concentration integrated value by an air-fuel ratio feedback correction amount shift reflection gain. An evaporated fuel processing device for an internal combustion engine according to any one of claims. 6. The purge rate calculating means is calculated from a purge flow passage area and a total flow passage area determined by a throttle valve opening. An evaporative fuel treatment device for an internal combustion engine according to claim 1.