JPH11101150A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the discharge quantity of HC and NOx at the time of resuming fuel supply by retarding ignition timing and increasing the intake air quantity at the time of increasing the fuel quantity in the case of resuming fuel supply in a device for cutting off fuel supply to an internal combustion engine during the speed reducing operation of the internal combustion engine. SOLUTION: During the operation of an engine 1, an ECU 5 controls a fuel injection valve 6 so as to cut off fuel supply to the engine during speed reducing operation while increasing the fuel quantity supplied to the engine at the time of resuming fuel supply. At the time of resuming fuel supply, whether to be in an air-fuel ratio feedback control operation area is judged. In the affirmative case, whether a target air-fuel ratio coefficient KBS is larger than 1.0 is discriminated. In the case of KBS>1.0 and fuel quantity increase being in progress, a retardation correction term and an increase correction term are computed according to throttle valve opening. The ignition timing of a spark plug 21 is therefore retarded, and the intake air quantity passing an auxiliary air quantity control valve 15 is increased.

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, and more particularly to a control device for increasing a fuel supply amount when restarting fuel supply from a state in which fuel supply to the internal combustion engine is shut off.

[0002]

2. Description of the Related Art When resuming fuel supply from a fuel supply cutoff state, a large amount of oxygen is accumulated in a catalytic converter provided in an engine exhaust system. A method of suppressing the amount of NOx emission by increasing the amount of fuel corresponding to a normal amount of fuel has been conventionally used (for example, Japanese Patent Publication No. 63-27533).

[0003]

However, in the conventional method, the amount of fuel supply is increased, so that NOx
Can be suppressed, but there is a problem that the amount of HC emission increases. This is considered to be because the amount of HC discharged to the exhaust system increases due to the increase in fuel, and the amount of HC discharged without reacting with the oxygen stored in the catalytic converter increases.

The present invention has been made in view of this point, and when the fuel supply is restarted from a state in which the fuel supply to the internal combustion engine is cut off, the NOx emission is increased without increasing the HC emission amount. It is an object of the present invention to provide a control device for an internal combustion engine capable of suppressing the amount.

[0005]

According to a first aspect of the present invention, a fuel supply to the engine is cut off during a deceleration operation of the internal combustion engine, and the fuel is supplied to the engine when the fuel supply is resumed. A control device for an internal combustion engine having a fuel supply control means for increasing the amount of fuel to be increased, wherein a retard means for retarding an ignition timing during execution of the fuel increase control, and an intake air amount of the engine is increased in synchronization with the retard. And an air amount increasing means.

According to this configuration, when the fuel supply is restarted from the state of shutting off the fuel supply to the engine, the fuel supply amount is increased, the ignition timing is retarded, and the intake air amount is increased. As a result, the temperature of the exhaust gas rises due to the retard of the ignition timing, the oxidation of HC in the exhaust gas in the catalytic converter is promoted, and the emission amount of NOx can be suppressed without increasing the emission amount of HC. . In addition, by increasing the intake air amount, it is possible to compensate for a decrease in engine output due to the ignition timing retard, and to maintain good operability.

According to a second aspect of the present invention, in the control device according to the first aspect, the fuel supply control means determines a deterioration state of a catalytic converter provided in an exhaust system of the engine and a temperature of the catalytic converter. The fuel supply amount is increased accordingly.

According to this configuration, the amount of fuel is increased at the time of resuming fuel supply in accordance with the state of deterioration of the catalytic converter provided in the exhaust system of the engine and the temperature of the catalytic converter. An appropriate and appropriate fuel increase can be performed.

According to a third aspect of the present invention, there is provided the control device for an internal combustion engine according to the first or second aspect, further comprising exhaust gas recirculation means for recirculating exhaust gas of the engine to an intake system, wherein the exhaust gas recirculation means is provided. The exhaust gas recirculation is performed during the fuel increase.

According to this configuration, when the fuel supply is restarted,
Since the exhaust gas recirculation is executed together with the fuel increase, the maximum value of the combustion temperature decreases, and the NOx amount generated in the combustion chamber of the engine can be reduced. As a result, the NOx emission can be further reduced.

[0011]

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

FIG. 1 is a diagram showing the configuration of an internal combustion engine (hereinafter referred to as "engine") and a control device therefor according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes, for example, a four-cylinder engine, and a throttle valve 3 is arranged in the intake pipe 2 of the engine 1. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and outputs an electric signal corresponding to the throttle valve opening θTH to supply it to an electronic control unit (hereinafter referred to as “ECU”) 5.

A fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of an intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). The ECU 5 is electrically connected to the ECU 5 and controls a valve opening time of the fuel injection valve 6 based on a signal from the ECU 5.

An auxiliary air passage 14 that bypasses the throttle valve 3 is provided in the intake pipe 2, and an auxiliary air amount control valve 15 is provided in the middle of the passage 14. The auxiliary air amount control valve 15 is connected to the ECU 5,
5 controls the valve opening amount.

On the other hand, an intake pipe absolute pressure (PBA) sensor 7 is provided immediately downstream of the throttle valve 3. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is supplied to the ECU 5. . Further, an intake air temperature (TA) sensor 8 is mounted downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies the electric signal to the ECU 5.

The engine water temperature (TW) sensor 9 mounted on the main body of the engine 1 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 5. The engine speed (NE) sensor 10 and the cylinder discrimination (CYL) sensor 11 are mounted around a camshaft or a crankshaft (not shown) of the engine 1. The engine speed sensor 10 outputs a pulse (hereinafter, referred to as a “TDC signal pulse”) at a predetermined crank angle position every time the crankshaft of the engine 1 rotates 180 degrees, and the cylinder discrimination sensor 11 outputs a predetermined crank angle position of a specific cylinder. And outputs a signal pulse. These signal pulses are supplied to the ECU 5.

The ignition plug 21 of the engine 1 is also electrically connected to the ECU 5, and the ignition timing IG is controlled by the ECU 5.
T is controlled.

An exhaust pipe 16 is provided with a catalytic converter 17 for purifying exhaust gas, and a wide area air-fuel ratio sensor (hereinafter, referred to as a "LAF sensor") 18 is provided upstream of the catalytic converter 17. Further, the catalytic converter 17
An oxygen concentration sensor (hereinafter referred to as “O2 sensor”) 19 is mounted on the downstream side of the sensor.

The LAF sensor 17 outputs an electric signal substantially proportional to the oxygen concentration (air-fuel ratio) in the exhaust gas, and supplies the electric signal to the ECU 5. The O2 sensor 19 has a characteristic that its output changes rapidly before and after the stoichiometric air-fuel ratio, and its output becomes higher on the rich side and lower on the lean side than the stoichiometric air-fuel ratio. The detection signal of the O2 sensor 19 is supplied to the ECU 5.

An exhaust gas recirculation path 30 connecting the intake pipe 2 and the exhaust pipe 16 is provided. An exhaust gas recirculation valve (EGR valve) 31 for controlling the amount of exhaust gas recirculation is provided in the exhaust gas recirculation path 30.
Is installed. The EGR valve 31 is connected to the ECU 5, and the opening amount thereof is controlled by the ECU 5. More specifically, the ECU 5 calculates the opening amount of the EGR valve 31 according to the engine operating state, and supplies the EGR valve 31 with a valve opening command signal IEGR corresponding to the opening amount.

The ECU 5 has an input circuit having a function of shaping the waveforms of the input signals from the various sensors described above, correcting the voltage level to a predetermined level, and changing an analog signal value to a digital signal value, and a central processing circuit. (CPU), a storage circuit including a ROM and a RAM for storing various arithmetic programs executed by the CPU, various maps and arithmetic results described below, and drive signals to various solenoid valves such as the fuel injection valve 6 and the ignition plug. And an output circuit for outputting the same.

The ECU 5 determines various engine operating states such as a feedback control operating area and an open control operating area according to the outputs of the LAF sensor 18 and the O2 sensor 19 based on the various engine operating parameter signals described above. Depending on the engine operating condition, the fuel injection valve 6
Fuel injection time TOUT, ignition timing I of the spark plug 21
GT, an opening command signal ICMD of the auxiliary air amount control valve 15 and an opening command signal IEGR of the EGR valve 31 are calculated, and a signal for driving the fuel injection valve 6, the ignition plug 21 and the like is output based on the calculation result. .

The fuel injection time TOUT is calculated by the following equation (1).

TOUT = TIM × KBS × KLAF × K1 + K2 (1) Here, TIM is a basic fuel injection time of the fuel injection valve 6, and is set according to the engine speed NE and the intake pipe absolute pressure PBA.

KBS is a target air-fuel ratio coefficient set by the processing of FIG. 2 described later, and KLAF is an air-fuel ratio detected by the LAF sensor 18 is a target air-fuel ratio coefficient KB.
This is an air-fuel ratio correction coefficient set by PID control so as to obtain an air-fuel ratio corresponding to S.

K1 and K2 are other correction coefficients and correction variables calculated in accordance with various engine operation parameter signals, respectively.
The setting is made so that the acceleration characteristics and the like can be optimized.

The ignition timing (advance angle) of the ignition plug 21
IGT is calculated by the following equation (2).

IGT = IGB-IGKBSR (2) Here, IGB is a basic ignition timing, and is set according to the engine speed NE and the intake pipe absolute pressure PBA.
The IGKBSR is calculated in a process of FIG. 3 described later, and is a retard correction term for retarding (retarding) the ignition timing when fuel supply is restarted from a fuel supply cutoff (hereinafter referred to as “fuel cut”) state. It is.

The valve opening command signal ICMD for the auxiliary air amount control valve 15 is calculated by the following equation (3).

ICMD = ICCMDB + IKBS (3) Here, ICMDB is a basic valve opening amount set according to the engine operating state such as whether or not the engine is in an idle state, and IKBS is FIG. Is an increase correction term for increasing the intake air amount when the fuel supply is restarted from the fuel cut state.

FIG. 2 is a flowchart of a process for setting the target air-fuel ratio coefficient KBS. This process is executed by the CPU of the ECU 5 every time a TDC signal pulse is generated.

First, in step S11, it is determined whether or not a feedback flag FLAFFBD indicating "1" that the engine operating state is in the feedback control operation area is "1". If not, the target air-fuel ratio coefficient KBS is set to 1.0 (step S12), and is indicated by "1" to indicate that it is an operation region where fuel supply to the engine 1 is cut off (hereinafter referred to as "fuel cut region"). It is determined whether or not the fuel cut flag FFC is "1" (step S13). The fuel cut flag FFC is set according to the throttle valve opening θTH, the engine speed NE, and the intake pipe absolute pressure PBA by the processing of FIG. 4 described later.

If FFC = 0 in step S13 and it is not in the fuel cut area, a counter CATO for measuring a period of time remaining in the fuel cut area is used.
The value of “2” is set to “0” (step S17), and the process ends. If FFC = 1 in step S13 and the vehicle is in the fuel cut area, the value of the counter CATO2 is incremented by a predetermined increment value DCATO2I (step S14), and whether or not the value of the counter CATO2 is larger than a predetermined upper limit value CATO2LMH. Is determined (step S15). CATO2 ≦ CATO2L
Immediately when MH, and CATO2> CATO2
If the value is LMH, the value of the counter CATO2 is set to the predetermined upper limit value CATO2LMH (step S1).
6), the process ends (see FIG. 6C).

If FLAFFBD = 1 in step S11 and the engine operating state is in the feedback control operating region, the counter CATO2 is decremented by a predetermined decrement value DCATO2D (step S1).
8) Then, the value of the counter CATO2 is changed to the lower threshold CA.
It is determined whether or not TO2LML or less (step S1)
9). When the fuel supply is restarted from the fuel cut state (see time t2 in FIG. 6C), this answer is negative (N
O), the process proceeds to step S20, and the counter CA
It is determined whether or not the value of TO2 is smaller than a predetermined intermediate value CATO2LMM that is set to a value between the predetermined upper limit value CATO2LMH and the lower threshold value CATO2LML. When CATO2≥CATO2LMM (as shown in FIG. 6), the target air-fuel ratio coefficient KBS is set to a predetermined enrichment value KBSRICH (for example, 1.03) (step S23), and the process ends.

In step S20, CATO2 <CAT
If it is O2LMM, a predetermined addition value DKSBP is added to the target air-fuel ratio coefficient KBS (step S21), and it is determined whether the target air-fuel ratio coefficient KBS is larger than the enrichment predetermined value KBSRICH (step S22). Then, when KBS ≦ KBSRICH, and immediately when KBS> KBSRICH, the target air-fuel ratio coefficient KBS is set to the enrichment predetermined value KBSRICH (step S23), and this processing ends.

According to steps S19 to S23, when the fuel cut period is relatively long (CATO2 ≧
CATO2LMM), the target air-fuel ratio coefficient KBS is immediately set to the enrichment predetermined value KBSRICH, and when the fuel cut period is relatively short (CATO2LML <
CATO2 <CATO2LMM), target air-fuel ratio coefficient KB
S is incremented by a predetermined addition value DKSBP with the enrichment predetermined value KBSRICH as an upper limit.

After restarting fuel supply from the fuel cut state,
When the value of the counter CATO2 reaches the lower threshold value CATO2LML (see time t3 in FIG. 6), the answer to step S19 becomes affirmative (YES), and the process proceeds to step S24. In step S24, a predetermined subtraction value DKBSM is subtracted from the target air-fuel ratio coefficient KBS, and then it is determined whether the target air-fuel ratio coefficient KBS is smaller than 1.0 (step S2).
5). When KBS ≧ 1.0, this process is immediately terminated. On the other hand, when KBS <1.0, KBS = 1.
The value is set to 0 (step S26), the value of the counter CATO2 is reset to "0" (step S27), and the process ends.

According to steps S24 to S26, CATO
While 2 ≦ CATO2LML (FIG. 6, after time t3)
Is decremented until the target air-fuel ratio coefficient KBS becomes 1.0 by a predetermined subtraction value DKBSM (FIG. 6, time t5).

As described above, according to the processing of FIG. 2, the target air-fuel ratio coefficient KBS at the time of restarting the fuel supply is set to a value larger than 1.0 according to the value of the counter CATO2 which measures the period during which the fuel cut is executed. Then, the fuel supply amount is increased, that is, the air-fuel ratio is made rich. As a result, the emission amount of NOx when the fuel supply is restarted from the fuel cut state can be reduced.

FIG. 3 shows the retard correction term I of the above equation (2).
5 is a flowchart of a process for calculating GKBSR and an increase correction term IKBS in the above equation (3).
It is executed by the CPU of the ECU 5 every time a DC signal pulse is generated.

In a step S31, it is determined whether or not the feedback flag FLAFFBD is "1".
When BD = 1 and in the feedback control operation region, it is determined whether the target air-fuel ratio coefficient KBS is greater than 1.0 (step S32). Then, step S3
1 or S32 is negative (NO), that is, FLAF
When FBD = 0 and not in the feedback control operation region, or when KBS ≦ 1.0 and fuel increase is not performed, both the retard correction term IGKBSR and the increase correction term IKBS are set to “0”. (Step S34).

On the other hand, when the answers of steps S31 and S32 are both affirmative (YES), that is, the target air-fuel ratio coefficient KB
When S is set to a value greater than 1.0, feedback control is performed, and the fuel supply amount is increased, the IGK shown in FIG. 5 is changed according to the throttle valve opening θTH.
The BSR table and the IKBS table are searched, and the retard correction term IGKBSR and the increase correction term IKBS are calculated (step S33). IGKBSR table and IK
The BS table indicates that the throttle valve opening θTH is equal to the predetermined opening θ.
In a range smaller than TH1 (for example, an opening of about 1/4 of the full opening), the retard correction term IGKBSR and the increase correction term IKBS are set so as to decrease as the throttle valve opening θTH increases, respectively. θTH ≧
In the range of θTH1, the retard correction term IGKBSR
And the increase correction term IKBS is set to “0”.

In step S33, the target air-fuel ratio coefficient KBS is further decreased gradually, and when it falls below a predetermined value KBSR1 (see FIG. 6B), the retard correction term IGKBSR and the retard correction term IGKBSR are set as shown in FIGS. A process for gradually decreasing the increase correction term IKBS with the passage of time is performed.

According to the processing of FIG. 3, the fuel supply is restarted from the fuel cut state, and the target air-fuel ratio coefficient KBS becomes 1.0.
If the value is set to a larger value (KBSRICH), the retard correction term IGKBSR and the increase correction term IKBS become the initial value IGKB corresponding to the throttle valve opening θTH, respectively.
SR0 and IKBS0 (see FIGS. 6D and 6E), and the initial values are maintained unless the throttle valve opening θTH changes. Thereafter, when the target air-fuel ratio coefficient KBS falls below the predetermined value KBSR1 (time t4), the retard correction term IGKBSR and the increase correction term IKBS are gradually reduced,
When KBS = 1.0 (time t5), it is reset to “0”.

As described above, in the present embodiment, when the fuel supply is restarted from the fuel cut state, the retard correction of the ignition timing IGT is performed together with the increase of the fuel, so that the temperature of the exhaust gas rises, and The oxidation of HC in the catalytic converter 17 is promoted, and the NOx emission can be suppressed without increasing the HC emission. In addition, by increasing the intake air amount, a decrease in engine output due to ignition timing retard can be compensated for, and good operability can be maintained.

FIG. 4 shows a fuel cut area for executing the deceleration fuel cut, and a fuel cut flag FFC.
Is a flowchart of a process for setting the time T.
It is executed by the CPU of the ECU 5 in synchronization with the generation of the DC signal pulse.

First, at step S101, the throttle valve opening .theta.TH is set to a predetermined opening .theta.
It is determined whether or not TIDLE (for example, once) or more, and θT
When H ≧ θTHIDLE, the absolute pressure PB in the intake pipe
It is determined whether or not A is equal to or higher than a predetermined pressure PBFC (for example, 130 mmHg) (step S102), and if PBA <PBFC, the engine speed NE becomes the predetermined speed NPBF.
It is determined whether or not CLM (for example, 1800 rpm) or less (step S103). As a result, when PBA ≧ PBFC or NE ≦ NPBFCLM, the down count timer tmTCDLY referred to in step S107 described later is set to a predetermined time TFCDLY (for example, 0.5
Second) and start (step S106)
The fuel cut flag FFC is set to "0" (step S108), and the process ends. On the other hand, PBA <PB
When FC and NE> NPBFCLM, it is determined whether or not the fuel cut flag FFC has already been set to "1" (step S104). If FFC = 1, the process proceeds to step S109 to maintain the state. . If FFC = 0 in step S104, the change amount of the intake pipe absolute pressure PBA (the difference between the previous detection value and the current detection value) DP
It is determined whether the absolute value of BACYL is equal to or greater than a predetermined change amount DPBDLY (for example, 5 mmHg) (step S10).
5) If | DPBACYL | ≧ DPBDLY and the fluctuation in the intake pipe absolute pressure PBA is large, the process proceeds to step S106, and the state of FFC = 0 is maintained.

In step S105, | DPBACYL | <
If DPBDLY and the variation in the intake pipe absolute pressure PBA is small, it is determined whether or not the value of the timer tmFCDLY started in step S106 is "0" (step S107). As long as tmFCDLY> 0, FFC is performed. =
0 (step S108), and tmFCDLY = 0
Then, the fuel cut flag FFC is set to "1" (step S109), and this processing ends.

As described above, the fuel cut flag F
FC is set to “1” when the engine 1 is decelerating and the state of low load and high rotation continues for a predetermined time TFCDLY. When FFC = 1, the ECU
5 stops the operation of the fuel injection valve 6 and shuts off the fuel supply to the engine 1.

FIG. 6 is a time chart for explaining the processing of FIGS. 2 and 3 described above. Each control parameter and fuel intake pipe in the case where fuel cut is started at time t1 and fuel supply is restarted at time t2. The transition of the absolute pressure PBA is shown. In the example shown in this figure, the duration of fuel cut is relatively long, and the counter CATO2 has a predetermined upper limit value C.
Since ATO2LMH is reached, fuel supply is resumed (time t
In 2), the target air-fuel ratio coefficient KBS is immediately set to the predetermined enrichment value KBSRICH. Accordingly, the ignition timing IGT is retarded by the retard correction term IGKBSR, and the opening amount of the auxiliary air amount control valve 15 is increased by the increase correction term IKBS. Thereafter, the value of the counter CATO2 is changed to the lower threshold value CATO2LML.
(Time t3), the target air-fuel ratio coefficient KBS is gradually reduced, and the target air-fuel ratio coefficient KBS is reduced to a predetermined value KBS.
When it decreases to R1 (time t4), the retard correction term IG
The process of gradually decreasing the KBSR and the increase correction term IKBS is started. When KBS = 1.0 at time t5, both the retard correction term IGKBSR and the increase correction term IKBS are reset to "0".

FIG. 9F shows the transition of the intake pipe absolute pressure PBA in this case for reference. When the intake air amount is increased, the intake pipe absolute pressure PBA increases correspondingly. The basic fuel injection time TI increases. Therefore, the effect of enriching the air-fuel ratio (by setting KBS = KBSRICH) is not offset by the increase correction of the intake air amount.

Further, by increasing the intake air amount, the EG
Since the drivability can be ensured even if R is executed, the valve opening command signal IEGR of the EGR valve 31 is changed as shown in FIG.
It is desirable to set a value at which exhaust gas recirculation of about 10% is performed from time t2 when fuel supply is restarted. As a result, the maximum value of the combustion temperature in the combustion chamber of the engine 1 can be reduced, the amount of NOx generated in the combustion chamber can be reduced, and the emission of NOx can be further reduced.

In this embodiment, the processing in FIG. 4 and steps S18 to S27 in FIG. 2 correspond to the fuel supply control means, and steps S31 to S33 in FIG. 3 correspond to the retard means and the air amount increasing means.

The present invention is not limited to the embodiment described above, and various modifications are possible. For example, the enrichment predetermined value KBSRICH when fuel supply is restarted from the fuel cut state may be corrected according to a deterioration parameter OSCINDEX indicating the degree of deterioration of the catalytic converter 17. The deterioration parameter OSCINDEX is
Oxygen concentration sensor 1 provided downstream of catalytic converter 17
9, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is feedback-controlled, and the cycle of reversal of the output of the oxygen concentration sensor at that time (determination of the deterioration of the catalytic converter based on the cycle of reversal is described in, for example, ), And the smaller the value, the greater the degree of deterioration. More specifically, the correction by the deterioration parameter OSCINDEX is performed by setting a correction coefficient KBSRC as shown in FIG. 7A and enriching the correction coefficient KBSRC with a predetermined value KB.
This is performed by multiplying the SRICH. In the figure,
When the deterioration parameter OSCINDEX decreases and the degree of deterioration increases, the correction coefficient KBSRC is reduced because the deterioration reduces the amount of oxygen stored in the catalytic converter when the fuel supply is restarted, and Even when the deterioration parameter OSCINDEX is large and the deterioration is not progressing, the correction coefficient KBSRC is reduced because the purification performance of the catalytic converter is good and the necessity of enriching the air-fuel ratio is low.

Also, the deterioration determination parameter OSCINDE
X indicates the inversion cycle of the oxygen concentration sensor 19 described above in FIG.
As shown in (b), it is desirable to calculate by correcting according to a correction coefficient KOSC set according to the temperature TCAT of the catalyst in the catalytic converter 17. In FIG. 3B, the predetermined temperature TCAT1 is a temperature at which the catalyst of the catalytic converter 17 is activated. Catalyst temperature TCA
T is the value detected by the sensor or the engine water temperature T
The estimated value estimated according to W is used. The enrichment predetermined value KBSR based on such a catalyst deterioration state and catalyst temperature
The setting of ICH is performed by the CPU of the ECU 5, and the CP
The arithmetic processing by U constitutes the fuel increasing means.

By doing so, the fuel can be increased according to the state of the catalytic converter 17. That is, when the catalytic converter 17 is deteriorated, the degree of fuel increase is reduced, so that the amount of HC which is not oxidized by the catalytic converter 17 and discharged as it is can be reduced.

In the case of performing so-called perturbation control in which the target air-fuel ratio coefficient KBS is periodically changed in the lean direction and the rich direction, the air-fuel ratio is increased when the fuel supply is restarted from the fuel cut state. It is desirable to stop the perturbation during the (increase) operation. As a result, it is possible to prevent the effect of increasing the amount of fuel from being reduced due to the perturbation, and to obtain a favorable NOx reduction effect.

[0058]

According to the first aspect of the present invention, when the fuel supply is restarted from the fuel supply cutoff state to the engine, the fuel supply amount is increased and the ignition timing is increased. Since the retard of the ignition timing is increased, the temperature of the exhaust gas is increased by the retard of the ignition timing, and the oxidation of HC in the exhaust gas in the catalytic converter is promoted. NO
x emission can be suppressed. In addition, by increasing the intake air amount, it is possible to compensate for a decrease in engine output due to the ignition timing retard, and to maintain good operability.

According to the second aspect of the present invention, the amount of fuel is increased at the time of resuming fuel supply according to the deterioration state of the catalytic converter provided in the exhaust system of the engine and the temperature of the catalytic converter. Therefore, it is possible to appropriately increase the fuel amount in accordance with the oxygen storage capacity of the fuel cell.

According to the third aspect of the present invention, when the fuel supply is restarted, the exhaust gas recirculation is executed together with the increase in the fuel, so that the maximum value of the combustion temperature decreases and the NOx amount generated in the combustion chamber of the engine is reduced. Can be reduced. As a result, the NOx emission can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process for calculating a target air-fuel ratio coefficient (KBS).

FIG. 3 is a flowchart of a process for calculating a retard correction term for ignition timing (IGKBSR) and an increase correction term for intake air amount (IKBS).

FIG. 4 is a flowchart of a process for determining an operation state for executing a deceleration fuel cut.

FIG. 5 is a diagram showing a table used in the processing of FIG. 3;

FIG. 6 is a diagram for specifically explaining the processing shown in FIGS. 2 and 3;

FIG. 7 is a diagram for explaining correction of a fuel increase according to a degree of deterioration of a catalytic converter.

[Explanation of symbols]

Reference Signs List 1 internal combustion engine 2 intake pipe 3 throttle valve 5 electronic control unit (ECU) (fuel supply control means, retard means, air amount increasing means, exhaust gas recirculation means) 6 fuel injection valve 14 auxiliary air passage (air amount increasing means) 15 auxiliary Air amount control valve (air amount increasing means) 21 Spark plug 30 Exhaust recirculation path (exhaust recirculation means) 31 Exhaust recirculation valve (exhaust recirculation means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/12 330 F02D 41/12 330Z F02M 25/07 550 F02M 25/07 550K F02P 5/15 F02P 5/15 F

Claims (3)

[Claims] 1. A control apparatus for an internal combustion engine, comprising: fuel supply control means for shutting off fuel supply to the engine during deceleration operation of the internal combustion engine and increasing the amount of fuel supplied to the engine when fuel supply is resumed. A control device for an internal combustion engine, comprising: retard means for retarding ignition timing during execution of the fuel increase control; and air amount increase means for increasing an intake air amount of the engine in synchronization with the retard. 2. The fuel supply control means increases the fuel supply amount according to a deterioration state of a catalytic converter provided in an exhaust system of the engine and a temperature of the catalytic converter. 2. The control device for an internal combustion engine according to claim 1. 3. An exhaust gas recirculation means for recirculating exhaust gas of the engine to an intake system, wherein the exhaust gas recirculation means performs exhaust gas recirculation during execution of the fuel increase. 3. The control device for an internal combustion engine according to claim 1.