JP2001342872A - Fuel control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently purify exhaust gas from an internal combustion engine by suitably activating catalytic converters arranged in a vehicle. SOLUTION: A fuel quantity by cylinders is successively increased or decreased with respective prescribed periods at steady operation time of this internal combustion engine 10. The fuel quantity by the cylinders is corrected on the basis of a difference between an average value of an exhaust gas temperature in an increasing quantity or decreasing quantity control period of the fuel quantity by the cylinders and an exhaust gas temperature with respective periods by an exhaust gas temperature sensor 31 arranged in the upstream of the first catalytic converter 22 in the outlet vicinity of an exhaust manifold 21 in the middle of an exhaust gas passage of the internal combustion engine 10. Thus, since a fluctuation in the air-fuel ratio of the respective cylinders of the internal combustion engine 10 can be eliminated, the first catalytic converter 22 and the second catalytic converter 24 are quickly activated, and emission is improved so that the exhaust gas temperature at high load time can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control device for an internal combustion engine that purifies exhaust gas from an internal combustion engine by a catalytic converter installed in a vehicle.

[0002]

2. Description of the Related Art Conventionally, a first catalytic converter is installed near an exhaust manifold outlet to purify exhaust gas from an internal combustion engine of a vehicle, and a second catalytic converter is installed downstream thereof to improve emission. Are known. Here, the first catalytic converter is quickly activated by the exhaust gas temperature of the exhaust gas from the internal combustion engine, and has a function of accelerating the purification of the exhaust gas. It is made of a relatively strong material.

[0003]

By the way, the above-mentioned first type is used.
Is quickly activated because it is installed in a portion where the exhaust temperature of the exhaust gas from the internal combustion engine is high, but the air-fuel ratio (A / F) of each cylinder based on the amount of fuel supplied to the internal combustion engine Is large, especially at high load, the combustion temperature tends to be high. As a result, when the exhaust gas temperature becomes too high and exceeds a predetermined temperature, the first catalytic converter is damaged. However, there is a problem that the purification of exhaust gas is hindered.

[0004] Therefore, the present invention has been made to solve such a problem, and a fuel control for an internal combustion engine capable of satisfactorily purifying exhaust gas from an internal combustion engine by suitably activating a catalytic converter installed in a vehicle. The task is to provide devices.

[0005]

According to the fuel control device for an internal combustion engine of the first aspect, the fuel supply control means sequentially controls the fuel amount for each cylinder by the fuel supply means at regular intervals during a steady operation of the internal combustion engine. Is increased or decreased. The first exhaust gas is located near the exhaust manifold outlet in the exhaust passage of the internal combustion engine.
The exhaust gas temperature during the control period by the fuel increase / decrease control means is detected by exhaust temperature detection means provided at least one of the upstream side of the catalytic converter, the downstream side of the first catalytic converter, and the upstream side of the second catalytic converter. The fuel amount for each cylinder is corrected by the fuel correcting means based on the difference between the average value and the exhaust temperature for each period. As a result, variations in the air-fuel ratio of each cylinder of the internal combustion engine can be eliminated.
The second catalytic converter and the second catalytic converter are quickly activated, the emission is improved, and the exhaust gas temperature at the time of high load is reduced.

[0006] In the fuel control device for an internal combustion engine according to claim 2,
The fact that the difference between the maximum exhaust gas temperature during the previous control period and the maximum exhaust gas temperature during the current control period by the fuel increase / decrease control means is larger than a predetermined value means that the correction of the fuel amount for each cylinder is still insufficient. And the correction of the fuel amount for each cylinder by the fuel correction means is continued. As a result, the variation in the air-fuel ratio of each cylinder of the internal combustion engine can be appropriately converged, so that the first catalytic converter and the second catalytic converter are quickly activated to improve emission, and at the time of high load. , The exhaust temperature is also reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples.

FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which an internal combustion engine fuel control device according to one embodiment of the present invention is applied, and peripheral devices thereof.

In FIG. 1, an internal combustion engine 10 is configured as a spark ignition type having four in-line four cylinders (# 1 cylinder to # 4 cylinder). Air drawn from an air cleaner (not shown) on the upstream side of the internal combustion engine 10 passes through the intake passage 11, the surge tank 12, and the intake manifold 13, and the injectors (fuel injection) corresponding to the # 1 to # 4 cylinders in the intake manifold 13 The valves are mixed with fuel injected from the valves 14a to 14d and distributed and supplied to each cylinder (# 1 cylinder to # 4 cylinder) as a mixture having a predetermined air-fuel ratio. Further, the spark plugs 15a to 15a-1 provided in the cylinders # 1 to # 4 of the internal combustion engine 10 are provided.
A high voltage is distributed and supplied to 5d from an ignition circuit (not shown) via a distributor, and a mixture of # 1 to # 4 cylinders is ignited at a predetermined timing. The ignition order is normally # 1 cylinder → # 3 cylinder → # 4 cylinder → # 2 cylinder.

The exhaust gas after combustion passes through a first catalytic converter (three-way catalyst) 22 and an exhaust passage 23 provided near the outlet of an exhaust manifold 21, and the exhaust passage 2
After passing through a second catalytic converter (three-way catalyst or NOx catalyst) 24 disposed near the three outlets, the exhaust gas is discharged into the atmosphere. An exhaust temperature sensor 31 for detecting the exhaust gas temperature of the exhaust gas is provided immediately before the first catalytic converter 22. The first catalytic converter 22 is also called a start catalyst or a pre-catalyst, and the second catalytic converter 24 is also called an underfloor type catalyst.

An ECU (Electronic Control Unit) 40 includes a CPU as a central processing unit for executing various known arithmetic processing, a ROM for storing control programs, a RAM for storing various data, and a B / U (backup). ) It is configured as a logical operation circuit including a RAM, an input / output circuit, and a bus line connecting them.
The ECU 40 reads the exhaust gas temperature signal of the exhaust gas from the exhaust gas temperature sensor 31 and various sensor signals 41 from various sensors (not shown), and performs arithmetic processing.
Various output signals 42 are output to 4a to 14d and various actuators (not shown) to control the operating state of the internal combustion engine 10. The calculation of the basic fuel injection amount based on the operating state of the internal combustion engine by the ECU 40 is well known, and is omitted in the description of the present embodiment.

Next, the ECU 4 used in the internal combustion engine fuel control apparatus according to one embodiment of the present invention will be described.
FIG. 4 will be described with reference to FIG. 4 based on the flowchart of FIGS. Here, FIG.
FIG. 4 is a time chart showing transition states of the final fuel injection correction amount for each cylinder, the exhaust temperature correction amount for each cylinder, and the exhaust temperature [° C.] from the exhaust temperature sensor 31 corresponding to the processing of FIGS. The routine for correcting the exhaust gas temperature for each cylinder is approximately 8
It is repeatedly executed by the CPU every [ms: millisecond].

In FIG. 2, first, in step S101, the intake air amount (intake air amount) G of the various sensor signals 41 is determined.
Change amount ΔGN of intake air amount per unit time of N [g / rev]
Is smaller than the predetermined value α. Here, when the determination condition of step S101 is not satisfied, that is, when the change amount ΔGN of the intake air amount is larger than the predetermined value α, the internal combustion engine 10
The routine is terminated assuming that the operation state of FIG. During the transient operation, all the cylinder-specific fuel injection correction amounts rChangTest (n) are reset to “0”. Here, (n) is a numerical value corresponding to # 1 to # 4 cylinders from 1 to 4.

On the other hand, when the determination condition of step S101 is satisfied, that is, when the change amount ΔGN of the intake air amount is smaller than the predetermined value α, it is determined that the operation state of the internal combustion engine 10 is in the steady operation, and the process proceeds to step S102. C is incremented by "+1". Next, step S103
Then, it is determined whether the timer counter C is "20". When the determination condition of step S103 is satisfied, the process proceeds to step S104, and in this embodiment, the increase correction is performed as the fuel injection amount correction for the # 1 cylinder. On the other hand, when the determination condition of step S103 is not satisfied, step S104 is skipped.

Next, the flow shifts to step S105, where it is determined whether or not the timer counter C is "39". here,
If the timer counter C is between "20" and "39",
The period is set to wait for the exhaust gas temperature to stabilize after the fuel injection amount correction for the cylinder is performed.
When the determination condition in step S105 is satisfied, the process proceeds to step S106, where the input value from the exhaust gas temperature sensor 31 is read, and the exhaust gas temperature T1 [° C.] corresponding to the # 1 cylinder is calculated. Next, the routine proceeds to step S107, in which the exhaust gas temperature T1 corresponding to the # 1 cylinder becomes the maximum exhaust gas temperature T so far.
It is determined whether it exceeds max. When the determination condition of step S107 is satisfied, the process proceeds to step S108, and the maximum exhaust temperature Tmax is updated to the exhaust temperature T1.
Here, when the determination condition of step S107 is not satisfied, step S108 is skipped and the maximum exhaust gas temperature T
max is left as is. On the other hand, when the determination condition of step S105 is not satisfied, steps S106 to S108 are skipped.

Next, the flow shifts to step S109, where it is determined whether or not the timer counter C is "40". When the determination condition of step S109 is satisfied, step S11
0, and as a fuel injection amount correction for the # 3 cylinder,
In the present embodiment, the increase correction is executed. On the other hand, step S
When the determination condition of 109 is not satisfied, step S11
0 is skipped.

Next, the flow shifts to step S111, where it is determined whether or not the timer counter C is "59". here,
If the timer counter C is between "40" and "59", the value of # 3
The period is set to wait for the exhaust gas temperature to stabilize after the fuel injection amount correction for the cylinder is performed.
When the determination condition of step S111 is satisfied, the process proceeds to step S112, where the input value from the exhaust gas temperature sensor 31 is read, and the exhaust gas temperature T3 [° C.] corresponding to the # 3 cylinder is calculated. Next, the routine proceeds to step S113, where the exhaust gas temperature T3 corresponding to the # 3 cylinder becomes the maximum exhaust gas temperature T so far.
It is determined whether it exceeds max. When the determination condition of step S113 is satisfied, the process proceeds to step S114, and the maximum exhaust temperature Tmax is updated to the exhaust temperature T3.
Here, when the determination condition of step S113 is not satisfied, step S114 is skipped and the maximum exhaust gas temperature T
max is left as is. On the other hand, when the determination condition of step S111 is not satisfied, steps S112 to S114 are skipped.

Next, the flow shifts to step S115 shown in FIG. 3, and it is determined whether or not the timer counter C is "60". When the determination condition of step S115 is satisfied, the process proceeds to step S116, and in this embodiment, the increase correction is executed as the fuel injection amount correction for the # 4 cylinder. On the other hand, when the determination condition of step S115 is not satisfied, step S116 is skipped.

Next, the flow shifts to step S117, where it is determined whether or not the timer counter C is "79". here,
If the timer counter C is from "60" to "79",
The period is set to wait for the exhaust gas temperature to stabilize after the fuel injection amount correction for the cylinder is performed.
When the determination condition of step S117 is satisfied, the process proceeds to step S118, where the input value from the exhaust temperature sensor 31 is read, and the exhaust temperature T4 [° C.] corresponding to the # 4 cylinder is calculated. Next, the routine proceeds to step S119, where the exhaust gas temperature T4 corresponding to the # 4 cylinder becomes the maximum exhaust gas temperature T so far.
It is determined whether it exceeds max. When the determination condition in step S119 is satisfied, the process proceeds to step S120, and the maximum exhaust temperature Tmax is updated to the exhaust temperature T4.
Here, when the determination condition of step S119 is not satisfied, step S120 is skipped and the maximum exhaust gas temperature T
max is left as is. On the other hand, when the determination condition of step S117 is not satisfied, steps S118 to S120 are skipped.

Next, the flow shifts to step S121, where it is determined whether or not the timer counter C is "80". When the determination condition of step S121 is satisfied, step S12
Then, the fuel injection amount correction for the # 2 cylinder (increase correction in this embodiment) is executed. On the other hand, step S12
When the determination condition of 1 is not satisfied, step S122 is skipped.

Next, the flow shifts to step S123, where it is determined whether or not the timer counter C is "99". here,
When the timer counter C is between “80” and “99”,
The period is set to wait for the exhaust gas temperature to stabilize after the fuel injection amount correction for the cylinder is performed.
When the determination condition of step S123 is satisfied, the process proceeds to step S124, where the input value from the exhaust gas temperature sensor 31 is read, and the exhaust gas temperature T2 [° C.] corresponding to the # 2 cylinder is calculated. Next, the routine proceeds to step S125, where the exhaust gas temperature T2 corresponding to the # 2 cylinder becomes the maximum exhaust gas temperature T so far.
It is determined whether it exceeds max. When the determination condition of step S125 is satisfied, the process proceeds to step S126, and the maximum exhaust temperature Tmax is updated to the exhaust temperature T2.
Here, when the determination condition of step S125 is not satisfied, step S126 is skipped and the maximum exhaust gas temperature T
max is left as is. On the other hand, when the determination condition of step S123 is not satisfied, steps S124 to S126 are skipped.

Next, the flow shifts to step S127, where it is determined whether or not the timer counter C is equal to or greater than "100". When the determination condition of step S127 is satisfied, the process proceeds to step S128, and the cylinder-specific fuel injection correction amount rChangTest
(n) are all reset to "0". On the other hand, step S
When the determination condition of 127 is not satisfied, step S12
8 is skipped. Next, the process proceeds to step S129 to determine whether the timer counter C is "100". When the determination condition of step S129 is satisfied, the process proceeds to step S130, and the average exhaust gas temperature rA when the fuel is increased or decreased.
veTempM is calculated by the following equation (1).

[0023]

RAveTempM = (rTempTest1 + rTempTest2 + rTempTest3 + rTempTest4) / 4 (1)

The average exhaust temperature rAveTempM when the fuel increases or decreases
The cylinder-specific exhaust temperature correction amount rAdapt (n) is calculated based on the following equation (2).
Is calculated. Here, rTempTest (n) indicates the exhaust temperature of each cylinder at the time of completion of the fuel increase and decrease, and γ indicates the smoothing (smoothing) coefficient.

[0025]

(2) rAdapt (n) = rAdapt (n) − {rTempTest (n) −rAveTempM} × γ (2)

On the other hand, if the condition of step S129 is not satisfied, step S130 is skipped. Next, the routine proceeds to step S131, where it is determined whether the timer counter C is "150" and whether the difference between the previous maximum exhaust gas temperature Tmax and the current maximum exhaust gas temperature TmaxP exceeds a predetermined value β. When the determination condition of step S131 is satisfied, the difference between the previous maximum exhaust gas temperature Tmax and the current maximum exhaust gas temperature TmaxP exceeds a predetermined value β and is large.
The timer counter C is reset to "0" and the current maximum exhaust temperature TmaxP is changed to the maximum exhaust temperature Tma.
After updating to x, this routine ends. On the other hand, when the determination condition of step S131 is not satisfied, the present routine is terminated as it is.

Based on the cylinder-by-cylinder fuel injection correction amount rChangTest (n) and the cylinder-by-cylinder exhaust temperature correction amount rAdapt (n) by the above-described cylinder-by-cylinder exhaust temperature correction routine every 8 [ms], the final fuel by cylinder of the internal combustion engine 10 is determined. The injection correction amount SfiCylAFComp (n) is calculated by the following equation (3), and the fuel injection for each cylinder is executed at a timing other than 8 [ms]. Here, rAdaptt (n) is the injector 14a to 14
This is a constant that is set in advance by d or the like and is unique to each cylinder.

[0028]

SfiCylAFComp (n) = rChangTest (n) + rAdapt (n) + rAdaptt (n) (3)

As described above, the fuel control apparatus for an internal combustion engine according to the present embodiment supplies the fuel to each cylinder of the internal combustion engine 10 having a plurality of cylinders (# 1 cylinder to # 4 cylinder).
a first catalytic converter 22 installed near the outlet of the exhaust manifold 21 in the middle of the exhaust passage of the internal combustion engine 10 and purifying the exhaust gas;
First catalytic converter 2 in the exhaust passage of internal combustion engine 10
A second catalytic converter 24 installed downstream of the first catalytic converter 22 for purifying exhaust gas, and an upstream of the first catalytic converter 22 near the outlet of the exhaust manifold 21 in the exhaust passage of the internal combustion engine 10; An exhaust gas temperature sensor 31 installed at least on one side of the upstream side of the second catalytic converter 24 on the downstream side of the second catalytic converter 24 and detecting the exhaust gas temperature of the exhaust gas; An ECU 4 for controlling the fuel supply unit to increase or decrease the fuel amount for each cylinder sequentially at predetermined intervals
0, an average exhaust temperature rAveTempM, which is an average value of the exhaust gas temperature during the control period by the fuel increase / decrease control means, and an exhaust gas temperature, which is the exhaust gas temperature for each period. A fuel correction means is provided by the ECU 40 for correcting a cylinder-specific final fuel injection correction amount SfiCylAFComp (n), which is a fuel amount for each cylinder, based on a difference from the temperature rTempTest (n).

That is, during the steady operation of the internal combustion engine 10, the fuel amount for each cylinder is sequentially increased or decreased every predetermined period. Then, an average exhaust gas during an increase or decrease control period of the fuel amount for each cylinder is detected by an exhaust temperature sensor 31 installed near the outlet of the exhaust manifold 21 in the middle of the exhaust passage of the internal combustion engine 10 and upstream of the first catalytic converter 22. temperature
rAveTempM and exhaust temperature rTempTes for each cylinder at the end of fuel change
The final fuel injection correction amount SfiCyl for each cylinder based on the difference from t (n)
AFComp (n) is corrected. As a result, variations in the air-fuel ratio of each cylinder of the internal combustion engine 10 can be eliminated,
First catalytic converter 22 and second catalytic converter 2
4 can be quickly activated to improve the emission and reduce the exhaust gas temperature under a high load.

The fuel correction means achieved by the ECU 40 of the fuel control system for an internal combustion engine according to the present embodiment comprises an ECU 4
If the difference between the maximum exhaust temperature Tmax during the previous control period and the maximum exhaust temperature TmaxP during the current control period by the fuel increase / decrease control means achieved at 0 is larger than a predetermined value β, the fuel amount is for each cylinder. Final fuel injection correction amount for each cylinder SfiCylAF
The correction of Comp (n) is performed again.

That is, the fact that the difference between the maximum exhaust gas temperature Tmax during the previous control period and the maximum exhaust gas temperature TmaxP during the current control period is larger than the predetermined value β means that the cylinder-specific final fuel injection correction amount SfiCylAFComp (n) It is determined that the correction is still insufficient, and the correction is continued until the correction becomes equal to or less than the predetermined value β. Thereby, since the variation in the air-fuel ratio of each cylinder of the internal combustion engine 10 can be appropriately converged, the first catalytic converter 22 and the second catalytic converter 24 are quickly activated, and the emission is improved. It is possible to achieve a reduction in the exhaust gas temperature under a high load.

In the above embodiment, the exhaust gas temperature sensor 31 is installed on the upstream side of the first catalytic converter 22. However, the present invention is not limited to this. 31 may be installed downstream of the first catalytic converter 22 and upstream of the second catalytic converter 24. Further, the exhaust temperature sensor 31 is connected to the first
It is also possible to install one each on the upstream side of the catalytic converter 22 and on the downstream side of the first catalytic converter 22 and on the upstream side of the second catalytic converter 24, and to appropriately adapt the calculation using their exhaust temperatures. Further, the exhaust temperature sensor 31
May be installed in the branch passage of the exhaust manifold 21 corresponding to each cylinder of the internal combustion engine 10 on the upstream side of the first catalytic converter 22. As a result, although the number of the exhaust gas temperature sensors 31 increases, the fuel injection amount correction for each cylinder of the internal combustion engine 10 can be more appropriately performed, and the catalytic converter is quickly activated, thereby improving the emission and increasing the exhaust gas temperature under a high load. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which a fuel control device for an internal combustion engine according to an embodiment of the present invention is applied, and peripheral devices thereof.

FIG. 2 is a process of correcting a cylinder-by-cylinder exhaust gas temperature for fuel injection by a cylinder in a CPU in an ECU used in a fuel control device for an internal combustion engine according to an embodiment of the present invention; It is a flowchart which shows a procedure.

FIG. 3 is a flowchart showing a continuation of FIG. 2;

FIG. 4 is a time chart showing transition states of various control amounts and the like corresponding to the processes of FIGS. 2 and 3;

[Explanation of symbols]

Reference Signs List 10 internal combustion engine 14a, 14b, 14c, 14d injector (fuel supply means) 21 exhaust manifold 22 first catalytic converter 24 second catalytic converter 31 exhaust temperature sensor 40 ECU (electronic control unit)

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FB03 FC07 FC08 HA03 HA08 HA36 HA37 HA42 3G301 HA01 HA06 JA25 JA26 JA33 KA09 KA21 LB02 MA01 MA12 NA01 NA02 NA06 NA07 NA08 NB04 NB11 NC08 ND04 ND12 ND15 NE03 NE08 PA01Z PB03A PD11A PD11Z

Claims (2)

[Claims] 1. A fuel supply means for supplying fuel to each cylinder of an internal combustion engine comprising a plurality of cylinders, and a first catalytic converter installed near an exhaust manifold outlet in an exhaust passage of the internal combustion engine to purify exhaust gas. A second catalytic converter installed downstream of the first catalytic converter in the exhaust passage of the internal combustion engine to purify exhaust gas; and a second catalytic converter in the vicinity of the exhaust manifold outlet in the exhaust passage of the internal combustion engine. Exhaust temperature detecting means for detecting an exhaust gas temperature, which is installed on at least one of an upstream side of the first catalytic converter and a downstream side of the first catalytic converter and an upstream side of the second catalytic converter; During steady-state operation of the internal combustion engine, sequentially for every predetermined period, a fuel increase / decrease control unit that controls the fuel supply unit to increase or decrease the amount of fuel for each cylinder, An internal combustion engine comprising fuel correction means for correcting a fuel amount for each cylinder based on a difference between an average value of the exhaust gas temperature during a control period by the fuel increase / decrease control means and an exhaust gas temperature for each period. For fuel control. 2. The fuel correction unit according to claim 1, wherein a difference between a maximum exhaust temperature during a previous control period and a maximum exhaust temperature during a current control period by said fuel increase / decrease control unit is larger than a predetermined value. The fuel control device for an internal combustion engine according to claim 1, wherein the correction of the amount is performed again.