JPH08312410A - Controlling method for air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE: To cool a catalyst by fuel by correcting fuel injection quantity, a base, by instantly increasing power without waiting for the elapse of delay time in a high-load operating state even when vehicular traveling speed exceeds predetermined speed over a predetermined period. CONSTITUTION: An O2 sensor 21, and a three way catalyst 22 are stationed in an exhaust system 20. In addition, provided are an electronic control device 6, an engine speed sensor 14 for detecting engine speed, and a speed sensor 15, etc. When vehicular traveling speed is detected, and a continuous operating state, the detected traveling speed exceeds predetermined speed, over a predetermined period is detected, delay time is inhibited to correct fuel injection quantity, a base, by increasing power under a high-load operating state. Thus, air-fuel ratio comes to rich to cool a catalyst by fuel. Therefore, the heating of the catalyst is effectively prevented without degrading drivability under high-load operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an air-fuel ratio control method for an internal combustion engine at high load in an automobile engine.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection type engine, so-called feedback control operation is usually performed by the stoichiometric air-fuel ratio. However, in order to secure output performance under high load, or in high rotation and high load range. In order to reduce the combustion temperature in the above and maintain the catalyst temperature at a predetermined temperature, the operation is performed with an output air-fuel ratio or an air-fuel ratio that is richer than it, a so-called power air-fuel ratio. In this case, the effective injection time is calculated by correcting the basic injection time that matches the theoretical air-fuel ratio with the power increase correction coefficient. In the air-fuel ratio control method of increasing the fuel injection amount using such a power increase correction coefficient, the operation in the high load region, that is, the high load operating state, and the operation under the normal load other than the high load region, that is, the normal load operating state In the case of repeatedly operating and, since the air-fuel ratio during normal load operation may change to the rich side when the increase is repeated each time, from the time when a certain period of time has passed after the transition to high load operation, That is, the fuel injection amount is increased after the set delay time has elapsed (for example, Japanese Patent Laid-Open No. 3-43640).

[0003]

However, as shown in FIG. 4 (a), when the normal load operating state (including feedback control operation) shifts to the high load operating state, a constant delay time T _{In the} control for performing the increase correction after the lapse of _D , as shown in (b) of FIG. 4, after the transition from the normal load operating state to the high load operating state, the normal load operating state is restored by the delay time T _D. , When the operating state is changed to the high load operating state again, the delay time T _D does not elapse after the operating state is changed to the high load operating state.
The fuel injection amount for the high load operation is not increased. In other words, despite the high load operation
Since the high load operation state is not continuously performed for the delay time T _D , the fuel injection amount increase is not executed in each high load operation state. As a result, the catalyst is not cooled by the rich air-fuel ratio, and since the high load operation is repeatedly performed, the catalyst temperature rises in the same manner as when the high load operation is continued, and the catalyst is deteriorated. Became.

An object of the present invention is to eliminate such a problem.

[0005]

In order to achieve the above object, the present invention takes the following measures. That is, an air-fuel ratio control control method for an internal combustion engine according to the present invention calculates a basic fuel injection amount based on at least the number of revolutions of an internal combustion engine equipped with a catalyst in an exhaust system and performs a high load operation. Sometimes, an internal combustion engine that determines the final fuel injection amount by correcting the basic fuel injection amount by a power increase set based on at least the number of revolutions after a predetermined delay time after shifting to high load operation In the air-fuel ratio control method, the traveling speed of the vehicle is detected, and the delay time is detected when it is detected that the operating state in which the detected traveling speed is higher than a predetermined speed is continuous for a predetermined time or longer. The feature is that the basic fuel injection amount is corrected by prohibiting and immediately increasing the power in a high load operation state.

[0006]

With such a structure, when the traveling speed of the vehicle exceeds the predetermined speed for more than the predetermined time, when the vehicle is in a high load operation state, the power is increased immediately without waiting for the delay time to elapse. Since the basic fuel injection amount is corrected by, the catalyst can be cooled by the fuel. That is, when the operating state of the internal combustion engine repeats the high load operation and the normal load operation, the fuel injection amount is corrected by increasing the power after the delay time has elapsed from the start of the transition in the high load operating state. Rather than performing it, the state in which the traveling speed is higher than the predetermined speed in the operating state in which the both operating states are repeated continues for more than the predetermined time, so that the high load operating state after the delay time has substantially passed. The power increase is corrected by considering it. Therefore, the air-fuel ratio becomes rich due to the increased amount correction, and the heating of the catalyst is suppressed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The engine schematically shown in FIG. 1 is for an automobile, and its intake system 1 is provided with a throttle valve 2 which opens and closes in response to an accelerator pedal (not shown), and a surge tank is provided downstream thereof. 3 is provided. In the vicinity of the cylinder head 30 side end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3, a fuel injection valve 5 is further provided.
An intake valve 31 is provided in the cylinder head 30 in front of the fuel injection valve 5. Further, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of a three-way catalyst 22 arranged in a pipe line leading to a muffler (not shown). The O ₂ sensor 21 outputs a voltage signal h corresponding to the oxygen concentration.

The electronic control unit 6 includes a central processing unit 7
An A / D converter (not shown) mainly composed of a microcomputer system including a memory device 8, an input interface 9, and an output interface 11 for converting an input analog signal into a digital signal. Is built in. The input interface 9 has an intake pressure sensor 1 for detecting the pressure in the surge tank 3, that is, the intake pipe negative pressure (hereinafter referred to as intake pressure).
3, an intake pressure signal a output from the engine 3, a rotational speed signal b output from the rotational speed sensor 14 to detect the engine rotational speed NE, a vehicle speed signal c output from a vehicle speed sensor 15 to detect the vehicle speed, and a throttle. A throttle switch 16 has a power switch 16a that outputs a full-open signal fs when the valve 2 is fully open, and a throttle opening signal d and a full-open signal fs output from a throttle sensor 16 for detecting the open / closed state of the throttle valve 2. The water temperature signal e output from the water temperature sensor 17 for detecting the cooling water temperature of the engine, the voltage signal h output from the O ₂ sensor 21, and the like are input. On the other hand, the output interface 11 outputs a fuel injection signal f corresponding to an effective injection time TAU described later to the fuel injection valve 5 and an ignition pulse g to the spark plug 18.

The electronic control unit 6 has an intake pressure signal a output from the intake pressure sensor 14 and a rotation speed signal b output from the rotation speed sensor 15 as main information, and is determined according to the rotation state of the engine. Various correction factors including a power increase correction factor FPOWER, for example, a post-starting amount increase correction factor FSE,
The basic injection time TP is corrected by the warm-up increase correction coefficient FWL, the air-fuel ratio feedback correction coefficient FAF, etc. to set the fuel injection valve opening time, that is, the effective injection time TAU, and the fuel injection valve 5 is controlled by the set time. The fuel corresponding to the engine load from the fuel injection valve 5 to the cylinder head 30.
A program for injecting into the nearby intake system 1 is built in. The correction by the power increase correction coefficient FPOWER is performed by the full open signal fs output from the power switch 16a.
When a high load operation is detected based on the above, it will be executed when the set delay time elapses in the state where the high load operation continues from the detection time, and at least the high load operation and the normal load operation are repeated. Even if continuous, if the traveling speed exceeds the predetermined speed and the state continues for a predetermined time or longer, the process is executed without delay after the lapse of the predetermined time. That is, in this program,
Detects the running speed of the vehicle, and if the detected running speed exceeds the specified speed and it is detected that the driving condition continues for more than the specified time, prohibits the delay time and immediately starts in the high load operating condition. It is programmed to correct the basic fuel injection amount by increasing the power.

The outline of this air-fuel ratio control program is shown in FIG.
As shown in. However, as the program itself for calculating the effective injection time TAU in consideration of various correction factors during steady operation, a conventionally known program can be used, and therefore illustration and description thereof will be omitted.

First, in step S1, it is determined whether the traveling speed (vehicle speed) V is higher than a predetermined speed V _D ,
If it is higher than the predetermined speed V _D
In the following cases, the process proceeds to step S4. Step S2
Then, the elapsed time T after the traveling speed exceeds the predetermined speed
Is above the predetermined time T _V, and if it is above the predetermined time T _V , the process proceeds to step S3. If the predetermined time T _V is not reached, the process proceeds to step S6. Elapsed time T
Is to count from the number of times this routine is executed,
It exceeds the predetermined time T _V when the predetermined number of times is counted. In step S3, the delay time T _D is prohibited (=
0) Specifically, for example, a counter that counts the delay time T _D is set to a count-up state, a state in which the delay time T _D has elapsed in a pseudo manner, and a state in which delay cannot be executed are set. In step S4, the elapsed time T is set to 0.
That is, the number of executions of the routine that has been counted up to that point is set to zero. In step S5, the delay time T _D is set to a normal time.

In such a structure, as shown in FIG. 3, a case where the traveling speed V of the vehicle gradually increases and exceeds the predetermined speed V _D in a high load operation state will be described. Running speed V
However, when the high load operation is performed at a speed equal to or lower than the predetermined speed V _D , the control proceeds to steps S1 → S4 → S5 to set the normal delay time T _D. After that, when the traveling speed V increases and exceeds the predetermined speed V _D , the traveling speed V becomes the predetermined speed V _D.
The control is repeated by repeating steps S1 → S2 → S6 until _D is continuously exceeded and the predetermined time T _V elapses. During this time, even when the load state is repeated between high load and normal load, the elapsed time T is measured by the traveling speed V and the power increase correction timing is controlled. Then, the running speed V is higher than the predetermined speed V _D, a predetermined time T _V has elapsed without becoming below a predetermined speed V _D, control, step S1
→ S2 → S3 and proceeds, prohibits the delay time T _D, by correcting the basic injection time TP by the high load becomes a driving state power enrichment coefficient FPOWER, the air-fuel ratio rich. In other words, if the vehicle is in the high load operation state when the predetermined time T _V has elapsed, the power increase correction is immediately executed, and then the traveling speed V does not fall below the predetermined speed V _D and the normal load operation state is set. At the same time as the load operation state is reached, the power increase correction is executed again.

As described above, even in an operating state in which the high load state and the normal load state are repeated, when the state in which the traveling speed V exceeds the predetermined speed V _D continues for a predetermined time T _V or more. In addition to the delay time T _D , if the high load operation state is reached after the predetermined time T _V has elapsed, the power increase correction coefficient FP
Since the basic injection amount TP is corrected by the OWER, the fuel amount is increased and corrected even when the operating state changes.
Therefore, the temperature of the three-way catalyst 22 rises according to the operating state at that time within the predetermined time T _V , but the increase correction is not delayed by the delay time T _D , that is, after the predetermined time T _{V has} elapsed. Since the increase correction is performed without delay, there is no problem that the temperature continues to rise and exceeds the allowable temperature as shown by the dotted line in FIG. As a result, the air-fuel ratio becomes rich,
The three-way catalyst 22 is cooled and its deterioration can be prevented. Further, since the increase correction of the fuel injection amount corresponding to the high load operating state can be performed, the air-fuel ratio can be maintained at a value adapted to the operating state, and drivability can be stabilized.

The present invention is not limited to the embodiment described above.

Besides, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0017]

As described in detail above, the present invention provides immediate operation without waiting for the delay time to elapse in the high load operation state when the traveling speed of the vehicle exceeds the predetermined speed for more than the predetermined time. Since the basic fuel injection amount is corrected by increasing the power, the air-fuel ratio becomes rich, and the catalyst can be cooled by the fuel. Therefore, heating of the catalyst can be effectively prevented without deteriorating the drivability during high-load operation.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is an operation explanatory view of the same embodiment.

FIG. 4 is an explanatory view of the operation of a conventional example.

[Explanation of symbols]

 1 ... Intake system 2 ... Throttle valve 5 ... Fuel injection valve 6 ... Electronic control unit 7 ... Central processing unit 8 ... Memory device 9 ... Input interface 11 ... Output interface 20 ... Exhaust system 22 ... Three-way catalyst

Claims (1)

[Claims] 1. A basic fuel injection amount is calculated based on at least the number of revolutions of an internal combustion engine mounted on a vehicle with a catalyst in an exhaust system, and is set based on at least the number of revolutions during high load operation. A method for controlling an air-fuel ratio of an internal combustion engine, which corrects a basic fuel injection amount by a power increase performed after a predetermined delay time after shifting to a high load operation to determine a final fuel injection amount. When the running speed is detected and the detected running speed exceeds the specified speed and it is detected that the operating condition continues for more than the specified time, the delay time is prohibited and the power is immediately applied in the high load operating condition. An air-fuel ratio control control method for an internal combustion engine, characterized in that a basic fuel injection amount is corrected by increasing the amount.