JPH0447134A - Air-fuel ratio correction method during transient period - Google Patents

Abstract

PURPOSE:To effectively suppress disturbance of an air-fuel ratio during acceleration by gradually damping an acceleration increase amount of fuel to be fed during acceleration at each feed period, in a device which transiently increases and corrects fuel according to an acceleration state. CONSTITUTION:An electronic control device 4 inputs output signals (d) from a crank angle sensor 10 and a pressure sensor 11 and outputs a fuel injection signal (a) to an injector 3 mounted on an intake air pipe 5. The electronic control device decides a fundamental injection time based on an intake air amount determined from the number of revolutions of an engine and an intake air pressure. Based on an intake air pressure change amount rapidly changed when an engine 1 is shifted to an acceleration state, a transient air-fuel ratio correction factor is decided, a fundamental injection time is corrected by means of a correction factor, and injection of fuel is effected at a given fuel injection period. When an acceleration state is continued, a transient air-fuel ratio correcting factor is damped according to an acceleration deciding circuit at a next fuel feed period, and a fundamental injection time is increased and corrected by means of the value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transient air-fuel ratio correction method mainly applied to automobile engines.

[Prior Art] Generally, when an engine transitions from a steady state to an accelerated state, the engine temporarily enters a state of excess air and insufficient fuel. Therefore,
As prior art of the present invention, for example, Japanese Patent Application Laid-Open No. 61-255
As shown in Japanese Patent No. 237, the acceleration state of the engine is detected and the amount of fuel is temporarily increased in accordance with the acceleration state. In a device that uses an injector as a fuel supply device, as shown in Fig. 4, a transient air-fuel ratio correction coefficient FAEW is set, and the intake JEEPM
The acceleration state is detected by PH, etc., and the transient air-fuel ratio correction coefficient PAEW is determined to be an appropriate value in accordance with the acceleration state, thereby adjusting the amount of fuel increase due to acceleration.

[Invention or Problem to be Solved] However, in the conventional method of iJ, once the acceleration amount increase is determined according to the acceleration state, the fuel is continuously increased by the acceleration amount from immediately after the start of acceleration until the end of acceleration. An increase in the amount is corrected. That is, as shown in FIG. 4, if the acceleration state continues, the fuel increase adjustment is continued by the acceleration increase amount every time fuel is supplied. For this reason, in the first fuel supply immediately after the start of acceleration, it is necessary to check whether the required amount and the fuel supply amount can match. , the amount of fuel supplied exceeds the amount requested, which tends to result in excess fuel. As a result, the air-fuel ratio A/F changes to the rich side from midway through acceleration to near the end of acceleration, resulting in worsening of emissions.

The present invention aims to solve the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, the transient air-fuel ratio correction method according to the present invention corrects the transient air-fuel ratio by transiently increasing the amount of fuel supplied to the combustion chamber when the engine shifts to an acceleration state, depending on the acceleration state. The correction method is characterized in that the acceleration increase amount of fuel to be supplied during acceleration is gradually attenuated at each fuel supply timing.

[Function] According to such a configuration, when acceleration is performed, the acceleration increase amount of fuel is determined according to the acceleration state, and at the beginning of acceleration where excess air tends to occur, the acceleration increase amount i is determined. The amount of fuel is corrected by increasing the amount. If the engine continues to accelerate, the increased amount of acceleration will be gradually attenuated at each fuel supply period. Therefore, the increased amount of fuel supplied to the combustion chamber due to acceleration gradually decreases as the acceleration continues.

[Example 1] An example of the present invention will be described below with reference to FIGS. 1 to 3.

The engine 1 shown schematically in FIG. 1 is of a motor vehicle and is equipped with an electronically controlled fuel injection system 2.

The electronically controlled fuel injection device 2 is configured to detect the amount of intake air based on the intake pressure and engine speed, and includes an injector 3 and an electronic control device 4.

The injector 3 is attached to the intake pipe 5 and has a built-in electromagnetic coil and the like. When a fuel injection signal a is applied to the electromagnetic coil from the electronic control device 4, an amount of fuel corresponding to the application time is injected into the vicinity of the intake port.

The electronic control device 4 includes a central processing unit 6 and a memory 7.
It is a microcomputer unit equipped with an input interface 8 and an output interface 9, and plays the role of adjusting the amount of fuel injected from the injector 3 based on information from various sensors.

The input interface 8 receives inputs such as an engine rotation signal and a crank angle signal C from the crank angle sensor 10, and an intake pressure signal d from the pressure sensor 11. A fuel injection signal a is output to the injector 3.The crank angle sensor 10 is built into the distributor 12, and generates a pulse corresponding to the crank angle like a normal sensor. The pressure sensor 11 is provided in the surge tank 13 and outputs an electrical signal in proportion to the intake pressure.

The electronic control device 4 determines the amount of intake air from the engine speed and intake pressure, and determines the basic injection time T based on the amount of intake air.
Determine P. Next, the basic injection time TP is adjusted to various correction coefficients determined depending on the engine condition, and the invalid injection time TA is adjusted.
The final injection time T for opening the injector 3 is determined for each fuel supply timing by correcting it by tJV.

Further, a program as schematically shown in FIG. 2 is set in the electronic control device 4. In step 51,
Based on the crank angle signal C, it is determined whether or not it is the fuel injection timing, and if it is the fuel injection timing, the process proceeds to step 52.

In step 52, based on the amount of change in intake pressure (absolute pressure), it is determined whether the engine 1 has transitioned to an acceleration state,
If the acceleration state has been entered, the process proceeds to step 53; if the acceleration state has not been entered, the process proceeds to step 56. In step 53, the acceleration determination counter CACC is incremented by 1, and the process proceeds to step 54. In step 54,
The transient air-fuel ratio correction coefficient FAEW is adjusted according to the amount of change in intake pressure.
is calculated, and the process proceeds to step 55. In step 55, the transient air-fuel ratio correction coefficient FAEW is set to a value of 1/N according to the value of the acceleration determination counter CACC, and then the process proceeds to step 57. In step 56, the acceleration determination counter CACC is cleared and the process proceeds to step 57.

In step 57, the final injection time T is determined based on the following equation, and the process proceeds to step 58.

T = TPX (1+FAEW) XK +TAUV In step 58, the injector 3 is opened for a time corresponding to the final injection time T to perform fuel injection. Note that the above control is repeatedly executed during engine operation.

According to such a configuration, when the engine 1 shifts to an acceleration state, the intake pressure PM75 (
Change rapidly. Then, based on the amount of change ΔPH, a transient air-fuel ratio correction coefficient FAEW is determined, and the basic injection time TP is corrected by this transient air-fuel ratio correction coefficient FAEW, and the fuel is injected from the injector 3 at a predetermined fuel injection timing. will be held. When the acceleration state continues, at the next fuel supply timing, the transient air-fuel ratio correction coefficient FAEW is attenuated in accordance with the number of acceleration determinations N, and the basic injection time TP is increased by the value. If the acceleration state continues, the transient air-fuel ratio correction coefficient PAEW is further attenuated at each fuel injection timing as described above. Therefore, the transient fuel increase amount corresponding to the transient air-fuel ratio correction coefficient FAEW gradually decreases from the middle of acceleration to near the end of acceleration.

Therefore, according to such a configuration, the required amount of fuel can be quickly supplied to the combustion chamber 14 at the beginning of acceleration when there is a tendency to have excess air. Excess/fuel shortage conditions can be effectively suppressed. In addition, as the acceleration state continues, the transient increase in fuel amount is gradually reduced, so the fuel supply amount decreases from the middle to the latter half of acceleration when the basic injection amount increases following the acceleration state. It is possible to prevent excess fuel from exceeding the required amount. As a result, as shown in FIG. 3, it is possible to effectively suppress disturbances in the air-fuel ratio A/F during acceleration, and to avoid deterioration of emissions.

Note that the present invention can also be effectively applied to cases where the amount of intake air is directly measured using an air flow meter or the like.

[Effects of the Invention] According to the present invention configured as described above, it is possible to effectively suppress disturbances in the air-fuel ratio during acceleration, thereby achieving control accuracy that can effectively reduce emissions during acceleration. An excellent transient air-fuel ratio correction method can be provided.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, FIG. 1 is a schematic overall configuration diagram, FIG. 2 is a flowchart diagram schematically showing a control procedure, and FIG. 3 is an action explanatory diagram. be. FIG. 4 is an operational explanatory diagram corresponding to FIG. 3 showing a conventional example. 1...Engine 3...Injector 4...Electronic control unit 11...Pressure sensor 14...Combustion chamber FAEW...Transient air-fuel ratio correction coefficient

Claims (1)

[Claims] In a transient air-fuel ratio correction method in which the amount of fuel supplied to the combustion chamber is temporarily increased depending on the acceleration state when the engine shifts to an acceleration state, the increase in fuel to be supplied during acceleration is A method for correcting an air-fuel ratio during a transient period, characterized by gradually attenuating the fuel at each fuel supply period.