JPH02199244A - Correcting method for air-fuel ratio at transition time - Google Patents

Abstract

PURPOSE:To quickly and properly regulate the quantity of fuel supply in response to transition conditions, and thereby prevent an air-fuel ratio from being fluctuated by increasing/decreasing a transition time air-fuel ratio correcting factor which regulates the quantity of fuel injection at the transition times in reverse proportion to the absolute value of intake air pressure. CONSTITUTION:The electronic control device 4 of an electronically controlled fuel injection system 1 determines a transition time air-fuel ratio correction factor in response to the variation of intake air pressure detected by a pressure sensor 9 so as to regulate the quantity of fuel injection at the transition time. In this case, the transition time air-fuel ratio correcting factor is increased/decreased in reverse proportion to the absolute value of intake air pressure. Which permits the transition time air-fuel ratio correction factor to be increased/decreased as the variation of intake air pressure is increased/decreased. Meanwhile, when the absolute value of intake air pressure is low, the correction factor becomes great, and when said value is high, the factor becomes little. For example, when an engine is shifted from a normal operation to an accelerating one, the quantity of fuel supply is regulated so as to be increased at the early stage of acceleration, being gradually regulated so as to be decreased as acceleration comes to an end. Thus, the quantity of fuel supply can thereby be regulated quickly and properly in response to transition conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transient air-fuel ratio correction method employed in an engine of an automobile or the like equipped with an electronically controlled fuel injection device.

[Prior Art] An electronically controlled fuel injection device equipped with a fuel injection valve is capable of determining changes in engine load based on regularly detected changes in intake pressure. As shown in Japanese Patent No. 144632, there are some systems in which the transient air-fuel ratio correction coefficient is determined in accordance with the amount of change in the intake pressure. The transient air-fuel ratio correction coefficient corrects the amount of fuel injected from the fuel injection valve during a transient period, and adjusts the air-fuel ratio of the air-fuel mixture supplied to the engine.

[Problems to be Solved by the Invention] However, although such a system is excellent in the responsiveness of injection amount adjustment to changes in intake pressure, it is insufficient in terms of control accuracy for transient situations. For example, it is desirable that the amount of fuel required during acceleration increases from the beginning of acceleration to the middle of acceleration, and gradually decreases as the engine shifts to steady operation from the latter half of acceleration. However, if the transient air-fuel ratio correction coefficient is determined only by the amount of change in intake pressure,
If the amount of change in intake pressure during acceleration is constant, the fourth
As schematically shown in the figure, even if the absolute value of the intake pressure increases and the load increases, the transient air-fuel ratio correction coefficient is determined to be a constant value, so the correction amount applied thereto also remains constant. Therefore, at the beginning of acceleration when the change in intake pressure is small, there is a fuel shortage and the air-fuel ratio shifts to the lean side, and in the latter half of acceleration and immediately after the transition to steady operation, the amount of fuel is not reduced enough and the air-fuel ratio becomes rich. It tends to shift to the side. These factors cause deterioration in transient emissions, drivability, and the like.

The present invention aims to solve such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention determines a transient air-fuel ratio correction coefficient corresponding to the amount of change in intake pressure, and uses the transient air-fuel ratio correction coefficient to adjust the transient air-fuel ratio correction coefficient of the engine. In the transient air-fuel ratio correction method for adjusting the fuel injection amount, the transient air-fuel ratio correction coefficient is increased or decreased in inverse proportion to the absolute value of the intake pressure.

[Operation] According to such a configuration, the transient air-fuel ratio correction coefficient is determined by at least two types of factors. In other words, this transient air-fuel ratio correction coefficient increases or decreases as the amount of change in intake pressure increases or decreases, and increases or decreases when the absolute value of intake pressure is small, and decreases when the absolute value of intake pressure increases. becomes. For this reason, for example, when acceleration is performed from steady-state operation, the amount of fuel supplied according to the transient air-fuel ratio correction coefficient is adjusted to increase at the beginning of acceleration, and as the acceleration reaches the end from the beginning of acceleration, the amount of fuel supplied according to the transient air-fuel ratio correction coefficient is increased. The supply amount will be gradually adjusted down.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

The engine schematically shown in FIG. 1 is used in an automobile and is equipped with an electronically controlled fuel injection device 1. The engine shown schematically in FIG. The electronically controlled fuel injection device 1 includes a fuel injection valve 3 attached to an intake pipe 2, and an electronic control device 4 that controls the opening time of the fuel injection valve 3 according to engine conditions.
Various information for adjusting the air-fuel ratio of the air-fuel mixture, etc. is input to the electronic control device 4.

The fuel injection valve 3 has a built-in electromagnetic coil, and when a fuel injection signal a is applied from the electronic control device 4 to the electromagnetic coil, fuel corresponding to the application time of the fuel injection signal a is injected into the intake port. It is designed to be sprayed nearby.

The electronic control device 4 includes a central processing unit 5 and a memory 6.
, an input interface 7 , and an output interface 8 . The input interface 7 receives at least an intake pressure signal from a pressure sensor 9 and a crank angle sensor 10 .
The engine rotation signal C from the engine, engine cooling water temperature information, etc. are input. The pressure sensor 9 is
The intake pressure PMTP in the surge tank 11 can be detected, and the crank angle sensor 10 provided in the distributor 12 is configured to be able to detect the engine speed. On the other hand, the output interface 8 outputs a fuel injection signal a toward the fuel injection valve 3.

Then, this electronic control device 4 calculates the amount of intake air from the intake pressure signal C, engine rotation signal C, etc., and adjusts the basic injection amount determined according to the intake air amount by various correction coefficients determined according to the engine situation. The fuel injection valve 3 is corrected by
It plays the role of adjusting the amount of fuel injected from the combustion chamber 13 to the combustion chamber 13.

For example, when accelerating the engine, the intake pressure PM
The base value DPMTPA of the transient air-fuel ratio correction coefficient FAEWA is determined in response to the change in TP fiDPMTP, and the base value DPMTPA is calculated as the absolute value of the intake pressure I PMTP.
It is designed to be adjusted in inverse proportion to I. Then, the basic injection amount is adjusted by multiplying the determined transient air-fuel ratio correction coefficient FAEWA by the basic injection amount, and the fuel injection amount during acceleration is set to be increased.

A program as schematically shown in FIG. 2 is set in the electronic control device 4 in order to determine the transient air-fuel ratio correction coefficient FAEWA, and the program is executed every time ignition dimming is performed. It is. First, in step 51, based on the intake pressure signal from the pressure sensor 9,
The intake pressure PMTP is detected and the process proceeds to step 52. In step 52, the latest intake pressure pMTp detected for each ignition is
Step 5: Calculate the amount of change DPMTP in the intake pressure PMTP from the difference between l and the previous intake pressure PMTPI-z.
Proceed to step 3. In step 53, the above change ffiDPMT
A base value DPMTPA of the transient air-fuel ratio correction coefficient FAEWA is determined in correspondence with P, and the process proceeds to step 54. In step 54, the absolute value I PMTP of the intake pressure PMTP
A correction coefficient KPPM inversely proportional to l is searched from a preset map, and the process proceeds to step 55. In step 55, the above-mentioned correction coefficient KPPM and a predetermined correction coefficient K determined by the engine cooling water temperature etc. are set to the base value DPMT.
The transient air-fuel ratio correction coefficient FAEWA is determined by multiplying by PA.

According to such a configuration, the intake pressure PMT during acceleration
If the amount of change in P increases or decreases, the transient air-fuel ratio correction coefficient FAEWA will basically change due to the change in intake pressure PMTP ff
It will increase or decrease according to iDPMTP (Step 5
1-53). In addition, the amount of change DPMTP in the intake pressure PMTP
When is constant, as schematically shown in FIG. 3, as the absolute value I of the intake pressure PMTP becomes smaller,
Contrary to the absolute value PMTPI, the transient air-fuel ratio correction coefficient F
AEWA is corrected to a large value. And the intake pressure PM
As the absolute value of TP l PMTP I gradually increases,
On the other hand, the transient air-fuel ratio correction coefficient FAEWA is gradually corrected to a smaller value. Therefore, the fuel supply amount related to the transient air-fuel ratio correction coefficient FAEWA is equal to the intake pressure PMT.
It is adjusted according to the amount of change in P DPMTP, and
The amount is gradually reduced from the beginning of acceleration to the end of acceleration.

Therefore, according to such a configuration, it is possible to eliminate fuel shortage from the beginning of acceleration to the middle of acceleration, and it is also possible to effectively eliminate excess fuel supply in the region from the latter half of acceleration to steady operation. It is possible to suppress variations in the air-fuel ratio from the time to immediately after the transition to steady operation. As a result, it is possible to reliably improve the deterioration of drivability during transient periods and the deterioration of emissions caused by variations in the air-fuel ratio and the like.

Note that the present invention is not limited to detecting the amount of intake air from intake pressure, engine speed, etc., but can also be applied to cases where the amount of intake air is directly detected using an air flow meter.

[Effects of the Invention] According to the present invention configured as described above, the fuel supply amount can be quickly and accurately adjusted according to the transient situation, and variations in the air-fuel ratio can be effectively suppressed. It is possible to provide an air-fuel ratio correction method during a transient period with excellent control accuracy that can effectively improve drivability, emissions, etc. during a transient period.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a schematic overall configuration diagram, FIG. 2 is a flowchart showing the control procedure, and FIG. 3 is a timing chart showing the control mode. It is. FIG. 4 is a timing chart corresponding to FIG. 3 showing a conventional example. 1...Electronically controlled fuel injection device 3...Fuel injection valve 4...Electronic control device 9...Pressure sensor

Claims (1)

[Claims] In the transient air-fuel ratio correction method, the transient air-fuel ratio correction coefficient is determined in accordance with the amount of change in the intake pressure, and the transient air-fuel ratio correction coefficient adjusts the fuel injection amount during the engine transient. A transient air-fuel ratio correction method characterized in that a temporal air-fuel ratio correction coefficient is increased or decreased in inverse proportion to the absolute value of intake pressure.