JPH02119651A - Air-fuel ratio control method for transient period - Google Patents

Abstract

PURPOSE:To eliminate delay of the controlling of fuel supply by discriminating the deceleration state of an engine, and controlling the fuel supply quantity in accordance with the amount of change in actually detected, newest intake pressure and previously detected intake pressure when the above amount of change exceeds a specified value. CONSTITUTION:An electrically controlled fuel injection device 1 loaded on an engine is provided with a fuel injection valve 3 loaded on an intake pipe 2, and an electronic control device 4 for controlling the fuel injection valve 3. The electronic control valve 4 controls the fuel injection valve 3 based on each detection signal from various sensors 11, 13 for detecting the operating state of the engine 1. Namely, when the engine is in transient state, the electronic control device controls the fuel supply quantity in accordance with the transient state. In this instance, when the amount of change in the newest intake pressure actually detected by the sensor 11 and previously detected intake pressure exceeds a specified value, the electronic control device discriminates the deceleration state of the engine, and reduces the fuel supply quantity in accordance with the above amount of change in the intake pressures.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transient air-fuel ratio control method that can be suitably used in engines such as automobiles equipped with an electronically controlled fuel injection device.

[Prior art] In this type of engine, the latest actual intake pressure actually detected by a pressure sensor and the previous actual intake pressure are smoothed,
By using the smoothed intake pressure, the adverse effects of pressure fluctuations caused by intake pulsation and the like are usually prevented. If the amount of change between the latest intake pressure subjected to the smoothing process and the previous intake pressure exceeds the set value, as a prior art of the present invention, for example, JP-A-58-13343
As shown in Publication No. 1, an electronic control device determines whether the engine is in an acceleration state or a deceleration state, and increases or decreases the amount of fuel supplied from the fuel injection valve to the combustion chamber according to the transient state. ing.

On the other hand, even if the engine shifts to a deceleration state, if the amount of change between the latest smoothed intake pressure and the previous intake pressure is less than the set value, the deceleration state of the engine cannot be determined and the fuel Also, weight loss adjustment is not performed.

[Problems to be Solved by the Invention] However, when measuring the pressure waveform of the intake pressure during deceleration, it was found that even in the case of extremely rapid deceleration, the amount of change is small at the beginning of deceleration, and it rapidly increases with time. have.

On the other hand, for the engine, it is necessary to reduce the amount of fuel supplied from the beginning of deceleration in synchronization with the actual deceleration state. However, the intake pressure does not immediately follow the change in throttle opening, and as schematically shown in FIG. 4, when the actually detected actual intake pressure P3 is rounded, the amount of change becomes smaller and Together with the characteristics of pressure fluctuation,
A delay occurs before transient determination is performed based on the intake pressure P4 after the smoothing process. Therefore, a transient determination is performed after the engine shifts to a deceleration state (T2), and a delay occurs until the fuel is actually reduced based on the transient determination (section A). As a result, the air-fuel ratio becomes overrich R, which deteriorates emissions, drivability, and the like. Such problems tend to become more noticeable during sudden deceleration.

The present invention aims to solve such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention determines the transient state of the engine based on the amount of change in the intake pressure that has been smoothed, and adjusts the fuel supply according to the transient state. In a transient air-fuel ratio control method configured to adjust the amount,
If the amount of change between the latest actual intake pressure actually detected and the previous actual intake pressure exceeds a predetermined value, the deceleration state of the engine is determined, and the latest actual intake pressure and the previous actual intake pressure are determined. The fuel supply amount is reduced in response to the amount of change in the amount of fuel supplied.

[Operation] According to such a configuration, the latest actual intake pressure actually detected and the previous actual intake pressure are successively compared.

If the amount of change exceeds a predetermined value, it is immediately determined that the engine has entered a deceleration state, and fuel reduction adjustment is performed in advance in accordance with the amount of change. If the amount of change between the latest intake pressure that has been smoothed and the previous intake pressure exceeds the set value and a transient state of the engine is determined, then the transient state will be determined based on the smoothed intake pressure. Fuel adjustments will be made at the time.

[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 installed in an automobile and is equipped with an electronically controlled fuel injection device 1. As shown 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 operation of the fuel injection valve 3. The amount of fuel supplied to the engine is adjusted by the electronic control device 4 based on information from various sensors and the like.

The fuel injection valve 3 has a built-in electromagnetic coil, and when the injection signal a is applied to the electromagnetic coil from the electronic control device 4, the fuel injection valve 3 injects an amount of fuel corresponding to the fuel injection time into the vicinity of the intake port. It has become.

The electronic control device 4 includes a central processing unit 6 and a memory 7.
, an input interface 8, an output interface 9, etc. At least the intake pressure signal from the pressure sensor 11 provided in the surge tank 10 and the engine rotation signal C from the rotation speed sensor 13 provided in the distributor 12 are input to the input interface 8, and the output interface 9 From then on, an injection signal a is output to the fuel injection valve 3. The pressure sensor 11 is capable of continuously detecting the intake pressure, and the intake pressure signal is converted into a digital electrical signal via an A/D converter (not shown). The rotation speed sensor 13 is for detecting the engine rotation speed. Then, the electronic control unit 4 smoothes the latest actual intake pressure actually detected and the previous actual intake pressure, and uses the smoothed intake pressure to calculate the fuel injection amount, determine the engine state, etc. It has a role to be used for.

For example, if the amount of change between the latest intake pressure subjected to the smoothing process and the previous intake pressure exceeds a set value, engine transient determination is performed. If the transient state is acceleration, the amount of fuel is increased for acceleration in accordance with the amount of change in the previous state, and if the transient state is deceleration, the amount of fuel is adjusted to decrease.

Furthermore, if the amount of change between the latest actual intake pressure actually detected and the previous actual intake pressure exceeds a predetermined value, the electronic control unit 4 performs fuel adjustment during deceleration prior to the transient determination. It is set to do so.

To be more specific, the latest actual intake pressure actually detected and the previous actual intake pressure are constantly compared, and if the difference is negative and the amount of change exceeds a predetermined value, transient discrimination is performed. Even if this is not done, the fuel reduction rate is determined in accordance with the amount of change, and the fuel deceleration reduction is performed based on the determined reduction rate. After engine deceleration is determined based on the smoothed intake pressure, fuel control is performed in accordance with the amount of change in the smoothed intake pressure.

In order to execute such control, a program as schematically shown in FIG. 3 is set in the electronic control device 4. First, in step 51, it is determined whether or not transient discrimination has been performed based on the smoothed intake pressure. If it is determined that transient discrimination has been performed, the process proceeds to step 52, and if it is determined that transient discrimination has not been performed. If it is determined that this is the case, the process advances to step 54. In step 52, if the transient state is acceleration, a fuel increase rate is calculated in accordance with the amount of change in intake pressure; if the transient state is deceleration, a fuel reduction rate is calculated in accordance with the amount of change in intake pressure. , proceed to step 53. In step 53, the fuel injection amount is multiplied by the increase/decrease rate,
The amount of fuel to be actually injected into the combustion chamber 5 during acceleration or deceleration is determined, and the process proceeds to the main routine.

On the other hand, in step 54, the amount of change ΔP in the actual intake pressure is calculated by subtracting the pressure value of the actual intake pressure a certain period of time Tms ago from the latest pressure value of the actual intake pressure actually detected, and in step 55
Proceed to. In step 55, it is determined whether the amount of change ΔP is negative or not. If it is determined that it is not negative, the process moves to the main routine, and if it is determined that it is negative, step 5
Proceed to step 6.

In step 56, it is determined whether or not the absolute value 1ΔP1 of the amount of change ΔP exceeds a predetermined value P1. If so, proceed to step 57.

In step 57, the fuel reduction rate is calculated in accordance with the amount of change ΔP in the actual intake pressure, and the process proceeds to step 58. In step 58, the fuel injection amount is multiplied by the above reduction rate to determine the fuel injection amount actually supplied to the combustion chamber 5 during deceleration, and the process proceeds to the main routine.

According to such a configuration, the latest actual intake pressure actually detected and the previous actual intake pressure are successively compared, and the amount of change ΔP is calculated.
is negative and exceeds the predetermined value P1, it is immediately determined that the engine has shifted to a deceleration state. Therefore, at the beginning of deceleration when the pressure change is relatively small, the fuel reduction adjustment according to the change amount ΔP is performed in advance, prior to the fuel adjustment based on the smoothed intake pressure (step 51 → 54-58).

Then, when the amount of change between the latest intake pressure that has been smoothed and the previous intake pressure exceeds the set value and the deceleration state of the engine is determined, the amount of change in the smoothed intake pressure Accordingly, fuel reduction adjustment during deceleration is performed (steps 51 to 53).

Therefore, according to such a configuration, as schematically shown in FIG. 2, in the initial deceleration region 14 where fuel reduction adjustment is required, the fuel reduction rate is adjusted according to the pressure change of the actual intake pressure P1. is increased (see Ft), and the amount of fuel supplied from the fuel injection valve 3 to the combustion chamber 5 is adjusted to decrease in accordance with the m reduction rate. After the transient determination is made as the deceleration state progresses, the fuel reduction rate is determined based on the smoothed intake pressure P2 (F2), and the fuel reduction adjustment is performed based on the reduction rate. This will prevent the negative effects of intake pulsation and the like. As a result, overrich air-fuel ratio caused by delay in fuel reduction adjustment during deceleration is eliminated, and the air-fuel ratio can be maintained near the stoichiometric air-fuel ratio during deceleration, effectively suppressing deterioration of emissions, drivability, etc. .

Note that the present invention is not limited to an electronically controlled fuel injection device that determines the fuel injection amount based on engine speed, intake pressure, etc., but also determines the fuel injection amount based on the intake air pressure, etc. directly calculated by an air flow meter, etc. The present invention can also be suitably implemented in an electronically controlled fuel injection device configured as described above.

[Effects of the Invention] According to the present invention configured as described above, the delay in fuel adjustment during deceleration can be effectively eliminated, and the air-fuel ratio can be effectively suppressed from becoming overrich.
It is possible to provide a transient air-fuel ratio control method that can reliably improve emissions, drivability, etc. during deceleration.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a configuration explanatory diagram, FIG. 2 is a timing chart diagram, and FIG. 3 is a flowchart diagram showing a control procedure. FIG. 4 is a timing chart showing a conventional example. 1... Electronically controlled fuel injection device 3... Fuel injection valve 4... Electronic control device 5... Combustion chamber 10... Surge tank 11... Pressure sensor

Claims (1)

[Claims] In an air-fuel ratio control method during a transient state, which determines the engine transient state based on the amount of change in intake pressure that has been smoothed, and adjusts the fuel supply amount according to the transient state, If the amount of change between the latest actual intake pressure and the previous actual intake pressure exceeds a predetermined value, the deceleration state of the engine is determined, and the amount of change between the latest actual intake pressure and the previous actual intake pressure is determined. 1. A method for controlling an air-fuel ratio during a transient period, characterized in that the amount of fuel supplied is reduced in response to.