JPH0275737A - Air/fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at the improvement of exhaust characteristics by setting air/fuel ratio feedback correction quantity through an integral component, etc, set according to the correction quantity and setting fuel supply quantity according to the correction quantity, at the time of air/fuel ratio feedback control. CONSTITUTION:A basic supply quantity setting means A for setting basic supply quantity according to the operating state of an engine and a correction quantity setting means B for setting correction quantity of every kind are provided and an integral component is set by an integral component setting means C according to the basic supply quantity. Air/fuel ratio feedback correction quantity is suddenly changed due to a proportional component so as to approach an air/fuel ratio detected by an air/fuel ratio detecting means D to a target air/fuel ratio, and a feedback correction quantity setting means E for gradually changing and setting a feedback correction quantity due to set integral component is provided. Fuel supply quantity is set by a fuel supply quantity setting means F according to the air/fuel ratio feedback correction quantity, the basic supply quantity and the correction quantity of every kind and a fuel supply means G is driven and controlled by a driving control means H according to the set fuel supply quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio control device for an internal combustion engine, and particularly to one that performs feedback control of the air-fuel ratio.

<Prior Art> In an air-fuel ratio control device for an internal combustion engine, particularly in an electronically controlled fuel injection type internal combustion engine, the intake air flow ff1Q generally detected by an air flow meter and the engine rotation speed N detected from an ignition signal of an ignition coil are used. Therefore, the basic injection amount T of fuel is
, (=KQ/N; is a constant), correct this as appropriate to obtain the fuel injection amount TI, and based on this, the output pulse of the pulse width is used to control the fuel injection at a predetermined timing, for example, once every engine rotation. The system drives the electromagnetic fuel injection valve to supply the optimum amount of fuel to the engine.

Here, the fuel injection amount (output pulse) Tt is calculated using the following formula (%). In addition, C0EF is various correction coefficients, α is the air-fuel ratio feedback correction coefficient described later, KBLRC is the learning correction coefficient, KM
ET is a methanol mixing ratio correction coefficient, and T is a voltage correction factor based on the battery voltage.

For feedback control of the air-fuel ratio, an oxygen sensor is attached to the exhaust manifold to detect the actual air-fuel ratio, and the slice level determines whether the air-fuel ratio is leaner or richer than the stoichiometric air-fuel ratio (target air-fuel ratio). The amount of fuel injected is controlled so that the above-described air-fuel ratio feedback correction coefficient α is determined, and by varying this α, the stoichiometric air-fuel ratio is maintained.

Here, the air-fuel ratio feedback correction coefficient αΦ value is changed by proportional-integral (PI) control to achieve stable control.

That is, compare the voltage value of the oxygen sensor with the slice level, and if the air-fuel ratio is rich (lean), first lower (raise) by the proportional bone P, then gradually lower it with the slope of the integral ■ ( control the air-fuel ratio to make it leaner (richer).

To specifically illustrate the state of this PI control, as shown in Figure 4, when the air-fuel mixture deviates to a direction richer than the stoichiometric air-fuel ratio, the air-fuel mixture is returned to near the stoichiometric air-fuel ratio based on the following principle. It will be done. In other words, as shown on the left side of the diagram, when the air-fuel mixture shifts to the richer side, the time for the air-fuel ratio to become richer than the stoichiometric air-fuel ratio is longer than for the air-fuel ratio to become leaner, resulting in a longer time for the oxygen sensor voltage to exceed the slice level. Become. Therefore, the air-fuel ratio feedback correction coefficient α is gradually shifted in the direction of decreasing as shown in the figure by the signal from the oxygen sensor, and as a result, the air-fuel ratio is controlled to be around the stoichiometric air-fuel ratio as shown on the right side of the figure.

Here, the integral I is determined by multiplying the basic integral i, which is looked up in a table based on the engine operating state, by the fuel injection T.

<Problems to be Solved by the Invention> However, in such a conventional air-fuel ratio control device, since the integral (2) is determined based on the fuel injection amount T, there are the following problems.

That is, since the fuel injection amount T1 includes a voltage correction numerator corresponding to the rising invalid pulse width required to open the fuel injector according to the battery voltage, during low load operation such as idling operation, the above-mentioned There is a problem in that the influence of the voltage correction numerator becomes large and .largecircle. becomes large, deteriorating the exhaust characteristics. Furthermore, in engines that use alcohol-mixed fuel, the methanol mixing ratio correction coefficient KMET changes greatly depending on the methanol mixing ratio, and even in the same operating range, the above I changes greatly, resulting in the same problem as above. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air-fuel ratio control device that can optimally set an integral during air-fuel ratio feedback control.

Means for Solving the Problems> For this reason, the present invention, as shown in FIG. a correction amount setting means B for setting an integral based on the set basic supply amount; an air-fuel ratio detecting means for detecting the actual air-fuel ratio of the engine; a feedback correction amount setting means E for rapidly changing the air-fuel ratio feedback correction amount using a proportional bone and then gradually changing it using the set integral so that the air-fuel ratio of the air-fuel ratio approaches the target air-fuel ratio; a fuel supply amount setting means F for setting a fuel supply amount based on the set air-fuel ratio feedback correction amount, the basic supply amount, and the various correction amounts; and a fuel supply amount setting means based on the set fuel supply amount. A drive control means H for controlling drive G is provided.

<Operation> In this way, during air-fuel ratio feedback control, the air-fuel ratio feedback correction amount is set using an integral set based on the basic supply amount, and the fuel supply amount is set based on this correction amount. did.

<Example> An example of the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, a control device 1 consisting of a microcomputer etc. receives an intake air flow rate signal Q detected by an air flow meter 2, an engine rotation speed signal N detected by a rotation speed sensor 3, and an air-fuel ratio detection means. The oxygen concentration detection signal in the exhaust gas detected by the oxygen sensor 4 and the water temperature detection signal detected by the water temperature sensor 5 are input.

The control device 1 operates according to the flowchart shown in FIG. 3, and outputs an injection pulse signal to the guest injection valve 6 as a fuel supply means via the drive circuit 7.

Here, the control device 1 constitutes a basic supply amount setting means, a correction amount setting means, an integral setting means, a feed pump/punk correction amount setting means, and a fuel supply amount setting means. Further, the control device 1 and the drive circuit 7 constitute a drive control means.

Next, the operation will be explained according to the flowchart shown in FIG.

At Sl, various signals from the air flow meter 2, rotation speed sensor 3, etc. are read.

In S2, a basic injection amount T9 as a basic supply amount is calculated based on the intake air flow rate signal Q from the air flow meter 2 and the engine speed signal N from the rotation speed sensor 3 using the following equation.

TP = -Q/N (K is a constant) In S3, various correction coefficients C0EF are calculated based on the water temperature signal from the water temperature sensor 5, the throttle valve opening signal from the throttle sensor (not shown), etc. .

In S4, a rising invalid pulse width T required for opening the fuel injection valve is calculated according to the battery voltage.

In S5, it is determined whether or not the operating state is one in which air-fuel ratio feedback control is performed. Specifically, when the water temperature detected by the water temperature sensor 5 is equal to or higher than a predetermined value and the throttle valve opening detected by the throttle sensor is Fully open (high load operation)
, and when the rate of change in throttle valve opening is below a predetermined value, such as slow acceleration/deceleration operation or steady operation conditions, and the oxygen sensor 4 is determined to be normal, etc., corresponds to the air-fuel ratio feedback control condition. . If air-fuel ratio feedback control is not to be performed, the process proceeds to S12, where the air-fuel ratio feedback correction coefficient α is set to a predetermined value α. (for example, α.=1) and proceed to S6.

In S6, the proportional component P and the basic integral 1 are searched from the map. The basic integral i is stored in a map in correspondence with the engine operating state. Further, the proportional portion P is stored in the map so that it decreases with time from the start of the air-fuel ratio feedback control and becomes a substantially constant value after a predetermined period of time has elapsed.

In S7, it is determined whether or not the output of the oxygen sensor 4 has been reversed. If NO, the process advances to S8, and if YES, the SIO
Proceed to. Here, when the actual air-fuel ratio detected based on the output voltage of the oxygen sensor 4 switches to the rich side or the lean side with respect to the target air-fuel ratio (λ-1), the output of the oxygen sensor 4 is reversed. It is determined that

In S8, after setting P found in S6 to zero, S
Proceed to step 9.

In S9, the integral I (=
After calculating i×2T,), the process proceeds to Sll.

On the other hand, in SIO, after setting the integral I to zero, S11
Proceed to.

Sll is the air-fuel ratio feedback correction coefficient α set in the previous routine. A new air-fuel ratio feedback correction coefficient α (-α. 10 P+1) is calculated based on the P minute set in S6 or S8, and the integral ■ set in S9 or 310.

In this way, the air-fuel ratio feedback correction coefficient α rapidly increases (decreases) immediately after the output of the oxygen sensor 4 is reversed, and then gradually increases (decreases) at the slope of the integral ■ until the next output is reversed.
decrease), change.

In S13, the fuel injection amount T1 is calculated using the following equation.

Ti = 2xT, xcOEFxαXKBLRCxKME
T+T.

Note that KBLRC is a learning correction coefficient, KMET is a methanol mixing ratio correction coefficient, and T is a voltage correction factor based on the battery voltage.

Then, an injection pulse signal corresponding to the calculated fuel injection amount T is outputted to the fuel injection valve 6 via the drive circuit 7 to cause fuel injection to be performed.

As explained above, since the integral I is set based on the basic injection amount Tp, the integral I can be set without being influenced by the voltage correction numerator or the methanol mixing ratio correction coefficient KMET. Integral I in driving leaning castle
are almost the same, thereby improving the exhaust characteristics.

<Effects of the Invention> As explained above, the present invention sets the integral based on the basic supply amount during air-fuel ratio feedback control to determine the air-fuel ratio feedback correction amount and perform fuel supply. can improve exhaust characteristics without being affected by various correction amounts.

[Brief explanation of the drawing]

Fig. 1 is a claim correspondence diagram of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Fig. 3 is a flowchart of the same as above,
FIG. 4 is a time chart showing an example of air-fuel ratio feedback control. l...Control device 2...Air flow meter 3
...Rotation speed sensor 4...Oxygen sensor 6...
・Fuel injection valve 7... Drive circuit patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney

Claims (1)

[Claims] basic supply amount setting means for setting the basic supply amount based on the engine operating state; correction amount setting means for setting various correction amounts; and integral setting means for setting the integral based on the set basic supply amount. means, an air-fuel ratio detection means for detecting the actual air-fuel ratio of the engine, and after rapidly changing the air-fuel ratio feedback correction amount by a proportional amount so that the detected actual air-fuel ratio approaches the target target air-fuel ratio. Feedback correction amount setting means that gradually changes and sets according to the set integral, and sets a fuel supply amount based on the set air-fuel ratio feedback correction amount, the basic supply amount, and the various correction amounts. 1. An air-fuel ratio control device for an internal combustion engine, comprising: a fuel supply amount setting means for controlling the fuel supply amount; and a drive control means for driving and controlling the fuel supply means based on the set fuel supply amount.