JPH0454246A - Fuel controller for engine - Google Patents

Abstract

PURPOSE:To prevent any over-riching after the middle period of acceleration by determining an acceleration degree on the basis of a deflection between a measured suction air quantity and a moderated suction air quantity of the measured suction air quantity with application of a moderating treatment to perform an acceleration increase, and restricting the acceleration increase when the measured suction air quantity is decreased. CONSTITUTION:Upon operation of an engine, a control unit 20 calculates a measured suction air quantity on the basis of an engine speed Ne and an air flow sensor output valve Qa, a moderated suction air quantity of the measured suction air quantity with application of a moderating treatment, and a basic injection pulse of a fuel injection valve 15 corresponding to the moderated suction quantity. An acceleration degree of an engine is determined on the basis of a suction quantity deflection between the measured suction quantity and the moderated suction quantity, and fuel is acceleratingly increased in an acceleration state. Furthermore, the acceleration increase is restricted if the measured suction quantity is decreased with the suction quantity deflection. With the restriction of increase, any over-riching after the middle period of acceleration can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control device for an engine that increases the amount of fuel at an accelerated rate.

[Prior art] Fuel is injected at a constant ratio to the intake air amount, and the air-fuel ratio (A
Fuel-injected engines that maintain the air-fuel ratio /F) at a stoichiometric air-fuel ratio are conventionally known. In such a fuel-injected engine, during acceleration, there is a slight time delay before an increase in fuel injection amount relative to an increase in intake air amount is actually reflected in the air-fuel ratio (A/F). For this reason,
A phenomenon in which the intake air becomes lean at the beginning of acceleration (hereinafter referred to as a lean spike) occurs. Therefore, a fuel injection type engine has been proposed in which the amount of fuel injected during acceleration is increased compared to normal times (hereinafter referred to as acceleration amount increase). (For example, see Japanese Patent Publication No. 60-17939).

In an engine configured to increase acceleration in this way, it is necessary to detect the degree of engine acceleration. ), an engine is known in which the degree of acceleration of the engine is detected based on the rate of change with respect to time. Such an engine has the advantage that it is possible to detect the degree of acceleration based on the output value of the existing airflow sensor and only by software support of the control unit, and there is no need to provide any particular acceleration detection means.

By the way, in general, in an engine, air pulsation or turbulence occurs in the intake passage due to blowback when the intake valve is opened, and air flow due to such pulsation is also detected by an air flow sensor, so the intake air amount There is a problem that the detection accuracy decreases. In addition, since changes in the intake air volume due to such pulsations occur within a short period of time, the rate of change with respect to that time becomes extremely large. There is a problem in that it particularly hinders detection. Note that the influence of such pulsation is particularly significant in hot wire type or hot film type air flow sensors.

Therefore, a fuel control device has been proposed that performs fuel injection based on a rounded intake air amount obtained by performing so-called smoothing processing, such as taking a weighted average of a plurality of recently measured intake air amounts.

In such a fuel control device, the smoothed intake air amount is calculated by taking into account the past actually measured intake air amount, so when accelerating (
During deceleration), a deviation (hereinafter referred to as intake air amount deviation) occurs between the currently measured intake air amount and the smoothed intake air amount depending on the degree of acceleration.

The applicant has focused on this fact and has already developed a fuel system that calculates the degree of acceleration of the engine based on the intake air amount deviation and increases the amount of fuel for acceleration when the engine is in a predetermined acceleration state. We are proposing a control device (Patent Application No. 1999).
-326447). In such a fuel control device, since the rate of change of the measured intake air amount over time is not used to calculate the degree of acceleration, it is possible to substantially eliminate the effects of pulsation, etc., and to make accurate acceleration determinations. There are advantages.

[Problems to be Solved by the Invention] However, when the inventors conducted further detailed research on an engine in which the amount of fuel is increased during acceleration based on the intake air amount deviation, it was found that the lean spike at the initial stage of acceleration was prevented. However, it has been found that a phenomenon in which the air-fuel ratio (A/F) significantly deviates to the rich side (hereinafter referred to as over-riching) occurs after the middle of acceleration (including after the end of acceleration).

In response to this, a possible solution is to terminate the acceleration increase after a certain period of time or after a certain number of ignitions after the start of the acceleration increase in fuel. However, with this countermeasure, the increase in acceleration is uniformly terminated regardless of whether the acceleration is slow or fast, so it is not possible to increase the acceleration amount appropriately depending on the speed or speed of acceleration.

Another possible measure is to raise the acceleration determination level and bring the end of the acceleration increase earlier. However, with this countermeasure, there is a problem in that the timing of starting the acceleration increase is delayed, making it impossible to sufficiently suppress lean spikes.

The present invention has been made in view of the above-mentioned problems of the conventional art, and it is an object of the present invention to appropriately increase the amount of acceleration according to the speed of acceleration in an engine that increases the amount of fuel for acceleration based on the intake air amount deviation. An object of the present invention is to provide an engine fuel control device that can prevent lean spikes in the early stages of acceleration and prevent over-richness after the middle stage of acceleration.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a measured intake air amount directly obtained from an output value of an intake air amount detection means and a smoothing process for the measured intake air amount. This engine fuel control device calculates the degree of acceleration of the engine based on the deviation of the intake air amount from the rounded intake air amount obtained by hand,
To provide a fuel control device for an engine, characterized in that an acceleration increase in fuel is limited when the measured intake air amount decreases in a state where there is a deviation between the measured intake air amount and the smoothed intake air amount.

[Operations and Effects of the Invention] In general, during acceleration, regardless of whether it is slow or fast, from the point at which the measured intake air amount begins to decrease (hereinafter this point is referred to as the inflection point), the air that is actually drawn into the cylinder starts to decrease. While the amount decreases and the intake condition is corrected, the lean spike is brought under control.
The trend is towards over-richness.

According to the present invention, at such an inflection point, the increase in acceleration is restricted by reducing or terminating the increase in acceleration, so that the lean spike at the initial stage of acceleration is effectively suppressed by increasing the acceleration before the inflection point. By restricting the increase after the inflection point, overriching after the middle period of acceleration is suppressed.

Therefore, depending on the speed of acceleration, it is possible to both prevent lean spikes from occurring in the early stages of acceleration and prevent over-richness from occurring after the middle stage of acceleration.

[Example] Examples of the present invention will be specifically described below.

As shown in FIG. 1, when the intake valve 1 is opened, the engine E sucks a mixture into the combustion chamber 4 from the intake passage 3 via the intake boat 2, and the piston 5 injects the mixture into the combustion chamber 4. After being compressed, it is ignited with a spark plug (not shown) to cause combustion.
The combustion gas is discharged into an exhaust passage 8 through an exhaust port 7 when the exhaust valve 6 is opened.

The intake passage 3 includes, in order from the upstream side, an air cleaner 11 that removes floating dust in the intake air, a hot film type air flow sensor 12, and a throttle valve I3 that opens and closes in conjunction with an accelerator pedal (not shown). , a surge tank 14 that stabilizes the flow of intake air, and a fuel injection valve 15 that injects fuel into intake air.

The intake passage 3 is provided with a small-diameter bypass intake passage 17 that bypasses the throttle valve 13, and a bypass valve 18 that opens and closes the bypass intake passage 17 is interposed. The bypass valve 18 is opened during high loads such as when the air conditioner is operating or when the power steering system is operating to increase the idle.

In order to control the fuel of the engine E, a control unit 20 composed of a microcomputer is provided.
The control unit 20 is provided with an air flow sensor output value Qas output from the air flow sensor 12, an idle switch signal Idle output from the idle switch 2I, a cooling water temperature Tw output from the water temperature sensor 22, and a rotation speed sensor. Fuel control is performed using the engine rotational speed Ne etc. output from 23 as control information. In addition, the control unit 20
corresponds to the fuel control device according to claim 1.

Hereinafter, a method of controlling fuel by the control unit 20 will be explained according to the flowcharts shown in FIGS. 2(a) and 2(b).

The control unit 20 basically controls the air-fuel ratio (A
/F) is maintained at the stoichiometric air-fuel ratio (excess air ratio λ = 1), but as mentioned above, lean spikes occur during acceleration, so to prevent this, fuel control is performed. Accelerated increase in dosage is now being carried out.

When the control is started, in step Sl, the engine rotation speed Ne, the air flow sensor output value Qa, and the cooling water temperature T are determined.
w and the idle switch signal Idle are read.

In step S2, using Equation 1, engine rotation speed Ne
The measured intake air amount CEo is directly calculated from the air flow sensor output value Qa. Note that in equation 1, K is a conversion coefficient.

CE○= K-Qa/ Ne・・・・・・・・・・・・
...... Formula 1 In Step S3, the rounded intake air amount CEcca is calculated using Formula 2, and the basic injection pulse width of the fuel injection valve 15 corresponding to this rounded intake air amount CEcca is calculated. Ccca is calculated using Equation 3.

CEcca= CEcca' ・Kcca+ CEo(
1-Kcca)-Formula 2Ccca=Kp-CEcca...
・・・・・・・・・・・・・・・・・・・・・Formula 3 Formula 2
In Equation 3, CEcca' is the previous rounded intake air amount, Kcca is the rounded coefficient, and Kp is a conversion coefficient for converting the intake air amount into the pulse width of the fuel injection valve 15.

As described above, in the intake passage 3, pulsation or turbulence of intake air occurs due to blowback or the like, so such a smoothing process is performed to eliminate this influence. Note that the smoothing coefficient Kcca is the previous smoothing intake jlcEc
The weight of ca', that is, the contribution rate of the past actually measured intake air amount to the current rounded intake air amount CEcca.

In step S4, the intake air amount deviation ΔCEA is calculated using Equation 4.

ΔCEA= CEo −CEcca・・・・・・・・・
・・・・・・・・・・・・・・・・・・Equation 4 Here, the annealed intake air amount CEcca is the previous annealed intake air amount CEcc.
Since it is calculated using a', that is, the past actually measured intake air amount, there is a time delay with respect to the actually measured intake air amount CEo during acceleration, so there is an intake air amount deviation ΔCE^ between CEo and CEcca. arise. For example, as shown in Fig. 3, when the measured intake air amount CEo changes as shown in curve G during acceleration, the rounded intake air amount CEcca changes as shown in curve G, and there is an acceleration difference between the two. An intake air amount deviation ΔCEA is generated depending on the situation. Therefore, this intake air amount deviation ΔCEA determines the degree of acceleration of the engine E. Therefore, in this embodiment, when the engine E is in an operating state such that the conditions of steps S5 to S7 below are satisfied, the intake air amount deviation ΔCEA is Accelerated fuel increase is performed.

First, in step S5, the idle switch signal Idl
A comparison is made to see if e is off. In this embodiment, the acceleration amount is not increased during idling (L).

Even if the accelerator pedal is depressed and a lean spike occurs when the engine is idling, there is no need to increase the amount of fuel since this state is idling. As a result of the comparison, the idle switch signal I
If dle is on (No), that is, if it is idling, step S9 is executed and the acceleration increase value Cac
c (pulse width) is set to 0.

On the other hand, as a result of the comparison in step S5, if the idle switch signal Idle is off (YES), that is, if it is not idling, step S6 is executed to determine whether the intake air amount deviation ΔCEA exceeds the acceleration determination level Kgacmn. are compared. This acceleration judgment level Kgacmn
is set to an appropriate value so that an increase in acceleration can be prohibited during trivial acceleration that does not occur substantially in a lean manner.

As a result of the comparison in step S6, ΔCEA≦Kgacmn
If so (No), the acceleration is small and there is no need to increase the acceleration, so step S9 is executed and the acceleration increase value Cacc is set to zero.

As a result of the comparison in step S6, ΔCEA > Kgac
If mn (YES), step S7 is executed, and it is determined whether the difference between the current measured intake air amount CEo and the previous measured intake air amount CEo' is greater than or equal to 0, that is, whether or not the actually measured intake air amount is increasing. are compared. As described above, if the acceleration amount is increased until the acceleration ends, over-riching will occur, so in order to prevent this, the acceleration amount increase is discontinued at the point when the measured intake air amount CEo starts to decrease (inflection point).

As a result of the comparison in step S7, if CEo-CEo'≧0 (YES), the measured intake air amount CEo is still increasing, so step S8 is executed to suppress the lean spike, and the acceleration increase value Cacc is calculated using Equation 5.

Cacc=(ΔCEA K1) 'Kt・Ks
・KP・"'-""" Equation 5 In Equation 5, Kl is a constant for setting the dead zone, K is a weighting coefficient for setting the weight of the acceleration increase, and K3 is a weight coefficient for setting the weight of the acceleration increase. is the temperature correction coefficient for correcting the accelerated increase.
Kl) is a conversion coefficient for converting the intake air amount into the pulse width of the fuel injection valve 15.

As a result of the comparison in step S7, CEo −CEo'<
If it is 0 (No), the inflection point has been reached and the measured intake air amount CE
.

is decreasing, so while the lean pressure will soon converge, over 1 hatch will occur.Therefore, step S9 is executed, and the acceleration increase value Cacc is increased.
is set to 0, acceleration increase is discontinued, and over-riching is suppressed. For example, as shown in FIG. 3, at time t. If acceleration starts at time t, and the measured intake air amount CEo starts to decrease at time t, the acceleration increase value Ca
cc (curve G,) becomes 0 after time t.

After this, in step S10, the final injection pulse width C is calculated using Equation 6.

C=Ccca+Cacc+Ce1se・・・・・・・・・
・・・・・・・・・・・・・・・・Equation 6 In Equation 6, Ce1se is the fuel increase value (injection pulse) due to causes other than acceleration, and depends on the operating state of engine E. , set in the usual way.

In step Sll, the final injection pulse width C is output to the fuel injection valve 15, and fuel injection corresponding to the final injection pulse width C is performed. After this, the process returns to step Sl.

When such fuel control is performed, the curve G in FIG.
As shown in 4, overriching hardly occurs after the middle stage of acceleration. Therefore, lean spikes can be suppressed and over-richness can be suppressed.

On the other hand, as shown in Fig. 4, if the acceleration increase is not stopped when the actual intake air amount decreases (curve HI, Ht
, Hs), significant overriching occurs after acceleration (curve H,).

In this embodiment, the acceleration increase is terminated when the measured intake air amount begins to decrease, but the method of limiting the acceleration increase is, of course, not limited to this. For example, at the point when the actually measured intake air amount starts to decrease, the weighting coefficient in Equation 5 may be reduced to limit the acceleration increase. Further, the acceleration increase value Cacc may be gradually decreased at an appropriate ratio from the point in time when the actually measured intake air amount begins to decrease.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an engine equipped with a fuel control device according to the present invention. FIGS. 2(a) and 2(b) are flowcharts showing the fuel control method by the control unit, respectively. FIG. 3 is a diagram showing the characteristics of the intake air amount, acceleration increase value, and excess air ratio with respect to time during acceleration. FIG. 4 is a diagram similar to FIG. 3 in the case where the acceleration increase is not limited when the measured intake air amount decreases. E... Engine, 3... Intake aL12... Air flow sensor, 13... Throttle valve, 15... Fuel injection valve, 20... Control unit, 21... Idle switch, 22... Water temperature sensor, 23 river rotation speed sensor. Figure 3

Claims (1)

[Claims] (1) Based on the intake air amount deviation between the measured intake air amount obtained directly from the output value of the intake air amount detection means and the smoothed intake air amount obtained by performing an annealing process on the measured intake air amount. ,
An engine fuel control device that calculates the degree of acceleration of the engine and increases the amount of fuel for acceleration when the engine is in an accelerating state, in a state where there is a deviation between the measured intake air amount and the smoothed intake air amount. 1. A fuel control device for an engine, characterized in that when an actual intake air amount decreases, an acceleration increase in fuel amount is limited.