JPS6155332A - Air-fuel ratio controlling method of electronic fuel-injection engine - Google Patents

Abstract

PURPOSE:To keep an air-fuel ratio in the desired value as well as to prevent an exhaust gas component from getting worse, by calculating a suction air quantity compensation factor, compensating a rising portion for pressure in a surge tank according to the time elapsed after starting or accelerating, while compenstaing the air quantity for decrement. CONSTITUTION:The air taken in by way of an air cleaner 12, after being metered by an air flow meter 14, is drawn in a combustion chamber 10A by suction together with fuel to be spouted out of an injector 20 installed in a suction manifold 19 via a suction pipe 15, a throttle valve 16 and a surge tank 18. An electronic fuel-injection controller 26 calculates an injection quantity on the basis of a suction air quantity or the like out of the air flow meter 14. And, in time of starting or accelerating, it calculates a decrement compensation factor for compensating a rising portion for pressure inside the surge tank and also calculates the injection quantity with the suction air quantity after compensation. With this constitution, in time of starting, an air-fuel ratio is preventing from being overrich and, what is more, an exhaust gas component is prevented from getting worse.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an air-fuel ratio control method for an electronic fuel injection engine, and in particular to an air-fuel ratio control method for an electronic fuel injection engine that detects the intake air amount measured upstream of a throttle valve and a surge tank, which is suitable for use in an automotive electronic fuel injection engine that senses the amount of intake air. The present invention relates to an improvement in an air-fuel ratio control method for an electronic fuel injection engine that determines the amount of fuel injected based on the air flow rate.

[Prior art 1] Generally, in an intake air amount sensing type multi-cylinder electronic fuel injection engine, a surge tank is provided to prevent intake air interference, and an air flow meter is used to measure air flow upstream of the surge tank and the throttle valve. The intake air flow rate (fuel injection!) is determined based on the air pressure and volume. Therefore, when the throttle valve is opened during a first start or acceleration, the intake air flow that passes through the air flow meter installed upstream of the surge tank will combine with the air supplied to the engine for combustion and the pressure inside the surge tank. It is the sum of the air to raise it. [Problems to be Solved by the Invention] However, conventionally, the air flow meter
Since the fixed intake air flow rate is used as is for calculating the fuel injection amount, the amount of fuel 11 injected becomes excessive by the amount of air consumed to increase the pressure in the surge tank. Therefore, the air-fuel ratio becomes overrich and deviates from the narrow window range necessary to generate the purification performance of the three-way catalyst, causing a deterioration of exhaust gas components, especially HC and C○.
It had the following problem. Incidentally, as something similar to the present invention, the applicant has already proposed in Japanese Patent Application No. 58-44094 that input data from an air flow meter be smoothed using a smoothing coefficient that is a function of engine speed. However, this is to compensate for variations in the measured value of the airflow meter output due to intake pulsation, and it was not possible to effectively compensate for the pressure rise in the surge tank. (Objective of the Invention 1) The present invention has been made to solve the above-mentioned conventional problems, and can effectively compensate for the increase in pressure in the surge tank at the time of starting or accelerating. An air-fuel ratio control method for an electronic fuel injection engine that can maintain the air-fuel ratio at a target air-fuel ratio, such as the stoichiometric air-fuel ratio, even during acceleration, improve the exhaust gas purification performance of a two-way catalyst, and prevent deterioration of exhaust gas components. [Means for solving the problem] The present invention determines the fuel injection o: 1 m based on the intake air flow rate measured upstream of the throttle valve and the surge tank. In the air-fuel ratio control method for an electronic fuel injection engine, as summarized in FIG. 71 for the increase in pressure in the surge tank
The above object has been achieved by including a procedure for determining a correction coefficient that changes to compensate for i, and a procedure for reducing the intake air flow rate using the correction coefficient when starting or accelerating. Further, in an embodiment of the present invention, the fact that the engine is starting or accelerating is detected when the intake air pressure per engine revolution or the differential value of the throttle opening exceeds a set value. , the weight loss correction is started at an appropriate timing. Further, in another embodiment of the present invention, the correction coefficient is first set based on tl! according to the elapsed time after starting or accelerating. Appropriate weight loss correction is performed to effectively compensate for the increase in pressure in the surge tank by gradually decreasing from the value to the set value and then gradually increasing from the set value to the reference value. It is. [Operation] In the present invention, when determining the fuel injection amount based on the intake air flow rate measured upstream of the throttle valve and the surge tank, when starting or accelerating, the elapsed time after starting or accelerating is determined. Accordingly, the intake air flow rate is corrected to decrease using a correction coefficient that changes to compensate for the increase in pressure in the surge tank, so changes in the intake air flow can be suppressed. Therefore, the fuel injection 1)'II is kept low, and the air-fuel ratio at the time of starting and acceleration is kept at the target air-fuel ratio, for example, the stoichiometric air-fuel ratio, and the exhaust gas purification performance of the catalyst is improved.
It is possible to prevent deterioration of exhaust gas components. [Example] Hereinafter, an example of an air-fuel ratio control method for an automobile electronic fuel injection engine to which the present invention is adopted will be described in detail with reference to the drawings. In this embodiment, as shown in FIG.
4, the fuel is injected into the combustion chamber 10Δ of the engine 10 through the intake pipe 15, throttle valve 16, and surge tank 18, along with the fuel that is intermittently injected from the injector 20 disposed in the intake manifold 19. be done. The exhaust gases combusted and formed in the combustion chamber 10A are collected in the exhaust manifold 22 and then exhausted through the exhaust pipe 24. An electronic fuel injection computer (hereinafter referred to as an EFI computer) 26 controls the injector 20 based on the engine rotational speed calculated from the intake air flow rate measured by the airflow meter 14 and the output of a crank angle sensor 30 built into the distributor 28. The basic fuel injection amount to be injected at one time is calculated from the above, and this is calculated from the intake air temperature sensor 32 disposed in the air flow meter 14, the throttle sensor 34 that detects the opening degree of the throttle valve 16, and the exhaust manifold 22. An oxygen concentration sensor (hereinafter referred to as 02 sensor) 36 and a water temperature sensor 38 are provided on the downstream side of the
The actual injection time is determined by correcting the output, etc., and the injector 20 is opened for the actual injection time to inject an appropriate amount of fuel. As shown in detail in FIG. 3, the EFI computer 26 includes a central processing unit (hereinafter referred to as CP IJ) 26A that performs various calculations, and a central processing unit (hereinafter referred to as CP IJ) 26A for temporarily storing calculation data, input data, etc. Random access memories (hereinafter referred to as RAM) 26B and 26C, and read-only memory (hereinafter referred to as RON11) for pre-storing data and control programs necessary for calculations.
26D, the air flow meter 14, and the intake air temperature sensor 3
2. An analog-to-digital converter (for converting analog signals input from the throttle sensor 34, 02 sensor 36, water temperature sensor 38, etc. into digital signals and importing them)
An input/output board (hereinafter referred to as an A/D converter) that directly receives digital signals input from the crank angle sensor 308 and outputs a control signal to the injector 20 etc. according to the calculation result of the CPU 26A. 26F (hereinafter referred to as the I10 boat) and the common bus 2 that connects each of the component counters and transfers data and instructions.
It is composed of 6G. In the engine 10 as described above, when starting and accelerating, the pressure in the surge tank 18 placed in front of the engine combustion chamber 10A increases, so the amount of intake air passing through the air flow meter 14 increases This is the sum of the amount of intake air supplied to 10Δ and the amount of intake air for increasing the pressure inside the surge tank 18. For this reason, the EF
The intake air amount Q/N per engine revolution calculated by the I computer 26 is determined by the measured value (Q/N) shown in FIG. 4(A).
N) becomes c. Here, To is the start time of start or acceleration. However, since the intake air JiQ/N per engine rotation required in the engine combustion chamber 10A is the required value <Q/N)r shown in FIG. 4 (A>),
Measured value (Q, /N) c by the air flow meter output
As shown in FIG. 4(B), the amount of fuel for which the injection amount is determined is extra by <Q/N)c-(Q/N)r. This (Q/N) c - (Q/N) r amount of air does not participate in combustion and is used only to increase the pressure in the surge tank 18 . Therefore, when starting or accelerating,
Until time T3 when the surge tank internal pressure reaches a steady state,
If the intake air amount Q/''N per engine revolution is corrected and the fuel injection amount is not determined by request II ('Q/N)r, the amount of fuel will be increased by (Q/N)c - (Q/N>r). The injection G-1m increases, the purification rate of the three-way catalyst, especially the purification rate of HC and Co, decreases, and the exhaust gas components deteriorate.In reality, the required value (Q/N>r Since it is not possible to reduce the total amount to 11J, it is required by the reduction correction using the following formula! (Q
/N)r is approximated to determine the fuel injection amount. (Q/N)r-×(Q/N)c...(1) Here,
K is a correction coefficient that has characteristics that change over time as shown in FIG.
Time T when o~(Q/N)c=(Q/N)r reaches its peak
1, as shown in the following equation (2), the peak value KP
From time T1, the surge tank pressure reaches a steady state and opens at time T3, when (Q/N)c=(Q/N)r, as shown in the following equation (3). , standard +
11. It is arranged to decrease by a certain amount until it reaches o. K=1. 〇-(1,0-KP) XI/'(T+-To)...<2)K=K
p+ (1,0-Kp) x(t-T+>, ・'(T 3-T+ n ・
... (3) Here, t is the elapsed time Ff from time To
It is between f. In addition, in FIG. 4, time T2 is measured ILfi(Q
/N) c is the time at which the peak occurs. The peak value Kp of each time and the correction coefficient can be determined and fixed by an experiment, for example, but in the case of a certain 4-cylinder 2000cc engine, the time To=T
+fJ is 100n+s, and between time bottom 1 and T3 is 200Il
lS, the beak la K p was 0.3. Although this correction coefficient is calculated once every fixed time, the same effect can be obtained even if it is performed every injection. In this way, the required value (
Determine the fuel injection amount (1) of the injector 20 using Q, -''N)r, for example, using the following formula. (1=kx(Q/'N)r... (4> Here, k is the injector This is a constant determined by the size of 20. The operation of the embodiment will be explained below with reference to FIG. When the determination result is positive, the process proceeds to step 110, and it is determined whether the positive coefficient K is equal to the standard 111!1.0.If the determination result is positive, that is, the weight loss correction according to the present invention is performed. 1, if it is not correct, the process proceeds to step 114, where, for example, the differential amount Δ(Q/N)c of the measured value (Q7'N)c or the differential amount ΔTA of the throttle opening TA is calculated.
, e.g., t tf O, OOO25u , -' rotations/ms
Or, since it is larger than 0.5°/4 Is, it is determined whether the vehicle is in the initial stage of starting or accelerating. If the determination result is positive, that is, if it is determined that the reduction correction according to the present invention is necessary, the process proceeds to step 115, and the correction coefficient K is
It is determined whether a flag fXK is set, which indicates that the value should be increased. If the determination result is negative and it is determined that the correction coefficient K should be decreased, the process proceeds to step 116, where the correction coefficient K is decreased by a fixed amount as shown in the following equation. K"K-(1,0-Kp)X4/(T+To)...
(5) Next, the process proceeds to step 118, and it is determined whether the integrated value of the correction coefficient aK has become smaller than the peak ImKp=0.3. If the determination result is positive, the process proceeds to step 120, where the peak value 0.3 is entered into the correction coefficient K to guard the lower limit of the correction coefficient. Next, the process proceeds to step 122, where the flag rXK is set. On the other hand, if the determination result in step 115 is positive,
That is, when it is determined that it is necessary to increase the correction (ilIItJ,K from the peak value Kp), step 12
Proceeding to step G, the sluggishness coefficient K is increased by a fixed amount as shown in the following equation. +(1,0-Kp)X4/'(T3 T+)・
(6) Next, the process proceeds to step 128, where it is determined whether the integrated value of the correction coefficient has become equal to or greater than the standard 1 m 1.0. If the determination result is positive, the process advances to step 130 and the reference value 1 is set.
．． 0 is put into the correction coefficient K to guard the upper limit of the correction coefficient, and at step 132 the flag fXK is reset in preparation for the next time. If the judgment result in steps 114, 118, and 128 is negative, or after steps 122 and 132 are completed, proceed to step 134 and calculate the required value of intake air amount per engine revolution (Q/ N)reli! and exit this routine. (Q/N)rl-×<Q/N)c...<7) In the above embodiment, the present invention was applied to an electronic fuel injection engine for automobiles; It is clear that the scope is not limited thereto and can be similarly applied to general electronic fuel injection engines.

【Effect of the invention】

As explained above, according to the present invention, it is possible to effectively reduce the surge tank pressure increase in the intake air flow rate when starting or accelerating. 4
@can do. Therefore, over-richness can be prevented during start-up and acceleration, and the air-fuel ratio can be maintained at the target air-fuel ratio, for example, the stoichiometric air-fuel ratio. It has the excellent effect of increasing the exhaust gas purification rate of the three-way catalyst and preventing deterioration of exhaust gas components.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the air-fuel ratio control method for an electronic fuel injection engine according to the present invention, and FIG.
FIG. 3 is a block diagram showing the configuration of the electronic fuel injection computer used in the embodiment, and FIG. 4 is a sectional view showing the configuration of the embodiment of the device. FIG. 5 is a diagram comparing and showing the measured value of the intake air amount per engine revolution, the required field, the difference between the two, and the state of change of the correction coefficient during acceleration, which is used in the above embodiment. 2 is a flowchart showing a routine for determining the required source of the amount of intake air per revolution of the engine. DESCRIPTION OF SYMBOLS 10... Engine, 14... Air 70-meter, 16... Throttle valve, 18... Surge tank, 20... Injector, 26... Electronic fuel injection (EFI) computer, K
...Correction coefficient, KP...Beak 1st shift. Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) In an air-fuel ratio control method for an electronic fuel injection engine in which the fuel injection amount is determined based on the intake air flow rate measured upstream of the throttle valve and surge tank, the method must be performed during starting or acceleration. A procedure for determining a correction coefficient that changes to compensate for the increase in pressure in the surge tank depending on the elapsed time after starting or accelerating. 1. A method for controlling an air-fuel ratio of an electronic fuel injection engine, the method comprising: a step of reducing and correcting an intake air flow rate; (2) The engine 1
The intake air amount per rotation or the differential value of the throttle opening is
An air-fuel ratio control method for an electronic fuel injection engine according to claim 1, wherein the air-fuel ratio control method for an electronic fuel injection engine is configured to detect when the air-fuel ratio exceeds a set value. (3) The correction coefficient is configured to first gradually decrease from a reference value to a set value, and then gradually increase from the set value to the reference value, depending on the elapsed time after starting or accelerating. An air-fuel ratio control method for an electronic fuel injection engine according to claim 1.