JPS60261944A - Air-fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the acceleration response by correcting the fuel supply with correspondence to the variation of the intake air-flow condition during rotation of engine by predetermined angle. CONSTITUTION:Intake air conditions such as the intake air pressure or intake air flow in an intake air path are detected. The variation of intake air condition during rotation of engine by predetermined angle is detected to correct fuel supply accordingly. Since the variation of intake air can be detected with timing synchronous with the engine rotation, it is never influenced by the variation within cycle resulting in accurate air-fuel ratio control.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention improves a control device that determines the amount of fuel to be supplied to an engine based on the operating state of the engine and achieves a predetermined air-fuel mixture and air flow. In particular, the present invention relates to improvements in air-fuel ratio control during transient operations such as acceleration and deceleration.

(Prior Art) An example of a device for supplying an air-fuel mixture of a predetermined air-fuel ratio to an internal combustion engine is the one disclosed in Japanese Patent Application Laid-open No. 144632/1983. This is done by installing a fuel injection valve in the intake passage to supply fuel to the engine, and opening the fuel injection valve for a predetermined time depending on the engine operating condition to supply a mixture with a predetermined air-fuel ratio to the engine. That is.

Here, the opening time of the fuel injection valve, that is, the amount of fuel supplied to the engine, is determined from the engine rotational speed and the intake air pressure in the intake passage downstream of the intake throttle valve, which corresponds to the intake air flow rate. Then, to the basic valve opening time determined in this way, air-fuel ratio feedback correction based on the oxygen concentration in the exhaust gas, engine cooling water temperature (water temperature correction, acceleration correction during acceleration, battery voltage correction, etc.) are added to the final valve opening time. The typical valve opening time is determined.

The acceleration correction is performed by detecting the amount of change in the intake air pressure within a predetermined period of time, making correction based on a value obtained by integrating a predetermined correction value increment according to the amount of change, and compensating for the lack of responsiveness due to this correction. Correction immediately after acceleration, that is, increase correction when the idle switch is detected to be off corresponding to cancellation of the intake throttle valve fully closed state, increase correction according to the rate of change of the intake throttle valve opening, etc.

(Problems to be Solved by the Invention) However, in this type of air-fuel ratio control, the fuel due to the above-mentioned increase correction for improving responsiveness adheres to the inner circumferential wall of the intake passage, and all of it contributes to the generation of air-fuel mixture. Moreover, the adhesion condition is not constant depending on the engine operating condition. Therefore, although this kind of correction is quick, the accuracy is not very good. For example, as shown in Fig. 7 (A).
As shown in the figure, the air-fuel ratio immediately after acceleration varies within the shaded area depending on the acceleration conditions, causing errors in the air-fuel ratio, resulting in an instantaneous increase in emissions such as Co, No, and HC, and a decrease in the generated torque. Problems such as poor drivability arise due to fluctuations.

Note that if these corrections are not made immediately after acceleration, the air-fuel ratio will be largely biased toward the lean side, as shown by the solid line in Figure 7 (A), and in addition to the above-mentioned disadvantages, there will also be a noticeable disadvantage of deterioration of acceleration response due to cylinder misfires. become.

In particular, in so-called lean-set internal combustion engines where the air-fuel ratio is set to the lean side, the tolerance range for the air-fuel ratio to the lean side is small, and if the air-fuel ratio of the air-fuel mixture supplied to the engine deviates to the lean side. It is easy to misfire, and on the other hand, if the engine deviates to the rich side, a large torque is suddenly generated and is easily affected by air-fuel ratio errors, so stable air-fuel ratio control is desired.

Such inconveniences also occur in air-fuel ratio control devices that determine the amount of fuel supplied to the engine based on the intake air flow rate and engine rotational speed, and acceleration correction based on the rate of change in intake air conditions per hour is generally not highly accurate. I couldn't say yes.

The present invention has been made to solve the problem of deviation of the air-fuel ratio from a predetermined value during such transient operation.
It is an object of the present invention to provide a control device that performs stable air-fuel ratio control even during transient operations such as acceleration and deceleration of an engine.

Means for Solving the Problems> To this end, the present invention, as shown in FIG. a means for detecting;
An air-fuel ratio control device comprising: means for determining the amount of fuel to be supplied to the engine based on the detection results of the two detecting means; and means for detecting the engine rotation angle; The engine is configured to include means for detecting the amount of change in the air condition, and means for correcting the amount of fuel supplied to the engine based on the detection result of the means.

According to this, changes in the intake air condition in the intake passage are detected at a timing synchronized with the engine rotation, and air-fuel ratio correction is performed based on the results, thereby preventing fluctuations within the cycle from being picked up. , accurate air-fuel ratio control becomes possible.

<Example) The present invention will be explained below based on an embodiment shown in FIG.

That is, in the figure, a fuel injection valve 3 is provided in an intake passage 2 downstream of an intake throttle valve 1, and the fuel injection valve 3 injects and supplies fuel fed under pressure from a fuel pump 4 to the engine. here,
Fuel is pumped up from the fuel tank 5 and passed through the fuel filter 6.
The fuel is filtered, regulated to a constant pressure by a pressure regulator 7, and guided to the fuel injection valve 3.

The fuel injection valve 3 is controlled by a signal issued from a control unit 8 configured by a microcomputer, for example, and the control unit 8 acts as an intake air condition detection means provided downstream of the intake throttle valve 1. The valve opening operating time of the fuel injection valve 3 is determined in a manner described later based on input signals from the pressure sensor 91, the crank angle sensor 10, and the water temperature sensor 11, which serve as engine rotation speed detection means and engine rotation angle detection means. ing.

Next, the operation will be explained with reference to the Lalo□-chart shown in FIG.

This routine is an interrupt routine that is activated by an interrupt signal issued at regular time intervals (for example, every 5 mS), and first, it is checked in Sl whether or not the start time of this interrupt routine is the fuel injection timing. If this time is the fuel injection timing, the process proceeds to step 3.17 and the fuel injection valve 3 is opened, whereas if it is not the fuel injection timing, the process proceeds to S2 and subsequent steps to calculate and determine the valve opening operation time.

In S2, the intake passage pressure MAP, which is the output of the pressure sensor 9 provided in the intake passage 2, is A/D converted, and in S3, this intake passage pressure MAP is smoothed. This is done to eliminate pulsations in the intake passage pressure MAP caused by the engine cycle, and is done, for example, by weighted averaging of new data and previous data with predetermined weights attached.

In S4, the current detected pressure value MAP and the previous detected pressure value M
Take the difference from APO, that is, the pressure change between S m s,
The value is integrated as KDM. This integration continues from the start of injection until the start of injection, so if one injection is performed per engine revolution, the change in intake passage pressure during one revolution of the engine can be obtained as KDM. Become. That is, this process corresponds to the intake air condition change rate detection means shown in FIG. 1, which detects the amount of change in the intake air condition while the engine rotates through a predetermined rotation angle. Next 3
In step 5, the current detected pressure value MAP is stored in MAPO.

In S6, the basic injection amount TP is calculated based on the intake passage pressure MAP read in S2 and the engine rotational speed N determined from the output of the crank angle sensor 10. This process corresponds to the supply fuel amount determining means shown in FIG.

In S7, it is determined from the magnitude of the absolute value of the integrated value KDM of pressure changes determined in S4 whether or not the engine is in a transient operating state that requires correction by KDM, and the integrated value KD of pressure changes is determined.
Determine whether the absolute value of M is greater than 20 mmHg,
If it is larger, it is regarded as a transient operating state, and the process proceeds to S8, where a correction value KN is calculated based on the rotational speed N. Next, in S9, a correction value KTW is calculated based on the engine cooling water temperature TW, which is the output of the water temperature sensor 11, and then in S'IO. The product of KDM multiplied by these correction values is added to TP to obtain the corrected injection amount TPI. With this correction, the injection amount increases as the change in the suction passage pressure, that is, KDM, increases while the engine rotates at a predetermined rotation angle. In other words, correction is performed that is appropriate for the degree of acceleration or deceleration.

Note that the correction value KN is calculated based on the rotational speed N,
The reason why this is multiplied by KDM is to compensate for the fact that the intake system differs depending on the rotational speed N, and the amount of fuel attached to the inner circumferential wall of the intake passage varies accordingly, which changes the actual amount of radiant radiation.
Although the specific value of KN varies depending on the engine, it may be set as shown in FIG. 4, for example.

In addition, the correction value KTW is calculated based on the engine cooling water temperature TW, and this is multiplied by KDM because the amount of fuel attached to the wall surface varies depending on the water temperature T and W, and the actual injection amount changes. This is for the purpose of correction, and the specific value of KTW may be, for example, as shown in FIG.

On the other hand, if the absolute value of KDM is smaller than 2QmmHg, proceed to 311 and use the TP determined in S6 as the corrected injection amount TP.
Let it be I.

In the next step 312, the value of KADM calculated in the routine for each injection timing after S17, which will be described later, is set to MAP/32.
It is determined whether or not there is a transient operating state in which correction by KADM should be performed by comparing with KADM. If it is determined that KADM is larger than MAP/32, the process proceeds to S13 and a correction coefficient KTW2 is calculated from the water temperature TW. , K in S14
TPI is corrected by TW2 and KADM.
PF is determined. This correction by KTW2 is performed in S9. S
This has the same meaning as the correction by KTW in IO, and although the value of KTW2 differs depending on the engine, it is sufficient to use the same value as KTW.

In this embodiment, the KADM is not corrected based on the rotational speed N, but the correction may be made in the same manner as the KDM.

On the other hand, if the process proceeds to S15 based on the determination of 312, TPL
is used as the TPF and the process proceeds to S16. At step 316, this TPF is corrected by a correction coefficient C0EF based on various operating conditions, an air-fuel ratio feedback correction coefficient α, and a correction coefficient TS based on battery voltage to determine the final fuel injection valve 3 opening operation pulse width TI. .

The above steps 32 to 316 are repeated until the next fuel injection timing. Then, when the fuel injection timing is reached, the process proceeds to 317 in the determination of Sl, the valve is opened for the time determined in S16, and fuel is injected. 31
In step 8, the amount of variation KDM in the intake air pressure from the previous injection to the current injection, that is, at a predetermined crank rotation angle, is added to KADM.

In 319, it is determined whether KADM is positive or not, and KADM is determined to be positive.
If DM is positive, IR is subtracted in step 320, and if it is negative, IL is added in step 321, so that the correction amount other than during transient operation is set to zero. In other words, each time this routine is passed, the KADM
Since IR or IL is subtracted from or added to, the correction amount becomes zero when the transient operation ends.

The KDM is then reset to zero at 322 and the process repeats.

FIG. 6 shows, as a time chart, how the fuel injection pulse width is determined through the above process. In other words, when the fluctuation in the intake passage pressure MAP is large, such as during sudden acceleration, KD
Along with a large increase in correction due to M, KADM
Also, an increase in the amount is corrected, and the air-fuel ratio during the transient period is maintained at a predetermined value.

On the other hand, in a steady state where there is little variation in the intake passage pressure MAP, the correction by KDM is small and KADM gradually approaches zero.

Unlike conventional methods, air-fuel ratio correction during transient operation is performed based on the amount of change in intake air pressure at a predetermined engine rotation angle, so the amount of correction may vary unduly due to fluctuations in intake air pressure within the cycle. Therefore, accurate air-fuel ratio control can be performed. In other words, as shown in Fig. 7(B), the correction amount by KDM and KADM is almost equal to the air-fuel ratio error without correction, and the actual :l air-fuel ratio is as shown by the broken line in Fig. 7(A). Even during transient operation, the air-fuel ratio is maintained close to a predetermined value, and accurate air-fuel ratio control is achieved. This improves exhaust emissions and fuel efficiency, eliminates acceleration response delays caused by misfires caused by supplying a lean air-fuel mixture, and improves acceleration performance. Originally, the throttle valve opening sensor, etc., which were necessary to correct the air-to-air ratio during transient operation in the past, were used to correct the air-to-air ratio during transient operation. Of course, it is controlled.

In addition, although this embodiment is an example of one injection per rotation, and the predetermined engine rotation angle is 360°, the predetermined rotation angle is as follows:
For example, it may be 0° or 2 rotations.

Furthermore, the present invention can also be applied to an engine in which the fuel injection pulse width is determined based on the engine rotational speed and the intake air flow rate, and similar effects can be achieved.

<Effects of the Invention> As explained above, in the present invention, the amount of change in the intake airflow state in the intake passage while the engine rotates at a predetermined rotation angle is detected, and based on this, the amount of fuel supplied to the engine is corrected. This allows for correction to be made based on the amount synchronized with the engine rotation without any fluctuations in the cycle being detected, so that even during transient operation, the air-fuel mixture is accurately supplied to the engine at the specified air-fuel ratio. Therefore, it is possible to improve exhaust emissions during transient operation, and particularly to improve acceleration response.

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a flowchart showing the operation process of the same, and Figs. 4 and 5 respectively show correction values. KN
, a diagram showing the value of KTW, and Figure 6 is a time chart showing the determination process of the fuel injection valve opening operation time in the same as above.
FIG. 7 is a diagram showing the air-fuel ratio correction effect according to the present invention (
A) is a diagram showing how the air-fuel ratio changes in comparison with the conventional example;
B) is a diagram showing changes in the air-fuel ratio correction factor.

2...Intake RR8...Control unit 9...
・Pressure sensor 10... Crank angle sensor Patent applicant Nissan Motor Co., Ltd. Representative Patent attorney Sasashima Fujio-ku MA Law

Claims (1)

[Claims] A means for detecting an engine rotation speed, a means for detecting an intake air condition such as an intake air pressure or an intake air flow rate in an intake passage, and an amount of fuel to be supplied to the engine is determined based on the detection results of the two detection means. means for detecting an engine rotation angle; An air-fuel ratio control device for an internal combustion engine, comprising means for detecting an amount of change in state, and means for correcting the amount of fuel supplied to the engine based on the detection result of the means.