JPH04362240A - Air-fuel ratio controlling device for internal combustion engine - Google Patents

Abstract

PURPOSE:To restrict disturbance in an air-fuel ratio in a transition period by controlling a fuel injection quantity with a transition determining means, a predicting means, a computation means, and a prediction prohibiting means. CONSTITUTION:A transition determining means M1 determines if a time is in a transition period in which a throttle opening is changed quickly or not. A predicting means M2 predicts a suction air quantity in the transition period based on the throttle opening and an engine rotation number, and a computation means M3 computes and controls a fuel injection quantity using a suction air quantity detected at a time other than the transition period, or a predicted suction air quantity instead of the detected suction air quantity in the transition period. A prediction prohibiting means M5 compares the first threshold value, which becomes larger as the rotation number is larger, and the second threshold value of a predetermined small value with the throttle opening, and prohibits prediction of the suction air quantity when the throttle opening exceeds the first threshold value, or when it is the second threshold value or less. At the time of prohibition, the computation means M3 computes the fuel injection quantity, thereby disturbance in air-fuel ration control by difference between the predicted and the actual suction air quantity can be restricted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine that controls the air-fuel ratio by calculating a fuel injection amount according to the operating state of the internal combustion engine.

0002

2. Description of the Related Art Conventionally, as described in Japanese Unexamined Patent Publication No. 63-215848, it has been possible to predict actual intake pipe pressure using a throttle opening without delay in response to changes in actual intake pipe pressure. Accordingly, there is an air-fuel ratio control device that determines the fuel injection amount actually required by the engine and controls the air-fuel ratio during transitions of acceleration and deceleration to an appropriate value.

0003

[Problem to be Solved by the Invention] Here, in an internal combustion engine that uses an air flow meter to detect the amount of intake air instead of detecting the intake pipe pressure, it is necessary to predict the actual amount of intake air using the throttle opening. It is possible that

In this case, the intake air amount is predicted using a map obtained by actually measuring the intake air amount while varying the rotational speed and throttle opening of a specific engine for each model.

However, the actual intake air amount with respect to the rotation speed and throttle opening varies depending on engine operating conditions and machine differences between engines. For example, as shown in FIG. 7, the predicted intake air amount QNTA shown by the solid line I An error d occurs between the intake air amount QN detected by the air flow meter and the solid line II even after the acceleration transition period ends.

Here, as shown in FIG. 8, the change in the intake air amount with respect to the change in the throttle opening is large when the throttle opening is small, and when the throttle opening is large, the change in the intake air amount is minute. The throttle opening degree at which the change in the amount of intake air becomes minute becomes smaller as the rotational speed NE becomes smaller. In such a state where the throttle opening is large, the change in the intake air amount is minute, so if the map is used to predict the intake air amount during a transient period, the influence of the error d will be large and the air-fuel ratio control will be disturbed.

[0007] Still, since the amount of intake air is small when the throttle opening is very small, there is a problem that if the map is used to predict the amount of intake air during a transient period, the influence of the error d is large and the air-fuel ratio control is disturbed. .

[0008] The present invention has been made in view of the above points.
An internal combustion engine that suppresses disturbances in air-fuel ratio control during a transient period by controlling the fuel injection amount using the detected intake air amount if the throttle opening exceeds a first threshold value or is less than a second threshold value during a transient period. The purpose of the present invention is to provide a fuel injection amount control device.

[0009]

Means for Solving the Problems FIG. 1 shows a diagram of the principle of the present invention. In the figure, a transient determining means M1 determines whether or not the throttle opening is in a transient state where the throttle opening changes suddenly.

The prediction means M2 predicts the intake air amount based on the throttle opening degree and the engine speed during a transient period.

The calculation means M3 calculates the fuel injection amount using the intake air amount detected when the transition is not occurring, and also uses the predicted intake air amount instead of the intake air amount detected during the transition, and calculates the fuel injection amount to control the internal combustion engine M4. control the fuel injection amount.

[0012] The prediction prohibition means M5 compares the throttle opening with a first threshold at which the rotational speed becomes a large value and a second threshold at a predetermined small value, and determines whether the throttle opening is at the first threshold. or is less than a second threshold, prediction of the intake air amount is prohibited. When prediction is prohibited by the prediction prohibition means M5, the calculation means M3 calculates the fuel injection amount using the detected intake air amount.

[0013]

[Operation] In the present invention, when the throttle opening exceeds the first threshold value and the change in the intake air amount during the transition is minute, and when the throttle opening is less than the second threshold and the intake air amount is small, the transition occurs. Prediction of intake air amount based on the throttle opening and rotational speed is prohibited, and the fuel injection amount is calculated using the detected intake air amount, so the predicted intake air amount and the actual intake air amount are Disturbances in air-fuel ratio control due to errors can be suppressed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram of an embodiment of an internal combustion engine to which the device of the present invention is applied.

In the figure, 1 is a gasoline engine body, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, and 5 is a gasoline engine body.
is an intake manifold, 6 is a surge tank that absorbs the pulsation of intake air, 7 is a throttle valve that adjusts the amount of intake air, and 8 is an air flow meter that measures the amount of intake air. The exhaust manifold 4 is provided with an oxygen sensor 9 that detects the residual oxygen concentration in the exhaust gas, and the intake manifold 5 is provided with a fuel injection valve 10 that injects fuel into the intake air of the gasoline engine body 1. The intake air temperature sensor 11 detects the temperature of intake air, the throttle sensor 12 detects the opening degree TA of the throttle valve 7, and the water temperature sensor 13 detects the temperature of cooling water.

Further, the igniter 16 generates a high voltage necessary for ignition and supplies it to the distributor 17, and the distributor 17, in conjunction with the rotation of the crankshaft (not shown), applies the high voltage to the spark plugs of each cylinder. Distribute and supply. The rotation angle sensor 18 outputs a rotation angle signal of 24 pulses per one revolution of the distributor 17, that is, two revolutions of the crankshaft, and the cylinder discrimination sensor 19 outputs a rotation detection signal G of 1 pulse per one revolution of the distributor 17.

The electronic control circuit 20 has a configuration shown in FIG. 3, and includes a central processing unit (CPU) 30, a read-only memory (ROM) 31 that stores processing programs, and a random access memory (RAM) used as a work area. 32 and a backup RAM 33 that retains data even after power is turned off.
, an A/D converter 34 with a multiplexer function, an I/O interface 35 with a buffer function, and a backup circuit 36 that performs backup control.
These are interconnected by a bus line 37.

The A/D converter 34 receives an air flow rate signal from the air flow meter 8, an intake air temperature signal from the intake air temperature sensor 11, a throttle opening signal from the throttle sensor 12, and a water temperature signal from the water temperature sensor 13. supplied with
Each signal is digitized and these digital signals are read by the CPU 30. Further, signals from the oxygen sensor 9, rotation angle sensor 18, and cylinder discrimination sensor 19 are input to the I/O interface 35, and each signal is connected to the C
The engine rotation speed NE is read by the PU 30 and calculated based on the signal from the rotation angle sensor 18.

The CPU 30 calculates the ignition timing and fuel injection amount based on the sensor detection data, and the obtained ignition signal and fuel injection signal are supplied to the igniter 16 and the fuel injection valve 10 through the I/O interface 35. Ru.

Next, a control program for an embodiment of the apparatus of the present invention will be explained.

FIG. 4 shows a flowchart of one embodiment of the fuel injection amount control process. This routine takes, for example, 8 msec.
is executed at predetermined intervals.

At step 50, the throttle opening TA and engine speed NE are taken in. In step 51, the throttle opening degree TAO taken in last time is subtracted from the throttle opening degree TA taken in this time, and the absolute value of this difference is set as an increment. In step 52, the increment DTA is compared with a predetermined value α to determine whether or not a transition is occurring.

When the increment DTA exceeds the predetermined value α, in step 53, the throttle opening TA and the rotation speed NE exceed the first threshold of the solid line III on the map shown in FIG. If the throttle opening TA is equal to or less than the solid line III, the process proceeds to step 54, where the throttle opening TA is in the diagonally shaded region below a predetermined value β, which is the second threshold shown by the solid line IV in FIG. Determine whether or not.

The region where the throttle opening exceeds the first threshold indicated by the solid line III is a region where the change in the amount of intake air is small even during a transient period. This solid line III is a curve corresponding to the fact that the smaller the engine speed NE is, the smaller the throttle opening is, and the smaller the change in the amount of intake air is. Further, a region where the throttle opening degree is less than the second threshold value indicated by the solid line IV is a region where the amount of intake air is small.

In step 52, when the increment DTA is less than the predetermined value α, the process proceeds to step 55 for normal control, and even in a transient state, when the throttle opening TA is in a region exceeding the solid line III, or when the throttle opening degree TA is in a region exceeding the solid line IV, If it is in the range below, prohibit transient control and proceed to step 5 for normal control.
Proceed to step 5. Step 55 takes in the intake air amount Q from the air flow meter 8 and divides it by the rotational speed NE to determine the intake air amount QN per engine revolution.Step 5
Proceed to step 7.

If the throttle opening TA is below the solid line III and exceeds the solid line IV during a transient period, the process proceeds to step 56 for transient control, where the slot opening TA and the rotational speed NE are determined as shown in FIG. Determine the predicted intake air amount QNTA by referring to the map shown in the figure, and calculate the predicted intake air amount QNTA.
The process proceeds to step 57 by setting NTA as the intake air amount QN. FIG. 6 shows a map when the rotational speed NE is 2000 rpm, and a separate map is referred to for each rotational speed.

In step 57, a basic injection amount TP is obtained from the intake air amount QN obtained in step 56 or 57, and a correction coefficient determined by the intake air temperature, cooling water temperature, etc. and an air-fuel ratio feedback correction coefficient are added to this basic injection amount TP. The fuel injection amount TAU is calculated by multiplying. After this, in step 58, the throttle opening degree TA taken this time is changed to the previous throttle opening degree T.
Set to AO and end the process.

Then, in a control routine (not shown), when a predetermined crank angle is reached, the fuel injection valve 10 is opened for a time corresponding to the fuel injection amount TAU to execute fuel injection.

In this way, if the throttle opening degree TA exceeds the first threshold value and the change in the intake air amount during the transition is minute, or if the throttle opening degree is less than the second threshold value and the intake air amount is small, the transition occurs. Prediction of the intake air amount based on the throttle opening TA and rotational speed NE is prohibited, and the fuel injection amount is calculated using the detected intake air amount QN. Disturbances in air-fuel ratio control due to errors with the air amount can be suppressed.

[0030]

As described above, the air-fuel ratio control device for an internal combustion engine of the present invention can suppress disturbances in air-fuel ratio control during transient periods, and is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of an internal combustion engine to which the device of the present invention is applied.

FIG. 3 is a block diagram of an electronic control circuit.

FIG. 4 is a flowchart of fuel injection control processing.

FIG. 5 is a map showing areas where prediction is prohibited.

FIG. 6 is a diagram showing a prediction map.

FIG. 7 is a diagram showing errors in intake air amount.

FIG. 8 is a diagram showing the relationship between throttle opening and intake air amount.

[Explanation of symbols]

M1 Transient determination means M2 Prediction means M3 calculation means M4 Internal combustion engine M5 Prediction inhibition means 8 Air flow meter 10 Fuel injection valve 12 Throttle sensor 18 Rotation angle sensor

Claims (1)

[Claims] Claim 1: Predicting the amount of intake air based on the throttle opening and engine speed during a transient period when the throttle opening suddenly changes, and injecting fuel using the predicted intake air amount instead of the detected intake air amount. In an air-fuel ratio control device for an internal combustion engine that controls an air-fuel ratio by calculating a quantity, a first threshold value that becomes a larger value as the rotation speed increases, a second threshold value that is a predetermined small value, and a throttle opening degree are respectively set. and a prediction inhibiting means for prohibiting prediction of the intake air amount when the throttle opening exceeds the first threshold value or is less than the second threshold value, and detects when prediction by the prediction inhibiting means is prohibited. An air-fuel ratio control device for an internal combustion engine, characterized in that a fuel injection amount is calculated using an intake air amount.