JPS635128A - Fuel injection amount control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of response delay during transient running, by a method wherein, based on an intake air amount and the number of revolutions, a fundamental injection amount is determined, and a method of computing an air-fuel ratio by means of a negative pressure sensor output and an injection amount is compared with an air-fuel ratio, detected by an O2 sensor during steady running, for correction. CONSTITUTION:A fundamental injection amount computing means 3 computes a fundamental injection amount from an intake air amount and the number of revolutions. Meanwhile, an air-fuel ratio computing means 7 computes an air-fuel ratio of air-fuel mixture, based on a suction negative pressure of a negative pressure sensor 6 and an injection amount control signal from an injection amount correcting means 8, when a steady and transient detecting means 5 detects a transient state from a change in a rotation. speed and a change in the opening of a throttle valve. Meanwhile, during steady running, an error compensating means 10 compares an air-fuel ratio, determined by the air-fuel ratio computing means 7, with that detected by an oxygen concentration detecting means 9 to correct the computing method of the air-fuel ratio computing means 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an improvement of a fuel injection amount control device for an internal combustion engine such as a gasoline engine.

Conventional technology A conventional fuel injection amount control device was developed by Japanese Patent Publication No. 55-36814.
As stated in the publication, the basic injection amount is determined from the air flow rate detected by an air flow meter installed in the intake passage of the engine and the engine rotation speed detected by the crank angle sensor. The configuration is such that the final fuel injection amount is determined by adding various increase corrections to the amount, and the opening time of the fuel injection valve is controlled accordingly. In this way, the method of detecting the air flow rate to determine the intake air m per intake stroke is more effective than the method of determining the intake air amount by detecting the suction negative pressure downstream of the throttle valve, due to exhaust gas recirculation and inertia. It has the advantage of not being affected by supercharging.

Problems to be Solved by the Invention However, since the air flow meter that detects the air flow rate as described above is generally installed upstream of the intake passage, if the air flow rate changes suddenly during engine transients, It is not possible to accurately detect the amount of intake air actually taken into the cylinder with good responsiveness, resulting in fluctuations in the air-fuel ratio and, in turn, deterioration in engine drivability.

- On the other hand, with the method of detecting suction negative pressure, it is possible to more accurately determine the amount of intake air even during transient conditions, but on the other hand, it is affected by exhaust gas recirculation and inertial supercharging as mentioned above, and is affected by changes in intake air temperature and engine There is a problem in that it is affected by changes in characteristics over time.

Means for Solving the Problems FIG. 1 is a functional block diagram showing the configuration of the present invention, in which 2 is an air flow rate detection means consisting of an air flow meter or the like that detects the air flow rate at an upstream position of the intake passage; Rotational speed detection means consisting of a crank angle sensor etc. that detects the rotational speed of the engine; 3 is a basic injection amount calculation means that calculates a basic injection amount from these air flow rates and rotational speed; 4 is a basic injection amount calculation means that calculates a basic injection amount based on this basic injection amount. This is a fuel injection valve that is controlled to open and close.

Reference numeral 5 indicates a steady/transient detection means for detecting whether the engine is in a steady state or a transient state based on changes in rotational speed or throttle valve opening, and reference numeral 6 indicates a negative detection means for detecting suction negative pressure downstream of the throttle valve. a pressure sensor; 7 is an air-fuel ratio calculating means for calculating the air-fuel ratio of the air-fuel mixture taken into the cylinder based on this suction negative pressure and the fuel injection amount based on a predetermined calculation formula; 8 is an air-fuel ratio calculation means for calculating the air-fuel ratio during engine transients; This is an injection amount correction means that corrects the fuel injection amount based on the air-fuel ratio determined by the calculation means.

Reference numeral 9 denotes an oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas; 10, when the engine is in steady state, compares the air-fuel ratio obtained by the air-fuel ratio calculation means 7 with the detected oxygen concentration to determine the air-fuel ratio; This is an error compensation means for correcting the calculation method.

When the operation is steady, the opening time of the fuel injection valve 4 is controlled based on the basic injection amount determined by the basic injection amount calculating means 3, with a slight correction increase added thereto. Then, the air-fuel ratio calculation means 7 calculates the air-fuel ratio of the air-fuel mixture taken into the cylinder with good responsiveness using a predetermined calculation formula from the actual fuel injection amount and the intake negative pressure.

During transitions such as acceleration and deceleration, the basic injection amount is corrected based on the air-fuel ratio determined by the air-fuel ratio calculation means 7.

On the other hand, the residual oxygen concentration in the exhaust gas detected by the oxygen concentration detection means 9 is an index indicating the air-fuel ratio, and when compared with the air-fuel ratio determined by the air-fuel ratio calculation means 7 when the engine is steady, It is possible to know the occurrence of errors due to changes in characteristics over time.

The error compensation means 10 compensates for the error by correcting the calculation method in the air-fuel ratio calculation means 7.

Embodiment FIG. 2 is a configuration explanatory diagram showing an embodiment of the fuel injection amount control device according to the present invention. 1 is an air flow meter such as a flap type or hot wire type installed relatively upstream of the intake passage 12, specifically, upstream of the throttle valve 13; The crank angle sensor 16 is the throttle valve 13 of the intake passage 12.
A negative pressure sensor 17 is provided downstream, specifically in the intake pipe collector section 12a, and an oxygen sensor 17 is provided in the exhaust passage 18. This oxygen sensor 17 has a characteristic that its output changes continuously depending on the oxygen concentration. In addition, 19 shows the change in the opening of the throttle valve 13 at an O
N, a throttle opening sensor that detects in an OFF or analog manner; 20, a water temperature sensor that detects the cooling water temperature of the internal combustion engine 15; 21, a fuel injection valve disposed toward the intake port of each cylinder; 22; is a control unit using a microcomputer that controls the opening and closing of this fuel injection valve 21, and includes an I10 boat 22a, a CPU'
22b.

It consists of a ROM 22c, a RAM 22d, an A/D converter 22e, etc.

3 to 6 are flowcharts showing the details of the control performed by the control unit 22,
This will be explained below.

FIG. 3 shows a program for detecting the steady state and transient state of the engine, and this program is repeatedly executed at every regular cycle. In step 1, the suction negative pressure detected by the negative pressure sensor 16 is compared with the previous detected value to determine whether there has been an increase or decrease by a predetermined value or more.

In step 2, the opening degree of the throttle valve 13 is compared with the previous opening degree to determine whether there has been a sudden increase or decrease. In step 3, regarding the rotational speed determined from the crank angle sensor 14,
In step 4, it is similarly determined whether the air flow rate detected by the air flow meter 11 has increased or decreased by a predetermined value or more. Further, in step 5, it is determined whether the output value of the oxygen sensor 17 and in step 6, the cooling water temperature detected by the water temperature sensor 20 are within predetermined ranges. Then, based on these determination results, it is comprehensively determined in step 7 whether the state is in a steady state or in a transient state. In this comprehensive determination, for example, when all factors are in a stable state, it is determined to be "steady", and when any one of the factors changes suddenly, it is determined to be "transient". Of course, these conditions can be changed as appropriate.

FIG. 4 shows a program for determining the air-fuel ratio of the air-fuel mixture taken into the cylinder. In step 8, the intake negative pressure detected by the negative pressure sensor 16 at the timing immediately before the intake valve closes is read, and in step 9 Now, the amount of intake air taken into the cylinder is calculated based on this intake negative pressure. For example,
It is determined by the following formula: intake air Ji=AX intake negative pressure+BJ (where A and B are constants). Also, in step 10,
The amount of fuel supplied is calculated from the pulse width of the injector drive pulse signal sent out between the previous intake stroke and the current intake stroke. For example, "Fuel supply amount = C x pulse width -
It is determined by the arithmetic expression DJ (where C and D are constants).

Then, in step 11, the actual air-fuel ratio in the cylinder is calculated as a ratio between the two.

FIG. 5 is a fuel injection amount correction program.

Although the flowchart is not shown, the basic injection amount is calculated from the air flow rate detected by the air flow meter 11 and the engine rotation speed, and various correction increases based on water temperature etc. are added to calculate the injection amount before correction in detail. The pulse width of the injection valve drive pulse signal is determined. Step 12 is to judge whether or not there is a transient state based on the above-mentioned program, and during the transient state,
It is determined whether the air-fuel ratio calculated by the program in Figure 4 is normal or not, that is, whether it is within a certain range (Step 1
3) If it is not normal, the injection amount is corrected (step 14.15). This correction can be appropriately selected, for example, by reducing or increasing the amount by a certain amount depending on whether the air-fuel ratio is rich or lean, or by changing the amount of increase or decrease depending on the magnitude of the deviation in the air-fuel ratio.

FIG. 6 is a program that sequentially calibrates the calculation formula in the air-fuel ratio calculation program (FIG. 4) so that the air-fuel ratio calculated by the negative pressure sensor 16 does not produce errors due to changes over time. Step 16 is to judge whether or not the engine is in a steady state based on the program described above. If the engine is in a steady state, the residual oxygen concentration in the exhaust gas detected by the oxygen sensor 17 (the air-fuel ratio at that time) is determined. It is determined whether there is an error between the air-fuel ratio (shown in FIG. 4) and the air-fuel ratio determined by the program shown in FIG. 4 (step 17). If this error exceeds a certain range, step 9 described above
The error is corrected by adding the correction amount S to the constant B in the equation. This correction can be performed by adding or subtracting a fixed value depending on whether the error is rich or lean, or by changing the correction amount depending on the magnitude of the error.

Therefore, even if various factors affect the detection of the air-fuel ratio by the negative pressure sensor 16, the error will be corrected each time a steady state is reached, and when the fuel injection amount is corrected in a subsequent transient state. Therefore, the air-fuel ratio can be detected with high accuracy and the injection amount can be corrected very appropriately without being influenced by these factors.

Effects of the Invention As is clear from the above explanation, according to the fuel injection amount control device for an internal combustion engine according to the present invention, the air-fuel ratio can be controlled based on the air flow rate during steady state without being affected by exhaust gas recirculation or inertial supercharging. On the other hand, it is possible to prevent the air-fuel ratio from fluctuating due to response delay during a transient period when the air flow rate changes rapidly, and the operability of the engine is not deteriorated. Since the calculation of the air-fuel ratio during the transient period is corrected sequentially based on the oxygen concentration, it is not affected by changes over time.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of this invention, FIG. 2 is a configuration explanatory diagram showing one embodiment of this invention, FIGS.
5 and 6 are flowcharts showing the details of control in this embodiment. l...Air flow rate detection means, 2...Rotational speed detection means, 3...Basic injection amount calculation means, 4...Fuel injection valve,
5... Steady/transient detection means, 7... Air-fuel ratio calculation means, 8... Injection amount correction means, 9... Oxygen concentration detection means, lO... Error compensation means. 2 people Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) Air flow rate detection means that detects the air flow rate at an upstream position of the intake passage, rotation speed detection means that detects the engine rotation speed, and basic injection amount calculation that calculates the basic injection amount from the air flow rate and rotation speed. In a fuel injection amount control device for an internal combustion engine that controls an opening time of a fuel injection valve based on the basic injection amount, the device includes a steady state/transient detection device that detects whether the engine is in a steady state or a transient state. a negative pressure sensor that detects the suction negative pressure downstream of the throttle valve; and an air-fuel ratio sensor that calculates the air-fuel ratio of the mixture taken into the cylinder based on the suction negative pressure and the fuel injection amount based on a predetermined calculation formula. a fuel ratio calculation means, an injection amount correction means for correcting the fuel injection amount based on the air-fuel ratio obtained by the air-fuel ratio calculation means during engine transient, and an oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas; An internal combustion engine, characterized in that it is provided with an error compensating means for correcting the method of calculating the air-fuel ratio by comparing the air-fuel ratio obtained by the air-fuel ratio calculating means with the detected oxygen concentration during the steady state of the engine. Fuel injection amount control device.