JPS6368742A - Fuel feeding control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the extensive variation of the air-fuel ratio in a transent operation, by delaying the object value found from the intake air amount as much as the time difference from the detection of the intake air related to the present combustion cycle to the actual participation of the intake air to the combustion. CONSTITUTION:An operational condition detecting device (a) to detect the engine load, the rotation frequency, and the like, and a pressure detecting device (b) to detect the combustion pressure are provided. And, responding to the engine operational condition and the combustion pressure, the object value of a parameter related to the output torque of the engine and the parameter detected vale are computed at an object value arithmetic device (c) and a detected value arithmetic device (e). Moreover, a delaying device (d) to delay the object value depending on the engine operational condition is provided, and the fuel correcting amount is computed from the delayed object value and the computed object value by a correction amount arithmetic device (f). Then the basic feeding amount is corrected depending on the fuel correction amount at a feeding amount arithmetic device (g), and a fuel feeding device (h) is controlled according to the feeding amount after correction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel supply control device for an internal combustion engine that detects a parameter correlated to output torque and corrects an air-fuel ratio.

(Prior Art) Generally, the amount of fuel required by an engine in a certain operating state uses the intake air amount of the engine at that time as one important parameter.

Conventional fuel supply control devices for internal combustion engines that determine the amount of fuel required by the engine from the amount of intake air include:
For example, there is one described in "New Automobile Engineering Handbook, Volume 4" (published by the Society of Automotive Engineers of Japan on September 30, 1981). In this device, the air flow rate is detected from the rotational displacement of a measuring plate of an air flow meter installed in the intake pipe, and converted into an electrical signal using a potentiometer. This electrical signal is input to the control unit and divided by a predetermined trigger corresponding to the engine speed. Since the divided electrical signals correspond to the intake air amount in a steady state for each cylinder, the fuel supply amount is determined based on this so that the air-fuel ratio becomes the target air-fuel ratio.

(Problems to be Solved by the Invention) However, in such a conventional fuel supply control device for an internal combustion engine, the fuel supply amount corresponding to the target air-fuel ratio is determined from the intake air amount in a steady state. Therefore, for example, when the throttle valve is suddenly opened when the vehicle is suddenly accelerated (hereinafter referred to as transient operation), the internal pressure of the air supply pipe is increased and the liquefaction of the fuel is promoted. A part of this liquid fuel becomes a wall flow and stays inside the air supply pipe, and further, as the amount of staying accumulation increases, a part of it flows into the combustion chamber. Therefore, during transient operation, the air-fuel ratio fluctuates significantly, making it impossible to obtain the required appropriate air-fuel ratio, resulting in a problem of deterioration of acceleration performance and other drivability.

(Purpose of the Invention) Therefore, the present invention focuses on the time difference from when intake air related to the current combustion cycle is detected until this intake air participates in combustion, and calculates a target value determined from the intake air amount. By delaying by the above-mentioned time difference and correcting the fuel supply amount based on the delayed target value and the actual combustion information, large fluctuations in the air-fuel ratio during transient operation can be eliminated and driveability can be improved. The aim is to improve.

(Means for Solving the Problems) In order to achieve the above object, the fuel supply control device for an internal combustion engine according to the present invention uses the engine load and rotation speed as parameters, as shown in the basic conceptual diagram in FIG. The operating state detection means a detects the operating state of the engine, and the pressure detection means detects the combustion pressure of the engine. a calculation means C, a delay means d for delaying the target value based on the operating state of the engine, and a detected value calculation means e for calculating a parameter correlated to the output torque of the engine as a parameter detection value based on the combustion pressure of the engine. and a correction amount calculation means f which calculates the fuel correction amount based on the detected parameter value and the delayed target value of the parameter, and a correction amount calculation means f which calculates the basic supply amount of fuel based on the operating state of the engine and calculates the fuel correction amount based on the engine operating state. The present invention includes a supply amount calculation means g that corrects the basic supply amount based on the supply amount calculation means g, and a fuel supply means that supplies fuel to the engine based on the output of the supply amount calculation means g.

(Function) In the present invention, the target value of the parameter determined from the intake air amount is delayed depending on the operating state, and this delayed target value is combined with the detected value of the parameter correlated to the output torque determined from the combustion pressure. The fuel supply amount is corrected based on. Therefore, the accuracy of estimating the combustion state is increased, the air-fuel ratio is appropriately controlled, and drivability is improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 7 are diagrams showing an embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes an engine. Intake air is supplied to each cylinder through an intake pipe 2 from an air cleaner (not shown), and fuel is injected by an injector (fuel supply means) 3 based on an injection signal Si. Then, the air-fuel mixture in the cylinder is ignited and exploded by the discharge action of the spark plug 4, becomes exhaust gas, and is introduced into a catalytic converter (not shown) through the exhaust pipe 5, where the harmful components (Co, HC, NOx) is purified by a three-way catalyst and discharged.

The intake air flow rate is detected by a flap-type airflow meter 6 and is expressed as an electric signal Q having an analog value A.
/D converter 7. A/D converter 7 converts this electrical signal Q into a digital signal Qa and outputs it. In addition, the combustion pressure in the cylinder is measured by an in-cylinder pressure sensor (pressure detection means) 9.
The cylinder pressure sensor 9 converts the combustion pressure into an electric charge using a piezoelectric element and outputs an electric charge signal S1. In addition,
Specifically, the cylinder pressure sensor 9 is screwed onto the cylinder head 10 and formed as a washer for the spark plug 4, as shown in detail in FIGS. 3(a) and 3(b).
The ignition plug 4 is pressed and fixed in the outer recess 0 by the portion 4a.

The sensor output S1 is input to the charger amplifier 11. The charger amplifier 11 constitutes a so-called charge-voltage conversion amplifier consisting of an operational amplifier OP, an input resistor R1, a feedback resistor R2, and an integrating capacitor C, and the sensor output S1
is converted into a voltage signal S2 and output to the A/D converter 12. The A/D converter 12 converts the voltage signal S2 into a digital signal S.
, and output it.

Furthermore, the crank angle of the engine is determined by a crank angle sensor 13.
The crank angle sensor 13 outputs a unit signal S4 corresponding to 2 degrees of crank angle and a discrimination signal S for cylinder discrimination.
, outputs. Note that the air flow meter 6 and the crank angle sensor 13 constitute an operating state detection means 14.

The microcomputer 20 has functions as target value calculation means, delay means, detected value calculation means, correction amount calculation means, and supply amount calculation means, and includes CPU 21, ROM 22, and R
It is composed of an AM23 and an I10 boat 24. C
The P U 21 reads necessary data from the I10 boat 24 according to the program written in the ROM 22, performs arithmetic processing while exchanging data with the RAM 23, and stores the processed data as necessary. Output to I10 port 24. That is, signals from the A/D converter 7.12 and the operating state detection means 14 are input to the I10 port 24, and an injection signal (injector drive pulse) Si is input from the I10 port 24 as a result of calculation. Output. ROM22 is CPU
21 is stored, and RAM2
3 temporarily stores data used in calculations, calculation results, etc.

Next, the effect will be explained.

Generally, the amount of fuel supplied to the engine is approximately proportional to the amount of intake air, and the desired amount of fuel can be estimated from this amount of air. By the way, during transient operation such as acceleration, the internal pressure of the suction pipe is increased due to a sudden increase in the amount of intake air, which promotes the condensation effect of the fuel and generates liquid fuel. A portion of this liquid fuel adheres to and remains on the tube wall as a wall flow, significantly reducing the amount of fuel involved in combustion. As a result, as shown in FIG. 7(b), immediately after acceleration, the air-fuel ratio becomes significantly lean (L) and thereafter gradually approaches the target. Looking at the change in the detected in-cylinder pressure (i.e. combustion state) at this time, as shown by the solid line in Figure (c), it drops significantly immediately after acceleration and gradually increases as the air-fuel ratio approaches the target value.
Stabilizes to a constant value.

In this way, during transient operations such as acceleration, part of the fuel becomes ineffective fuel such as wall flow, so the mixture ratio actually involved in combustion and the mixture ratio estimated from the intake air amount are different. do not necessarily match. That is, the air-fuel ratio during transient operation can be appropriately set by understanding the above-mentioned ineffective fuel amount and increasing the amount.

Therefore, in this embodiment, we focus on the fact that the intake air detected by the air flow meter 6 becomes involved in combustion after a predetermined period of time has elapsed. By delaying the time and comparing it with the detected parameter value indicating the actual combustion state, the above-mentioned invalid fuel can be accurately grasped.
Fuel correction is performed appropriately to improve driveability during transient conditions.

4 to 6 are flowcharts showing fuel supply control programs based on the above basic principle.

FIG. 4 is a flowchart showing an interrupt subroutine program (hereinafter referred to as IRQI program) for determining the fuel injection amount.
This process is executed once every time the cylinder discrimination signal S is input. First, the engine rotation speed N is calculated from the input interval of the cylinder discrimination signal S at Pl, and the intake air iQa is read at P2. Next, in P3, the basic fuel supply amount 'rp is calculated using the following equation (2).

Qa 'rp = KX □ ・・・・・・■ However, K: constant step P4 is the entry point to the fuel correction subroutine program (SUBR) shown in FIG.
The 5UBR program calculates a target value of a parameter that correlates to the output torque of the engine, delays the target value, compares it with a detected parameter value, and sets a fuel correction amount.

In the same figure, first, 1/4 of the basic supply amount Tp in PZI
Calculate the moving average value according to the following formula (2).

However, below -1: Previous value Next, based on the detected indicated effective pressure (parameter detected value correlated with engine output torque) Pi and the basic supply ff1Tp, which will be described later in P2□, the 1/64 moving average of these The calculation coefficient K is calculated according to the following equation (2).

However, for K-1: previous value PZI, the target value PiM of the parameter correlated with the output torque of the engine is calculated according to the following equation (2).

PiM=TpXK　・・・・・・■ Next, delay processing of the target value PiM is performed in Pi4.

This delay processing is performed by setting a predetermined number of memory areas (three areas in this embodiment) in a so-called first-in, first-out system.
iM is stored, and the target value PiM in the memory is sequentially moved each time this program is executed (each time the cylinder discrimination signal S is input). In other words, the target (direct PiM) stored in the IIFO memory in the current process will be moved in the memory in the next process, and will be taken out from the FIFO memory in the next process.
iM is compared with a detected indicated effective pressure Pi (a detected value of a parameter correlated with the output torque of the engine) obtained by an IRQ2 program to be described later, and it is determined whether or not to perform an increase correction of fuel. That is, when the target value PiM is large (Pi<PiM), it is determined that invalid fuel is generated due to liquid fuel and the air-fuel ratio tends to be lean, and pzb increases the basic supply ITp according to the following formula (■). IRQ
Return to I program.

Tp = Tp +C0N5T ・・・・・・■However,
C0N5T: constant In Figure 4, P is various correction coefficients (for example, C
0FE: correction coefficient represented by water temperature, etc.), the basic supply jJiTp is corrected, and the final injection pulse width Ti is calculated. Next, at P6, when the designated injection timing is reached, an injection signal Si having a pulse width corresponding to this Ti is output to the injector 3, the current IRQI program is ended, and the process returns to the main program (not shown).

FIG. 5 is a flowchart showing an interrupt subroutine program (hereinafter referred to as IRQ2 program) for determining parameters correlated with output torque.
The RQ2 program is executed once every time the crank angle unit signal S4 is input.

First, the current crank angle (crank angle at the interrupt timing) θ is calculated based on the unit signal S4 at pH, and P,
□ reads the combustion pressure signal S, and this combustion pressure signal S,
is replaced with the current cylinder pressure P. Next, in Pi3, the cylinder internal volume corresponding to the crank angle θ at the interrupt timing is calculated.
At the same time, the cylinder internal volume difference Δ■ (ΔV=V'-V) between this cylinder volume v' and the previous cylinder internal volume v' is calculated. Pi
4, the cylinder internal pressure P is multiplied by the cylinder internal volume difference ΔV to obtain PΔ
Find ■. This PΔ■ is the area per predetermined crank angle (for example, 2°) in the so-called P-■ diagram,
This becomes the unit area for determining the detected indicated effective pressure Pi, which will be described later.

Next, use pus to determine the current interrupt timing crank angle θ
PΔV calculated corresponding to and cumulative SU of PΔV up to the previous time
M is added and the process proceeds to crank angle O° determination step PI6. In Pi6, when the crank angle is 0°, the process advances to pat and the cumulative value SUM is replaced as the detected indicated effective pressure Pi. Furthermore, after clearing the cumulative value SUM at pH 1,
This ends the processing of the current IRQ2 program. on the other hand,
When θ≠O° at pH 6, it is determined that the cumulative SUMO value has not yet reached the area of the closed surface in the so-called P-■ diagram, and I
End the RQ2 program.

In this way, in this embodiment, the target value PiM obtained from the intake air amount is delayed depending on the operating condition, so the parameter detection value Pi obtained from the combustion pressure and the delayed target value PiM are the same. The parameter information is based on the intake air amount. Therefore, the accuracy of estimating the combustion state obtained from these parameter information is improved, and the air-fuel ratio during transient times is appropriately controlled. As a result, the rise of the detected indicated effective pressure Pi as shown in FIG. 7(d) becomes faster (that is, torque increases). Further, the Tp correction amount at that time is shown in FIG. 7(e).

Although this embodiment has been described using a single-cylinder engine as an example, the present invention is not limited to this. In short, it is sufficient to delay the target value obtained from the intake air amount and compare and examine the combustion information related to the intake air amount with the target value. For example, the combustion information can be changed for each cylinder or for the same fuel. It can also be applied to multi-cylinder engines by detecting each injection cylinder group and comparing it with a target value.

(Effects) According to the present invention, the target value of the parameter determined from the intake air amount is delayed, and the detected parameter value determined from the combustion pressure related to the intake air amount and the delayed target value are Since the fuel correction amount is determined by comparing the values, it is possible to control the fuel supply amount in accordance with the actual combustion state, eliminating large fluctuations in the air-fuel ratio during transient operation, and improving drivability. be able to.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing an embodiment of the present invention, Fig. 2 is a schematic configuration diagram thereof, and Fig. 3 is a diagram showing an embodiment of the present invention.
Figure (a) is a sectional view showing the installation state of the cylinder pressure sensor,
Fig. 3(b) is a plan view of only the cylinder pressure sensor, Fig. 4 is a flowchart showing the interrupt subroutine program (■RQI) for determining the fuel injection amount, and Fig. 5 is a correlation with the output torque. FIG. 6 is a flowchart showing the fuel correction subroutine program (SUBR), and FIGS. 7(a)-(
e) is a timing chart for explaining the effect. 3... Injector (fuel supply means), 9...
...Cylinder pressure sensor (pressure detection means), 14...
... Operating state detection means, 20... Microcomputer (target value calculation means, delay means, detected value calculation means, correction amount calculation means, supply amount calculation means).

Claims (1)

[Scope of Claims] a) Operating state detecting means for detecting the operating state of the engine using engine load and rotation speed as parameters; b) Pressure detecting means for detecting the combustion pressure of the engine; and c) Operating state detecting means for detecting the operating state of the engine. d) delay means for delaying the target value based on the operating state of the engine; and e) based on the combustion pressure of the engine. a detection value calculation means for calculating a parameter correlated to the output torque of the engine as a parameter detection value; f) a correction amount calculation means for calculating a fuel correction amount based on the parameter detection value and the delayed target value of the parameter; ) supply amount calculation means for calculating the basic supply amount of fuel based on the operating state of the engine and correcting the basic supply amount based on the fuel correction amount; h) supply amount calculation means for calculating the basic supply amount of fuel based on the engine operating state; A fuel supply control device for an internal combustion engine, comprising: a fuel supply means for supplying fuel;