JPS62276234A - Fuel feed control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent production of a wide fluctuation in an air-fuel ratio during transient running, by a method wherein a fuel feed amount is corrected so that parameter correlated to output torque of an engine is adjusted to a target value, and a given amount is decreased for correction so that overrich is prevented from occurring. CONSTITUTION:Detecting values from an airflow meter 6, a crank angle sensor 13, and an in-cylinder pressure sensor 9, situated to the seat metal of an ignition plug 4, and the like are inputted to a microcomputer 8 to compute and control the opening time of an injector 3. Namely, the microcomputer 8 computes fundamental injection amount from an intake air amount and the number of revolutions and the fundamental injection amount is corrected so that a detecting value from the in-cylinder pressure sensor 9 is adjusted to a given target value. After an amount of unburnt fuel due to adhesion of fuel to a wall surface is increased to a specified value according to the number of revolutions, the unburnt fuel flows in a cylinder and an air-fuel ratio is shifted to the rich side, and a reducing correction value, by means of which the shifting to the rich side is prevented from occurring, is computed to control the injector 3.

Description

Detailed Description of the Invention 3. 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.

The following three methods are known as methods for determining the amount of intake air. Namely, there are 1) a method of directly detecting the amount of air, 2) a method of detecting the pressure inside the intake pipe, and 2) a method of detecting the opening degree of the throttle valve.

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 Automotive 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 extracted from the rotational displacement of a metering 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. The divided electrical signals correspond to the intake air amount for each cylinder, and based on this, the fuel supply amount is determined based on steady state conditions so as to achieve the target air-fuel ratio.

(Problems to be Solved by the Invention) However, such conventional fuel supply control devices are configured to determine the fuel supply amount corresponding to the target air-fuel ratio from the intake air amount in a steady state. Therefore, when the throttle valve is suddenly opened when the car is suddenly accelerated (hereinafter referred to as transient operation), the amount of incoming air increases rapidly.
The amount of fuel to be supplied is determined based on the air flow rate and is supplied into the air supply pipe.

However, the internal pressure of the intake pipe is increased due to the above-mentioned rapid increase in air flow rate, and the supplied fuel condenses and becomes liquid fuel. The generation of liquid fuel causes some ineffective fuel to adhere to and accumulate on the pipe wall, temporarily diluting the air-fuel mixture flowing into the combustion chamber.

Furthermore, the amount of accumulated fuel increases over time, and a portion of it flows into the combustion chamber, causing the air-fuel mixture to become overrich.

Therefore, since the appropriate air-fuel ratio required for transient operation cannot be obtained (that is, the air-fuel ratio deviates from the target air-fuel ratio), the engine output torque does not follow the throttle opening, resulting in poor acceleration performance and other drivability. There was a problem.

(Object of the Invention) Therefore, the present invention detects a parameter correlated with the output torque of the engine, corrects the fuel supply amount based on the parameter, and adds a predetermined amount to the fuel supply amount so as to suppress the liver richness. By performing the reduction correction, the purpose is to improve drivability by eliminating large fluctuations in the air-fuel ratio (particularly over-rich conditions) due to fuel adhering to the wall surface during transient operation.

(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, as shown in the basic conceptual diagram in FIG. Operating state detecting means a for detecting the operating state, pressure detecting means for detecting the combustion pressure of the engine, basic value calculating means C for calculating the basic supply amount of fuel based on the engine load and rotation speed, and pressure detecting means for detecting the engine combustion pressure. Torque calculation means d calculates a parameter correlated to the output torque of the engine as a detected parameter value based on the output of the means d, and a supply correcting the basic supply amount of fuel so that the detected parameter value matches a predetermined target value. an amount correcting means e; an overrich prevention means f for further reducing the fuel supply amount corrected by the supply amount correcting means e by a predetermined amount to prevent overrich;
and fuel supply means g for supplying the engine with the final supply amount of fuel determined by the overrich prevention means r.

(Function) In the present invention, the fuel supply amount is corrected using a parameter that correlates with the output torque of the engine, and the fuel supply amount is further corrected to decrease by a predetermined amount so as to prevent over-richness. Therefore, large fluctuations in the mixture ratio during transient operation are suppressed, and drivability is improved.

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

2 to 7 are diagrams showing a first 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 an air flow meter 6,
It is output to the A/D converter 7 as an electrical signal Q having an analog value. The A/D converter 7 converts this electric signal Q into a digital signal Qa and outputs it to the microcomputer 8.

On the other hand, 9 is a cylinder pressure sensor (pressure detection means), and the cylinder pressure sensor 9 converts the combustion pressure in the cylinder into an electric charge using a piezoelectric element, and outputs an electric charge signal S1. Specifically, as shown in detail in FIGS. 3(A) and 3(B), the cylinder pressure sensor 9 is screwed onto the cylinder head 10 and formed as a washer for the spark plug 4. The ignition plug 4 is pressed and fixed in place by the portion 4a.

The sensor output S1 is input to a charger amplifier 11, and the charger amplifier 11 is an operational amplifier OP.

A so-called charge-voltage conversion amplifier is constituted by an input resistor R1, a feedback resistor R2, and an integrating capacitor C, and converts the sensor output S into a voltage signal S2 and outputs the voltage signal S2 to the A/D converter 12. The A/D converter 12 converts the voltage signal S2 into a digital signal S3 and outputs it to the microcomputer 8.

Further, the crank angle of the engine is detected by the crank angle sensor 13, and the crank angle sensor 13 is
A unit signal S4 corresponding to ° and a discrimination signal S for cylinder discrimination,
is output to the microcomputer 8.

The air flow meter 6 and the crank angle sensor 13 constitute an operating state detection means 14.

The microcomputer 8 has functions as a basic value calculation means, a torque calculation means, a supply amount correction means, an over-linch prevention means, and a supply amount correction means, and has the functions of a CPU 21, RO
It is composed of an M22, a RAM 23, and an I10 boat 24. The CPU 21 reads necessary external 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 boat 24. 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.
is output. The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 is a so-called working memory that temporarily stores data used in calculations, calculation results, etc.

Next, the effect will be explained.

Generally, the amount of fuel supplied to the engine during transient operations such as acceleration is approximately proportional to the amount of intake air. A sudden increase in the amount of intake air due to acceleration or the like increases the internal pressure of the intake pipe, promotes fuel condensation, and generates liquid fuel. A portion of the liquid fuel adheres to and remains on the pipe wall, significantly reducing the amount of fuel involved in combustion. Taking the case of acceleration as an example of such a state during transient operation, immediately after acceleration, the air-fuel ratio becomes significantly lean and thereafter gradually approaches the target, as shown in FIG. 8(A). Looking at the change in the detected cylinder pressure at this time, as shown by the solid line in Figure (B), it drops significantly immediately after acceleration, gradually increases as the air-fuel ratio approaches the target value, and then stabilizes at a constant value. .

Here, the target cylinder pressure (approximately equal to the intake air amount) required for acceleration is shown by a broken line.

By the way, the accumulated amount of fuel attached to the pipe wall increases with the passage of time, and a portion flows into the combustion chamber, causing the air-fuel ratio to become over-rich.

Therefore, in this example, we focused on the causal relationship that the difference between the detected cylinder pressure and the target cylinder pressure (that is, the difference in output torque) corresponds to the amount of ineffective fuel stuck to the wall surface, and correlated it with the output torque during transient operation. The above-mentioned ineffective fuel is calculated by determining the parameters for the air-fuel ratio, and the air-fuel ratio is estimated from this to correct the fuel supply amount, and the fuel supply amount is further corrected to decrease by a predetermined amount. This suppresses the significantly lean state of the fuel ratio and the subsequent overrich state.

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 (IRQI) for determining the fuel injection amount, and this interrupt subroutine (IRQI) 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 P+, and the intake air IQa is read at P2. Next, in P3, the basic supply amount T of fuel is determined as a function of N and Qa.
p is calculated, for example, according to the following equation (2).

However, for F: constant P4, the background job program (B
Using the basic transient correction amount Cpwo calculated by GJ), the transient correction amount Cp- for correcting the basic supply amount 'rp to obtain the final injection pulse width Ti is calculated by the following equation (2).

Cpw=Cpwo' +Cpwo-A...
...■However, ~Cp decay 0': Previous value A: Coefficient Here, the coefficient A in equation 0 is when unburned fuel due to wall surface accumulation flows into the cylinder after a certain amount of accumulation, and the air-fuel ratio is on the rich side. This is a correction term for preventing the deviation from occurring, and a predetermined amount of reduction correction, which is the key point of the present invention, is performed using this correction term.

To explain this, when the final fuel injection pulse width Ti is controlled only by the basic transient correction it Cpwa, the amount of unburned fuel flowing into the fuel chamber is not included as a control operator, so the air-fuel ratio becomes overrich. There is a risk of becoming If overrich occurs, the detected value of the parameter correlated to the output torque decreases, thereby increasing the final fuel injection pulse width Ti.

As a result, over-richness is further promoted and the situation becomes uncontrollable. Therefore, by performing a predetermined amount of reduction correction, the correction function is performed within the range of vibration indicated by the scale in FIG. In this embodiment, this correction term is calculated by the following equation
It is determined by

A=f, +11(N) −・−・・・■However, N:
At the rotation speed P, use the current transient correction amount Cpw to calculate the basic supply amount'
rp is corrected, and the final injection pulse width Ti is calculated using the following equation (2).

Ti=TpxCp 匈...Next, when the specified injection timing is reached in P6, an injector drive signal (injection signal) Si having an injection pulse width corresponding to this Ti is output, and an interrupt subroutine (IRQI) is executed. end.

FIG. 5 is a flowchart showing an interrupt subroutine (I RQ2) for determining parameters correlated to output torque, and this interrupt subroutine (I RQ2) is executed once every time a crank angle unit signal S4 is input. be done.

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 s3, and this combustion pressure signal S3
is replaced with the current cylinder pressure P. Next, at P+3, the cylinder internal volume V corresponding to the crank angle θ at the interrupt timing is
At the same time, the cylinder internal volume difference Δ■ between this V and the previous cylinder internal volume v' is calculated using the following equation.

Δv=v' -v ・・・・・・■ In P14, PΔ■ is obtained by multiplying the cylinder internal pressure P by the cylinder internal volume difference Δ■, and this PΔV is determined by the predetermined crank angle in the so-called P-V diagram (e.g. 2°), and serves as a unit area for determining the detected indicated effective pressure Pi, which will be described later.

Next, PI3 determines the current interrupt timing crank angle θ.
PΔV calculated corresponding to and the cumulative value S of PΔ■ up to the previous time
Add UM and crank angle O° determination step l”+6
Proceed to. At Po, when the crank angle is 0°, the process advances to P+7 and the cumulative value SUM is replaced as the detected indicated effective pressure Pi. Furthermore, the cumulative value SUM is cleared with pH+, and the interrupt subroutine (IRQ2) is ended.

On the other hand, when θ≠0° in Pl&, it is determined that the value of the cumulative value SUM has not yet reached the area of the closed surface in the so-called PV diagram, and the value of SUM up to the present is retained. The input subroutine (IRQ2) ends.

In this way, a parameter (detected indicated effective pressure Pi) that correlates with the output torque is obtained, but the parameter is not limited to this method and may be obtained by other methods as long as they are based on the piecewise quadrature method.

FIG. 6 is a flowchart showing the bank ground job program (BGJ) for determining the basic transient correction amount Cpwo, and includes the above-mentioned interrupt subroutine (IRQI),
This is a program that is always executed while (IRQ2) is not executed.

First, the calculation coefficient K in PZI is determined by the following equation (2).

However, K': Previous value Next, the target indicated effective pressure Pi', which becomes a predetermined target value at PX3, is calculated using the following equation (2).

Pi=TpXK...■ Furthermore, the difference ΔPi between the detected indicated effective pressure Pi and the target indicated effective pressure Pi' is determined using Pal. As will be described in detail later, this difference ΔPi becomes a value corresponding to the division ratio of fuel divided into a combusted portion and an unburned phosphorus portion due to adhesion to the wall surface, etc. during transient operation. Furthermore, in P24, the basic transient correction amount Cpwo is obtained using the above-mentioned difference ΔPi, the concept of which is shown in FIG. That is, in the same figure, the difference ΔP between the target indicated effective pressure Pi′ and the detected indicated effective pressure Pi
If i is the difference value a, the basic transient correction i1cpwo is determined so that the air-fuel ratio becomes lynch by an amount that becomes b. To state this specifically, the relationship between the fuel supply amount and the indicated effective pressure is expressed by the following equation (2).

Fuel supply amount: Unburnt phosphorus content = Pi': Pi...■ However, Pi': Target indicated effective pressure Pi: Detected indicated effective pressure When the above formula (■) is expanded to a formula for calculating the unburned phosphorus content, The following formula 〇 is obtained.

In other words, the unburned phosphorus content determined in this manner is determined as the basic transient correction 11cpwo. As a result, as shown in FIG. 8(C), the final injection pulse width Ti is appropriately increased by this Cpwo and follows the lean change in the air-fuel ratio during acceleration. Furthermore, since the final injection pulse width Ti is corrected to decrease by the correction term 18, the air-fuel ratio is prevented from swinging toward the over-rich side.

Therefore, as shown in FIG. 2D, the change in the cylinder pressure after correction has a characteristic that is more or less in line with the target cylinder pressure, and the transient operation performance during acceleration is improved.

Therefore, the effect of this example is the same as that of the 9th experimental result.
．． As shown in Figure 10, there are some notable cases.

Specifications shown in three types of line graphs in Figure 9 ■～■
The contents are as shown in the table below.

(This page, blank space below) The experimental method is as shown in Figure 10, from when the throttle switch is turned on to the position indicated by T in the figure, where the detected cylinder internal pressure Pi reaches the target cylinder internal pressure Pi'. This was done every time the time was measured.

As is clear from FIG. 9, according to this embodiment, the time required to reach the target cylinder internal pressure Pi' is shortened to about ⅓, and acceleration performance is significantly improved.

FIG. 11 is a diagram showing a second embodiment of the present invention. In the interrupt subroutine (IRQI) for determining the fuel injection amount, the transient correction amount Cpw is calculated according to the following equation [phase], and the The difference from the first embodiment is that the coefficient B is set to 1 or less (
(See the same figure (P3.)).

Cpw= (Cpwo 'tenCpwo) xB
...@1 Comparing this with the correction term -A of the first embodiment, the value for - is set by A=fuNc (N). Here, N is the engine speed, and its set value changes depending on the acceleration conditions.

On the other hand, B is a constant value that does not depend on the acceleration conditions,
This has the advantage of simplifying the program and improving processing speed.

Therefore, in this embodiment as well, the same effects as in the first embodiment can be obtained.

FIG. 12 is a diagram showing a third embodiment of the present invention, in which the final fuel injection pulse width Ti is determined from the basic transient correction amount Cpwo only for this time in the interrupt subroutine (IRQI) for determining the fuel injection amount. (CP in the same figure,
,)reference). In other words, the current basic transient correction amount Cpwo
As a result, the next detected cylinder pressure Pi becomes approximately equal to the target cylinder pressure Pi'. Therefore, the next basic transient correction amount Cpwo based on this naturally becomes smaller, causing a deviation between the next detected cylinder pressure Pi and the target cylinder pressure Pi'.

To make this easier to understand, let's start with C.
T i = r P i = corrected by pwo
Find Cpwo from Pi'J-Pi → T i-r P i # P i ' J corrected by Cpwo
- Calculate Cpwo from Pi - Ti corrected by Cpwo → rPi = Pi 'J..., and rPi = Pi' and Pi≠Pi 'J are repeated in order. Therefore, rPi#Pt As can be understood from the fact that 'J occurs every other time, this embodiment aims to speed up the program processing (real-time) by keeping the correction accuracy to a level that is sufficient for practical use. Also, the same effects as in the first embodiment can be obtained.

FIG. 13 is a diagram showing a fourth embodiment of the present invention. In the interrupt subroutine (IRQI) for determining the fuel injection amount, the final fuel injection pulse width Ti is changed to the basic transient correction amount Cρ−0 for this time only. , and the coefficient B is set to 1 or less (see the same figure (PSI)).

According to this embodiment, correction accuracy sufficient for practical use can be obtained, and further speeding up of program processing (real-time implementation) can be achieved.

FIG. 14 is a diagram showing a fifth embodiment of the present invention, and is an example in which the target indicated effective pressure Pi' is corrected to decrease in the background job program (BGJ) for determining the basic transient correction amount (the figure (See PSI). That is,
The target indicated effective pressure Pi' is corrected to decrease by the coefficient A set according to the acceleration conditions, and thereby the same effect as the first embodiment can be obtained. Note that the same effect can be obtained by multiplying by a constant B instead of using the coefficient.

Furthermore, as another example, it is clear that the same effect as the reduction correction of the present invention can be obtained by increasing the value of the detected indicated effective pressure Pi.

(Effects) According to the present invention, a parameter correlated with the output torque of the engine is detected, the fuel supply amount is corrected based on the parameter, and a predetermined amount of reduction is corrected for the fuel supply amount so as to suppress over-richness. Therefore, it is possible to eliminate large fluctuations in the mixture ratio (particularly over-rich) during transient operation, and improve drivability.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing a first embodiment of the present invention, Fig. 2 is a schematic configuration diagram thereof, and Fig. 3 (A) is a cylinder pressure sensor thereof. Fig. 3 (B) is a plan view of only the cylinder pressure sensor;
The figure is a flowchart showing the interrupt subroutine (IRQI) for determining the fuel injection amount, FIG. A flowchart showing the bank grand job program (BGJ), FIG. 7 is a characteristic diagram showing the concept of correction,
FIGS. 8(A) to (D) are diagrams for explaining the action,
Fig. 9 is a graph for explaining the effect, Fig. 10 is a timing chart showing the method of the experiment, and Fig. 11 is an interrupt for determining the fuel injection amount showing the second embodiment of the present invention. FIG. 12 is a flowchart showing the subroutine of the third embodiment of the present invention, and FIG.
FIG. 1 is a flowchart showing an interrupt subroutine for determining the fuel injection amount according to a fourth embodiment of the present invention.
FIG. 4 is a flowchart showing a bank grand job program according to a fifth embodiment of the present invention. 3... Injector (fuel supply means), 8...
... Microcomputer (basic value calculation means, torque calculation means, supply amount correction means, overrich prevention means), 9 ... Cylinder pressure sensor (pressure detection means), 14.
...Operating state detection means. Patent applicant: Nissan Motor Co., Ltd., patent attorney, part of Arigagun (1 person) Fig. 3 Fig. 7 LEAN RIC) l A/F Fig. 8 (l) Fig. 9 Control I Master Figure 10 Figure 11 Figure 12 Figure 13

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine using engine load and rotation speed as parameters; b) Pressure detection means for detecting combustion pressure of the engine; c) Engine load and rotation speed. d) a torque calculation means that calculates a parameter correlated to the output torque of the engine as a parameter detection value based on the output of the pressure detection means; e) a parameter. supply amount correction means for correcting the basic supply amount of fuel so that the detected value matches a predetermined target value; 1. A fuel supply control device for an internal combustion engine, comprising: overrich prevention means for preventing overrichness; and g) fuel supply means for supplying the final supply amount of fuel determined by the overrich prevention means to the engine.