JP2579914B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply control device for an internal combustion engine that detects a parameter correlated with output torque and corrects an air-fuel ratio.

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

As a conventional fuel supply control device for an internal combustion engine that determines the amount of fuel required by an engine from the amount of intake air of this type, for example, “New Automobile Engineering Handbook, Vol. 4” (September 1983)
Issued by the Society of Automotive Engineers of Japan on March 30). In this device, an air flow rate is detected from a rotational displacement of a measurement plate of an air flow meter provided in an intake pipe, and is converted into an electric signal by a potentiometer. This electric signal is input to the control unit and divided by a predetermined trigger corresponding to the engine speed. Since the divided electric signals correspond to the steady-state intake air amount 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. For example, sudden acceleration of the car (hereinafter, referred to as
When the throttle valve is suddenly opened during the transient operation), the pressure in the 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 a part of the liquid fuel flows into the combustion chamber as the amount of accumulated fuel increases. For this reason, during the transient operation, the air-fuel ratio fluctuates greatly, and a required appropriate air-fuel ratio cannot be obtained, resulting in a problem that the drivability is deteriorated including acceleration performance.

Therefore, the present invention focuses on the time difference between the time when the intake air related to the current combustion cycle is detected and the time when the intake air participates in the combustion, and sets a target value obtained from the intake air amount. Is delayed by the above-described time difference, and the fuel supply amount is corrected based on the delayed target value and the actual combustion information, thereby eliminating a significant change in the air-fuel ratio during the transient operation and improving the drivability. The purpose is to improve.

(Means for Solving the Problems) A fuel supply control device for an internal combustion engine according to the present invention has a basic conceptual diagram as shown in FIG. Operating state detecting means a for detecting the amount and the number of revolutions; target value calculating means b for calculating a target value correlated with the output torque of the engine based on the operating state of the engine; Delay means c for delaying the value, pressure detection means d for detecting the combustion pressure of the engine, detection value calculation means e for calculating a detection value correlated with the output torque of the engine based on the combustion pressure, And a delayed target value, and when the detected value is smaller than the delayed target value, a correction amount calculating means f for calculating a fuel correction amount for increasing and correcting the fuel, and an operating state of the engine. Supply amount calculating means g for calculating a basic supply amount of fuel based on the fuel supply amount and correcting the basic supply amount based on the fuel correction amount.
Fuel supply means h for supplying fuel to the engine based on the output value of the supply amount calculation means.

(Action) In the present invention, a target value correlated with the output torque of the engine is obtained from the state quantity of the intake air, and this target value is delayed according to the operating state, and a detection value correlated with the output torque of the engine is obtained. Determined from the combustion pressure of the engine,
When the detected value becomes smaller than the delayed target value, it is determined that the engine is in a transient state, and the fuel supply amount is increased and corrected. Therefore, the estimation accuracy of the combustion state is improved, the air-fuel ratio during the transient operation is appropriately controlled, and the drivability is improved.

Hereinafter, the present invention will be described with reference to the drawings.

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

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

The flow rate of the intake air is detected by a flap-type air flow meter 6 and A / A is represented as an electric signal Q having an analog value.
Output to the D converter 7. The A / D converter 7 outputs the electric signal Q
Is converted to a digital signal Qa and output. The combustion pressure in the cylinder is detected by the cylinder pressure sensor (pressure detecting means) 9, the cylinder pressure sensor 9 outputs a charge signals S ₁ converts the combustion pressure in the charge by the piezoelectric element. The in-cylinder pressure sensor 9 is screwed to the cylinder head 10 as shown in detail in FIGS. 3 (a) and 3 (b).
And is fixed to the outer recess of the cylinder head 10 by being pressed by the fastening portion 4a of the ignition plug 4.

Sensor output S ₁ is input to the charger amplifier 11, charger amplifier 11 operational amplifier OP, an input resistor R1,
Feedback resistor R2 and the so-called charge consisting integrating capacitor C - form a voltage conversion amplifier, a voltage signal of the sensor output S ₁
It is converted to S ₂ and outputs it to the A / D converter 12. A / D converter 12 converts the voltage signal S ₂ to the digital signal S _3.

Further, the crank angle of the engine is measured by a crank angle sensor 13.
And the crank angle sensor 13 detects the crank angle 2
Outputting a discrimination signal S ₅ of degrees corresponding unit signals S ₄ and a cylinder discrimination. The air flow meter 6 and the crank angle sensor 13 constitute operating state detecting means 14.

The microcomputer 20 has functions as target value calculation means, delay means, detection value calculation means, correction amount calculation means and supply amount calculation means, and includes a CPU 21, a ROM 22, a RAM 23 and
It is configured by the / O port 24. The CPU 21 fetches necessary data from the I / O port 24 in accordance with the program written in the ROM 22, and performs data processing while transmitting and receiving data to and from the RAM 23, and processes the processed data as necessary. Is output to the I / O port 24. That is, I / O
The port 24 has A / D converters 7 and 12 and operating state detecting means 1
4 and the injection signal (injector drive pulse) from the I / O port 24
Si is output. The ROM 22 stores a calculation program for the CPU 21, and the RAM 23 temporarily stores data used for calculation, calculation results, and the like.

 Next, the operation will be described.

Generally, the amount of fuel supplied to the engine is substantially proportional to the amount of intake air, and a 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, and the fuel condensing action is promoted to generate liquid fuel. Part of this liquid fuel adheres and accumulates on the pipe wall as a wall flow, greatly reducing the 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 at this time (that is, the combustion state), as shown by the solid line in FIG. 9C, the pressure drops greatly immediately after acceleration and gradually increases as the air-fuel ratio approaches the target value. Stabilizes at a constant value.

As described above, during a transient operation such as acceleration, a part of the fuel becomes ineffective fuel such as a wall flow, so that the mixing ratio actually involved in combustion and the mixing ratio estimated from the intake air amount are different. Do not always match. That is, the air-fuel ratio during the transient operation can be appropriately set by grasping the ineffective fuel described above and correcting the amount of the ineffective fuel.

Therefore, in the present embodiment, attention is paid to the fact that the state quantity of the intake air represented by the engine load, for example, the intake air detected by the air flow meter 6 participates in combustion after a lapse of a predetermined time. By obtaining the parameter target value based on the amount and delaying it for a predetermined time, and further comparing and examining the parameter detection value indicating the actual combustion state, the above-mentioned inactive fuel component is accurately grasped,
The fuel is properly corrected to improve the drivability during the transition.

FIGS. 4 to 6 are flowcharts showing a program for fuel supply control based on the above basic principle.

Figure 4 is an interrupt subroutine program for determining the fuel injection amount (hereinafter, referred IRQ1 program) is a flowchart illustrating a The IRQ1 program is executed once each time the cylinder discrimination signal S ₅ is input. First, it calculates the engine rotational speed N from the input interval of the cylinder judgment signal S ₅ at P _1, reads the intake air quantity Qa at P _2. Then, the basic supply quantity Tp of fuel P _3, is calculated by the following equation.

Step P ₄ is the entry point into the fuel correction subroutine program shown in FIG. 6 (SUBR), SUBR
The program calculates a target value of a parameter correlated with the output torque of the engine, delays the target value, compares it with the detected parameter value, and sets a fuel correction amount.

In the figure, first, 1/4 moving average value of the basic supply quantity Tp at P ₂₁ ▲ ▼ to be calculated according to the following equation.

Then, based on the detection shown effective pressure (parameter detection value correlated with the output torque of the engine) Pi and the basic supply quantity Tp later in P _22, a calculation coefficient K to be those 1/64 moving average, according to the following equation Calculate.

In P _23, the target value PiM parameters that correlate with the output torque of the engine is calculated according to the following equation.

PiM = ▲ ▼ × K ...... then performs delay processing of the target value PiM at P _24. This delay processing is performed by using a predetermined number of memory areas (three areas in this embodiment) and a so-called first-in first-out method (FIFO: Fast in Fast).
made by the memory configuration of the out), and stores the target value PiM in this memory, each time each time of execution of the program (cylinder determination signal S ₅ inputs) target value in memory
Move the PiM sequentially. That is, the target value PiM stored in the FIFO memory in this process moves in the memory in the next process, and is taken out of the FIFO memory in the next process. In P ₂₅ and the retrieved target value PiM, detection shown effective pressure Pi obtained in later-described IRQ2 program
(The detected value of the parameter correlated with the output torque of the engine) to determine whether or not to perform the fuel increase correction. That is, when the target value PiM is large (Pi <Pi
M), disable fuel occurs due to the liquid fuel, air-fuel ratio is determined to be in a lean tendency, the basic supply quantity Tp at P _26, returns to increasing correction to IRQ1 programmed according to the following equation.

Tp = Tp + CONST ...... However, CONST: in Figure 4 constant, P ₅ the various correction coefficients (e.g., CO
FE: correction coefficient represented by water temperature, etc.)
Correct p and calculate the final injection pulse width Ti. Then P
_When the injection timing specified in ₆ is reached, an injection signal Si having a pulse width corresponding to this Ti is output to the injector 3, and this time
The IRQ1 program ends, and the program returns to the main program (not shown).

Figure 5 is an interrupt subroutine program for determining a parameter correlated with the output torque (hereinafter, referred to as IRQ2 program) and uronium chart showing a the IRQ2 program each time the unit signal S ₄ of the crank angle is input Executed once.

First, based on the unit signal S ₄ at P ₁₁ calculates the theta (crank angle interrupt timing) present crank angle, P ₁₂
In reading the combustion pressure signal S _3, replacing the combustion pressure signal S ₃ to the current cylinder pressure P. Then, operation with obtaining the cylinder volume V corresponding to the crank angle θ of the interrupt timing, the cylinder volume difference [Delta] V between the V and the last cylinder volume V '(ΔV = V'-V ) with P ₁₃ I do. Multiplying the cylinder internal pressure P in P ₁₄ and cylinder volume difference ΔV seek PΔV by. This PΔV is an area per predetermined crank angle (for example, 2 °) in a so-called PV diagram, and is a unit area for obtaining a detected indicated effective pressure Pi described later.

Then, current interrupt timing crank angle θ with P ₁₅
Cumulative SUM of PΔV obtained corresponding to and PΔV up to the previous time
Adds, the process proceeds to a crank angle of 0 ° determination step P _16. P
In ₁₆ when the crank angle is 0 °, the accumulated value SUM proceeds to P ₁₇
Is replaced as the detected indicated effective pressure Pi. In addition, P ₁₈
After clearing the accumulated value SUM with, the processing of the current IRQ2 program ends. Meanwhile, while when the theta ≠ 0 ° with P _16, and determines that the value of the accumulated value SUM has not yet reached the area of the closed surface in the so-called P-V diagram, and hold the value of SUM to date Quit the IRQ2 program.

As described above, in the present embodiment, the target value PiM obtained from the intake air amount is delayed according to the operating state, so that the detected parameter Pi obtained from the combustion pressure and the delayed target value PiM are the same. Is the parameter information based on the intake air amount. Then, the detected value Pi and the delayed target value PiM
When the detected value Pi becomes smaller than the target value PiM, it is determined that the engine is in the transient operation state, and the fuel supply amount is increased and corrected. Accordingly, the accuracy of estimating the combustion state obtained from these parameter information is improved, and the air-fuel ratio at the time of transition is appropriately controlled. As a result, as shown in FIG. (Ie, the torque increases). Also, at that time
The Tp correction amount is shown in FIG.

In the present embodiment, a single cylinder engine has been described as an example, but the present invention is not limited to this. In short, it is sufficient that the target value obtained from the intake air amount is delayed so that the combustion information involving the intake air amount is compared with the target value. By detecting each injection cylinder group and comparing it with a target value, it can be applied to a multi-cylinder engine.

(Effects) According to the present invention, the target value of the parameter obtained from the intake air amount is delayed according to the operating state of the engine, and the target value is obtained from the delayed target value and the combustion pressure related to the intake air amount. When the detected value is smaller than the delayed target value, it is judged as a transient state and the fuel correction amount for increasing and correcting the fuel supply amount is determined. Thus, the fuel supply amount can be controlled, and a large change in the air-fuel ratio during the transient operation can be eliminated, so that the drivability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic concept of the present invention, FIGS. 2 to 7 are diagrams showing an embodiment of the present invention, FIG.
FIG. 1A is a cross-sectional view showing a mounting state of the in-cylinder pressure sensor.
3 (b) is a plan view of only the in-cylinder pressure sensor, FIG. 4 is a flowchart showing an interrupt subroutine program (IRQ1) for determining the fuel injection amount, and FIG. 5 correlates with the output torque. Flowchart showing an interrupt subroutine program (IRQ2) for obtaining parameters;
FIG. 6 shows the fuel correction subroutine program (SUBR).
7 (a) to 7 (e) are timing charts for explaining the operation. 3 ... injector (fuel supply means) 9 ... cylinder pressure sensor (pressure detection means) 14 ... operation state detection means 20 ... microcomputer (target value calculation means, delay means, detection value calculation means, correction Amount calculating means, supply amount calculating means).

Claims (1)

(57) [Claims] A) operating state detecting means for detecting a state quantity and a rotation speed of intake air represented by an engine load; and b) setting a target value correlated with an output torque of the engine based on the operating state of the engine. Target value calculating means for calculating; c) delay means for delaying the target value based on the operating state of the engine; d) pressure detecting means for detecting combustion pressure of the engine; e) engine based on the combustion pressure And f) comparing the detected value with the delayed target value, and when the detected value is smaller than the delayed target value, increasing the fuel amount. Correction amount calculating means for calculating the amount of fuel correction to be performed; g) calculating a 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. The amount calculating means and, h) supply amount calculating means in the fuel supply control system for an internal combustion engine, characterized by comprising: a fuel supply means for supplying fuel to the engine based on the output value.