JPH0625558B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine that corrects an air-fuel ratio by detecting a parameter correlated with output torque.

(Prior Art) In general, the amount of fuel required by an engine under a certain operating condition has an intake air amount 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 the engine from this type of intake air amount,
For example, (New Edition Automotive Engineering Handbook 4th Edition) (September 30, 1983)
Published by Japan Automotive Engineering Society).

In this device, the air flow rate is extracted from the rotational displacement of the measuring plate of the air flow meter provided in the intake pipe and converted into an electric signal by the potentiometer. This electric signal is input to the control unit and divided by a predetermined trigger corresponding to the engine speed. The divided electric signal corresponds to the intake air amount for each cylinder, and the fuel supply amount is determined based on the intake air amount so that the target air-fuel ratio is achieved based on the steady state condition.

(Problems to be Solved by the Invention) However, such a conventional fuel supply control device is configured to determine the fuel supply amount corresponding to the target air-fuel ratio from the intake air amount in the steady state. Therefore, when suddenly accelerating the vehicle (hereinafter referred to as transient operation), if the throttle valve is opened suddenly, the inflow air will also increase rapidly, and the fuel supply amount will be determined based on the air flow rate and supplied to the air supply pipe. To be done.

However, the internal pressure of the air supply pipe is increased by the above-mentioned rapid increase in the air flow rate, and the supplied fuel condenses into liquid fuel. After the air-fuel mixture that has been generated and flows into the combustion chamber is temporarily diluted, the fuel adhering and accumulated in the combustion chamber flows into the combustion chamber, and the mixture ratio is shifted to the rich state.

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

(Object of the Invention) Adhesion of fuel to the pipe surface is a phenomenon during transient operation and does not occur during steady operation.

Therefore, the present invention eliminates a large change in the air-fuel ratio during transient operation by detecting that the engine is in a transient operation state and correcting the mixture ratio based on the parameter that correlates with the output torque during the detection period. The purpose is to improve drivability.

(Means for Solving Problems) In order to achieve the above object, a combustion supply control apparatus for an internal combustion engine according to the present invention has a basic conceptual diagram thereof as shown in FIG. An operating state detecting means a for detecting an operating state, a pressure detecting means b for detecting an engine combustion pressure, a first calculating means c for calculating a basic fuel supply amount based on an engine load and a rotational speed, and a pressure detecting Second computing means d for computing a parameter correlated with the output torque of the engine as a parameter detection value based on the output of the means, and a target value of the parameter correlated with the output torque of the engine based on the detection value by the operating state detection means a. A target value setting means e for setting the transient value, a transient start detection means f for detecting that the engine has transitioned to a predetermined transient state, and an end of the predetermined transient state. End detecting means g for detecting the end of the engine, non-transient state supply amount determining means h for determining the fuel supply amount based on the output of the first calculating means c when the engine is not in a predetermined transient state, and a predetermined transient state. , The excess or deficiency of the fuel supply amount is obtained from the difference between the parameter detection value from the second calculating means d and the target value from the target value setting means e, and the next fuel supply quantity is calculated based on this excess or deficiency amount. Transient state correction amount calculation means i for calculating the correction amount for
And a transient state supply amount calculation means j for calculating the fuel supply amount to the engine by correcting the basic supply amount with the correction amount,
Fuel supply means k for supplying fuel to the engine based on the outputs of the transient state supply amount calculation means i and the non-transient state supply amount determination means h.

(Operation) In the present invention, the transient operation state is detected from the change in the basic fuel amount, and the fuel supply amount is corrected based on the parameter correlated with the output torque during the detection period.
Therefore, a large change in the air-fuel ratio during transient operation is suppressed and the air-fuel ratio during steady state is appropriately maintained,
The drivability is improved.

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

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

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an engine, intake air is supplied to each cylinder from an air cleaner (not shown) through an intake pipe 2, 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 explodes 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, and harmful components (CO, HC, NOx) is cleaned by a three-way catalyst and discharged.

The flow rate of the intake air is detected by the air flow meter 6,
The electric signal Q having an analog value is output to the A / D converter 7. 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 an in-cylinder pressure sensor (pressure detection means), and the in-cylinder pressure sensor 9 changes the combustion pressure in the cylinder into an electric charge by a piezoelectric element and outputs an electric charge signal S ₁ . As shown in detail in FIGS. 3A and 3B, the in-cylinder pressure sensor 9 is screwed to the cylinder head 10 and is formed as a washer of the ignition plug 4, and is formed on the outer recess of the cylinder head 10. The spark plug 4 is pressed and fixed by the tightening portion 4a of the spark plug 4.

The sensor output S ₁ is input to the charger amplifier 11, and the charger amplifier 11 has an operational amplifier OP and an input resistor R.
1, the so-called charge consisting feedback resistor R2 and the integrating capacitor C - form a voltage conversion amplifier, and outputs to the A / D converter 12 converts the sensor output S ₁ into a voltage signal S _2. A
The / D converter 12 converts the voltage signal S ₂ into a digital signal S ₃ and outputs the digital signal S ₃ 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 outputs a unit signal S ₄ corresponding to 2 ° of the crank angle and a discrimination signal S ₅ for cylinder discrimination to the microcomputer 8.

The air flow meter 6 and the crank angle sensor
Reference numeral 13 constitutes an operating state detecting means 14.

The microcomputer 8 includes a first calculating means, a second calculating means, a target value setting means, a transient start detecting means, a transient end detecting means, a non-transient state supply amount determining means, a transient state correction amount calculating means and a transient state supply amount calculating means. CPU21, ROM22, RAM23 and I / O port
Composed of 24. The CPU 21 performs arithmetic processing while fetching required data of each part from the I / O port 24 according to a program written in the ROM 22 and exchanging data with the RAM 23, and processes as necessary. Outputs data to I / O port 24. I / O
Signals from the A / D converters 7 and 12 and the operating state detecting means 14 are input to the port 24, and the I / O port 24
Outputs an injection signal (injector drive pulse) Si. The ROM 22 stores a calculation program in the CPU 21, and the RAM 23 is a so-called working memory that temporarily stores data used for calculation, calculation results, and the like.

Next, the operation will be described.

In general, the amount of fuel supplied to the engine during a transient operation such as acceleration has a relationship substantially proportional to the intake air amount. The sudden increase in the intake air amount due to acceleration or the like increases the internal pressure of the intake pipe and promotes the condensation action of the fuel to generate liquid fuel. A part of the liquid fuel adheres and accumulates on the pipe wall, and the fuel involved in combustion is greatly reduced. Taking the case of acceleration as an example of the state during such transient operation, the air-fuel ratio becomes significantly lean immediately after acceleration as shown in FIG. 8 (A), and then gradually approaches the target. Looking at the change in the detected cylinder pressure at this time, as shown by the solid line in FIG. 7B, it drops sharply immediately after acceleration and gradually increases as the air-fuel ratio approaches the target value, and stabilizes at a constant value. . Here, the target in-cylinder pressure required for acceleration (substantially equal to the intake air amount) is indicated by a broken line.

By the way, the accumulated amount of the fuel adhering to and accumulated on the pipe wall increases with the passage of time, and a part of the fuel flows into the combustion chamber to make the air-fuel ratio into an overrich state.

Therefore, in the present embodiment, the start of transient operation is detected by focusing on the causal relationship that the difference between the detected in-cylinder pressure and the target in-cylinder pressure (that is, the difference in output torque) corresponds to the amount of ineffective fuel adhering to and accumulated on the pipe wall. Then, a parameter correlating to the output torque at that time is obtained to calculate the above-mentioned ineffective fuel amount, and from this, the air-fuel ratio is estimated and the fuel supply amount is appropriately corrected. Further, when the operation is shifted to the steady operation, the above-mentioned correction is promptly stopped to prevent the air-fuel ratio from becoming rich.

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

FIG. 4 is a flowchart showing an interrupt subroutine (IRQ1) for determining the fuel injection amount, and this interrupt subroutine (IRQ1) is executed once every time the cylinder discrimination signal S ₅ is input.

First, at P ₁ , the engine speed N is calculated from the input interval of the cylinder discrimination signal S ₅ , and at P ₂ , the intake air amount Qa is read. Then, at P ₃ , the basic fuel supply amount T as a function of N, Qa
p is calculated, which is obtained, for example, according to the following equation.

However, when K: constant P ₄ , the start of the transient operation state is detected by the following equation.

However, Tp: current basic supply amount T _POLD : previous basic supply amount Co: predetermined value That is, when the change rate of the basic supply amount Tp is larger than the predetermined value Co, the intake air amount Qa tends to increase, This indicates that the engine has entered a transient state.
When the start of the transient state is detected in this way, the counter is cleared at P ₅ , and then at P ₆ , the basic supply correction amount C _pwo calculated using the background job program (BGJ) described later is used. Correct the amount of increase in Tp. At P ₇ , when the designated injection timing is reached, an injector drive signal (injection signal) Si having an injection pulse width corresponding to this increased supply-corrected basic supply amount Tp is output.
Next, at P ₈ , the basic supply amount Tp is stored as T _POLD ,
Terminate the interrupt subroutine.

On the other hand, the rate of change of the basic supply amount Tp at P ₄ (Tp / T _POLD )
When is less than or equal to the predetermined value Co, the process proceeds to P ₉ to compare the counter value with the predetermined value C ₁ (determined by the acceleration condition),
The state of transient operation shown in Table 1 below is determined.

If it is determined that the state of the transient operation is continuing, the counter value is incremented by +1 at P ₁₀ , then the process proceeds to P ₆ , and the increase correction using the basic transient correction amount C _pwo is _performed as described above. To do. On the other hand, when it is determined that the state of the transient operation is finished, the value of the basic transient correction amount C _pwo is cleared at P ₁₁ (C _pwo = 0), and the increase correction for the basic supply amount Tp is not performed.

Therefore, at the next P ₇ , the injector drive signal Si having the injection pulse width corresponding to this basic supply amount Tp is output.

FIG. 5 is a flowchart showing an interrupt subroutine (IRQ2) for obtaining a parameter correlated with the output torque. This interrupt subroutine (IRQ2) is executed once every time the crank angle unit signal S ₄ is input. It

First, at P ₂₁ , the present crank angle (crank angle at the interrupt timing) θ is calculated based on the unit signal S ₄ , and P ₂₂
The combustion pressure signal S ₃ is read in and the combustion pressure signal S ₃ is replaced with the current cylinder pressure P. Next, at P ₂₃ , the cylinder internal volume V corresponding to the crank angle θ at the interrupt timing is obtained, and the cylinder internal volume difference ΔV between this V and the previous cylinder internal volume V ′ (ΔV = V′−V) is calculated. To do.

At P ₂₄ , the cylinder internal pressure P is multiplied by the cylinder internal volume difference ΔV to obtain P
Calculate ΔV. This PΔV is an area per predetermined crank angle (for example, 2 °) in the so-called P-V diagram, and is a unit area for obtaining a detected indicated effective pressure Pi described later.

Next, at P ₂₅ , the cumulative value SU of PΔV obtained corresponding to the current interrupt timing crank angle θ and PΔV up to the previous time is calculated.
M is added, and the process proceeds to the crank angle 0 ° determination step P ₂₆ . At P ₂₆ , when the crank angle is 0 °, the routine proceeds to P ₂₇ , where the accumulated value SUM is replaced as the detected indicated effective pressure Pi.
Further, at P ₂₈ , the cumulative value SUM is cleared and the interrupt subroutine (IRQ2) is ended.

On the other hand, when θ ≠ 0 ° at P ₂₆ , it is determined that the value of the cumulative value SUM has not yet reached the area of the closed curved surface in the so-called PV chart, and the value of SUM up to the present is retained. The interrupt subroutine (IRQ2) is completed.

In this way, the parameter correlated with the output torque is obtained, but the point is that the method is not limited to this method as long as it is based on the piecewise quadrature method, and may be obtained by another method.

FIG. 6 is a flow chart showing the background job program (BGJ) for obtaining the basic transient correction amount, which is the above-mentioned interrupt subroutine (IRQ1), (IRQ1).
It is a program that is always executed while 2) is not executed.

First, P ₃₁ is a step for calculating the target indicated effective pressure Pi ′, which is obtained as a function of the engine speed N and the basic fuel injection pulse width Tp.

Next, P ₃₂ is a step for _{obtaining the} basic transient correction amount C _pwo , which is the target _indicated effective pressure Pi ′ and the detected _indicated effective pressure Pi.
Required from. To explain this, the fuel supplied from the injector is divided into a combusted component and an uncombusted component due to adhesion of wall surfaces and the like in a transient operation such as acceleration.

The concept of correction is shown in FIG. That is, in the figure, if the difference between the target indicated effective pressure Pi 'and the detected indicated effective pressure Pi is the difference value a, the basic transient correction amount C _pwo is set so that the air-fuel ratio becomes rich by the amount b. Is determined. To describe this concretely, the relationship between the fuel supply amount (the previously corrected basic supply amount P _POLD and the _indicated effective pressure is
It is expressed by the following equation.

Fuel supply amount: unburned amount = Pi ': a, where Pi': target indicated effective pressure Pi: detected indicated effective pressure a = Pi'-Pi It becomes as follows.

The unburned component thus obtained is determined as the basic transient correction amount C _pwo . As a result, the basic supply amount Tp is appropriately increased and corrected by this C _pwo as shown in FIG. 8 (C) to follow the lean change of the air-fuel ratio during acceleration. Therefore, the change in the in-cylinder pressure after the correction has a characteristic substantially in accordance with the target in-cylinder pressure, and the transient operation performance during acceleration is improved.

On the other hand, if such a correction is performed in the steady operation, the correction amount varies due to a detection error (so-called variation) in the detected in-cylinder pressure, and combustion becomes unstable. Further, when the in-cylinder pressure sensor changes over time, the detected in-cylinder pressure is detected to be smaller than the actual value, and as a result, the air-fuel ratio becomes overrich.

According to the present embodiment, the increase correction is performed immediately after the start of the transient operation, and the increase correction is continued for the number of times of the predetermined value C ₁ determined by the acceleration condition. Therefore, since the fuel amount is determined from the uncorrected basic supply amount Tp after the number of times of the predetermined value C ₁ , that is, in the steady operation, the problem in the steady operation as described above can be solved.

The experimental results of this example are shown in FIGS. The contents of specifications 1 to 3 shown in FIG. 9 as three types of line graphs are as shown in Table 2 below.

As shown in FIG. 10, the experimental method is as follows. The detected cylinder pressure Pi is the target cylinder pressure P after the throttle switch is turned on.
It was carried out by measuring the time to reach the position indicated by T in FIG. As is clear from FIG. 9, according to this embodiment, the time required to reach the target cylinder pressure Pi 'is 1 /
It is shortened to about 3 and the acceleration performance is greatly improved.

11 and 12 are diagrams showing a second embodiment of the present invention. In the description of this embodiment, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted.

In FIG. 11, reference numeral 30 denotes an oxygen sensor, and the oxygen sensor 30
Detects the oxygen concentration in the exhaust gas and outputs a signal Vs to the microcomputer 31. The microcomputer 31 is the first
Similar to the embodiment, the CPU 32, ROM 33, RAM 34 and I
The I / O port 35 receives the signal Vs from the oxygen sensor 30. In this embodiment, the oxygen sensor 30 and the microcomputer 31 are integrated to have a function as a transition end detecting means.

FIG. 12 is a flowchart showing an interrupt subroutine (IRQ1) for determining the fuel injection amount written in the ROM 33, and the procedure for detecting the transition end is different from that in the first embodiment. The differences will be described below.

First, when the transient start is detected in P ₄ , the transient flag is set in [P ₄₁ ] and the basic supply correction amount C _{pwo is used} to _perform the increase correction of the basic supply amount Tp.

On the other hand, when the NO command is followed in P ₄ , step [P ₄₂ ]
Then, the signal Vs indicating the oxygen concentration is compared with a predetermined value C _2, and when Vs> C ₂ , it is determined that the air-fuel ratio is in the lean state. That is, if the air-fuel ratio is in the lean state, at least a problematic overrich does not occur, and therefore there is a possibility of increasing correction for the fuel supply amount Tp. When the lean state is discriminated in this way, the process proceeds to step [ _P43 ], where the transient flag is inspected. This transient flag is set at the start of transient operation,
As will be described later, resetting is performed when the air-fuel ratio is not lean,
That is, it is performed when overrich is detected.
Thus, during the set period of the transient flag is considered to be in transient operation, the process proceeds to step P _6, increasing correction of the basic supply quantity Tp is performed by the basic transient correction amount C _pwo.

On the other hand, when the air-fuel ratio is not lean in [P ₄₂ ] (that is, overrich), or when the transient flag is reset in [P ₄₃ ], it is determined that the engine is in a steady operation, and the process proceeds to step [P ₄₄ ]. Here, the basic transient correction amount C _pwo
Clears the value of and resets the transient flag if it is set. The program then proceeds to P _7, the injector driving signal Si having an injection pulse width corresponding to the basic supply quantity Tp which is not increasing correction is output.

As described above, according to this embodiment, the oxygen concentration in the exhaust gas is directly measured and the correction period is set. Therefore, in addition to the effect of the first embodiment, a more accurate feedback control of the air-fuel ratio can be performed. it can.

(Effect) According to the present invention, the transient operation state is detected, and the mixture ratio is corrected based on the parameter that correlates with the output torque within that period. A large change in the air-fuel ratio due to adhesion can be suppressed, and drivability can be improved.

[Brief description of drawings]

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 its schematic configuration diagram, and FIG. 3 (A) is its cylinder pressure sensor. 3B is a plan view showing only the in-cylinder pressure sensor, FIG. 4 is a flow chart showing an interrupt subroutine (IRQ1) for determining the fuel injection amount, and FIG. Is a flowchart showing an interrupt subroutine (IRQ2) for obtaining a parameter correlated with the output torque, FIG. 6 is a flowchart showing the background job program (BGJ), and FIG. 7 is a characteristic diagram showing the concept of the correction. 8 (A) to 8 (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, FIG. 12
FIG. 11 is a diagram showing a second embodiment of the present invention, FIG. 11 is a schematic configuration diagram thereof, and FIG. 12 is a flowchart showing an interrupt subroutine (IRQ1) for determining the fuel injection amount. 3 ... Injector (fuel supply means), 8, 31 ... Microcomputer (first computing means, second)
Calculating means, target value setting means, transient start detecting means, transient end detecting means, non-transient state supply amount determining means, transient state correction amount calculating means, transient state supply amount calculating means, 9 ... In-cylinder pressure sensor (pressure detection) Means), 14 ... Operating state detection means.

Claims (1)

[Claims] 1. An a) operating condition detecting means for detecting an operating condition of the engine using the engine load and a rotational speed as parameters; b) a pressure detecting means for detecting a combustion pressure of the engine; and c) an engine load and a rotational speed. First calculation means for calculating a basic supply amount of fuel based on the above; d) second calculation means for calculating a parameter correlated with the output torque of the engine as a parameter detection value based on the output of the pressure detection means; and e) operation. Target value setting means for setting a target value of a parameter that correlates to the output torque of the engine based on the value detected by the state detecting means; f) transient start detecting means for detecting that the engine has transitioned to a predetermined transient state; g) transient end detecting means for detecting the end of a predetermined transient state, and h) based on the output of the first computing means when the engine is not in the predetermined transient state. Non-transient state supply amount determining means for determining the fuel supply amount by means of: i) fuel supply based on the difference between the parameter detection value from the second calculating means and the target value from the target value setting means when in a predetermined transient state And a transient state correction amount calculating means for calculating a correction amount for the next fuel supply amount based on the excess or deficiency amount, and j) correcting the basic supply amount with the correction amount to the engine. And a fuel supply unit for supplying fuel to the engine based on the outputs of the transient state supply amount calculation unit and the non-transient state supply amount determination unit. A fuel supply control device for an internal combustion engine, comprising: