JPH0571402A - Fuel supply controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an optimum air-fuel ratio all times by finding an injection amount for every cylinder on the basis of the increased injection amount of fuel equivalent to the amount of air in a cylinder during previous injection to the cylinder so that the amount of fuel corresponding to a change in a driving condition for every cylinder can be supplied. CONSTITUTION:The injection amount of fuel equivalent to the amount of air in a cylinder is computed (b) in accordance with the output of a driving condition detecting means (a) and the injection amount of fuel equivalent to the amount of air in the cylinder in the previous injection timing of fuel in each cylinder is memorized (c) so that a difference between the previous value and the current value of the injection amount of fuel equivalent to the amount of air in the cylinder can be computed (d). When judgement is made by a determining means (e) that fuel is cut off, the memorized value is renewed (f) for every cylinder so as to be gradually smaller and the final injection amount of fuel is set to be zero during fuel cut. On the other hand, when fuel is not cut off, the synchronous injection amount of fuel is computed (g) in accordance with the size of the difference, and if the difference is over a preset value the asynchronous injection amount of fuel is computed (h) in accordance with the size of the difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine such as an automobile, and more particularly to a fuel supply device for calculating the fuel supply amount based on the intake air amount.

[0002]

2. Description of the Related Art Recently, demands for internal combustion engines such as automobiles have become more sophisticated, and there is a tendency to achieve high levels of conflicting problems such as reduction of harmful exhaust gas, high output, and low fuel consumption. It is in. Further, such a requirement is the same for the wall flow correction, and it is desired to improve the accuracy of the wall flow correction.

In the conventional fuel supply control device of this type, the required load per unit rotation of the engine is obtained from the output of the air flow meter provided on the upstream side of the throttle valve, and the fuel injection amount is calculated from this. Further, at the time of transition, it is dealt with by correcting the fuel injection amount (for example, JP-A-59-53).
No. 8). However, in the conventional device, an appropriate injection amount calculation (particularly, wall flow correction) in consideration of the capacity of the intake pipe between the mounting position of the air flow meter and the mounting position of the injection valve (injector), that is, the intake volume is performed.
However, there is a problem in that the injection characteristic during the transition is delayed from the required characteristic of the engine and the driving performance is poor.

Therefore, in order to solve such a problem, the present applicant has previously proposed a fuel supply control device (Japanese Patent Laid-Open No. 60-1620).
No. 66 publication). In the device according to this prior application, the output of the air flow meter is smoothed with a first-order delay in order to accurately obtain the amount of air flowing through the injection valve unit, and the fuel injection amount (hereinafter simply referred to as smooth injection) is based on the smoothed air amount. The amount; called AvTp) is calculated. In addition, AvTp
Is calculated as a pulse width corresponding to the cylinder air amount, but the calculation method is similar to that of the embodiment described later, and will be described in detail later.

[0005]

By the way, in such a device according to the prior application, the fuel is injected by using the smooth injection amount AvTp. In this case, it may take time until the air-fuel ratio returns to the target value (eg, λ = 1) immediately after the fuel cut is released (during recovery), and exhaust emission characteristics and drivability may be poor (occurrence of breathing phenomenon, etc.). There is.

That is, although AvTp contributes to the stabilization of the air-fuel ratio, since the determination of recovery is made based on the following equation, the asynchronous injection amount during recovery may be inappropriate. AvTp-AvTpoin ≧ LASN1 ... In the formula, LASNI is a cylinder-by-cylinder asynchronous injection determination value (hereinafter, simply referred to as a determination value), and AvTpoin is an n-th injection valve (injector) and indicates AvTp used for previous injection. However, the value AvTpoin is just the smooth injection amount immediately before the start of the fuel cut, and includes the fuel amount taken by the wall flow. On the other hand, during the fuel cut, the wall flow is gradually removed (suctioned into the cylinder),
At the time of recovery, it is possible that there is almost no wall flow.
However, in the prior application, the parameter of AvTpoin that remains the wall flow is used for the determination of the recovery amount, so the recovery amount is actually insufficient and the air-fuel ratio does not reach the target value. In this case, a large part of the recovery fuel is taken up by the wall flow, and the air-fuel ratio becomes lean.

Therefore, according to the present invention, during the fuel cut, by setting the value of the previous smooth injection amount to a predetermined small value, the asynchronous injection determination at lean and the injection amount are made appropriate, and the exhaust characteristic and drivability are set. Is intended to improve.

[0008]

In order to achieve the above-mentioned object, a fuel supply control apparatus for an internal combustion engine according to the present invention has a basic conceptual diagram thereof as shown in FIG. 1, and detects an intake air amount for detecting an intake air amount of the engine. The means a, the operating state detecting means b for detecting the operating state of the engine, and the fuel injection command at the synchronous injection timing based on the output of the intake air amount detecting means a. The synchronous injection calculation means c that stops, the asynchronous injection calculation means d that determines the timing and the asynchronous injection amount of the asynchronous injection based on the set value of the supply amount during the fuel cut when the fuel cut is released, and the fuel cut by the engine. In the fuel cut period, the set value of the supply amount is set to a predetermined value that correlates with the remaining amount of the wall flow from the start of fuel cut. Setting means e that, and a, and fuel injection means f for injecting fuel into the engine based on the output of the synchronous injection calculating means c and the asynchronous injection calculating means d.

[0009]

In the present invention, the basic fuel supply amount is calculated based on the output of the intake air amount detecting means (air flow meter).
Then, during recovery, the injection calculation value Av based on the smooth intake air amount.
The asynchronous injection determination and the recovery amount are determined by comparing Tp with a predetermined small recovery reference value. Therefore, the wall flow during recovery is sufficiently added, the air-fuel ratio during recovery quickly returns to the target value, and exhaust characteristics and drivability are improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 2 to 7 are views showing an embodiment of a fuel supply control device for an internal combustion engine according to the present invention. First, the configuration will be described. Figure 2
FIG. 3 is a diagram showing an overall configuration of the present device.

In FIG. 2, reference numeral 1 denotes an engine, intake air passes from an air cleaner 2 through an intake pipe 3, and fuel is injected from an injector (fuel injection means) 4 based on an injection signal Si. The exhaust gas burned in the cylinder is exhaust pipe 5.
Is introduced into the catalytic converter 6 through the catalytic converter 6 and the harmful components (CO, HC, NOx) in the exhaust gas are cleaned by the three-way catalyst and discharged.

The flow rate Qa of the intake air is detected by a hot wire type air flow meter (intake amount detecting means) 7,
It is controlled by the throttle valve 8 in the intake pipe 3. The type of the air flow meter 7 may be a hot film type, and any type that measures the flow rate of intake air may be used. Therefore, a flap type sensor or a negative pressure sensor may be used.

The opening TVO of the throttle valve 8 is detected by the throttle valve opening sensor 9, and the rotation speed N of the engine 1 is detected by the crank angle sensor 10. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by the water temperature sensor 11,
The oxygen concentration in the exhaust gas is detected by the oxygen sensor 12. As the oxygen sensor 12, a sensor having a characteristic that the output Vs thereof suddenly changes depending on the stoichiometric air-fuel ratio is used. Further, the idle state of the engine 1 is detected by the idle switch 13.

The throttle valve opening sensor 9 and the crank angle sensor
10, the water temperature sensor 11, the oxygen sensor 12, and the idle switch 13 constitute the operating state detecting means 14, and the outputs from the operating state detecting means 14 and the air flow meter 7 are input to the control unit 20. control unit
20 has a function as a smoothed value calculation means, a synchronous injection calculation means, an asynchronous injection calculation means and a setting means, a CPU 21,
It is composed of a ROM 22, a RAM 23 and an I / O port 24. The CPU 21 fetches external data required from the I / O port 24 according to the program written in the ROM 22 and exchanges data with the RAM 23 while performing processing required for smooth intake amount and injection control. I / O the data by processing the values and processing them as necessary
Output to port 24. Sensor group 7, I / O port 24
The signal from 14 is input, and the injection signal Si is output from the I / O port 24. The ROM 22 stores the calculation program in the CPU 21, and the RAM 23 stores the data used for the calculation in the form of a map or the like.

Next, the operation will be described. The main program of this embodiment is shown in FIG. 5, and AvTp calculated in this main program is calculated in a subroutine. For convenience of explanation, the subroutine for obtaining AvTp will be described first. FIG. 3 is a subroutine for obtaining the smooth injection amount AvTp.

First, at P ₁ , the output of the air flow meter 7 is read to obtain the intake air amount Qa. This is due to table lookup, for example. Then, the basic pulse width before smoothing Tp ₀ is calculated at P ₂ according to the following equation. Tp ₀ = (Qa / N) × K ...... Then, the weighted average of Tp ₀ is calculated at P ₃ to obtain the basic pulse width Tp.
Is calculated. Thereby, the pulsation based on the output of the air flow meter 7 is smoothed. At P ₄ , the flat corrected basic pulse width TrTp is calculated according to the following equation.

TrTp = Tp × Kflat In the equation, Kflat is a flat A / F correction coefficient, and is calculated from the map allocated by the rotational speed N and the α-N flow rate Qho with interpolation calculation. It should be noted that the α-N flow rate is an air flow rate obtained from the throttle valve opening TVO and the rotation speed N, and is already known.

Next, at P ₅ , TrTp is compared with a predetermined maximum limit value Tp _max, and when TrTp> Tp _max , TrTp is limited to Tp _max at P ₆ and the routine proceeds to P _7.
When Tp ≦ Tp _max , P ₆ is jumped to P ₇ . At P ₇ , the delay correction pulse width THSTP as the α-N pre-correction pulse width is obtained. This is the α-N flow rate Q
The value TTHSTP is looked up from the table with interpolation calculation based on ho, and is calculated as the amount of change every 10 ms. However,
If the amount of change is less than or equal to the correction determination level, THSTP =
If the change amount is 0 (deceleration), the change amount is multiplied by a predetermined deceleration correction rate. THSTP is a term for correcting the injection amount with good responsiveness in advance of changes in the throttle valve 8. Next, at P ₈ , the smooth injection amount AvTp (corresponding to the smooth intake amount) is calculated according to the following equation.

AvTp = TrTp × FLOAD / AvTp ₋₁ × (1−FLOAD) + THSTP In the formula, FLOAD is a weighted average coefficient, and FL
Given by OAD = TFLOAD + K2D (deceleration only). Since TFLOAD is a function of only the intake volume, it is obtained by a map from the flow rate area AA determined by the throttle valve 8 and (displacement amount × rotation speed) NVM. Therefore, the first term and the second term of the formula are the weighted average value using the FLOAD for the flat corrected basic pulse width TrTp calculated based on the value obtained by pulsating the output of the air flow meter 7, in other words, the primary delay of TrTp. Corresponds to the part for calculating (by software). Further, the third term of the equation is a portion for pre-correction by the throttle valve opening TVO, and this portion is not disclosed in the prior application and is disclosed for the first time in this embodiment.

The effect of adding THSTP of the third term is shown in FIG. In FIG. 4, when acceleration is performed at a certain timing, the basic pulse widths Tp ₀ and Tp change with a slight delay after the change of the throttle opening, and the waveform in which Tp ₀ and Tp are corrected is a flat corrected basic pulse width TrTp. It changes like. On the other hand, the α-N flow rate changes stepwise according to the opening degree of the throttle valve 8, and the delay correction pulse width THSTP is calculated by this opening change amount. Further, the smooth injection amount AvTp is given with a first-order delay of TrTp, and in the case of the conventional phase control without THSTP, the change is indicated by the one-dot chain line in the figure, and the response is lacking. At this time,
The suction negative pressure is shown by a broken line, and the injection valve portion (injector 4
Although it is substantially equal to the air flow rate of the (part), it cannot follow the change in the opening degree of the throttle valve 8 without delay. Further, the intake volume also affects the amount of fuel adhering to the wall surface of the intake pipe 3.

On the other hand, AvTp of this embodiment is shown in the figure.
As shown by the solid line, the correction term THSTP is ahead of α-N.
It is added as a pre-correction (pre-correction of 10 ms)
Therefore, the responsiveness is extremely good, and it is
It will be the one. An example of highlands is also shown. Figure
5 is a flow chart showing a program for calculating the standard value of recovery
This program is interrupted for each injection.
It First, P₁₁Then, the injection cylinder of this time is determined, and P ₁₂Fu
It is determined whether or not the L-cut is being performed. Fuel cut
P when not in₁₃And this injection cylinder (represented by the nth)
RA as the smooth injection amount AvTp of the previous time AvTpoin
Store in M23. Therefore, during fuel cut
When it is not, the asynchronous injection is performed based on the smooth injection amount AvTp.
Interrupt processing is performed (the program is not shown), but Av
Tp itself considers the wall flow, and the amount of fuel flowing into the cylinder
Would be appropriate. On the other hand, if you are in a fuel cut
Ki P₁₄Then, calculate AvTpoin for the previous minute according to the following formula.
It

[0022] AvTpoin = AvTpoin -T _PFC ...... Here, T _PFC is a predetermined subtraction value (constant value). Therefore, AvTpoin-T _PFC (= the current AvTpoin
As shown in FIG. 6,) gradually decreases with the lapse of time due to the repetition of this program from the start of fuel cut, and finally becomes almost zero. This corresponds to the state in which the wall flow amount remaining in the intake pipe 3 decreases from the start of fuel cut. In the calculation of the above equation, AvTp
Even if AvTpoin = 0 immediately instead of seeking oin. However, in this embodiment, when the fuel cut is immediately recovered, the wall flow may still remain. Therefore, it is not immediately set to zero, but T _{PEC is} subtracted each time the routine is executed.

FIG. 7 shows a timing chart during the fuel cut. In FIG. 7, before reaching the fuel cut, the final injection amount Ti is calculated according to the following equation based on AvTp. Ti = (AvTp + Kathos) × Tfbya × (α + αm) + Ts In the formula, Kathos has positive and negative values of the wall flow correction pulse width, and the fuel adhesion speed Vmf (ms) and the correction rate Ghf (%)
Given by the function. α is a λ control correction coefficient for the air-fuel ratio based on the output of the oxygen sensor 12, and αm is a mixture ratio learning control correction coefficient. Ts is an invalid pulse width.

When the throttle valve 8 shifts to the fully closed state and the fuel cut is determined, the smooth injection amount AvTp decreases from before the throttle valve 8 is fully closed and becomes the minimum at the same time as the fuel cut determination. As a result, the air-fuel ratio rapidly increases, and A / F = ∞ when the inside of the exhaust pipe 5 becomes the atmosphere. Also, the torque sharply decreases, and the vehicle travels with the running inertia force during the fuel cut. At this time, in the previous application, the previous AvTp was stored during the fuel cut on the assumption that there is a wall flow.

On the other hand, in this embodiment, AvTp is calculated based on the above equation during the fuel cut, and its value becomes smaller with the lapse of time. It should be noted that FCAVO in FIG. 6 is the minimum limit value of AvTpoin. Then, at the time of recovery, it is first determined according to the above formula whether or not the asynchronous injection accompanying the recovery is performed. In this case AvT
Since the poin gradually becomes smaller as the wall flow decreases, asynchronous injection can be performed without delay, unlike the previous application. Further, for the same reason, the recovery injection amount is calculated in consideration of the wall flow amount. Therefore, as shown by the solid line in FIG. 6, in the present embodiment, the air-fuel ratio quickly shifts to the target value and at the time of recovery. Torque will be immediately restored. Therefore,
Exhaust characteristics and drivability (particularly effective prevention of the breathing phenomenon) can be improved.

AvTpoin may gradually approach 0 depending on the number of revolutions as well as the elapsed time of fuel cut. Further, this change may include data of the cooling water temperature Tw.

[0027]

According to the present invention, the value of the previous smooth injection amount is set to a predetermined small value during the fuel cut, so that the asynchronous injection determination and the injection amount during recovery are appropriate. It is possible to improve exhaust characteristics and drivability.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a fuel supply control device for an internal combustion engine according to the present invention.

FIG. 3 is a flowchart of a subroutine for calculating the smooth injection amount.

FIG. 4 is a timing chart illustrating an operation based on the smooth supply amount.

FIG. 5 is a flowchart showing a main program for calculating the injection amount.

FIG. 6 is a diagram showing the tendency of AvTpoin.

FIG. 7 is a timing chart explaining the operation during the fuel cut.

[Explanation of symbols]

1 Engine 4 Injector (Fuel Injection Means) 7 Air Flow Meter (Intake Amount Detection Means) 14 Operating State Detection Means 20 Control Unit (Smooth Value Calculation Means, Synchronous Injection Calculation Means, Asynchronous Injection Calculation Means, Setting Means)

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[Procedure amendment]

[Submission date] May 7, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Patent application title: Fuel supply control device for internal combustion engine

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine such as an automobile, and more particularly to a fuel supply device for calculating the fuel supply amount based on the intake air amount.

[0002]

2. Description of the Related Art Recently, demands for internal combustion engines such as automobiles have become more sophisticated, and there is a tendency to achieve high levels of conflicting problems such as reduction of harmful exhaust gas, high output, and low fuel consumption. It is in. Further, such a requirement is the same for the wall flow correction, and it is desired to improve the accuracy of the wall flow correction.

In the conventional fuel supply control device of this type, the required load per unit rotation of the engine is obtained from the output of the air flow meter provided on the upstream side of the throttle valve, and the fuel injection amount per unit rotation is calculated from this. .. Further, at the time of transition, it is dealt with by correcting the fuel injection amount (for example, refer to JP-A-59-538). However, in the conventional device, an appropriate injection amount calculation considering the capacity of the intake pipe between the mounting position of the air flow meter and the mounting position of the injection valve (injector), that is, the intake volume is not performed, and the transient time However, there was a problem that the injection performance of was delayed from the required characteristics of the engine and the driving performance was poor.

In order to solve such a problem, improvement is aimed at.
For example, see Japanese Patent Application Laid-Open No. 60-162066.
The ones listed here (also referred to simply as prior applications in the following explanation)
It With this device, the actual intake air flowing into the cylinder
Change with a first-order lag response to changes in engine speed.
This causes changes in the set air-fuel ratio and a delay in the generated torque response.
The output of the air flow meter is smoothed with a first-order lag in order to accurately obtain the amount of air flowing through the injection valve , and the fuel injection amount is based on the smoothed air amount.
Fuel injection by calculating (fuel injection amount equivalent to cylinder air amount)
It is in control. Note that fuel injection equivalent to cylinder air amount
The injection amount is predetermined as the pulse width AvTp equivalent to the cylinder air amount.
It is calculated by the calculation method.

[0005]

The object of the invention is to, however, this
In such a device, the output of the air flow meter is delayed for the first time.
What is smoothed by this to perform transient correction of air amount
Of the so-called wall flow
Therefore, for example, in the case of a vehicle that performs fuel cut, the air-fuel ratio immediately after the fuel cut is released (during recovery) is the target value (for example, the theoretical air-fuel ratio in which the excess air ratio λ is λ = 1).
It takes a long time to return to the ratio , and exhaust emission characteristics and drivability may be deteriorated (a breathing phenomenon may occur).

Therefore, the present invention is directed to such a fuel cell.
The purpose is to improve the exhaust characteristics and drivability by making the asynchronous injection determination and the injection amount at the time of lean appropriate so as to avoid the adverse effect of the engine.

[0007]

In order to achieve the above object, the present invention is directed to an intake pipe as shown in the basic conceptual diagram of FIG.
Synchronized with the fuel injection valve provided and the combustion cycle of each cylinder
Fuel synchronous injection for each cylinder at the timing
And under certain conditions, the timing differs from the above timing.
The fuel for causing the asynchronous fuel injection of the iming is executed.
An internal combustion engine including a fuel injection valve control device for controlling an injection valve
In the fuel supply control device of the engine, the operating state detecting means a
And the cylinder is sucked based on the output of the operating state detection means a.
Fuel injection equivalent to the cylinder air amount corresponding to the input air amount
Cylinder air amount equivalent fuel injection to calculate amount (AvTp)
The amount calculation means b and the previous fuel injection timing for each cylinder
Cylinder air amount equivalent fuel injection amount (AvTpio
n) is stored as a stored value for each cylinder,
For each cylinder, the fuel injection amount (Av
Tp) and cylinder empty at the last fuel injection timing
Difference value (AvT) from the fuel injection amount (AvTpoin)
Cylinder air amount equivalent fuel for calculating p-AvTpoin)
The output of the injection amount difference value calculation means d and the operating state detection means a
Based on the fuel cut start and end
Fuel cut start / end decision means e and fuel cut
To gradually decrease the memory value (AvTpoin)
The stored value for each cylinder is synchronized with the combustion cycle of each cylinder.
A stored value updating means f for updating (AvTpoin);
While setting the final fuel injection amount to zero during L-cut,
When the fuel cut is not in progress, the difference value (AvTp-
The fuel synchronous injection amount is played based on the size of AvTpoin).
The synchronous injection amount calculation means g for calculating and the difference value (AvTp-
If AvTpoin) is larger than a predetermined value, the difference value (A
vTp-AvTpoin) based on fuel asynchronous
And an asynchronous injection amount calculation means h for calculating the injection amount .

[0008]

In the present invention, the final fuel injection is performed during the fuel cut.
The target is set to zero, but the fuel is not cut
In this case, the fuel injection amount corresponding to the current cylinder air amount for each cylinder
(AvTp) and the series at the previous fuel injection timing
Difference value from the fuel injection amount (AvTpoin)
(AvTp-AvTpoin) based on the size of the fuel
When the initial injection amount is calculated and the difference value is larger than a predetermined value,
The fuel asynchronous injection amount is calculated based on the magnitude.
That is, during recovery, the difference value (AvTp-AvT
Poin) is compared with the specified value (small recovery standard value)
By doing so, the asynchronous injection is determined and the recovery amount is determined.
It Therefore, changes in the cylinder intake air amount and
Responding to fuel transportation delay (effect of wall flow) at an appropriate time
Proper amount of asynchronous and synchronous injection without delay
It will be possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 2 to 7 are views showing an embodiment of a fuel supply control device for an internal combustion engine according to the present invention. First, the configuration will be described. Figure 2
FIG. 3 is a diagram showing an overall configuration of the present device.

In FIG. 2, reference numeral 1 denotes an engine, intake air passes from an air cleaner 2 to an intake pipe 3, and fuel is injected from an injector (fuel injection means) 4 based on an injection signal Si. The exhaust gas burned in the cylinder is exhaust pipe 5.
Is introduced into the catalytic converter 6 through the catalytic converter 6 and the harmful components (CO, HC, NOx) in the exhaust gas are cleaned by the three-way catalyst and discharged.

The flow rate Qa of the intake air is detected by a hot wire type air flow meter 7, and a throttle valve 8 in the intake pipe 3 is detected.
Controlled by. The type of the air flow meter 7 may be a hot film type, and any type that measures the flow rate of intake air may be used. Therefore, a flap type sensor or a negative pressure sensor may be used. Throttle 8
The opening degree TVO is detected by the throttle opening degree sensor 9, and the rotation speed N of the engine 1 is detected by the crank angle sensor 10. In addition, the temperature T of the cooling water flowing through the water jacket
w is detected by the water temperature sensor 11, and the oxygen concentration in the exhaust gas is detected by the oxygen sensor 12. As the oxygen sensor 12, a sensor having a characteristic that the output Vs thereof suddenly changes depending on the stoichiometric air-fuel ratio is used. Further, the idle state of the engine 1 is detected by the idle switch 13.

The air flow meter 7, throttle valve opening sensor 9, crank angle sensor 10, water temperature sensor 11, oxygen sensor 12
Further, the idle switch 13 constitutes an operating state detecting means 14, and the output of the operating state detecting means 14 is input to the control unit 20. The control unit 20 is a book
Cylinder air amount equivalent fuel injection amount calculator in the invention of application
Stage, storage means, cylinder air amount equivalent fuel injection amount difference value calculation
Means, fuel cut start / end determination means, stored value update hands
Stage, synchronous injection amount calculation means and asynchronous injection calculation means
It has all the functions of CPU21, ROM22, RAM23
And I / O port 24. CPU21
I according to the program written in ROM22
While fetching necessary external data from the / O port 24 and exchanging data with the RAM 23
Cylinder air corresponding to the fuel injection amount equivalent to the cylinder air amount
Amount equivalent pulse width AvTp and other processing values required for injection control
The data (to be described later) is processed, and the processed data is output to the I / O port 24 as necessary. Signals from the sensor groups 7 and 14 are input to the I / O port 24, and I / O
The injection signal Si is output from the port 24. The ROM 22 stores the calculation program in the CPU 21, and RA
M23 stores the data used for the calculation in the form of a map or the like.

Pulse width AvTp equivalent to the cylinder air amount
Smooths the output of the air flow meter 7 with a first-order delay and absorbs it.
It is obtained by performing transient correction of the amount of incoming air.
It can contribute to stabilization of the ratio. Also, the CPU 21
This cylinder air amount equivalent pulse width AvTp calculation result
Based on this, the asynchronous injection is determined by the following equation. AvTp-AvTpoin ≥LASNI ... where LASNI is a cylinder-specific asynchronous injection determination value
(Hereinafter, simply referred to as a threshold), AvTpoin is
The last injection timing with the nth injection valve (injector)
Cylinder air amount equivalent pulse width AvT used for injection
It is the value of p. AvTp-AvTpoin is
Later, it is also simply referred to as a difference value.

Next, the operation will be described. The main program of this embodiment is shown in FIG. 5, but for convenience of explanation,
First, the subroutine for obtaining the pulse width (cylinder air amount equivalent fuel injection amount) AvTp corresponding to the cylinder air amount shown in FIG. 3 will be described. Further, the description will be given based on the control waveform of FIG.

As shown in FIG. 3, in this subroutine, first, in step P ₁ , the output of the air flow meter 7 is read to obtain the intake air amount Qa. This is due to table lookup, for example. Next, in step P ₂ , the basic pulse width Tp ₀ before smoothing is calculated according to the following equation. Tp ₀ = (Qa / N) × K where N is the engine speed, K is the proportional constant, and Qa is the intake air.
It is a generous amount.

Next, in step P ₃ , the basic pulse width Tp ₀ before smoothing is weighted and averaged to calculate the basic pulse width Tp, and then in step P ₄ , the flat corrected basic pulse width TrTp is obtained according to the following equation. As a result, the pulsation based on the output of the air flow meter 7 is smoothed. TrTp = Tp × Kflat In the equation, Kflat is a flat A / F (air-fuel ratio) correction coefficient, and is calculated with interpolation calculation from a map allocated by the rotation speed N and an α-N flow rate Qho described later. Note that the α-N flow rate is an air flow rate obtained from the throttle valve opening TVO and the engine speed N, and is already known.

Next, in step P ₅ , the flat correction basic pulse width TrTp is compared with a predetermined maximum limit value Tp _max . If TrTp> Tp _max , the flat correction basic pulse width TrTp is changed to the maximum limit value Tp in the next step P _6.
Limit to _max and proceed to step P ₇ , TrTp ≦ Tp
_{If max} , jump to step P ₆ and skip to step P _7.
Proceed to. In step P ₇ obtains a delay corrected pulse width THSTP as alpha-N precorrection pulse width. This delay correction pulse width THSTP is for correcting the injection amount with good response by anticipating the change in the opening of the throttle valve 8.
The value TTHSTP is looked up from the table with interpolation calculation based on ho, and is calculated as the amount of change every 10 ms. However,
If the amount of change is less than or equal to the correction determination level, THSTP
= 0, and when the amount of change is negative (deceleration), the amount of change is multiplied by a predetermined deceleration correction rate.

[0018] Subsequently, in accordance with the following formula in step P ₈ sheet
Cylinder air as pulse width AvTp equivalent to Linda air amount
Calculate the fuel injection amount corresponding to the amount . AvTp = TrTp * FLOAD / AvTp- ₁ * (1-FLOAD) + THSTP ... In the formula, FLOAD is a weighted average coefficient and FL
It is given by an arithmetic expression of OAD = TFLOAD + K2D (deceleration only). TFLOAD is a function of only the intake volume, and is obtained by a map from the flow passage area AA of the throttle valve 8 and [displacement amount × rotation speed] NVM. Therefore,
The first and second terms of the equation are values obtained by performing a weighted average using FLOAD on the flat corrected basic pulse width TrTp calculated based on the value obtained by pulsatingly correcting the output of the air flow meter 7, in other words, calculating the first-order lag of TrTp. It corresponds to the part calculated by (by software). Further, the third term of the equation is a portion for pre-correction by the throttle valve opening TVO, and this portion is not disclosed in the prior application and is disclosed for the first time in this embodiment.

The delay correction pulse width TH of the third term
The effect of adding STP is shown in FIG. In FIG. 4, when acceleration is performed at a certain timing, the basic pulse widths Tp ₀ and Tp change with a slight delay with respect to the change in the throttle valve opening.
The waveform obtained by modifying p ₀ and Tp changes as shown in FIG. 4 as the flat modified basic pulse width TrTp. On the other hand, the α-N flow rate Qho changes stepwise according to the opening degree of the throttle valve 8, and the delay correction pulse width THS is changed by this opening change amount.
TP is calculated. Further, the cylinder air amount equivalent pulse width AvTp is given with a first-order delay of the flat correction basic pulse width TrTp.

In the case of the conventional phase control without the delay correction pulse width THSTP, the change is shown by the alternate long and short dash line in the figure, and the response is lacking. At this time, the suction negative pressure is indicated by a broken line and is substantially equal to the air flow rate of the injection valve portion (injector 4 portion), but this cannot follow the change in the opening degree of the throttle valve 8 without delay. Further, the intake volume also affects the amount of fuel adhering to the wall surface of the intake pipe 3. Therefore, Siri
The pulse width AvTp corresponding to the air flow rate is required to stabilize the air-fuel ratio.
Although it contributes, the determination of recovery is based on the above formula.
Just doing it will make the asynchronous injection amount during recovery inappropriate.
May be. Also, the injection at the previous injection timing
Cylinder air amount equivalent pulse width AvTp value (A
vTpoin) is just before the start of fuel cut
It is the fuel injection amount equivalent to the cylinder air amount and is taken by the wall flow
It also includes fuel. On the other hand, the wall during the fuel cut
The flow is gradually removed (sucked into the cylinder),
At the time of recovery, it is possible that there is almost no wall flow.
In the earlier application, a fue called AvTPoin despite recovery
Since the parameters that are unrelated to Lecat are used, the injection amount during recovery is actually insufficient and the air-fuel ratio does not reach the target value.

On the other hand, in the cylinder air amount equivalent pulse width AvTp of this embodiment, as shown by the solid line in the figure, the correction term for the delay correction pulse width THSTP is the advance correction of the α-N flow rate (the advance correction of 10 ms). Therefore, the response is extremely good and it matches the actual change in the air flow rate. An example in the highlands is also shown. FIG. 5 is a flowchart showing a program for calculating the recovery reference value. This program is executed at each injection timing of each cylinder.
It is executed in the interrupt. First, in step P ₁₁ , the injection cylinder of this time is determined, and in step P ₁₂ , it is determined whether or not fuel cut is in progress. Cylinder air amount equivalent pulse width AvTp preceding fuel injection Timing of this injection cylinder in Step P ₁₃ (represented by n-th) when not in fuel cut
Corresponding to fuel injection amount equivalent to cylinder air amount in engine
It is stored in the RAM 23 as a stored value AvTpoin.

Therefore, when the fuel cut is not in progress, the asynchronous injection interrupt processing is performed based on the cylinder air amount equivalent pulse width AvTp (the program is not shown), but as described above, it corresponds to the cylinder air amount shown in the equation. The pulse width AvTp itself considers the wall flow, and the cylinder inflow fuel amount becomes appropriate. On the other hand, if the fuel cut is in progress, proceed to Step P ₁₄ and perform the previous fuel injection.
Description of pulse width equivalent to cylinder air amount at injection timing
The memorized value AvTpoin is gradually reduced by the following formula.
To update .

[0023] AvTpoin = AvTpoin -T _PFC ...... Here, T _PFC is a predetermined subtraction value (constant value). Engine speed is high immediately after the fuel cut start, since come gradually decreases with time, the calculation of the equation to be executed in rotation synchronization, AvTpoin -T _PFC (= the current AvTpoin) is 6 As shown in the figure, with the passage of time from the start of the fuel cut, the program decreases rapidly at first, but the rate of decrease gradually decreases.
Eventually it will be almost zero. This corresponds to the state in which the wall flow amount remaining in the intake pipe 3 decreases from the start of fuel cut.

FIG. 7 shows a timing chart during the fuel cut. In the figure, before reaching the fuel cut, the final injection amount Ti is calculated according to the following equation based on the cylinder air amount equivalent pulse width AvTp. Ti = (AvTp + Kathos) × Tfbya × (α + αm) + Ts In the formula, Kathos has positive and negative values of the wall flow correction pulse width, and the fuel adhesion speed Vmf (ms) and the correction rate Ghf (%)
Given by the function. Tfbya is the target air-fuel ratio. α
Is a λ control correction coefficient for the air-fuel ratio based on the output of the oxygen sensor 12, and αm is a mixture ratio learning control correction coefficient. Ts is an invalid pulse width.

In the figure, when the throttle valve 8 shifts to the fully closed state, the cylinder air amount equivalent pulse width AvTp decreases from the fully closed state of the throttle valve 8 and becomes the minimum. And of the throttle valve 8
It is judged that the fuel cut has started after a lapse of a predetermined time from full closure.
Fuel supply for both synchronous and asynchronous injection is prohibited
To be done. As a result, the air-fuel ratio rapidly increases, and when the exhaust pipe 5 becomes the atmosphere, the air-fuel ratio A / F = ∞. Also,
The torque also suddenly decreases, and the vehicle runs with the inertial force during fuel cut.

During the fuel cut, the stored value AvTpoin is calculated by the above equation, the value becomes smaller with the lapse of time, and finally reaches the minimum limit value.
That is, the final fuel injection amount during fuel cut is zero.
Set to (zero). Driver depresses the accelerator pedal
As soon as the throttle valve 8 is no longer fully closed,
End is determined, both synchronous and asynchronous injection
The prohibition of fuel supply is lifted.

Then, at the time of recovery, it is first determined whether or not the asynchronous injection accompanying the recovery is performed according to the above formula. In this case, the stored value AvTpoin is the actual wall flow.
It gradually becomes smaller, reflecting the decrease in minutes,
Pulse width AvTp and stored value AvTpoin
Difference becomes large, and asynchronous injection is performed promptly during recovery.
It is decided that the asynchronous injection with excellent responsiveness will be delayed.
You can do it. For the same reason, the cylinder
Air amount equivalent pulse width AvTp and the stored value AvTpoin
Difference becomes larger and the difference value (AvTp-AvTpoin
) Will the recovery injection amount be calculated based on
As shown in FIG. 7, in this embodiment, the air-fuel ratio quickly shifts to the target value and the torque during recovery is immediately recovered.

Specifically, in (a) in the figure, the difference value (Av
Tp-AvTpoin) is larger than a predetermined threshold LASNI.
Since it is above the limit, it is enough depending on the magnitude of this difference value.
Asynchronous injection is performed. In addition, in (b) in the figure,
Since the injection timing has come,
New with AvTpoin stored in Ming
The difference value (AvTp-AvTpoin) is calculated, and the difference is calculated.
The same synchronous injection is executed. After that, sucking into the cylinder
Inlet air volume increases, cylinder air volume equivalent pulse width AvT
As p becomes larger, the difference value (AvTp-AvTpoin) becomes greater.
Synchronous injection is executed when the threshold value LASNI is exceeded.
Be done. When the rate of increase of the intake air amount becomes gentle,
Before the difference value (AvTp-AvTpoin) exceeds the threshold value
Synchronous injection timing comes, and AvTp
oin is newly changed. After that, synchronous injection,
Only synchronous injection will be performed.

As described above, in this embodiment , the fuel is
The final fuel injection amount is set to zero during cutting, while
When the fuel cut is not in progress,
This time for each cylinder, which is calculated as the width AvTp
D Air amount equivalent fuel injection amount and stored value AvTpoin
Equivalent to the cylinder air amount at the previous fuel injection timing
Large difference (AvTp-AvTpoin) from the fuel injection amount
The fuel synchronous injection amount is calculated based on the
When it is larger than the fixed value, fuel asynchronous based on its size
The injection amount is calculated. Therefore, the cylinder intake air amount
Change and fuel transfer delay after injection (effect of wall flow)
The right amount of asynchronous injection at the right time and
It becomes possible to perform synchronous injection, and to improve the air-fuel ratio during acceleration.
It can be controlled as desired. As a result, for example, three
Deviation from the three-way point of the original catalyst (excess air ratio λ = 1)
The emission emission is suppressed and the exhaust gas purification performance is improved.
And improve driving performance (response
Improvement and prevention of breathing).

Further , in this embodiment, the injection amount for each cylinder is
Cylinder air amount equivalent pulse for the previous injection of the cylinder
For each cylinder based on the amount of increase in memory width (memorized value AvTpoin)
Since it is designed to
Although the combustion cycle time in
For changes in driving conditions during the period that exactly matches this period
A corresponding amount of fuel can be supplied to the injector 4.
The air-fuel ratio A / F can be set optimally for each cylinder.
It

Further, in this embodiment, during fuel cut
The stored value AvTp in synchronization with the fuel injection timing.
I updated the oin so that I could decrease it
The operating conditions during the set-up period, such as rotation speed and length of time.
Instead, as shown in Figure 7, an appropriate amount at an appropriate time (early)
Asynchronous injection or synchronous injection (by increasing the amount) of
And improve emissions and driveability during recovery
You can

The reduction rate of the stored value AvTpoin
Is changed by the data of the cooling water temperature Tw
Good.

[0033]

According to the present invention, the cylinder intake air amount
In response to changes and fuel transport delay after injection (effect of wall flow)
The right amount of asynchronous injection at the right time and
It becomes possible to perform synchronous injection, and to improve the air-fuel ratio during acceleration.
Controllable as desired, improving exhaust gas purification performance
And it is possible to prevent breathing. Also, for each cylinder
The injection amount of the cylinder air for the previous injection of the cylinder concerned
Based on the amount of increase in the fuel injection amount
Operation during the combustion cycle period for each cylinder.
Supply the fuel injection valve with the amount of fuel corresponding to the change in state
The air-fuel ratio can be set optimally for each cylinder.
Wear. In addition, fuel injection timing during fuel cut
The stored value of the previous injection quantity is updated and reduced in synchronization with
Therefore, the operating condition during the fuel cut period is
Regardless of the time, the asynchronous injection and synchronous injection of the right amount at the right time
The exhaust emission and luck during recovery
It is possible to improve the convertibility.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a fuel supply control device for an internal combustion engine according to the present invention.

FIG. 3 is a flowchart of a subroutine for calculating a pulse width corresponding to the cylinder air amount.

FIG. 4 is a timing chart illustrating an operation based on a smooth supply amount.

FIG. 5 is a flowchart showing a main program for calculating the injection amount.

FIG. 6 is a diagram showing the tendency of the stored value AvTpoin.

FIG. 7 is a timing chart explaining the operation during the fuel cut.

[Explanation of reference numerals] 1 engine 4 injector (fuel injection means) 7 air flow meter (intake air amount detection means) 14 operating state detection means 20 control unit ( cylinder air amount equivalent fuel)
Injection amount calculation means, storage means, fuel injection equivalent to cylinder air amount
Radiation difference value calculation means, fuel cut start / end determination means,
Memorized value update means, synchronous injection amount calculation means, and asynchronous injection
(Calculation means)

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (1)

[Claims] 1. A) intake air amount detecting means for detecting an intake air amount of an engine; b) operating state detecting means for detecting an operating state of an engine; and c) synchronous injection timing based on an output of the intake air amount detecting means. The fuel injection is commanded by and the fuel injection is shifted to the fuel cut, the synchronous injection calculation means for stopping the fuel injection command, and d) The asynchronous injection based on the set value of the supply amount during the fuel cut when the fuel cut is released. And the asynchronous injection calculation means for determining the asynchronous injection amount, and e) when the engine shifts to the fuel cut, the set value of the supply amount is set to the residual amount of the wall flow from the start of the fuel cut during the fuel cut period. Setting means for setting a predetermined correlated value, and f) Fuel is injected into the engine based on the outputs of the synchronous injection calculating means and the asynchronous injection calculating means. The fuel supply control apparatus for an internal combustion engine characterized by comprising a fuel injection means.