JPH0821277A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To keep continuity of control and to correct fuel to a proper value right after starting. CONSTITUTION:An air-fuel ratio device for an internal combustion engine is formed in such a manner that based on an operation condition, an adhesion and floating fuel amount, and a balance amount, the fluctuation speed of the adhesion and floating fuel amount is determined and based on the fluctuation speed, a fuel injection amount through a fuel injection valve is corrected and controlled. The air-fuel ratio device comprises a control means 8 for an injection amount for starting to compute and control a starting fuel injection amount from a fuel injection value based on at least an engine temperature and the number of revolutions of an engine during the starting of an engine; a computing means 9 for a balance amount during starting to compute a balance amount of adhesion and floating fuel of an intake system during staring based on the injection amount and an operation condition; a computing means 10 for an adhesion and floating amount during starting to compute an adhesion and floating amount of an intake system during starting based on a balancing amount and an engine temperature; and a setting means for an initial value after starting to set a final computing value of an adhesion and floating amount during starting as an initial value of the adhesion and floating fuel amount of the fluctuation speed after starting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine.

[0002]

2. Description of the Related Art Electronically controlled fuel injection type engines are widely used because of their high fuel metering accuracy, and their fuel injection control calculates the basic injection amount from the engine load and engine speed.
This is corrected according to the engine temperature, the actual air-fuel ratio and other operating variables to determine the actual injection amount, and an injection pulse signal is output to the fuel injection valve based on this injection amount.

By the way, in such control, the amount of fuel (hereinafter, collectively referred to as “adhered” or “floating fuel”) that adheres to or floats on the inner wall surface of the intake pipe or the intake port between the fuel injection valve and the cylinder is reached. The quantity occurs as a fuel delay during the transition, which affects the control accuracy of the air-fuel ratio.

Therefore, based on the adhering amount of the intake system, the equilibrium amount of the floating fuel, and the adhering amount that changes with a first-order lag with respect to the equilibrium amount, the calculated amount of the floating fuel amount, the adhering or floating state (adhesion, floating fuel The applicant of the present invention has proposed a method in which the fuel injection amount is corrected by determining the transient correction amount based on the determination of the increase / decrease speed of the fuel injection amount (Japanese Patent Application Laid-Open No. 62-101855). , 63-38629).

[0005]

However, in such control, the adhesion of the intake system and the floating fuel amount are set to the same amount as the equilibrium amount at the time of starting the engine, or the adhesion and the floating fuel amount are increased during the starting. Assuming that there is no increase or decrease in the amount of fuel, the amount of adhered and floating fuel is calculated at the start of starting, and after the start, the amount of adhered and floating fuel is corrected based on the increase / decrease speed of the amount of floating fuel. It is difficult to keep the air-fuel ratio optimum.

That is, at the time of starting, the fuel injection amount is set to the increasing side depending on the engine temperature, the cranking speed, the time after starting, and the equilibrium amount MFH becomes a large value, but the intake system adheres and the floating fuel amount When MF is made equal to the equilibrium amount MFH, the increase / decrease speed VMF of the amount of adhered and floating fuel becomes a negative value (decreasing side) immediately after the start when the equilibrium amount MFH decreases as shown in FIG. The fuel correction amount based on the above becomes a reduction correction. As a result, the air-fuel ratio becomes temporarily lean immediately after starting.

Also, the amount of floating fuel adhered and M at the start of start-up
If F is still calculated, it is inevitable that the air-fuel ratio will be temporarily leaned immediately after the start because of the adhesion and the floating fuel amount that are deviated immediately after the start.

If the fuel injection amount is excessively set to the rich side as a countermeasure against these problems, HC will increase at the time of cold start.

The object of the present invention is to solve such a problem.

[0010]

The first invention is, as shown in FIG. 1, an operating condition detecting means 1 for detecting at least operating conditions of engine speed, engine load and engine temperature, and fuel based on the operating conditions. Injection amount calculation means 2 for calculating the basic injection amount of, and balance amount calculation means 3 for calculating the adhesion amount of the intake system and the equilibrium amount of the floating fuel based on the operating condition, the operation condition and the adhesion of the intake system, the floating fuel Adhesion based on quantity and equilibrium quantity,
Increasing / decreasing speed calculating means 4 for calculating the increasing / decreasing speed of the floating fuel amount
And an injection amount control means 5 for controlling the fuel injection amount from the fuel injection valve based on the increase / decrease speed and the basic injection amount, and an adhesion / floating amount calculation for updating the adhesion / floating fuel amount based on the increase / decrease speed. In an air-fuel ratio device for an internal combustion engine, which comprises means (6), starting determination means (7) for determining whether or not the engine is starting, and starting from a fuel injection valve based on at least the engine temperature and the engine speed at the time of starting. A starting injection amount control means 8 for calculating and controlling the fuel injection amount, and a starting equilibrium amount calculating means 9 for calculating the adhering amount of the intake system and the floating fuel equilibrium amount at the time of starting based on the injection amount and the operating conditions. And the adhesion of the intake system at the time of starting based on the equilibrium amount and the engine temperature, the adhesion at the time of starting for calculating the amount of floating fuel, the floating amount calculation means 10, and the adhesion at the time of starting,
After the start, the increase / decrease speed calculation means 4 is attached to the final calculated value of the floating fuel amount, and the post-start initial value setting means 11 is set as the initial value of the floating fuel amount.

According to a second aspect of the present invention, the starting equilibrium amount calculating means 9 calculates the starting equilibrium amount by multiplying the fuel injection amount by the fuel adhesion and the floating rate based on the engine temperature. Has become.

A third aspect of the present invention is the adhesion at the time of starting of the first aspect of the invention,
The floating amount calculation means 10 determines the equilibrium amount at the time of starting and the previous adhesion,
The difference between the amount of floating fuel and the amount of floating fuel is determined by multiplying the adhesion and floating fuel response coefficient determined by the engine temperature.

[0013]

According to the first aspect of the present invention, the intake system adheres from the start of the engine, the amount of floating fuel equilibrium and the amount of floating fuel are calculated based on the equilibrium amount and the engine temperature. Since the final calculated value of the fuel amount is set as the initial value of the adhered and floating fuel amount after the start, based on this initial value of the adhered and floating fuel amount and the equilibrium amount based on the operating conditions at that time, immediately after the start Can be accurately obtained, and the fuel injection amount can be appropriately corrected based on the increase / decrease speed.

In the second aspect of the present invention, the fuel injection amount at the time of starting is multiplied by the adherence and floating rate of the fuel based on the engine temperature,
The equilibrium amount at the time of starting can be accurately obtained.

In the third aspect of the invention, the amount of equilibrium at the time of starting and the previous amount of adhesion, the amount of floating fuel determined by the temperature of the engine,
By multiplying the response factor of floating fuel, adhesion at start,
The amount of floating fuel can be accurately determined.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, 20 is an engine body, 21
Is an intake passage, 22 is a throttle valve, 23 is a fuel injection valve installed in the intake port 24, 25 is a spark plug, 26 is an exhaust passage, and 27 is a catalytic converter.

Reference numeral 30 is an air flow sensor for detecting the intake air amount (load) of the engine, 31 is a throttle valve opening sensor for detecting the opening of the throttle valve 22, 32 is a water temperature sensor for detecting the engine temperature (cooling water temperature). , 33, 34 are air-fuel ratio sensors that detect the air-fuel ratio from the oxygen concentration in the exhaust gas.

These sensor signals are input to the control unit 35 together with the signals from the crank angle sensor for detecting the engine speed, the vehicle speed sensor, and the engine start switch.

The control unit 35 calculates the fuel injection pulse width of the fuel injection valve 23 based on each sensor signal and the signal from the engine start switch to control the fuel injection amount.

An idle speed control valve 37 is installed in the bypass passage 36 of the throttle valve 22.

Next, the fuel injection amount control will be described with reference to the flow charts of FIGS. FIG. 3 shows a calculation flow of the fuel injection pulse width at the time of starting and after the start, and FIG. 4 shows a calculation flow of the adhesion of the intake system at the time of starting, the floating fuel amount, the adhesion after the starting, the increase / decrease speed of the floating fuel amount, etc. FIG. 5 shows a calculation flow of the target air-fuel ratio after starting. Each flow is executed in a predetermined cycle.

First, at the time of starting, when it is determined that the engine start switch is ON in steps 1 and 21, as shown in FIGS. 3 and 4, the process proceeds to steps 9 and 27, respectively.

In step 9 of FIG. 3, the starting water temperature basic injection pulse width TCST is calculated based on the water temperature TWST. This starting water temperature basic injection pulse width TCST is given in a table as shown in FIG. 6, and is set to a larger value as the water temperature TWST is lower.

In step 10, the cranking rotation correction value TCS at starting is calculated according to the engine cranking rotation speed.
Calculate N. This starting cranking rotation correction value TC
The SN is given in a table as shown in FIG. 7, and is set to 1 on the side where the rotation speed is low, and to a small value as the rotation speed increases.

In step 11, the post-starting time correction value TKCS is calculated from the post-starting time (elapsed time after the engine start switch is turned on) TAS. This post-startup time correction value TKCS is given in the table as shown in FIG.
Decrease the value after the specified start time.

In step 12, the injection pulse width TIST at the time of starting is calculated from the following equation (1) from the water temperature basic injection pulse width at the starting TCTC, the cranking rotation correction value at the starting TCSN, and the post-start time correction value TKCS. To do.

TIST = TCST × TCSN × TKCS (1) Then, the pulse signal of the injection pulse width TIST at the time of starting is output to the fuel injection valve 23 in step 13.

The injection pulse width TIST at the start is
The basic injection pulse width Tp is calculated from the engine speed and the engine load, and the correction is performed by adding a predetermined mixture ratio allocation coefficient, water temperature increase correction coefficient, starting increase coefficient, etc.
You may ask.

On the other hand, in step 27 of FIG. 4, the water temperature TW
Equilibrium adhesion at start-up based on ST, buoyancy rate KMFHS
From the injection pulse width TIST at the time of starting shown in FIG. 3 and the equilibrium adhesion at the time of starting, and the floating rate KMFHST, the intake system adhesion at the time of starting and the equilibrium amount MFHST of the floating fuel are calculated by the following equation (2). To do.

MFHST = TIST × KMFHST (2) Here, the equilibrium adhesion at start-up and the floating rate KMFHST are shown in FIG.
It is given by a table such as, and the larger the water temperature TWST, the larger the value.

That is, the lower the temperature of the fuel adhering portion (which is approximately equal to the water temperature TWST) at the time of starting, the greater the amount of fuel that can be adhering. For example, when the water temperature TWST = 0 ° C., the equilibrium amount MFHST is equal to that at the time of starting. About 11 of fuel injection amount
It is twice. After the engine is started, the equilibrium amount is reduced by reducing the fuel amount.

In step 28, the adhesion at the start, which is determined by the water temperature TWST, the adhesion at the start regarding the responsiveness (increase / decrease rate) of the floating fuel, and the floating fuel response coefficient KMFST are obtained. The adhesion and floating fuel response coefficient KMFST at the time of starting is
It is given in the table as shown in FIG. 10, and the higher the water temperature TWST, the larger the value.

In step 29, these equilibrium quantities MFH are calculated.
ST, adhesion at startup, floating fuel response coefficient KMFST,
The following equation (3) calculates the adhesion of the intake system and the floating fuel amount MF at the time of starting.

MF = MF (-1) + [MFHST-MF (-1)] × KMFST (3) Note that MF (-1) is the previously calculated MF and is 0 at the start of starting.

In this way, the fuel is injected at the time of starting, the adhesion of the intake system at the time of starting, the floating fuel amount MF, the equilibrium amount MFHST.
When the start is finished, the adhesion and floating fuel amount MF calculated immediately before the start is set as the initial value of the adhesion and floating fuel amount after the start.

Next, after starting, the routine proceeds to steps 2 and 22 of FIGS.

In step 22 of FIG. 4, the adhering amount of the intake system and the equilibrium amount MFH of the floating fuel after the start are calculated based on the engine load and the water temperature TW after the start. This equilibrium amount MFH is
Given the map as shown in FIG. 11, the value becomes small when the engine load is small (basic fuel injection amount is small) and the water temperature TW is high, the engine load is large (basic fuel injection amount is large), and the water temperature TW is The lower the value, the larger the value.

In step 23, the engine load and the water temperature T
Adhesion after start-up determined by W and adhesion regarding floating fuel response (rate of increase / decrease), and floating fuel response coefficient KMF are obtained. The adhesion / floating fuel response coefficient KMF is given in the table shown in FIG. 12, and the engine load is large and the water temperature T
The value becomes small when W is low, and becomes large as the engine load is small and the water temperature TW is high. The influence of the water temperature TW is strong as shown in FIG.

In step 24, these equilibrium quantities MF are
From the H, adhered and suspended fuel response coefficient KMF, the adhered and suspended fuel amount MF of the intake system after the start is calculated by the following equation (4).

MF = MF (−1) + [MFH−MF (−1)] × KMF (4) Note that MF (−1) is the previously calculated MF, and in this case,
As the initial value, the amount of adhered and floating fuel calculated immediately before the start of the above-mentioned start is used.

In step 25, the increasing / decreasing speed VMF of the amount of adhered and floating fuel after the start is calculated from the equation (4). That is,
Increasing / decreasing amount of adhered and suspended fuel amount MF [MFH-MF (-1)] ×
KMF = increasing / decreasing speed VMF.

The increasing / decreasing speed VMF is the amount of fuel adhering to the engine when it is positive, and the amount of fuel taken as floating amount, and the amount of fuel that is sucked into the engine from the amount of adhering and floating when it is negative. Fuel injection transient correction amount KA
Calculate THOS (= increase / decrease speed VMF).

On the other hand, in step 2 of FIG. 3, the basic injection pulse width T after starting is calculated from the engine speed and the intake air amount.
p is calculated, and in step 3, the target air-fuel ratio TFBYA is calculated from each engine condition.

In step 4, the air-fuel ratio correction coefficient α is calculated according to the air-fuel ratio feedback signal from the air-fuel ratio sensor 33, and in step 5, the air-fuel ratio correction learning value αm is calculated based on the air-fuel ratio correction coefficient α. To do. The air-fuel ratio correction learning value αm is obtained when the correction width by the air-fuel ratio correction coefficient α is large. When not in the air-fuel ratio control range, α, αm
To 1.

In step 6, the transient correction amount KATHOS obtained in step 26 of FIG. 4 is read, and in step 7, the voltage correction Ts for correcting the valve opening delay of the fuel injection valve 23 due to the voltage drop is calculated.

In step 8, the basic injection pulse width Tp, the target air-fuel ratio TFBYA, the air-fuel ratio correction coefficient α, the air-fuel ratio correction learning value αm, the transient correction amount KATHOS, and the voltage correction Ts are used to start by the following equation (5). The subsequent injection pulse width Ti is calculated.

Ti = (Tp + KATHOS) × TFBYA × (α + αm) + Ts (5) Then, the pulse signal of the injection pulse width Ti is output to the fuel injection valve 23 in step 13.

As described above, the adhesion of the intake system after the start, the equilibrium amount MFH of the floating fuel, the adhesion just before the start, the adhesion after the starting with the floating fuel amount to the initial value, the floating fuel amount MF, and the starting fuel amount based on these The increase / decrease speed VMF of the amount of adhered and floating fuel, that is, the transient correction amount KATHOS is calculated, and fuel injection is performed.

Next, the operation from the start to immediately after the start will be described. As shown in FIG. 13, the engine start switch is turned on.
Then, the fuel injection is started and the intake system is attached,
Equilibrium amount MFH (MFHST) of floating fuel, adhesion, and calculation of floating fuel amount MF are performed.

In this starting process, the equilibrium amount MFH is slightly reduced, and the adhered and suspended fuel amount MF is gradually increased from zero.
Adhesion and floating fuel amount increase / decrease speed VMF = [MFHST-M
F (-1)] × KMFST gradually decreases.

When the start is completed, the balance amount MFH after start-up, adhesion, floating fuel quantity MF, adhesion, and floating fuel quantity increase / decrease speed VMF are calculated according to the engine load and the water temperature. As the initial value of the floating fuel amount MF, the value calculated immediately before the start is set.

For this reason, the continuity of control is maintained, and the adhering and floating fuel amount MF, the adhering and floating fuel amount increasing / decreasing speed VM.
F is required accurately.

In this way, the adhesion, floating fuel amount MF, adhesion,
Since the increase / decrease speed VMF of the floating fuel amount is accurately calculated,
The fuel injection amount is appropriately corrected by the transient correction amount KATHOS based on the increase / decrease speed VMF, so that the air-fuel ratio is smoothly shifted to the target air-fuel ratio immediately after the start.

Therefore, unlike the conventional case, the air-fuel ratio does not become lean immediately after the start, and as a result, the stability can be maintained without performing the excessive fuel amount increase correction immediately after the start. It is possible to reduce the emission amount immediately after starting.

In this case, the equilibrium amount MFHST at the time of starting
Since the fuel injection amount and the equilibrium adhesion and the floating rate KMFHST are obtained, the equilibrium amount MFHST at the time of starting can be accurately obtained, and this equilibrium amount MFHST and the previous adhesion and floating fuel amount MF (-1) By multiplying the difference by the adherence and floating fuel response coefficient KMFST determined by the engine temperature, and adding the previous adherence and floating fuel amount MF (-1) to this, the adhesion and floating fuel amount MF during starting can be easily performed. Can be accurately determined.

The target air-fuel ratio TFBYA after starting is
As shown in FIG. 5, in steps 41 to 45, the water temperature,
From the tables and maps preset based on the engine speed, knocking state, throttle valve opening, etc., the post-start amount increase correction coefficient KAS, the water temperature increase coefficient KTW, the high water temperature increase coefficient K
The HOT, the knock control retarding increase coefficient MRKNK, and the mixture ratio allocation coefficient KMR are read, and in step 46, these values are calculated by the following equation (6).

TFBYA = KAS + KTW + KHOT + MRKNK + KMR (6)

[0059]

As described above, according to the first invention, the operating condition detecting means for detecting at least the operating conditions of the engine speed, the engine load, and the engine temperature, and the basic fuel injection amount based on the operating conditions. Based on operating conditions and intake system adhesion, floating fuel amount and equilibrium amount, and basic injection amount computing device for computing, equilibrium amount computing device for computing intake system adhesion and floating fuel equilibrium amount based on operating conditions Increase / decrease speed calculation means for calculating the increase / decrease speed of the adhered / floating fuel amount, injection amount control means for controlling the fuel injection amount from the fuel injection valve based on the increase / decrease speed and the basic injection amount, and the increase / decrease speed based on the increase / decrease speed. In the air-fuel ratio device for an internal combustion engine, comprising: the adhesion, the adhesion for updating the amount of floating fuel, and the floating amount calculation means, a start determination means for determining whether or not the engine is at startup, and at least the engine temperature at startup. Engine speed and Based on the injection amount control means for calculating and controlling the starting fuel injection amount from the fuel injection valve, and the injection amount and the operating condition, the adhesion of the intake system at the time of starting and the equilibrium amount of the floating fuel are calculated. Start-up equilibrium amount calculation means, adhesion of intake system at start-up based on the equilibrium amount and engine temperature, start-time adhesion and floating amount calculation means for calculating floating fuel amount, and start-time adhesion and floating fuel amount Since the final calculated value is attached to the speed increase / decrease calculation means after the start and the initial value setting means after the start for setting the initial value of the floating fuel amount, the continuity of the control is maintained from the time of the start and immediately after the start. It is possible to accurately correct the amount of fuel injection and the amount of floating fuel to be increased / decreased according to the speed of increase / decrease of the amount of floating fuel.

According to the second aspect of the present invention, the equilibrium amount at the time of starting can be accurately obtained, and the fuel injection amount immediately after starting can be corrected more accurately.

According to the third aspect of the present invention, the amount of adhered and floating fuel at the time of starting can be accurately obtained, and the fuel injection amount immediately after starting can be corrected more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a flowchart showing control contents.

FIG. 5 is a flowchart showing control contents.

FIG. 6 is a characteristic diagram of a water temperature basic injection pulse width at startup.

FIG. 7 is a characteristic diagram of a cranking rotation correction value.

FIG. 8 is a characteristic diagram of a post-startup time correction value.

FIG. 9 is a characteristic diagram of equilibrium adhesion at start-up and floating rate.

FIG. 10 is a characteristic diagram of adhesion at start-up and floating fuel response coefficient.

FIG. 11 is a characteristic diagram of an equilibrium amount after starting.

FIG. 12 is a characteristic diagram of adhesion and floating fuel response coefficient after starting.

FIG. 13 is a waveform diagram illustrating the operation of the embodiment.

FIG. 14 is a conventional waveform diagram.

[Explanation of symbols]

 20 engine body 21 intake passage 22 throttle valve 23 fuel injection valve 24 intake port 30 air flow sensor 31 throttle valve opening sensor 32 water temperature sensor 33, 34 air-fuel ratio sensor 35 control unit

Claims (3)

[Claims] 1. An operating condition detecting means for detecting at least an operating condition of an engine speed, an engine load and an engine temperature, a basic injection amount calculating means for calculating a basic injection amount of fuel based on the operating condition, and an operating condition. Adhesion of the intake system based on the equilibrium amount calculation means for calculating the equilibrium amount of floating fuel, operation conditions and adhesion of the intake system, adhesion based on the floating fuel amount and the equilibrium amount,
An increase / decrease speed calculation means for calculating an increase / decrease speed of the floating fuel amount,
An injection amount control means for controlling the fuel injection amount from the fuel injection valve based on the increase / decrease speed and the basic injection amount, and an adhesion / floating amount calculation means for updating the adhesion and floating fuel quantity based on the increase / decrease speed. In an air-fuel ratio device for an internal combustion engine, which is provided with a start determination means for determining whether or not the engine is being started, and a start fuel injection amount from a fuel injection valve is calculated based on at least the engine temperature and the engine speed at the start. , A starting injection amount control means for controlling, a starting equilibrium amount calculating means for calculating the adhering amount of the intake system and a floating fuel equilibrium amount at the time of starting based on the injection amount and operating conditions, and the equilibrium amount and the engine. Adhesion of the intake system at the time of starting based on the temperature, adhesion at the time of starting to calculate the floating fuel amount, floating amount calculation means, and the final calculated value of the adhesion at the time of starting and the floating fuel amount Set as the initial value for the amount of adhered and floating fuel. Air-fuel ratio control system for an internal combustion engine, characterized in that a and starting after the initial value setting means for. 2. The start-up equilibrium amount calculation means is adapted to obtain a start-up equilibrium amount by multiplying a fuel injection amount by a fuel adhesion and a floating rate based on an engine temperature. Air-fuel ratio control device for internal combustion engine. 3. The adhering at start-up, floating amount calculating means multiplies the difference between the equilibrium amount at start-up and the previous adhering or floating fuel amount by the adhering amount determined by the engine temperature or the response coefficient of the floating fuel, and adhering. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the floating fuel amount is obtained.