JPH03210033A - Fuel supply control method at high load time of internal combustion engine - Google Patents

Abstract

PURPOSE:To properly perform cooling of an engine at a high load operation time according to a load condition by gradually increasing an increase value of fuel which is supplied to the engine being under the high load condition, to a set target increase value from an initial value which corresponds to the set target value. CONSTITUTION:An electronic controller 40, when high load of an engine 12 is judged from a signal of a throttle sensor 48 and the like, sets a target increase value of fuel according to a high load operation condition. When the target increase value is larger than a specified judgement value, an increase value of fuel which is supplied to a fuel injection valve 16 is increased from an initial increase value to a set target increase value according to a target increase value. The increase is performed at every crank angle position detected by a sensor 52, and at every rate according to a generation quantity of Karman's vortex detected by an air flow sensor 42. In this case, since an initial increase value is set at a large value when the load is large, namely the initial increase value is set richer than a theoretic air-fuel ratio, cooling of the engine is properly and surely performed according the load condition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for controlling fuel supply to an internal combustion engine during high-load operation, and in particular, to a method for controlling the fuel supply to an internal combustion engine during high-load operation such as sudden acceleration. The present invention relates to a fuel supply control method for an internal combustion engine that requires cooling.

(Prior Art and Problems to be Solved) Conventionally, when an internal combustion engine is operated under high load, the amount of fuel supplied to the engine is increased depending on the load state. The purpose of this fuel increase is not only to obtain an output according to the load state, but also to cool the engine, which is operating under a high load, with the supplied fuel.

Thus, when cooling the engine with fuel is required, it may be necessary to supply more fuel than is necessary to obtain the required output.

Excessive fuel in this case will deteriorate the fuel efficiency of the engine.

By the way, the engine is not in a high temperature state at the beginning of the high-load operation, and there is often no need to increase the amount of fuel for cooling at the beginning of such high-load operation. Therefore, conventionally, even when the engine enters a high-load operating state, the fuel increase value is not immediately set to the target increase value, but instead it is started from a constant value, for example, an increase value corresponding to the stoichiometric air-fuel ratio, toward the target increase value. A fuel supply method is known that aims to improve fuel efficiency by gradually increasing fuel consumption.

However, according to this fuel supply method, in order to always increase the fuel amount from a constant value, for example, an increase value corresponding to the stoichiometric air-fuel ratio, regardless of the degree of high load, it is necessary to In addition, under high load operating conditions, the temperature of the exhaust gas from the engine rises rapidly, causing a delay in cooling the engine with fuel, which may cause problems.

The present invention has been made to solve these problems, and is an internal combustion engine that properly and reliably cools the engine during high-load operation depending on the load condition, and improves fuel efficiency. The purpose of the present invention is to provide a fuel supply control method during high engine load.

(Means for Solving the Problems) In order to achieve the above-mentioned object, according to the present invention, when a predetermined high-load operating state of an internal combustion engine is detected, supply to the engine is controlled according to the detected high-load operating state. In the fuel supply control method for increasing the amount of fuel to be used, a target increase value is set according to the detected high-load operating state, and when this target increase value is larger than a predetermined judgment value, the amount of fuel is increased according to the set target increase value. Fuel supply during high load to an internal combustion engine, characterized in that an initial increase value is set, and the increase value of the amount of fuel supplied to the engine in the high load operating state is gradually increased from the initial increase value to the target increase value. A control method is provided.

The amount of fuel supplied during high-load operation may be gradually increased by detecting a predetermined crank angle position of the internal combustion engine and gradually increasing the fuel amount at a predetermined rate each time the predetermined crank angle position is detected. The amount of intake air may be detected by Karman vortices generated in the intake passage, and the amount of fuel may be gradually increased at a rate corresponding to the amount of Karman vortices generated.

Preferably, the predetermined determination value is set in accordance with a detected engine rotational speed value.

(Function) The initial increase value of the present invention is a variable value that is set according to the target increase value. Then, if the load is large, this initial increase value is set to a larger value (a value corresponding to a smaller air-fuel ratio on the richer side than the stoichiometric air-fuel ratio) depending on the load level. During heavy-duty operation, the amount of fuel is gradually increased from an initial increase value that is greater than when the load is low, and engine cooling is appropriately and reliably performed in accordance with the load condition.

(Example) An example of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of a fuel supply control device for an internal combustion engine according to the present invention, and this control device is applied to, for example, a four-cylinder gasoline engine (hereinafter simply referred to as "engine") 12.

Intake manifold 1 connected to each cylinder of this engine 12
4, an electromagnetic fuel injection valve 16 is disposed adjacent to each intake port. One end of an intake pipe 20 is connected to the intake manifold I4 via a surge tank 18, and an air cleaner 22 is attached to the other end (the end open to the atmosphere) of the intake pipe 20. A throttle valve 24 is disposed in the middle of the intake pipe 20. Fuel whose fuel pressure is adjusted to a constant level by a fuel pressure regulator 26 is supplied to each fuel injection valve 16 from a fuel pump (not shown) via a fuel passage 25.

On the other hand, an exhaust manifold 30 is connected to the exhaust side of each cylinder of the engine 12.
The atmospheric side end is connected to an exhaust pipe 34. Exhaust pipe 34
A three-way catalytic converter (catalytic exhaust gas after-treatment device) 36 is disposed in the middle of the exhaust gas. Then, the amount of oxygen in the exhaust gas is detected at 3 degrees of the exhaust manifold. Two sensors 44 are attached. The o2 sensor 44 is electrically connected to the input side of the electronic control unit (ECU) 40, and supplies an oxygen 1 degree detection signal to the electronic control bag W40.

The electronic control device 40 includes a central processing unit (not shown), a storage device that stores a control program for calculating the fuel supply amount, various program variables, and the like, an input/output device, and the like. In addition to ROM and RAM, the storage device includes a non-volatile battery backup RAM whose stored contents do not disappear even after the engine 12 is stopped.

Each of the fuel injection valves 16 described above is electrically connected to the output side of the electronic control device 40, and is opened by a drive signal from the electronic control device 40, and the required amount of fuel is injected into each cylinder as will be described in detail later. Supply injection.

On the input side of the electronic control device 40, there are various sensors for detecting the operating state of the engine 12, such as the above-mentioned 02 sensor 4.
In addition to 4, an air flow sensor 42 is installed near the end of the intake pipe 2o that is open to the atmosphere and outputs a pulse proportional to the amount of intake air by detecting Karman vortices; The intake air temperature sensor 4G detects, the throttle opening sensor 48 detects the valve opening of the throttle valve 24, and the distributor 38 connected to the camshaft is provided to detect a predetermined crank angle position at or slightly before top dead center. A crank angle sensor 50 that outputs a pulse signal (TDC signal) every time is also provided in the distributor 38, and is connected to a specific cylinder (
A cylinder discrimination sensor 52 detects that the first cylinder (for example, the first cylinder) is at a predetermined crank angular position (for example, an angular position at or slightly before compression top dead center), and a water temperature sensor 54 detects the cooling water temperature TV of the engine 12. , throttle valve 24
The idle switch 56 detects the fully closed position of the atmospheric pressure P.
An atmospheric pressure sensor 58 that detects air pressure a is further connected to sensors (not shown) such as an air conditioner switch that detects the operating state of the air conditioner, and a battery sensor that detects battery voltage, and these sensors send detection signals to the electronic control device. 40
supply to.

The electronic control unit 40 determines operating states such as a predetermined high load operating state, low load operating state, deceleration fuel cut operating state, 02 feedback control operating state, etc., based on detection signals from the various sensors described above, as will be described in detail later. is detected, the fuel injection amount corresponding to the detected engine operating state, that is, the valve opening time TINJ of the fuel injection valve 16 is calculated, and a drive signal corresponding to the calculated valve opening time TrNJ is supplied to each fuel injection valve 16. This opens the valves and injects and supplies the required amount of fuel to each cylinder.

The electronic control device 40 calculates the above-mentioned valve opening time T using the following equation (1).
Calculate INJ.

T INJ= TBX KAFX KTWX KTAX
KPAX KACX K+TO・・・・・・(1) Here, TB is the basic valve opening time set according to the intake air amount A/N, and KAF is set according to the output of the 02 sensor during air-fuel ratio feedback control. This is an air-fuel ratio correction coefficient that is set according to the intake air amount A/N and the engine rotational speed Ne during open loop control, and the details of how to set the value will be described later. KTW is a correction coefficient set according to the engine cooling water temperature TW, KTA and KPA are correction coefficients set according to the intake air temperature Ta and atmospheric pressure Pa, respectively, and KAC is a correction coefficient set according to the opening speed of the throttle valve 24. The acceleration increase correction coefficient K is another correction coefficient, and by this correction coefficient, for example, fuel increase correction after fuel cut, engine start increase correction, etc. are performed. TD is an invalid time correction value set according to the battery voltage. Details of the calculation procedure for these correction coefficient values and correction values will be described later.

In addition, since the electronic control device 40 outputs a TDC signal every 180 degrees at a crank angle sensor of 5 degrees,
From the pulse generation interval of this TDC signal, the engine rotation speed N
e can be detected. Further, the electronic control device 40 stores the ignition order of the cylinders, that is, the order of fuel supply to each cylinder, and when the above-mentioned cylinder discrimination sensor 52 detects the predetermined crank angle position of the above-mentioned specific cylinder, Next, it is possible to determine which cylinder should be injected with fuel.

Next, details of the fuel supply control procedure by the electronic control device 40 described above will be explained with reference to a program flowchart.

FIGS. 2A and 2B show a main routine, which starts execution at the same time as an ignition key switch (not shown) is turned on, and is constantly repeatedly executed during idle time when an interrupt routine, which will be described later, is not executed.

The electronic control device 40 first performs step 520 in FIG. 2A.
0, various program control variable values, correction coefficient values, etc. are initialized. The program control variable values to be initialized include a lean timer value T, a timer count flag value FLGT, etc., which will be described later. This step is executed only once immediately after the ignition key switch is turned on, and in the subsequent loop, the steps from step 5202 onward, which will be described later, are repeatedly executed from the entry point M1.

Next, in step 5202, various operating state values are read. The operating status values read in this step include:
Cooling water temperature signal value TW from water temperature sensor 54, voltage value VO2 from 02 sensor 44, intake air temperature signal value Ta from intake temperature sensor 46, atmospheric pressure signal value Pa from atmospheric pressure sensor 58, throttle opening sensor 48 This includes the throttle opening signal value θ[h, etc. Signals from these sensors are amplified, filtered, and
A/D conversion and the like are performed, and the signal is read into the electronic control device 40 as a digital signal.

The electronic control unit 40 determines whether the engine 12 is being operated in a predetermined deceleration fuel cut zone based on the read various operating state signal values (step 5206). This determination is made, for example, if the idle switch 56 is on, that is,
The determination can be made based on whether the throttle valve 24 is fully closed and the engine speed Ne is greater than or equal to a predetermined rotation speed, and whether the intake air amount A/N is a predetermined value (A/N).
The determination can also be made based on whether or not the engine rotational speed Ne is smaller than sl and the engine rotational speed Ne is equal to or higher than a predetermined rotational speed.

If this determination result is affirmative (Yes), step 820
Proceed to step 8 and set the fuel cut flag FLGC to the value l. This flag FLGC is a program control variable for instructing a fuel cut.

Then, the process proceeds to step 5209, where the lean timer value T1 and flag value FLGT are each reset to 0, and then the process returns to step 5202 to repeat the routine. Note that the timer count flag FLGT is a program control variable that allows the lean timer T to continue counting.

On the other hand, if the determination result in step 8206 is negative (No), that is, if the engine 12 is not operated in the predetermined deceleration fuel cut zone, the fuel cut flag FLGC is reset to the value O (step 5207), and the fuel cut flag FLGC is reset to the value O (step 5207). Proceed to step 5210 in Figure 2B.

In step 5210, it is determined whether the engine 12 is being operated in a predetermined air-fuel ratio feedback control zone. This determination is made, for example, if the 02 sensor 44 is sufficiently activated and the engine 12 is in a warmed-up state (cooling water temperature TW
>TWS) and the intake air amount A/N is smaller than a predetermined value (A/N) s2.

Note that the above-mentioned predetermined value (A/N) s2 means that when the amount of intake air supplied to the engine 12 is greater than this value, the engine 12 is in a high-load operating state, and such In this case, air-fuel ratio feedback control is not executed. Moreover, this predetermined value (A/N) s2 is larger than the predetermined value (A/N) sl for determining the deceleration fuel cut zone described above ((
It goes without saying that A/N)s2 > (A/N)sl).

When the engine 12 is operated in the air-fuel ratio feedback control zone, the feedback correction coefficient value KFB is calculated according to the output VO2 of the 02 sensor 44 (step 5212), and this is calculated as the air-fuel ratio correction coefficient value KAF (-
KFB) (step 5214). Note that the method for calculating the feedback correction coefficient value KFB does not need to be particularly limited, and a conventionally known method can be applied.

On the other hand, if the determination result in step 5210 is negative and the engine 12 is not operated in the above-mentioned air-fuel ratio feedback control zone, the process proceeds to step 5216, where the target Read the increase coefficient value K AFM from the air-fuel ratio map. The air-fuel ratio map is stored in advance in the storage device mentioned above, and the target increase coefficient value K AFM is stored as a map value in this map for each operating range using the intake air amount A/N and the engine speed Ne as parameters. . The high-load operation region of the air-fuel ratio map is divided into multiple regions according to the load condition expressed by the intake air amount A/N and the engine speed Ne, and the target increase coefficient value KAFM is set for each region. remembered. Each target increase coefficient value K AFM stored in the high-load operation region is set in consideration of the increase in fuel amount to obtain the required output and the increase in fuel amount to cool the engine with fuel. There is.

Next, the engine rotation speed Ne detected by the crank angle sensor 50 is set to a predetermined value Ns (for example, 3000 rpm).
) (step 3218
). If the result of this determination is negative, the target increase coefficient value KAFM obtained in step 5216 described above is compared with the first predetermined value KAFSI (for example, set to a value corresponding to an air-fuel ratio of 13). 5220), and if affirmative, it is compared with a second predetermined value KAFS2 (for example, set to a value corresponding to an air-fuel ratio of 14) (step S224).

Then, the target increase coefficient value K AFM is set to a predetermined value KAFSI.
Or, if it is smaller than K AFS2, that is, if the degree of load is smaller than the predetermined value, the target increase coefficient value K AFM obtained in step 8216 is directly used as the air-fuel ratio correction coefficient value KA.
Store as F (=KAFM) (step 5
222.226).

On the other hand, the target increase coefficient value K A obtained in step 5216
If FM is larger than the predetermined value KAFSI or K AFS2 (if the determination result in step 5220 or step 5224 is affirmative), the process proceeds to step 8228, where the timer count flag FLGT is set to the value 1, and then the target increase coefficient value K The initial increase coefficient value KAFI corresponding to the AFM is read from the table (step 5230).

FIG. 3 shows an example of a table of the relationship between the target increase coefficient value KAFM and the initial increase coefficient value KAFI set accordingly. value KAFMO (for example, value 1.0
5), the target increase coefficient value K AF is set to a value that increases linearly as the target increase coefficient value K AF increases.
M exceeds the predetermined value K AFMO and the second predetermined value K AF
The predetermined value KAFIO is maintained until reaching M2, and when the second predetermined value K AFM2 is exceeded, the target increase coefficient value KA is maintained again.
It is set to a value that increases in proportion to FM.

The electronic control unit 40 calculates the air-fuel ratio correction coefficient value KAF using the following equation (A1) from the target increase coefficient value KAFM and the initial increase coefficient value KAFI obtained as described above (step 5232).

KAF=(T/TO)X KAFM ++(TO-T)/TOI XKAFI...(AI)
Here, TO is a constant and T is a timer value. When the timer value T is 0, as is clear from the above formula (AI), the air-fuel ratio correction coefficient value KAF is set to the same value as the initial increase coefficient value KAF[, and as the timer value T increases, the air-fuel ratio The correction coefficient value KAF increases and the timer value T reaches the predetermined value TO.
Then, it is set to the same value as the target increase coefficient value KAFM. Therefore, it is desirable to set the predetermined value TO so that when the timer value T reaches the predetermined value TO, the engine 12 is at a high temperature that requires cooling with fuel. In reality, the predetermined value TO is experimentally set to an appropriate value.

As described above, the first predetermined value KAFSI is set to a value larger than the second predetermined value KAFS2 (a smaller value when compared with the corresponding air-fuel ratio), and the air-fuel ratio correction coefficient value As for KAF, the read value is used as is until the target increase coefficient value K AFM read in step 5216 is larger in the low engine speed Ne range than in the high engine speed range. That is, the lean air-fuel ratio at the start of high-load operation is limited in the low rotation speed range. This is because it is often necessary to rapidly accelerate the engine 12 in a high-load operating state in a low rotation range, and in such a case, it is necessary to enrich the fuel (air-fuel ratio) and increase the output from an early stage.

In this way, when the setting of the air-fuel ratio correction coefficient value KAF is completed, the process proceeds to step 5234, and the electronic control unit 40 calculates the fuel injection amount, that is, the valve opening time TIN of the fuel injection valve 16, from the read various operating state signal values. Necessary to calculate 1,
Calculates other various correction coefficient values, etc. The correction coefficient values calculated here include a water temperature correction coefficient value KTW set according to the cooling water temperature TW, an atmospheric pressure correction coefficient value KPA set according to the atmospheric pressure Pa, and a correction coefficient value set according to the intake air temperature Ta. This includes an intake air temperature correction coefficient value KTA, an invalid time correction variable value TD set according to the battery voltage, and the like.

Various conventionally known methods can be used to set these correction coefficient values and correction variable values.

When the calculation of the correction coefficient value etc. in step 5234 is completed, the process returns to step 5202 and the routine is repeatedly executed.

4A and 4B show a flowchart of a crank pulse interrupt routine that is executed every time a crank pulse signal from the crank angle sensor 50 is input, and this interrupt routine is executed with the highest priority. Electronic control device 40
First, in step 8300, it is determined whether the fuel cut flag value FLGC is set to the value 1, that is, whether the engine 12 is being operated in a predetermined deceleration fuel cut region. If this determination result is positive,
The routine ends without performing calculation of the valve opening time TINJ, which will be described later, and without injecting fuel to the engine 12.

On the other hand, if the determination result in step 5300 is negative, the process proceeds to step 5302 and calculates the intake air amount A/N. The intake air amount A/N is calculated based on the number of Karman vortex pulses that occurred between the previous crank pulse and the current crank pulse, and the periodic data between the Karman vortex pulses. corner 180
It represents the amount of intake air per °. Note that the detection of the engine rotational speed Ne described above is performed in this step.

Next, the electronic control unit 40 calculates the basic valve opening time TB of the fuel injection valve 16 according to the intake air amount A/N calculated in step 5302 (step 5304). At this time, the basic valve opening time TB is the engine 12 in the standard state.
The valve opening time is calculated based on the amount of fuel that provides the stoichiometric air-fuel ratio for the intake air amount A/N.

Step 5306) calculates the valve opening time TINJ of the fuel injection valve 16 based on the above formula (1) using the basic valve opening time TB obtained in this way and the various correction coefficients and correction values described above. Valve time TINJ is set in the injection timer (step 8308). Then, from the time when the execution of the routine is started by the crank pulse signal, that is, when a predetermined time has elapsed from the time when the predetermined crank angle position is detected, the above-mentioned injection timer is triggered,
A drive signal is output to the fuel injection valve 16 corresponding to the cylinder to which fuel is to be injected during the current loop for a period of time corresponding to the valve opening time TINJ (step 5310).

Thus, the valve opening time TIN calculated as described above
An amount of fuel corresponding to J will be injected and supplied to the engine 12.

Next, the process proceeds to step 5312 in FIG. 4B, where it is determined whether the timer count flag value FLGT is set to the value l. If the timer value T is not set, the routine ends without doing anything, but if the value is set to 1, the process proceeds to step 5314, where it is determined whether the timer value T is greater than or equal to a predetermined value of 10. If the determination result is negative, the timer value T
If T has not yet reached the predetermined value TO, the timer value T is incremented by 1 (step 3316).
, terminate the routine.

As described above, in this embodiment, the timer value T is incremented every time a predetermined crank angle position is detected by the crank angle sensor 50, and this timer value T is determined by adjusting the air-fuel ratio correction coefficient value KAF in step 5232 of the main routine described above. It is used for calculation, and the increase value of the fuel supply amount at the time of entering high-load operation according to the timer value T is the initial increase coefficient value KA.
The value is gradually increased from the value corresponding to FI to the value corresponding to the target increase coefficient value KAFM.

As long as the high-load operation continues, step 8228 of the main routine described above is executed, the timer count flag value FLGT is held at the value 1, and the timer value T is incremented. Timer value T is predetermined value T
When the timer value T reaches O, the timer value T is thereafter held at the predetermined value TO which is the upper limit value (step 3318). When the timer value T is set to the predetermined value TO, the air-fuel ratio correction coefficient value KAF is set to the target increase coefficient value K AFM read from the air-fuel ratio map in step 5216.

Before the timer value T reaches the predetermined value TO, the engine 12
When the motor leaves the high-load operating state and enters the predetermined deceleration fuel cut zone, the timer value T and timer count flag value FLGT are both reset to the value 0 in step 8208 described above, and after this, the When the high-load operating state starts, the air-fuel ratio correction coefficient value KAF is set to a value that gradually increases from the initial increase correction coefficient value KAFI to the target increase coefficient value KAFM, as described above.

On the other hand, if the high load operation state is entered again without entering the deceleration fuel cut zone after leaving the high load operation state, the timer value T and the timer count flag value F
LGT is not reset to the value 0 and timer T continues counting. Therefore, at the time when the high-load operating state enters again, the air-fuel ratio correction coefficient value KAF is equal to the target increase coefficient value KA read out in step 5216.
FM.

Initial increase coefficient value KAF read in step 5230
I and the timer value T to a value calculated based on equation (AI). - If the engine 12 returns to the high-load operating state after a short period of time after leaving the high-load operating state, the engine 12 maintains a high temperature state, and in such a case, the fuel supply amount may be reduced. If the engine is made lean, the engine will not be cooled enough, which will cause some inconvenience, but this inconvenience can be avoided by holding the timer value T instead of resetting it as described above. When the engine 12 re-enters the high load operating state via the fuel cut operation zone, the engine 12 is sufficiently cooled during the fuel cut zone operation, and the fuel supply amount becomes lean at the beginning of entering the high load operating state. There is no problem in doing so.

Note that in the above embodiment, the timer value T and timer count flag value FLGT were reset to 0 during operation in the fuel cut zone, but the timing to reset these values is not limited to when the engine enters the fuel cut zone; 12 should be reset when the engine exits from a high temperature state during high load operation. For example, it may be reset when entering a predetermined low load operating state where the intake air amount A/N becomes less than a predetermined value. Good too. Further, this low-load operating state can also be detected by the pressure inside the intake passage.

FIG. 5 shows a modification of the control procedure shown in FIG. 2A described above. In this embodiment, after reading various operating state values in step 5202,
It is determined whether /N is smaller than a predetermined value (A/N) s3. This predetermined value (A/N) s3 is set to a value smaller than the predetermined feedback upper limit value (A/N) s2 used for the above-mentioned air-fuel ratio feedback zone determination.
It is set larger than the above-mentioned predetermined value (A/N) sl used for determining the deceleration fuel cut zone.

Then, if the determination result in step 5203 is affirmative, that is, if the engine 12 enters a predetermined low-load operating state, the timer value T and the timer count flag value FL
Both GTs are reset to the value 0 (step 5204).
. Note that the other steps shown in FIG. 5 are given the same reference numerals as the corresponding steps in FIG. 2A, and detailed explanation thereof will be omitted.

Further, in the above embodiment, the timer value T is incremented by a value l every time a predetermined crank angle position is detected. This means that the air-fuel ratio correction coefficient value KAF is gradually increased according to the number of engine rotations. The present invention is not limited to this, and the air-fuel ratio correction coefficient value KAF may be gradually increased according to the amount of Karman vortices detected by the air flow sensor 42, or the timer value T may be increased every time a clock pulse is generated a predetermined number of times. may be incremented. In the latter case, the above-mentioned predetermined number of times may be set to a different value for each engine operating region determined by, for example, the engine speed Ne and/or the intake air amount (A/N). Furthermore, instead of setting this predetermined number of times to a different value for each engine operating region, the aforementioned predetermined value TO may be set to a different value for each engine operating region.

6 and 7 show program flowcharts for incrementing the timer value T according to the amount of Karman vortices generated, and the timer value T is incremented in the crank pulse interrupt routine of FIG. Variable value AF that counts the amount of Karman vortex generation instead of incrementing
Step 5311 of resetting the
It should be executed after 310. This variable value AF
is used to count the amount of Karman vortices generated between the previous crank pulse and the current crank pulse detected by the crank angle sensor 50, and the amount of intake air A in step 5304 is calculated.
/N is used for calculation. When the calculation of the intake air amount A/N is completed, the Karman vortex variable AF fulfills its role and is reset in step 5311.

The number of Karman vortex generation pulses is counted by the Karman pulse interrupt routine shown in FIG.

That is, the electronic control unit 40 executes this interrupt routine with priority over the aforementioned main routine every time the air flow sensor 42 detects a Karman vortex, and executes the interrupt routine in step 540.
0, the value 1 is added to the aforementioned variable value AF, and the added value is stored as a new variable value AF.

Then, in the following step 5402, it is determined whether the timer count flag value FLGT is set to the value l. If it is not set, the routine ends without doing anything, but if it is set to the value I, the process proceeds to step 5404, where it is determined whether or not the timer value T is greater than or equal to a predetermined value T1. If the determination result is negative and the timer value T has not yet reached the predetermined value T1, the timer value T is incremented by 1 (step 5406), and the routine ends. On the other hand, the timer value T is the predetermined value Tl
When the timer value T reaches the predetermined value T, which is the upper limit value,
I (step 3408). still,
The above-mentioned predetermined Tl is set to an appropriate value based on the same idea as the above-mentioned predetermined value TO.

As described above, in this embodiment, the timer value T is incremented each time a Karman vortex occurs in the intake passage, and this timer value T is set at step 523 of the main routine described above.
2, it is used to calculate the air-fuel ratio correction coefficient value KAF. The amount of Karman vortices generated is proportional to the amount of intake air, and the amount of intake air corresponds to the heat generated in the cylinders of the engine 12 or the exhaust temperature. As a method of setting the timer value T used for calculating the air-fuel ratio correction coefficient value KAF, it is superior to a method of incrementing the timer value T every time a crank pulse occurs, that is, every time the engine rotates.

Note that the fuel supply control device of the above embodiment was applied to inject fuel into each cylinder from a fuel injection valve disposed for each cylinder, but a single fuel injection valve disposed upstream of the throttle valve was used. The present invention may be applied to a so-called single-point type fuel supply control device that supplies fuel to an engine from a valve, or to an electronic carburetor type fuel supply control device.

(Effects of the Invention) As detailed above, according to the fuel supply control method during high load of an internal combustion engine of the present invention, a target increase value is set according to the high load operating state, and this target increase value is set as a predetermined value. When the value is greater than the discrimination value, an initial increase value is set according to the set target increase value, and the increase value of the amount of fuel supplied to the engine in the high load operation state is gradually increased from this initial increase value to the target increase value. As a result, engine cooling during high-load operation can be carried out in a timely manner according to the load condition, that is, according to the engine temperature condition. Since the amount of fuel is finely set, fuel efficiency can be significantly improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show one embodiment of the present invention, FIG. 1 is a block diagram showing the outline of the configuration of a fuel supply control device to which the method of the present invention is applied, and FIGS. 2A and 2B are fuel supply control devices. The main routine flowchart showing the control procedure is shown in Fig. 3, which shows the target increase coefficient value K.
A graph showing the relationship between AFM and the initial increase correction coefficient KAPI, FIGS. 4A and 4B are a flowchart of a crank pulse interrupt routine showing a fuel control procedure, and FIG. 5 is a modification of the control procedure shown in FIG. 2A. A flowchart showing
FIG. 6 is a flowchart showing a modification of the control procedure shown in FIG. 4A, and FIG. 7 is a flowchart of the Kalman pulse interrupt routine. 12... Internal combustion engine, 14... Intake manifold, 16... Fuel injection valve, 20... Intake pipe, 24...
・Throttle valve, 38...Distributor, 40
...Electronic control device, 42...Air flow sensor, 4
Sensor, 48...Throttle opening sensor, rank angle sensor, 54...Water temperature sensor. 4...02 50...ri

Claims (4)

[Claims] (1) In a fuel supply control method, when a predetermined high-load operating state of an internal combustion engine is detected, the amount of fuel supplied to the engine is increased in accordance with the detected high-load operating state; Set the target increase value using
When this target fuel increase value is larger than the predetermined judgment value, an initial fuel increase value is set according to the set target fuel increase value, and the fuel amount increase value to be supplied to the engine in the high load operation state is determined from this initial fuel increase value. A method for controlling fuel supply during high load of an internal combustion engine, characterized in that the fuel supply is gradually increased to the target increase value. (2) When a predetermined crank angle position of the internal combustion engine is detected, and each time the predetermined crank angle position is detected, the amount of fuel is gradually increased at a predetermined rate. fuel supply control method. (3) The internal combustion engine according to claim 1, wherein the intake air amount of the internal combustion engine is detected by a Karman vortex generated in the intake passage, and the fuel amount is gradually increased at a rate corresponding to the amount of the Karman vortex generated. Fuel supply control method during high engine load. (4) The fuel supply control method during high load of an internal combustion engine according to claim 1, characterized in that an engine rotation speed is detected, and the predetermined discrimination value is set in accordance with the detected engine rotation speed.