JPS59176444A - Method of controlling air-fuel ratio of internal- combustion engine - Google Patents

Abstract

PURPOSE:To stabilize combustion and improve a driving property, by selecting feedback control or open-loop control depending on the temperature of an engine at its starting and by prohibiting the feedback control within a prescribed time after the starting. CONSTITUTION:Feedback control for maintaining the air-fuel ratio of an engine at a theoretical value or open-loop control for keeping the air-fuel ratio at a too low value or at a high value is selected. A basic fuel injection time is compensatorily increased by a warm-up increase coefficient FWL in a step P11 and a transient air-fuel compensation coefficient FTC in a step P13. Except when the feedback control for maintaining the air-fuel ratio at the theoretical value by a feedback compensation coefficient FAF determined in a step P12 is effected, the open-loop control is performed. The atomization of fuel is thus made adequate to stabilize the combustion of the engine to improve its running performance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection valve provided in an intake passage, and a relatively long-distance system for guiding the air-fuel mixture injected from the fuel injection valve and mixed with intake air through an engine combustion chamber housing. Feedback control that maintains the air-fuel ratio at the stoichiometric air-fuel ratio under conditions including at least that the engine temperature is above a predetermined temperature, and adjusts the air-fuel ratio to the stoichiometric air-fuel ratio according to the engine operating condition. The present invention relates to an air-fuel ratio control method for an internal combustion engine that selectively performs open-loop control that controls the rich side or the lean side.

In an internal combustion engine that uses a three-way catalyst to purify exhaust scum, it is necessary to feedback-control the air-fuel ratio to maintain it near the stoichiometric air-fuel ratio from the viewpoint of purification efficiency. However, from the viewpoint of fuel efficiency, it is preferable to control the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio because the amount of accumulated nitride oxides is small when the engine is continuously operated under a light load. When the engine is cold or under high load, it is best to control the air-fuel ratio to 14 richer than the stoichiometric air-fuel ratio.

In air-fuel ratio feedback control, one execution condition is that the engine temperature be above a predetermined value. However, when the engine temperature is detected by the engine cooling water temperature or engine oil temperature, Even if the temperature of the intake passage wall surface is lower than the cooling water temperature or oil temperature, feedback control is performed if other feedback control conditions other than engine temperature are satisfied.

By the way, in an engine having a relatively long intake passage from the fuel injection valve to the combustion chamber as described above, the fuel injected from the fuel injection valve is atomized in the intake passage and guided to the combustion chamber. When the temperature of the passage wall surface is low, fuel atomization is difficult to promote.

Therefore, in environments where the temperature of the intake passage wall surface is less likely to rise than the engine cooling water temperature, such as during extremely cold weather,
When feedback control is performed because the engine cooling water temperature is higher than the feedback control execution condition, fuel atomization will not be sufficient and combustion will be unstable until the intake passage wall temperature rises sufficiently. Therefore, the desired engine-vehicle inspection performance may not be achieved.

An object of the present invention is to provide an air-fuel ratio control method for an internal combustion engine in which feedback control is not executed under operating conditions in which there is a temperature difference between the wall surface temperature of the intake passage from the fuel injection valve to the combustion type and the engine temperature. It is about doing everything.

The method of the present invention includes a fuel*+ injection valve provided in the intake path;
The air-fuel mixture injected from the fuel injection valve and mixed with intake air is transported over a relatively long distance to the Enson combustion chamber.
The air-fuel ratio is controlled by feedback control to maintain the air-fuel ratio at the stoichiometric fuel-fuel ratio under conditions including at least the engine temperature being set at I [foot-F], and the air-fuel ratio is adjusted according to the engine operating state. Excessive (j or lean 1) from the stoichiometric air-fuel ratio
In order to alternatively execute the auto-run control that controls the frost level according to the rules, the above-mentioned feedback is applied within a certain period of time after the engine starts, which is determined depending on the engine start time or the engine temperature immediately after the start. It is characterized by prohibiting control.

According to the present invention, without detecting the hot water temperature on the wall surface of the intake passage from the fuel injection valve to the combustion chamber, it is possible to detect the engine cooling water temperature, engine oil temperature, or cylinder block temperature representing the engine temperature, and the temperature on the wall surface of the intake passage. By compensating for the difference in temperature, it is possible to prevent feedback control from being executed when the wall surface temperature of the air passageway is not sufficient to atomize the fuel. Therefore, it is possible to avoid the problem of adding the above-mentioned intake passage wall temperature detection sensor and the accompanying new wiring and control [11] without causing the problem of increasing the input terminals of the circuit, and moreover, causing unstable combustion. Feedback control is possible without any problems.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 shows an example of the configuration of an internal combustion engine for an automobile having an air-fuel ratio control device to which the present invention is applied. The air filter 1 is connected to a throttle body 5 via an inlet vibe 3. The throttle body 5 is provided with a fuel injection valve 7 on its upstream side, and an intake throttle valve 9 is provided downstream of the fuel injection valve 7 to adjust the intake air pressure in conjunction with an accelerator pedal (not shown). An intake pipe absolute pressure sensor 11 is provided downstream of the intake throttle valve 9 to measure the absolute pressure at that location. Further, there is a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9, an idle switch 4 that operates only when the intake throttle valve 9 is fully closed, and a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9. A power switch 6 that is turned on only when the temperature is 40 degrees or higher is added in conjunction with the intake throttle valve 9.

The throttle body 5 is connected to an intake manifold 13 having branch pipes connected to each cylinder of the engine,
The intake manifold 13 is provided with an intake temperature sensor 15 that measures the temperature of intake air therein. The bottom wall 13aK of the intake manifold 13 before branching is a live part 17 where engine cooling water is circulated and heats the air-fuel mixture.
is provided.

Reference numeral 19 designates a well-known engine body, which includes a piston 21, a cylinder 23, and a cylinder head 25, and a combustion chamber 27.
The air-fuel mixture sucked into the combustion chamber 27 via the intake valve 29 is ignited by the ignition plug 31 . A water jacket 33 is formed around the cylinder 23, and engine cooling water is circulated through the water jacket 33 to cool parts including the crank 23. An engine coolant temperature sensor 37 is provided on the outer wall of the cylinder block 35 to measure the temperature of the engine coolant in the water jacket 33.

An exhaust manifold 39 is connected to an exhaust port (not shown) of the cylinder head 25, and an exhaust manifold 39 is connected downstream thereof.
I is provided with an 02 sensor 41 that measures the residual oxygen concentration in the exhaust gas. The exhaust manifold 39 is connected to the exhaust pipe 45 through the three-way catalyst 43! :It is connected.

47 is a transmission connected to the engine body 19;
A vehicle speed sensor 49 is attached to measure the speed of the vehicle based on the rotational speed of the final output shaft.

Further, 51 is a key switch, 53 is an igniter, and 55 is a distributor. The distributor 55 is provided with a Ne sensor 57 that outputs a fl-on/off signal at every predetermined crank angle θ1, and the output signal is used to output a fl-on/off signal. A G sensor 59 is provided that outputs an on/off signal at every angle θ2 that is larger than the above angle θl, and the output signal is used to determine the cylinder Dead center position detection is performed.

Further, 60 indicates a battery.

The control circuit 61 includes a valve opening position sensor 2, an idle switch 4, a power switch 6, an intake pressure sensor 11, an intake pressure sensor 15, an engine coolant temperature sensor 37.02 sensor 4
1. Vehicle speed sensor 49, key switch 51, Ne sensor 5
7, are connected to the G sensor 59 and the battery 60, respectively, and receive a valve opening signal Sl, an idle signal S2, a power signal S3, an intake pressure signal S4, an intake temperature signal S5, a water temperature signal S6. Air-fuel ratio signal S7. Vehicle speed signal S8, start signal S
9. The engine rotational speed signal StO, the cylinder discrimination signal Sll, and the battery voltage 1 stroke number 814 are input from each sensor. The control circuit 61 is also connected to the fuel injection valve 7 and the igniter 53, and outputs a fuel injection signal 812 and an ignition signal Sla based on a predetermined operation n.

As shown in FIG. 2, the control circuit 61 includes a central processing unit (CPU) 61a that controls each rod device, and a memory IJ (ROM) in which the numbers 1 and 2 of each arm are written in advance. 6'l b, Random access memory in which numerical values and flags of the calculation process are stored in a predetermined area 7'J (RAM) 61c, 'A/D converter (ADC) that converts analog signals into digital signals
) 61d, input/output interface (I /
O) 61 e, Backup memory (BU-R
AM) 61f, and a path line 61g to which each of these devices is connected. A program to be described later is preloaded into the ROM 61b.

In the engine described above, fuel is injected according to the flowchart shown in FIG. Looking at Figure 3,
In step pt vc, the engine speed Ne is read based on the engine speed signal Sl, which is a base position signal, and the intake pipe pressure PM is read based on the intake pipe pressure signal S4.
Incorporate. In step P2, (b) the basic injection time 1'P is determined from the map shown in FIG. Execute to obtain the corrected injection time τ.

Here, the calculation at the corrected injection time by the correction calculation process of hand 1 [I P 3 will be described in detail.

The injection time is generally determined by the following formula.

r = TP X FWLX F”AF X FTHA
X (FTC 10 FPO + FSE 10 F LEAN)...
(1) Where: TP = Basic fuel injection time FWL - Warm-up increase coefficient F A 11 - Air-fuel ratio feedback correction coefficient FTC = Transient air-fuel ratio correction coefficient FTHA - Intake temperature correction coefficient PSE = Start Post-increase coefficient FPO=power increase coefficient F'LEAN=lean correction coefficient Therefore, each coefficient is calculated based on the calculation routine shown in FIG. 5, and the injection time τ is determined.

That is, the hand @ptl executes the calculation process of the warm-up increase coefficient pFWL, the hand +1iiP12 executes the calculation process of the air-fuel ratio feedback correction coefficient FAF, and step P13
In step P14, the calculation process of the transient air-fuel ratio correction coefficient FTC is executed, and in step P14, the power increase maintenance 'e! The calculation process of FPO is executed, the calculation process of the post-start increase coefficient PSE is executed in step P15, the calculation process of the lean correction coefficient FLEAN is executed in step P16, and the calculation process of the intake temperature correction coefficient F T HA is executed in step P17.
k is determined, and then the above equation (1) is calculated in step 11jkPts, and the process returns to step P4 in FIG.

In step P4, the corrected injection time τ is corrected according to the battery voltage to obtain the final injection time Fτ, and if the injection timing is determined in step P5, the injection time corresponding to the final injection time Fτ is obtained from the fuel injection valve 7 at the timing of step P6. Inject fuel for the required amount of time.

Before explaining each calculation process of the hands 11fiPtt to P17, an example of the calculation process of the starting temperature correction value ADD will be described.

The starting temperature correction value ADD is based on the temperature difference between the engine cooling water temperature or engine oil temperature, etc., which substitutes for the engine temperature, and the wall temperature of the intake passage, for example, the intake manifold, from the fuel valve to the combustion chamber. This is to compensate for the temperature difference until the engine is sufficiently warmed up in extremely cold weather.

At the timing specified by the Agency, the correction value ADD shown in 6th ['21]
When the arithmetic processing routine is started, first in step P21 it is determined whether the engine is being started. This determination is performed based on the engine rotational speed signal SIO. If an affirmative determination is made, that is, if starting is in progress, then in step P22, the engine starting temperature and the starting intake air temperature THA are read based on the intake air temperature signal S5 at that time. Next, in step p23, from the map of the correction value ADD and the intake air temperature THA as shown in FIG. Load correction 1+M, A D i).JV P24
In step P25, it is determined whether or not a fixed period for attenuating all of the read correction values ADD by a predetermined number α has elapsed. Find (ADD-α) and store the result as a new correction ADD in the storage area of H1 bar.Next iteration, Q
= order P 26 vc, supplement 41! If LA D D is smaller than Rei, it will be decided that it is better than Rei, and it will be rejected.
f) At '27, the correction value ADD'i is set to zero and "r'ADDm calculation runan?! - ends. If the judgment is negative, + order P27 is skipped and the ADD calculation runan is once terminated."

When this routine is started after the engine has been started, a negative judgment is made in hand 1@P21, +, l1lt
P2' 4 VC jumps, and if the procedure is affirmed, +order P25 to P27 are executed, and if it is negative, +order P25 to P27 are skipped, and the series of procedures ends.

As mentioned above, the starting warm sleeve positive value ADD, which is calculated based on the intake air temperature THA at the time of engine starting, is shown in Fig. 8.
As shown in FIG.

Next, the calculation process of the air-fuel ratio feedback correction coefficient p''AF executed in the bow "11Jp+2" will be explained with reference to FIG.

An example of the calculation process of the feedback correction coefficient FAF is shown in the ninth section.
As shown in the figure. Step P31 In VC, it is determined whether a feedback condition is satisfied.

For example, when the engine is not in the starting state, the start-up cover increase coefficient FSE is zero, the engine temperature is present, the power production increase coefficient 1FPo is zero, and the lean correction coefficient F' L E A N is 1.0, the feedback control is performed. The following conditions hold true. If the conditions for feedback control are not satisfied, the feedback correction coefficient F A F 1c1. Feedback as O''1llll (preventing t[41 from being executed,
This process ends. If the conditions are met, proceed to step p33
Proceed to.

At +11iap33, it is determined whether the starting warm sleeve positive value ADD obtained as described above is smaller than a predetermined number, for example 8, and if it is smaller, the process proceeds to step P34.

In step P34, the air-fuel ratio signal S7 is read. 1 hand P3
5, the voltage value of the air-fuel ratio signal S7 is compared with the reference value REF2, and if the voltage value S7 is larger than the reference value REF2, it is determined that the air-fuel ratio is too rich, and the air-fuel ratio is set to the lean side. Perform the steps. In other words, in order P 36, the correction coefficient It
' Judge whether AF is smaller than 1.0, and if the judgment is negative, move 1 [P37Ti, LIE coefficient F'
If A F fl is 0, and it is determined that ``W'' is determined, proceed to step P3.
In step 8, the result of (1,0-β) is set as the correction coefficient FAF, and the FAF calculation processing procedure is completed.

On the other hand, hand +1* P 3 s-c number S7 is 4M (I
If it is smaller than Rz F2, it is determined that the air-fuel ratio is lean, and a procedure to make the air-fuel ratio rich is executed. That is, it is determined in step P39 whether the correction coefficient FAF is greater than 1.0, and if the determination is negative, step PjO
The correction coefficient FAF' (1, 0 is set. If the judgment is affirmative, the result of (1, 0+β) is set as the correction coefficient FAF at P41, and the procedure of the F'AF calculation process ends.

Furthermore, if the signal S7 is equal to the reference value REF2 in step P35, the correction coefficient FAF is set to 1.0 in step P42, and this process ends.

Note that the reason why the correction coefficient FAF is set to 1.0 when negative judgments are made in steps P36 and F39 is based on the air-fuel ratio signal S.
7 changes from below the reference value to above the reference value, and from above the reference value to below the reference value, and when each change occurs, the correction coefficient FAF is set to 10 once.

Further, β in hands ll1iP38 and F41 is a predetermined value.

The feedback correction coefficient F AF obtained by this calculation procedure is shown in FIG. 10 together with the air-fuel ratio signal S7.

Referring to this figure, Shingetsu S7 is the reference value RE t' 2
When the signal S7 becomes larger or smaller than the reference value REF2, the correction coefficient FAF is first skipped to 1.0, and then, if the signal S7 is higher than the reference value, a predetermined number β is sequentially subtracted, and the signal S7 If is greater than or equal to the reference value, the predetermined number β is
is added.

Next, the lean correction coefficient FLEA executed in step pts
Refer to FIG. 11 for the calculation process of N.

I will explain.

When the program shown in FIG. 11 is started, first step P
At step 5t, it is determined whether the mode condition XMODE is satisfied or not. This condition is satisfied when the engine is not in the starting state, is not in the tank volume after starting, and is not in the engine output increase state, and the starting state is determined based on the start signal S9 and the engine rotation speed signal SIO, Whether or not the tank is being refilled is determined based on the post-starting increase coefficient FSg stored in a predetermined storage area, and whether or not the output is being increased is determined based on the power increase coefficient FSg stored in a predetermined storage area. 6F
It is determined based on p and o. If this condition is satisfied, the process proceeds to step 1@P52, where it is determined whether the starting temperature correction value ADD obtained as described above is smaller than a predetermined number, for example 8. If it is smaller, the process proceeds to step P53. Step P5
In step 3, it is determined whether lean control is currently being performed. This judgment is made based on whether or not the value of the correction coefficient FLEAN stored in the RM-borrowed area is 1.0.
If it is 1 or 0, it is determined that lean control is not in progress but feedback control is in progress to control the air-fuel ratio to the stoichiometric air-fuel ratio.

If it is determined that feedback control is in progress, the engine coolant temperature THW is determined to be 75°C or higher in step P54, and the intake pipe pressure PM is determined to be 450 ml in step P55.
Only when it is determined that the HP is lower than the HP, the process proceeds to step P56 to execute lean control.

If lean control is in progress, proceed to step P54', and judge whether the engine cooling water temperature THW is 65°C or higher.If the judgment is affirmative, proceed to step P55', where the intake pipe pressure PM is 65°C or higher.
50 Determine whether or not the dragon is below Hri.

If it is determined that the intake pipe pressure PM is 650 nmHP or less, in other words, the engine is not under high load, the process proceeds to step P567. In step P56, the rate of change ΔN of the engine speed Ne is determined.
e1500 ms is 2 of the engine speed Ne at that time.
Determine whether or not it is within one cent.

If an affirmative judgment is made, the above-mentioned move flX is performed in step P57.
Similarly to P53, it is determined whether lean control is being performed. If lean control is not in progress, proceed to step P58;
The rate of change of the vehicle speed SPD ΔSPD/2sec is
For example, it is determined whether or not the distance is less than or equal to a determination value of 0.7 Km. If lean control is in progress, the rate of change of vehicle speed 1fsPD △5PD72sec is determined by step P58'.
The judgment value is, for example, 5 km or less.

In ζ, depending on the poor behavior of lean control, step P54,
The reason why each determination value is changed like P54', P55, P2S5, P58, and P2S5 is to prevent hunting.

If an affirmative determination is made in step P58 or P2S5, step P,
59, it is determined whether the intake throttle valve 9 is below a determination value, for example 30 degrees. If affirmative judgment is made, step P6
0, and the idle signal S indicates whether the intake throttle valve 9 is fully closed or not.
Judgment is made by turning on/off 2. If the idle signal S2 is on, in other words, the intake throttle valve 9 is fully closed, the lean correction coefficient fiFLEAN is set to a predetermined value, for example 0.92, in step Pal, so that lean control is performed. Finish the procedure.

On the other hand, if it is determined in step PFIO that the intake throttle valve 9 is not fully closed, the RO
From the map of the lying air V pressure PM and the IJ-ton correction coefficient FLEAN as shown in FIG. 12 stored in the M61b, the lean correction coefficient FLEAN is determined based on the intake pipe pressure PM including the bladder Store this value in register A and proceed to move +1 [1j P 63.

P+1@I) At 63, it is determined whether the engine speed Ne is equal to or higher than a predetermined value, for example, 2500 rpm. -J-
At tlEIP64, the value stored in register A is increased by A%Ne/2500 to shift the air-fuel ratio to the fully enriched side.

Next, in step P65, it is determined whether the increased and newly stored value in register AVc is greater than 1.0, and if so, in step P66, the contents of register A are set to 1.0.
Then, proceed to step P67. Move 1 [P63 If a negative determination is made in PO2, also proceed to Move 1@1P67.

+j-P67, steps P63 and P6 described in Ai1
It is determined whether lean control is in progress in the same way as in step P68, and if it is not in lean control 1#, that is, if feedback control is in progress, the running speed SPD of the vehicle is determined in step P68.
exceeds a predetermined value, for example, 10 km/h. If the determination is affirmative, the process proceeds to step P69; if the determination is negative, the lean correction coefficient FLEAN is set in step p7o so as not to execute lean control. 1.0 and this process ends. On the other hand, if lean control is in progress in step P67, hand j-pupil P6.8 is skipped and the process proceeds to step P69.

In step P69, the lean correction coefficient FLEAN is stored in the RAM61 CLDP)T constant area.

The value is set as the value of register A, and this process ends.

Each of the above steps P61, P62, P64, P64', PO2
, P65', P66, P68, P68', P69, if a negative determination is made, proceed to step P71, and the RAM61
The predetermined area correction coefficient FLEAN in C is set to 1.0, and this process ends. In this case, line control is not executed.

Note that the warm-up increase coefficient FWL of hand JdpH in FIG.
Based on C, water temperature THW is low and engine speed &ll! N
The smaller e is, the larger the value obtained, and the basic fuel injection time TP is corrected to increase. The transient nitrate-fuel ratio correction coefficient FTC in step P13 is determined by calculating the change in intake pipe pressure tiifc based on the intake pressure signal S4 from the intake pipe pressure sensor 11, and calculating the change amount based on the amount of change. If a larger value is obtained, the basic fuel injection time TP is corrected by increasing the amount.

Furthermore, the power increase coefficient FPO of + order P14 is, for example,
The engine cooling water temperature TI (W is 1.5 when W is 20 degrees Celsius or higher, the rotational speed Ne is 350 Orpm or more and 4000 rpm or less, and the intake throttle valve 9 is opened 40 degrees or more; otherwise it is zero) .The post-start increase coefficient PSE in step P15 is, for example, based on the engine water temperature TH immediately after starting.
It is obtained by selecting an initial value according to W and attenuating that value at a predetermined period. In addition, it is 1, step 1) l The intake temperature correction coefficient FTHA of 7 compensates for the density of the intake air, which varies depending on the temperature f? This is done to increase the intake temperature T.
It is obtained by adding a predetermined value k to the digital ff[ of the HA.

Note that, except for the feedback control that maintains the air-fuel ratio at the stoichiometric air-fuel ratio using the feedback correction coefficient FAF obtained in step 1.2, all control is open-loop control.

As described above, in this embodiment, the starting temperature correction value, which is selected according to the engine temperature at the time of engine starting and is reduced as LU during the elapsed time after engine starting, is set to be larger than the predetermined value 8. The air-fuel ratio feedback control j was prohibited and the engine was operated with air-fuel ratio maple loop control7. Here, the correction value ADD is monotonically attenuated according to the elapsed time after the engine start, and the correction value A'D for the engine start width shown in FIG. 7 is adjusted according to the engine specifications.
A map of D and a predetermined damping value α are determined, so that when the wall temperature of the intake manifold reaches a temperature sufficient to atomize the fuel, the value of the correction value ADD is set to a value close to zero or zero. It will become as follows. In this embodiment, if the correction value A D l) is smaller than 8, it is assumed that the wall surface temperature of the intake manifold has reached the above temperature.

In the above embodiment, the temperature difference between the intake passage wall surface temperature and the engine temperature is compensated for by subtracting a predetermined number α from the starting temperature correction value ADD selected according to the engine temperature at the time of engine starting. However, the engine starts (fi) JtM
Initialize the counter with a value corresponding to 17c so that it counts down every Nr regular cycle, or operate the timer at the same time as the engine starts, and end the time measurement when the time corresponding to the engine start width has elapsed. However, the above compensation is possible.

In addition, the starting temperature correction value ADD is defined as the intake temperature T at the time of engine starting.
Although the selection is made based on the HAVC, the selection may be made based on the engine cooling water temperature THW, engine oil temperature, or cylinder block temperature. In history,
Correction value AD based on engine temperature immediately after engine startup
You may choose D.

Figure 1 is a configuration diagram showing an example of an internal combustion engine for automobiles in which the present invention is fully applied, Figure 2 is a detailed block diagram of an example of its control circuit, and Figure 3 is a detailed block diagram of an example of the control circuit. A flowchart showing an example of the procedure for IJA error, Fig. 4 is a diagram showing an example of a map for reading out the basic fuel injection time TP from the engine speed Ne and intake pipe pressure PM, and Fig. 5 is a diagram showing an example of the corrected injection time. FIG. 6 is a flowchart showing an example of a procedure for elongating the temperature. FIG. 6 is a flowchart showing an example of a procedure for determining the starting temperature correction value ADD.
The figure is a graph showing the relationship Qk between the intake air temperature 1' HA at startup and the starting temperature correction value ADD, and Figure 8 shows the starting temperature correction value ADD.
FIG. 9 is a diagram showing the time decay of the feedback correction coefficient FAF.
Figure 0 is a time chart showing changes over time in the air-fuel ratio signal S7 and the correction coefficient pFAF, and Figure 11 is the horizontal correction coefficient FL.
Flowchart showing an example of EAN calculation processing, 12th
The figure shows the intake pipe pressure P M correction coefficient if・'LEAN
It is a graph showing the relationship between

7... Injection valve, 9... Intake throttle square, 11... Intake pipe pressure sensor, 13... Intake manifold, 15
... Intake temperature sensor, 17... Riser section, 19... Engine body, 27... Combustion chamber, 33... Walk jacket, 37... Engine cooling water temperature sensor, 41...
...02 sensor, 49...vehicle speed sensor, 51...key switch, 53...igniter, 55...distributor, 57...bow Qe sensor, 59...G sensor, 61...control circuit.

Agent Tatsuyuki Unuma (1 other person) Figure 2 514 5/! :ibsko54Sl Figure 3 −3( Figure 5 Figure 6 Figure 7 Figure 8 OYfTvIt→

Claims (1)

[Scope of claims] Feedback control that maintains the air-fuel ratio at the stoichiometric air-fuel ratio under conditions that include at least the engine temperature being above a predetermined temperature, and a feedback control that maintains the air-fuel ratio at the stoichiometric air-fuel ratio depending on the engine operating condition. Open loop controlled by?
In order to alternatively execute the l+ control, the feedback control is prohibited within a certain period of time after the engine is started, which is determined according to the engine temperature at or immediately after the engine is started. Air-fuel ratio control method for internal combustion engines. (2. In the method set forth in claim 1, an initial value of the starting temperature correction value is set based on the engine temperature at the time of engine starting, and the starting temperature correction value is set according to the elapsed time after the engine starting. 1. An air-fuel ratio control method for an internal combustion engine, characterized in that the feedback control is inhibited when the monotonically decreased starting temperature correction value is equal to or higher than a predetermined value.