JPH0861199A - Control device of internal combustion engine - Google Patents

Abstract

PURPOSE: To excellently activate a catalyst to the maximum extent in its early stages, and reduce discharge of an exhaust harmful component, without incurring hunting or the like by fixing an air-fuel ratio to a prescribed air-fuel ratio when it becomes leaner than a prescribed lean air-fuel ratio by a first feedback control means, and changing the ignition timing by a second feedback control means. CONSTITUTION: A control device B of an internal combustion engine is provided with an engine stability detecting means A to detect engine stability, and makes an air fuel ratio of an engine sucking air-fuel mixture lean within a prescribed engine stability limit in a prescribed time after an engine is started. When a present air-fuel ratio is richer than a prescribed lean air fuel ratio, the ignition timing is fixed to the prescribed ignition timing and the air-fuel ratio is changed by a first feedback control means C so that prescribed engine stability is obtained. When it becomes leaner than the prescribed lean air-fuel ratio by the control means C, the air-fuel ratio is fixed to the prescribed lean air-fuel ratio and the ignition timing is changed by a second feedback control means D so that the prescribed engine stability is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, to a lean air-fuel ratio (lean air-fuel ratio) after starting, while keeping the engine stability limit within a predetermined range. ) Related to the improvement of the control device.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, in order to reduce the early activation of the catalyst and the emission of exhaust harmful components (particularly unburned fuel HC), the engine intake is performed within a predetermined time after starting. There is disclosed an air-fuel ratio control device that makes the air-fuel ratio of the air-fuel mixture lean (makes the air-fuel ratio leaner, for example, sets intake air weight / fuel weight (A / F = λ) = 18).

However, when the air-fuel ratio is made lean in this way, if ignition control is performed at the same ignition timing as when operating near the stoichiometric air-fuel ratio, ignition is performed at an ignition timing that greatly deviates from the required ignition timing at the time of leaning. Therefore, the stability of the engine is impaired. Therefore, for example, Japanese Patent Laid-Open No. 61-
According to Japanese Patent No. 258954, even during lean control, M
In order to obtain BT [Minimum spark advance for Best Torque], the ignition timing is changed according to the air-fuel ratio to improve the engine stability.

[0004]

By the way, in the lean control, even if the engine individual difference, the change over time, or the change in the outside air condition, the lean is maximized within the engine stability limit and the catalyst is activated early. Based on the detection result of engine stability (combustion fluctuation, rotation fluctuation, etc.), the control amount of the air-fuel ratio (for example, fuel supply amount or intake Feedback control technology to increase / decrease the air flow rate) has been proposed,
In this case, conventionally, the above-mentioned JP-A-61-2589 is used.
Based on the technique disclosed in Japanese Patent Publication No. 54-54, the ignition timing was changed in accordance with the air-fuel ratio that was increased / decreased during the feedback control. Therefore, as shown in FIG. 10, the air-fuel ratio change amount (Δ
In the range where the required ignition timing change amount (ΔT) is large with respect to λ) (in the figure or), the required ignition timing changes significantly with a slight change in the air-fuel ratio, causing hunting and the like to limit engine stability. Within that, it became difficult to maintain a good condition, and there was a problem that the engine drivability deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and the lean control after engine start is optimized to satisfactorily prevent hunting and the like.
An object of the present invention is to provide a control device for an internal combustion engine, which is capable of maximally activating the catalyst and reducing the emission of exhaust gas harmful components within the engine stability limit. It is also an object of the present invention to improve the accuracy of the control.

[0006]

Therefore, in the control device for an internal combustion engine according to the invention described in claim 1, as shown in FIG. 1, an engine stability detecting means A for detecting the engine stability is provided. In a control device B for an internal combustion engine, which is configured to lean the air-fuel ratio of the engine intake air-fuel mixture within a predetermined engine stability limit within a predetermined time after the engine is started, the current air-fuel ratio is richer than a predetermined lean air-fuel ratio. In this case, the first feedback control means C for changing the air-fuel ratio by fixing the ignition timing to the predetermined ignition timing so as to obtain the predetermined engine stability, and the air-fuel ratio by the first feedback control means C. When the air-fuel ratio becomes leaner than the predetermined lean air-fuel ratio due to the change of, the air-fuel ratio is fixed to the predetermined lean air-fuel ratio and the ignition timing is changed so that a predetermined engine stability is obtained. Let A second feedback control means D,
It was composed including.

According to the second aspect of the present invention, as indicated by the broken line in FIG.
However, if the predetermined engine stability cannot be obtained even if the ignition timing is advanced to a predetermined value or more, the feedback control of the ignition timing by the second feedback control means D is stopped,
The sixth feedback control means E for changing the air-fuel ratio is provided so as to obtain a predetermined engine stability.

According to the third aspect of the present invention, as shown in FIG. 2, the engine stability detecting means A for detecting the engine stability is provided, and within a predetermined time after engine start within a predetermined engine stability limit, In the control device B for the internal combustion engine, which is designed to make the air-fuel ratio of the engine intake air-fuel mixture lean, when the current air-fuel ratio is richer than the first target lean air-fuel ratio, a predetermined engine stability is obtained. A third feedback control means F for fixing the ignition timing to a predetermined ignition timing to change the air-fuel ratio, and a change in the air-fuel ratio by the third feedback control means F causes the air-fuel ratio to become the first target lean air-fuel ratio. , And the second target lean air-fuel ratio which is set to the lean side, the control amount of the air-fuel ratio and the ignition timing are simultaneously adjusted so that a predetermined engine stability is obtained. 4th change And Dobakku control unit G, the fourth
By the change of the air-fuel ratio by the feedback control means G,
When the air-fuel ratio becomes leaner than the second target lean air-fuel ratio, the ignition timing is changed by fixing the air-fuel ratio to the second target lean air-fuel ratio so that a predetermined engine stability is obtained. And 5 feedback control means H.

According to the fourth aspect of the present invention, as shown by the broken line in FIG. 2, even if the fourth feedback control means F advances the ignition timing beyond a predetermined value, a predetermined engine stability cannot be obtained. In this case, the seventh feedback control means I for stopping the feedback control of the air-fuel ratio and the ignition timing by the fourth feedback control means F and changing the air-fuel ratio so as to obtain a predetermined engine stability is provided. .

In a fifth aspect of the invention, when the fifth feedback control means G cannot advance a predetermined engine stability even if the ignition timing is advanced to a predetermined value or more, the fifth feedback control means G is used.
Eighth feedback control means J is provided which stops feedback control of only the ignition timing by the feedback control means G and changes at least the air-fuel ratio so as to obtain a predetermined engine stability.

[0011]

The invention according to claim 1 having the above-mentioned structure,
When the air-fuel ratio of the engine intake air-fuel mixture is made lean to the maximum within the predetermined time after engine start within the predetermined engine stability limit, while eliminating variations in engine individual differences and operating conditions, the current air-fuel ratio is When the air-fuel ratio is richer than the predetermined lean air-fuel ratio, the first feedback control means fixes the ignition timing to the predetermined ignition timing and changes only the air-fuel ratio to obtain the predetermined engine stability. If the predetermined engine stability cannot be obtained even when the air-fuel ratio becomes leaner than the predetermined lean air-fuel ratio due to the change in the air-fuel ratio by the first feedback control means, the second feedback control means The air-fuel ratio is fixed to the predetermined lean air-fuel ratio and the ignition timing is changed to obtain a predetermined engine stability. Therefore, unlike the conventional case, the catalyst can be satisfactorily eliminated while avoiding hunting or the like caused by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit, while eliminating the engine individual difference and the variation in the operating conditions. The early activation of the exhaust gas and the reduction of the emission of harmful components of the exhaust gas can be achieved.

According to a second aspect of the invention, in the case of the first aspect of the invention, when a predetermined engine stability is obtained by the second feedback control means, thereafter, atmospheric conditions and other factors (for example, The engine stability limit changes due to changes in fuel temperature and specific gravity, etc., and it is necessary to advance the ignition timing more than necessary (for example, to the extent that it greatly deviates from MBT and fuel consumption, drivability, and exhaust characteristics deteriorate). When it occurs, the ignition timing is fixed to a predetermined value and the air-fuel ratio is corrected to the rich side. Therefore, it is possible to reliably prevent the fuel efficiency, drivability, and exhaust characteristics from being greatly deviated from the MBT and being extremely deteriorated.

According to the third aspect of the present invention, within a predetermined time after the engine is started, within a predetermined engine stability limit, the air-fuel ratio of the engine intake air-fuel mixture is maximized while eliminating differences in individual engines and variations in operating conditions. If the present lean air-fuel ratio is richer than the first target lean air-fuel ratio in the case of the lean limit, the third feedback control means fixes the ignition timing to a predetermined ignition timing and changes only the air-fuel ratio. While the predetermined engine stability is not obtained by this feedback control while the predetermined engine stability is obtained by the fourth control.
The air-fuel ratio and the ignition timing are simultaneously changed by the feedback control means until the second target lean air-fuel ratio is reached, so that a predetermined engine stability is obtained, and further, by the feedback control, the predetermined engine is also achieved. When the stability cannot be obtained, the fifth feedback control means fixes the air-fuel ratio to the second target lean air-fuel ratio and changes only the ignition timing to obtain the desired engine stability. Therefore, as in the conventional case, without causing control hunting by simultaneously changing the ignition timing and the air-fuel ratio at the engine stability limit, it is possible to satisfactorily eliminate variations between engine individual differences and operating conditions, etc., It becomes possible to early activate the catalyst and reduce the emission of harmful components in the exhaust gas.

Further, the fourth feedback control means makes it possible to change the air-fuel ratio and the ignition timing at the same time in a region where hunting or the like does not occur even if the air-fuel ratio and the ignition timing are changed at the same time. Therefore, claim 1
As compared with the invention described in (1), it becomes possible to converge the engine stability within a predetermined stability limit more quickly, reduce exhaust harmful components by increasing leanness, increase exhaust oxygen concentration, and delay ignition timing. It is possible to increase the exhaust temperature due to the corners at the same time, so that it is possible to more effectively reduce the emission amount of exhaust harmful components and quickly activate the three-way catalyst.

According to the invention described in claim 4, in the invention described in claim 3, when the predetermined engine stability is obtained by the fourth feedback control means, thereafter, atmospheric conditions and other factors (for example, The engine stability limit changes due to changes in fuel temperature and specific gravity, etc., and it is necessary to advance the ignition timing more than necessary (for example, to the extent that it greatly deviates from MBT and fuel consumption, drivability, and exhaust characteristics deteriorate). When it occurs, the ignition timing is fixed to a predetermined value and the air-fuel ratio is corrected to the rich side. Therefore, it is possible to reliably prevent the fuel efficiency, drivability, and exhaust characteristics from being greatly deviated from the MBT and being extremely deteriorated.

According to the invention described in claim 5, in the invention described in claim 3 (or claim 4), when the predetermined engine stability is obtained by the fifth feedback control means, the atmospheric condition is then satisfied. And other factors (for example, changes in fuel temperature and specific gravity) change the engine stability limit, and the ignition timing is unnecessarily increased (for example, the fuel efficiency, drivability, and exhaust characteristics deteriorate as the MBT largely deviates. ) When it becomes necessary to advance the ignition timing, the ignition timing is fixed to a predetermined value and the air-fuel ratio is corrected to the rich side. Therefore, MB
It is possible to reliably prevent the fuel efficiency, drivability, and exhaust characteristics from deviating significantly from T and being extremely deteriorated.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3 showing the first embodiment of the present invention, an intake air is interlocked with an air flow meter 3 for detecting an intake air flow rate Q of intake air sucked through an air cleaner in an intake passage 2 of an engine 1 and an accelerator pedal. A throttle valve 4 for controlling the flow rate Q is provided. An electromagnetic fuel injection valve 6 arranged to inject and supply fuel toward an intake valve (not shown) is provided for each cylinder in a manifold portion 5 downstream of the throttle valve 4.

The fuel injection valve 6 is opened and driven by an injection pulse signal from a control unit 50, which will be described later. The fuel injection valve 6 is pressure-fed by a fuel pump (not shown) and a predetermined amount of fuel controlled by a pressure regulator is injected and supplied. . The air-fuel mixture sucked into the combustion chamber is ignited and burned by the ignition plug 7 provided facing the combustion chamber of each cylinder at an ignition timing set by the control unit 50.

Further, a combustion pressure sensor 8 for detecting the in-cylinder pressure (combustion pressure) of each cylinder is provided, and the combustion pressure signal from the combustion pressure sensor 8 is input to the control unit 50, and the control unit 50 Based on the combustion pressure signal, it is possible to detect the combustion fluctuation of each cylinder and the like to detect the stability of the engine. In this example,
A so-called washer-type combustion pressure sensor in which the combustion pressure sensor 8 is embedded in the washer portion of the spark plug 7 is used, but of course, the combustion pressure sensor faces the combustion chamber of each cylinder separately from the spark plug 7. You may provide it.

In the exhaust passage 9 of the engine 1, an oxygen sensor 10 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas is provided in the manifold collecting portion, and the theoretical sensor 10 is provided downstream of the oxygen sensor 10. Maximum C in the exhaust near the fuel ratio
O, oxidation of HC, and exhibit the reducing action of NO _X, is provided a three-way catalyst 11 as an exhaust gas purifying catalyst for purifying exhaust.

The oxygen sensor 10 outputs a voltage according to the oxygen concentration in the exhaust gas and compares this voltage with a predetermined slice level SL (for example, equivalent to the theoretical air-fuel ratio), A rich / lean determination of the air-fuel ratio can be performed. By the way, the control unit 50 is composed of a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors, and performs various controls as described later. Is supposed to do.
That is, in this embodiment, the function as the first to eighth feedback control means of the present invention is provided by the control unit 50 as software.

The various sensors include the combustion pressure sensor 8, the oxygen sensor 10 and the air flow meter 3 described above, and the crank angle sensor 13 is provided on the crank shaft or the cam shaft of the engine 1. The engine rotation speed Ne is detected by counting the crank unit angle signal output from the crank angle sensor 12 in synchronization with the engine rotation for a certain period of time or measuring the cycle of the crank reference angle signal. .

A water temperature sensor 13 is provided facing the cooling jacket of the engine 1 so that the cooling water temperature Tw can be detected. Below, control unit 50
The calculation routine of the fuel injection amount performed by the above will be described with reference to the flowchart of FIG. In step (indicated as S in the figure. The same applies hereinafter) 1, the air flow meter 3 is used.
From the intake air flow rate Q obtained from the voltage signal from the engine and the engine speed Ne obtained from the signal from the crank angle sensor 12, from the basic fuel injection pulse width (corresponding to the fuel injection amount) Tp = k × Q / Ne ( k is a constant).

In step 2, increase in high load / high speed range
Air-fuel ratio correction coefficient (K _MR+ K_TMR), Low
Water temperature correction coefficient (K
w), starting and post-starting amount increase correction coefficient (Kas),
Various correction factors COEF (1 + K_MR+ K_TMR＋ Kw ＋ Kas
+ ...) is set. In step 3, the oxygen sensor 10
Of the air-fuel ratio based on the rich / lean inversion signal of
Air-fuel ratio feed-back set in feedback control
The clock correction coefficient α is read.

The above air-fuel ratio feedback correction coefficient α
In order to correct the product error of the fuel injection valve 6, etc., except in a predetermined case (for example, during lean control, at startup, before activation of oxygen sensor, at high load, at acceleration / deceleration, etc.), Based on the rich / lean inversion output of the oxygen sensor 10, proportional integral (P
I) The amount is increased / decreased by the control, whereby the air-fuel ratio of the air-fuel mixture for combustion is feedback-controlled near the target air-fuel ratio (theoretical air-fuel ratio). During the lean control, the air-fuel ratio feedback correction coefficient α during the previous operation is
The average value of C is clamped as α, and the lean control is performed in a state where the product error of the fuel injection valve 6 is eliminated. However, if the learning function of the so-called air-fuel ratio feedback correction coefficient α is provided, The so-called learning value K is multiplied by TI described later to obtain α
May be clamped to a predetermined value (eg 1.0). Even if the learning function is not provided, the value may be clamped to an appropriate value (for example, 1.0).

In step 4, the lean target value C determined from the operating state (eg, the rotation speed Ne, the load Tp, the water temperature, etc.) is obtained by searching a table or the like. When the lean control is not being performed, the C is set to 0. Step 5
Then, the voltage correction amount TS for correcting the valve opening time of the injection valve 6 due to the battery voltage drop is set.

In step 6, the final effective fuel injection pulse width TI = Tp * (COEF- [C + A]) * α + T
Calculate s. The A is a lean correction coefficient that is increased or decreased in the feedback control for keeping the combustion fluctuation (engine stability) during the lean control within a predetermined range, as described later. Therefore, when the lean control is not being performed, the A is set to 0.

In step 7, the effective fuel injection pulse width T
I is sent to the fuel injection valve 6 as a drive pulse signal to perform fuel injection. Next, a routine for setting the ignition timing during the lean control performed by the control unit 50 will be described with reference to the flowchart of FIG.

In step 11, the basic ignition timing (Tbase) during lean control, which is determined from the engine speed (Ne) and the engine load (for example, Tp), is set by referring to a table or the like. The basic ignition timing (Tbase) is a value (advance side) with a margin up to the engine stability limit with respect to changes in the air-fuel ratio.
Is set to In step 12, the ignition timing correction amount (Tad) for correcting the ignition timing in accordance with the cooling water temperature Tw, etc.
Set j).

In step 13, the ignition timing correction amount (FBADV) set in the feedback control for keeping the engine stability during the lean control performed within the predetermined range according to the flowchart of FIG. 6 (or FIG. 7) described later.
Read. In step 14, the ignition timing (Tign)
Determined as follows. Tign = Tbase + Tadj-FBADV That is, when the later-described flowchart of FIG. 6 (or FIG. 7) is executed, the ignition timing is gradually changed by the FBADV so that the ignition timing can be converged to a predetermined engine stability. It has become.

In step 15, the ignition timing Tign is set to
Send it to a power transistor (not shown) as an ignition signal,
Ignition is performed by the spark plug 7. Next, the feedback control performed by the control unit 50 so that the engine stability is within the predetermined range during the lean control will be described with reference to the flowchart of FIG. 6 with reference to FIG. 8.

In step 21, it is determined whether or not the permission condition for the feedback control during lean control is satisfied. The determination is made based on that the cooling water temperature Tw is within a predetermined range after a predetermined time has elapsed after the start (for example, after the start and the post-start increase control). This is because when the cooling water temperature Tw is lower than a predetermined value (at an extremely low temperature, etc.), if the engine is made lean, misfires and stalls are likely to occur and stable engine operation may not be ensured, so the air-fuel ratio is controlled to the stoichiometric or rich side. Therefore, it is necessary to prevent lean control. Further, at the time of restarting when the cooling water temperature Tw is relatively high, the three-way catalyst 11 is in a state of being easily activated. Therefore, even if the lean control is not performed, the theoretical space based on the signal of the oxygen sensor 10 is immediately obtained after restarting. This is because the exhaust gas can be sufficiently purified by the air-fuel ratio feedback control to the vicinity of the fuel ratio.

Therefore, if YES, the routine proceeds to step 22, and if NO, the routine proceeds to steps 33 and 34, where the lean correction coefficient (A) and the ignition timing correction amount (FBADV) are set to 0, and this flow is completed. To finish. In step 22, the present engine stability (combustion stability) (B) is detected. The stability (B) can be detected from the fluctuation amount of the combustion pressure signal of the combustion pressure sensor 10 or the fluctuation amount of the indicated mean effective pressure. Although the detection accuracy is reduced, the engine stability (B) may be detected based on the engine rotation fluctuation or the like for cost reduction. The step 22 constitutes engine stability detection means.

In step 23, the current engine stability (B)
Is within a predetermined range (B ₁ ≦ B ≦ B ₂ ). If YES, it is determined that the engine 1 can be operated in a state where the current air-fuel ratio (that is, the fuel injection pulse width TI) and the ignition timing (Tign) have been successfully made lean, and this flow ends. To do. If NO, within a range where desired engine stability is obtained, variations such as individual engine differences are eliminated, and early activation of the three-way catalyst 11 and reduction of exhaust harmful components are satisfactorily achieved. To retard the ignition timing, proceed to step 24 and thereafter.

In step 24, the lean target value (C)
Then, it is determined whether the total value (C + A) of the lean correction coefficient (A) currently set in the feedback control is less than or equal to a predetermined value (C + A ≦ A ₁ ). The predetermined value (A ₁ ; see FIGS. 8 and 10) is a value set for each engine operating state, and as shown in FIG. 10, even if leaning is further advanced, the degree of influence on exhaust performance is small, and The required ignition timing change amount (ΔT) for engine stabilization with respect to the air-fuel ratio change amount (Δλ) is set to a value within a region where it does not increase. The lean target value (C) is a predetermined value (A
It is set to a value with a margin for ₁ ). Also,
The lean correction coefficient (A) is set to a value that is sufficiently small with respect to the difference between the lean target value (C) and the predetermined value (A ₁ ).

If YES, the process proceeds to step 25. In this case, the feedback control for changing the ignition timing to maintain the engine stability within the predetermined range is not performed. That is, in the state where the ignition timing (Tign) is clamped to the initial value,
Control in a region (see FIG. 8) in which the air-fuel ratio side (that is, the fuel injection pulse width TI) is gradually changed to set the air-fuel ratio that can reduce the emission amount of exhaust harmful components most within the desired engine stability limit. Will be done. Since the basic ignition timing (Tbase) is clamped to a value (advance side) that has a margin up to the engine stability limit with respect to the change in the air-fuel ratio, the ignition timing has a value (advancement) that has a margin up to the engine stability limit. It will be clamped to the corner side).

On the other hand, if NO, the process proceeds to step 28.
In this case, the total value (C + A) used for the calculation of TI is
Feedback control is performed so that a desired engine stability is obtained on the ignition timing side in a state where the engine is clamped to a predetermined value (A ₁ ). That is, a predetermined value (A ₁ ) within a region in which the effect of reducing the exhaust performance is small even if it is made leaner and the required ignition timing change amount (ΔT) for engine stabilization with respect to the air-fuel ratio change amount (Δλ) does not increase. Then, the air-fuel ratio is clamped, the ignition timing side is gradually changed, and control is performed in a region where the ignition timing is set so that the exhaust gas temperature can be raised most within the desired engine stability limit.

More specifically, in step 25, the current engine stability (B) is below the upper limit value B ₂ (B ≦
B ₂ ) is determined. If YES, it is judged that the engine stability still has a margin and can be made leaner, and the routine proceeds to step 26 to proceed to leaner. On the other hand, if NO, it is determined that the stability has deteriorated due to excessive leaning, and the process proceeds to step 27.

In step 26, a new lean correction coefficient (A = A + IA) is set by adding a predetermined amount (IA) to the current lean correction coefficient (A) in order to further promote leaning. As a result, the effective fuel injection pulse width TI obtained in the flowchart of FIG. 4 is reduced, and the air-fuel ratio is corrected to the lean side. Therefore, as shown in FIG. 10, the emission amount of exhaust harmful components is reduced.

On the other hand, at step 27, the lean correction is performed too much, so a predetermined amount (IA) is subtracted from the current lean correction coefficient (A) to obtain a new lean correction coefficient (A = A).
-IA) is set. As a result, the effective fuel injection pulse width TI found in the flowchart of FIG. 4 is increased and the air-fuel ratio is corrected to the rich side. Therefore, the engine stability will be in the recovery direction.

In other words, the steps 26 and 27 enable the leanest air-fuel ratio within the engine stability limit in the state where the ignition timing is clamped (control in the region of FIG. 8). In this case, the ignition timing is clamped to the initial value (while the air-fuel ratio is lean, and the engine is stable enough to reach the engine stability limit) so that the air-fuel ratio falls within the desired engine stability limit. Changing only
The catalyst is activated early by activating the oxidation reaction of the catalyst with the increase in oxygen concentration due to the lean air-fuel ratio, and the amount of unburned fuel itself is reduced by lean combustion.
In other words, unlike the conventional case, without causing hunting or the like by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit, it is possible to satisfactorily eliminate the engine individual difference and the variation in the operating conditions, while maximizing the maximum. In addition, we are trying to activate the catalyst early and reduce harmful components of exhaust gas.

By repeating such a flow, steps
When the engine stability (B) falls within the predetermined range at 23, this flow is ended. The above steps 23 to 27 and the like correspond to the first feedback control means according to the present invention. By the way, by repeating step 26,
In step 24, if the total value (C + A) exceeds the predetermined value (A ₁ ), even if it is made leaner,
There is little reduction in the amount of harmful exhaust emissions (see Fig. 10), and the required ignition timing change amount (ΔT) for engine stabilization with respect to the air-fuel ratio change amount (Δλ) is large, so that engine stabilization control is severe. Therefore, in such a case, the ignition timing side is changed in a state where the total value (C + A) is clamped to the predetermined value (A ₁ ), and the three-way catalyst 11 due to the increase in the exhaust gas temperature 11
It is designed to proceed to step 28 for the purpose of early activation of.

That is, at step 28, the current ignition timing correction amount (FBADV) is smaller than 0 (FBADV <0).
It is determined whether or not. That is, once in step 24, C + A
Even if it is determined that ≦ A ₁ , even after the same operating state (even if C and A ₁ do not change) due to atmospheric conditions and other factors (for example, changes in fuel temperature and specific gravity), There is a case where the engine stability limit changes and it is necessary to return the air-fuel ratio to the rich side, that is, the ignition timing correction amount (FBAD
If V) is smaller than 0 (that is, if the engine stability limit cannot be found even if the ignition timing is advanced with the air-fuel ratio clamped), the step to return the air-fuel ratio to the rich side again is performed. It is designed to move to 27.

That is, if YES, the procedure proceeds to step 27, and if NO, the procedure proceeds to step 29. Here, steps 23, 24, 28, 27, etc. are the sixth step according to the present invention.
It corresponds to the feedback control means. It should be noted that, for example, even if the ignition timing is advanced to the initial value or more (MBT
However, if the fuel consumption, drivability, and exhaust characteristics are within the permissible range, they may be omitted.

In step 29, the total value (C + A) is clamped to a predetermined value (A ₁ ). In step 30, it is determined whether or not the current engine stability (B) is equal to or less than the upper limit value B ₂ (B ≦ B ₂ ). If YES, it is determined that the engine stability still has a margin and the ignition timing can be retarded, and the routine proceeds to step 31. In step 31, a predetermined amount (IADV) is added to the current ignition timing correction amount (FBADV) to obtain a new ignition timing correction amount (FBADV = FBADV + IAD).
V) is set. As a result, the ignition timing (Tign) found in the flowchart of FIG. 5 is set to a more retarded side. It should be noted that due to the retarded ignition timing, FIG.
As shown in, the effect of increasing the exhaust temperature can be expected. Therefore, the early activation of the three-way catalyst 11 can be further promoted.

On the other hand, if NO at step 30, it is judged that the ignition timing has been delayed too much and engine stability has deteriorated, and the routine proceeds to step 32. In step 32, the current ignition timing correction amount (FBADV) is changed by a predetermined amount (IADV).
V) to obtain a new ignition timing correction amount (FBAD
V = FBADV-IADV) is set. This allows
The ignition timing (Tign) found in the flowchart of FIG.
It will be set to the advance side. Therefore, the engine stability will be in the recovery direction.

As described above, steps 30 and 31 allow the ignition timing to be retarded most within the engine stability limit. That is, the air-fuel ratio is set to a predetermined value (that is, the total value [C + A]).
Is clamped to a predetermined value [A ₁ ]) (corresponding to the region shown in FIG. 8), that is, the air-fuel ratio has a small influence on the exhaust performance even if it is made lean, and the engine stability with respect to the air-fuel ratio change amount (Δλ) In the state of clamping to the air-fuel ratio within the range where the required ignition timing change amount (ΔT) for achieving
Within the desired engine stability limit, the exhaust temperature is raised by retarding the ignition timing so that the three-way catalyst 11 can be activated early. Therefore, unlike the conventional case, without causing hunting by changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit at the same time, it is possible to satisfactorily eliminate the difference between the individual engines and the variation of the operating conditions, while maximizing the maximum. In addition, the three-way catalyst 11 can be activated early.

The above steps 23, 24, 29 to 32 and the like correspond to the second feedback control means according to the present invention. Then, when the engine stability (B) falls within the predetermined range in step 23, this flow is ended. in this way,
In the first embodiment, in the initial stage of the lean control, the ignition timing is clamped at a predetermined ignition timing, and the total value (C + A) used to calculate the fuel injection pulse width TI is the predetermined value (A
₁ ) Within the range below, gradually change only the air-fuel ratio,
While trying to find the air-fuel ratio that gives the desired engine stability, if the desired engine stability cannot be obtained by this control on the air-fuel ratio side, the air-fuel ratio is further set to the upper limit value (that is, the total value). The value [C + A] is clamped to a predetermined value [A ₁ ], and only the ignition timing (Tign) is gradually changed to obtain a desired engine stability.

Therefore, unlike the conventional case, hunting or the like caused by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit is not caused, and variations in engine individual differences and operating conditions can be satisfactorily eliminated. Meanwhile, three-way catalyst
It is possible to achieve early activation of 11 and reduction of emission of exhaust harmful components (in particular, HC). Next, a second embodiment will be described.

The second embodiment has the same overall structure, fuel injection amount setting routine, and ignition timing setting routine as those of the first embodiment, and is controlled by the control unit 50 so as to obtain a desired engine stability. Since only the feedback control performed is different, only the feedback control will be described with reference to the flowchart of FIG. 7. Step
At 41, it is determined whether or not the permission condition for the feedback control during lean control is satisfied. The determination is similar to step 21 described above.

If YES, the process proceeds to step 42, and if NO, proceeds to step 60 and step 61, sets the lean correction coefficient (A) and the ignition timing correction amount (FBADV) to 0, and ends this flow. To do. In step 42, the current engine stability (B) is detected. The stability (B) is detected in the same manner as in step 22 described above.

In step 43, the current engine stability (B)
Is within a predetermined range (B ₁ ≦ B ≦ B ₂ ). If YES, it is determined that the engine is operating well with the current air-fuel ratio (that is, the fuel injection pulse width TI) and the ignition timing (Tign), and this flow is ended as it is,
If NO, step 44 and subsequent steps are performed in order to make the lean or retard the ignition timing in order to maximize the early activation of the three-way catalyst 11 and the reduction of exhaust harmful components within the range where the desired engine stability is obtained. Go to.

In step 44, the lean target value (C)
Then, it is determined whether the total value (C + A) of the lean correction coefficient (A) currently set in the feedback control is less than or equal to a predetermined value (C + A ≦ A ₂ ). The predetermined value (A ₂ ; see FIGS. 9 and 10, corresponding to the first target lean air-fuel ratio of the present invention) is a value set for each operating state,
As shown in FIG. 10, the required ignition timing change amount (ΔT) for engine stabilization with respect to the air-fuel ratio change amount (Δλ) is set to a value within a region where it does not increase. The lean target value (C) is set to a value that has a margin up to a predetermined value (A ₂ ). The lean correction coefficient (A) is set to a value that is sufficiently small with respect to the difference between the lean target value (C) and the predetermined value (A ₂ ). If yes, step 45
Go to. In this case, the feedback control for changing the ignition timing to converge the engine stability within the predetermined range is not performed. That is, in the state where the ignition timing is clamped to the initial value, the air-fuel ratio side (that is, the fuel injection pulse width TI) is gradually changed, and the emission amount of exhaust harmful components can be reduced most within the desired engine stability limit. Area set for air-fuel ratio (Fig. 9
Control). Since the basic ignition timing (Tbase) is clamped to a value (advance side) that has a margin up to the engine stability limit with respect to the change in the air-fuel ratio, the ignition timing has a value (advancement) that has a margin up to the engine stability limit. Corner side) is set.

On the other hand, if NO, the process proceeds to step 48.
In this case, the air-fuel ratio (that is, the total value [C + A] used for the calculation of TI) and the ignition timing are changed at the same time, and feedback control is performed to obtain a desired engine stability (FIG. 9, etc.). Feedback control so that the desired engine stability can be obtained on the ignition timing side in the state where the total value (C + A) used in the calculation of the fuel injection pulse width TI is clamped to a predetermined value (A ₃ ). The control proceeds to the area to be controlled (see FIG. 9).

The details will be described below. That is, step 45
Then, the current engine stability (B) is less than or equal to the upper limit value B ₂ (B
It is determined whether or not ≦ B ₂ ). If YES, it is determined that the engine stability still has a margin and can be made leaner, and the routine proceeds to step 46 in order to proceed with leaning. On the other hand, if NO, it is determined that the engine stability has deteriorated due to excessive leaning, and the routine proceeds to step 47.

In step 46, a new lean correction coefficient (A = A + IA) is set by adding a predetermined amount (IA) to the current lean correction coefficient (A) in order to promote leaning. As a result, the effective fuel injection pulse width TI determined by the flowchart of FIG. 4 is reduced, the air-fuel ratio is corrected to a leaner side, and the emission amount of exhaust harmful components is reduced.

On the other hand, in step 47, the lean correction is performed too much, so a predetermined amount (IA) is subtracted from the current lean correction coefficient (A) to obtain a new lean correction coefficient (A = A).
-IA) is set. As a result, the effective fuel injection pulse width TI obtained in the flowchart of FIG. 4 is increased, the air-fuel ratio is corrected to the rich side, and the engine stability is in the recovery direction.

In other words, steps 46 and 47 make it possible to make the air-fuel ratio leanest within the engine stability limit with the ignition timing clamped. In this case, the ignition timing is clamped to the initial value (while the air-fuel ratio is lean and clamped at the ignition timing that has a margin up to the engine stability limit), and only the air-fuel ratio is adjusted so that it falls within the desired engine stability limit. Is changed so that the catalyst is activated early due to activation of the oxidation reaction of the catalyst accompanying increase in oxygen concentration due to lean air-fuel ratio, and the amount of unburned fuel itself is reduced by lean combustion. That is, unlike the conventional case, without causing hunting or the like caused by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit, it is possible to satisfactorily eliminate the engine individual difference and the variation in the operating condition, and It is possible to early activate the original catalyst 11 and reduce harmful components in exhaust gas.

In this way, when the engine stability (B) falls within the predetermined range in step 43, this flow is ended. The above steps 43 to 47 and the like correspond to the third feedback control means according to the present invention. By the way, by repeating step 46, when the total value (C + A) becomes equal to or larger than the predetermined value (A ₂ ) in step 44, the total value (C + A) becomes larger than the predetermined value (A ₃ ). Up to step 48, the air-fuel ratio and the ignition timing are simultaneously changed.

That is, in step 48, the total value (C + A)
Is below a predetermined value (A ₃ , see FIGS. 9 and 10, corresponding to the second target lean air-fuel ratio of the present invention). If YES, the process proceeds to step 49, and if NO, the process proceeds to step 55. In step 49, it is determined whether or not the current engine stability (B) is equal to or less than the upper limit value B ₂ (B ≦ B ₂ ). YE
If it is S, it is determined that there is still a margin in engine stability, the air-fuel ratio can be made lean, and the ignition timing can be retarded, and the routine proceeds to step 50.

In step 50, a new lean correction coefficient (A = A + IA2) is set by adding a predetermined amount (IA2) to the current lean correction coefficient (A) in order to promote leaning. As a result, the effective fuel injection pulse width TI obtained in the flowchart of FIG. 4 is reduced, and the air-fuel ratio is corrected to the lean side. In step 51, the current ignition timing correction amount (FBADV) is set to a predetermined amount (IADV).
2) is added to add a new ignition timing correction amount (FBADV = F
Set BADV + IADV2). As a result, FIG.
The ignition timing (Tign) found by the flowchart of is set to the retard side.

On the other hand, if NO in step 49, it is determined that the engine stability has deteriorated due to excessive leaning and retardation of the ignition timing, and the routine proceeds to step 52. In step 52, it is determined whether or not the current ignition timing correction amount (FBADV) is smaller than 0 (FBADV <0). Y
In case of ES, proceed to step 47, and in case of NO,
Go to step 53.

That is, even if it is determined in step 44 that C + A ≦ A ₂ , the same operating state is subsequently caused due to atmospheric conditions and other factors (for example, changes in fuel temperature and specific gravity). Also (even if C and A ₂ are unchanged),
In some cases, the engine stability limit may change and the ignition timing may be fixed to the initial value to return the air-fuel ratio to the rich side. Therefore, in order to respond to this, the routine proceeds to step 47.

The steps 43, 44, 49, 52, etc. correspond to the seventh feedback control means according to the present invention. The means is omitted if the fuel consumption, drivability, and exhaust characteristics are within the permissible range even if the ignition timing is advanced beyond the initial value (advanced by a predetermined amount or more from the MBT). It may be configured with. At step 53, a new lean correction coefficient (A = A-IA2) is subtracted from the current lean correction coefficient (A) by a predetermined amount (IA2).
Set. As a result, the effective fuel injection pulse width TI found in the flowchart of FIG. 4 is increased and the air-fuel ratio is corrected to the rich side.

In step 54, a new ignition timing correction amount (FBADV = FBADV-) is subtracted from the current ignition timing correction amount (FBADV) by a predetermined amount (IADV2).
IADV2) is set. As a result, the ignition timing (Tign) found in the flowchart of FIG. 5 is set to the advance side. Therefore, the engine stability will be in the recovery direction.

In this way, steps 50, 51 and step 5
By controlling the air-fuel ratio and the ignition timing at the same time by 3, 54, the air-fuel ratio is made as lean as possible and the ignition timing is retarded within the engine stability limit.
As described above, in the region where the air-fuel ratio and the ignition timing are simultaneously controlled (see FIG. 9), the required ignition timing change amount (ΔT) for engine stabilization with respect to the air-fuel ratio change amount (Δλ) is large. There is no area, and in such areas,
Even if the air-fuel ratio and the ignition timing are controlled simultaneously, hunting or the like is unlikely to occur. Therefore, the air-fuel ratio and the ignition timing are simultaneously controlled so that the air-fuel ratio and the ignition timing are made to converge within the engine stability limit more quickly than in the first embodiment, and the harmful exhaust gas components due to leaning are eliminated. Reduction and increase of exhaust oxygen concentration, and increase of exhaust temperature due to retard of ignition timing are achieved at the same time to more effectively reduce emission amount of exhaust harmful components and early activation of three-way catalyst 11. I am trying to achieve.

Here, the above steps 43, 44, 48,
49, 50 to 54 and the like correspond to the fourth feedback control means according to the present invention. By repeating step 50, the total value (C + A) is obtained in step 48.
However, if it exceeds the predetermined value (A ₃ ) (corresponding to the range), even if it is made leaner than this, there is little reduction in the amount of harmful exhaust gas emissions, and to stabilize the engine against the air-fuel ratio change amount (Δλ). Since the required ignition timing change amount (ΔT) becomes large, hunting is likely to occur, and in order to avoid this, the air-fuel ratio is clamped (that is, the total value [C + A] is set to a predetermined value [A ₃ ]). Then, in order to change only the ignition timing side, the process proceeds to step 55 and thereafter.

That is, in step 55, it is determined whether or not the current ignition timing correction amount (FBADV) is smaller than a predetermined value (FBADV1) (FBADV <FBADV1). Y
In case of ES, proceed to step 49, and in case of NO,
Go to step 56. That is, in step 48, C + A ≦ A
_Even if it is determined to be ₃ , even after the same operating state (even if C and A ₃ do not change due to atmospheric conditions and other factors (for example, changes in fuel temperature and specific gravity)) ), It may be necessary to return the air-fuel ratio to the rich side and the ignition timing to the advance side due to changes in the engine stability limit, so in order to respond to this, it is made to proceed to step 49. .

The steps 43, 44, 48, 55 and the like correspond to the eighth feedback control means according to the present invention. It should be noted that the means is omitted if, for example, even if the ignition timing is advanced to a predetermined value or more (even if it is advanced from the MBT by a predetermined amount or more), the fuel economy, drivability, and exhaust characteristics are within the allowable range. It may be configured with. Further, in this embodiment, so as to control both the air-fuel ratio and the ignition timing, it is returned to step 49, but after determining YES in step 55, proceed to step 47, only the air-fuel ratio. By returning to the rich direction, the desired engine stability can be restored without lowering the exhaust temperature.

At step 56, the total value (C + A) is clamped to a predetermined value (A ₃ ). In step 57, it is determined whether or not the current engine stability (B) is the upper limit value B ₂ or less (B ≦ B ₂ ). If YES, it is determined that the engine stability still has a margin and the ignition timing can be retarded, and the routine proceeds to step 58. In step 58, a predetermined amount (IADV) is added to the current ignition timing correction amount (FBADV) to obtain a new ignition timing correction amount (FBADV = FBADV + IAD).
V) is set. As a result, the ignition timing (Tign) found in the flowchart of FIG. 5 is set to a more retarded side. It should be noted that an effect of further increasing the exhaust temperature can be expected by delaying the ignition timing. Therefore, the three-way catalyst 11
It is possible to further promote the early activation of the.

On the other hand, if NO at step 57, it is judged that the ignition timing has been delayed too much and engine stability has deteriorated, and the routine proceeds to step 59. In step 59, a new ignition timing correction amount (FBADV = FBADV-IADV) is set by subtracting a predetermined amount (IADV) from the current ignition timing correction amount (FBADV). As a result, the ignition timing (T
ign) will be set to the advance side. Therefore, the engine stability will be in the recovery direction.

As described above, steps 58 and 59 make it possible to retard the ignition timing most within the engine stability limit. That is, the air-fuel ratio is clamped to a predetermined value (the region shown in FIG. 9, even if the air-fuel ratio is made leaner than this, the exhaust performance is less affected, and the required ignition timing change amount (ΔT) with respect to the air-fuel ratio change amount (Δλ) ) Is clamped to the air-fuel ratio in a region where it does not increase), and the exhaust temperature is further raised by retarding the ignition timing so that the three-way catalyst 11 is activated early. Therefore, unlike the conventional case, the engine stability is not deteriorated by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability limit, and the
It is possible to achieve early activation of the three-way catalyst 11 while eliminating differences between individual engines and variations in operating conditions.

The above steps 43, 44, 48, 57 to 59, etc.
It corresponds to the fifth feedback control means according to the present invention. Then, when the engine stability (B) falls within the predetermined range in step 43, this flow is ended. As described above, according to the second embodiment, in the initial stage of the lean control, the ignition timing is clamped at a predetermined ignition timing, and the total value (C + A) used for calculating the fuel injection pulse width TI is predetermined. Within the range of the value (A ₂ ) or less, only the air-fuel ratio is gradually changed to find the air-fuel ratio at which the desired engine stability is obtained (corresponding to the range). If the desired engine stability cannot be obtained, further control the air-fuel ratio and the ignition timing at the same time to make the air-fuel ratio lean and retard the ignition timing as much as possible within the engine stability limit. (Corresponding to the area).
Then, after that, the air-fuel ratio is set to the upper limit value (that is, the total value [C +
A] is clamped to a predetermined value [A ₃ ], and the ignition timing (Ti
Only the gn) is gradually changed to obtain the desired engine stability.

Therefore, unlike the prior art, it is possible to satisfactorily eliminate variations between engine individual differences and operating conditions without causing control hunting by simultaneously changing the ignition timing and the air-fuel ratio at the engine stability limit. At the same time, early activation of the three-way catalyst 11 and reduction of emission of exhaust harmful components (particularly HC) can be achieved. Further, the region where the air-fuel ratio and the ignition timing are simultaneously controlled is the air-fuel ratio change amount (Δ
This is an area where the required ignition timing change amount (ΔT) for engine stabilization with respect to λ) is not large. In such an area, hunting etc. occurs even if the air-fuel ratio and the ignition timing are controlled at the same time. hard. Therefore, in such a region, if the air-fuel ratio and the ignition timing are changed at the same time, two parameters having a great influence on the engine stability can be changed at the same time. Compared with the first embodiment, it becomes possible to converge the engine stability within a predetermined limit more quickly, reduce exhaust harmful components due to leaning, increase exhaust oxygen concentration, and retard ignition timing. It is possible to increase the exhaust gas temperature at the same time, and thus, it is possible to more effectively reduce the discharge amount of the exhaust harmful component and to quickly activate the three-way catalyst 11.

In each of the above embodiments, the predetermined value (A
₁ or A ₃ ) has a small effect on the exhaust performance even if leaner is advanced, and the air-fuel ratio change amount (Δλ)
Required ignition timing change amount for engine stabilization (Δ
It has been described that T) is set to a value within the range where it does not increase, but if the engine stability is prioritized, the required ignition timing change amount (ΔT) for engine stability with respect to the air-fuel ratio change amount (Δλ) is set. It may be set to a value within the area that does not increase.

[0076]

As described above, according to the invention as set forth in claim 1, within the predetermined time after the engine is started, within the predetermined engine stability limit, the individual difference of the engine and the variation of the operating conditions are eliminated. Meanwhile, when the air-fuel ratio of the engine intake air-fuel mixture is made lean to the maximum, if the current air-fuel ratio is richer than the predetermined lean air-fuel ratio, the ignition timing is fixed to the predetermined ignition timing by the first feedback control means. Then, only the air-fuel ratio is changed to obtain a predetermined engine stability, while the change of the air-fuel ratio by the first feedback control means makes the air-fuel ratio leaner than the predetermined lean air-fuel ratio. Even when the predetermined engine stability is not obtained, the second feedback control means fixes the air-fuel ratio to the predetermined lean air-fuel ratio and changes the ignition timing to obtain the predetermined engine stability. Since this is done, it is possible to satisfactorily eliminate individual differences in engine and variations in operating conditions without causing hunting due to changing the ignition timing and the air-fuel ratio at the engine stability limit at the same time as before. At the same time, it is possible to early activate the catalyst and reduce the emission of harmful components in the exhaust gas.

According to the invention of claim 2, claim 1
In the invention described in (1), when a predetermined engine stability is obtained by the second feedback control means,
The engine stability limit changes due to atmospheric conditions and other factors (for example, changes in fuel temperature and specific gravity, etc.), and the ignition timing becomes unnecessarily large (for example, it greatly deviates from MBT and fuel consumption, drivability, and exhaust characteristics deteriorate If it is necessary to advance the ignition timing, the ignition timing can be fixed to a predetermined value and the air-fuel ratio can be corrected to the rich side, so that the fuel efficiency, drivability, and exhaust characteristics are extremely deviated from the MBT. It is possible to reliably prevent the deterioration.

According to the third aspect of the present invention, within the predetermined time after the engine is started, within the predetermined engine stability limit, the air-fuel ratio of the engine intake air-fuel mixture is eliminated while eliminating the differences among the individual engines and the variations in the operating conditions. If the current air-fuel ratio is richer than the first target lean air-fuel ratio when making the maximum lean,
The feedback control means fixes the ignition timing to a predetermined ignition timing and changes only the air-fuel ratio to obtain a predetermined engine stability, while this feedback control provides a predetermined engine stability. If not,
By the fourth feedback control means, the air-fuel ratio and the ignition timing are changed at the same time until the second target lean air-fuel ratio is reached so that a predetermined engine stability is obtained.
If the predetermined engine stability cannot be obtained even by the feedback control, the fifth feedback control means fixes the air-fuel ratio to the second target lean air-fuel ratio and changes only the ignition timing to obtain a desired value. Since the engine stability is obtained, there is no control hunting caused by simultaneously changing the ignition timing and the air-fuel ratio at the limit of the engine stability as in the conventional case, and it is possible to satisfactorily improve the engine individual difference and the operating condition. It is possible to achieve early activation of the catalyst and reduction of the emission of harmful components in the exhaust gas while eliminating the variation of the above.

Further, by the fourth feedback control means, the air-fuel ratio and the ignition timing can be changed at the same time in a region where hunting or the like does not occur even if the air-fuel ratio and the ignition timing are changed at the same time. Therefore, claim 1
As compared with the invention described in (1), it becomes possible to converge the engine stability within a predetermined stability limit more quickly, reduce exhaust harmful components by increasing leanness, increase exhaust oxygen concentration, and delay ignition timing. It is possible to increase the exhaust gas temperature due to the corners at the same time, so that it is possible to more effectively reduce the emission amount of the exhaust harmful components and quickly activate the three-way catalyst.

According to the invention of claim 4, claim 3
In the invention described in (3), when the predetermined engine stability is obtained by the fourth feedback control means,
The engine stability limit changes due to atmospheric conditions and other factors (for example, changes in fuel temperature and specific gravity, etc.), and the ignition timing becomes unnecessarily large (for example, it greatly deviates from MBT and fuel efficiency, drivability, and exhaust characteristics deteriorate. If it is necessary to advance the ignition timing, the ignition timing can be fixed to a predetermined value and the air-fuel ratio can be corrected to the rich side, so that the fuel efficiency, drivability, and exhaust characteristics are extremely deviated from the MBT. It is possible to reliably prevent the deterioration.

According to the invention of claim 5, claim 3
In the invention described in (or claim 4), when a predetermined engine stability is obtained by the fifth feedback control means, after that, atmospheric conditions and other factors (for example,
Due to changes in fuel temperature and specific gravity, etc., the engine stability limit changes, and it becomes necessary to advance the ignition timing more than necessary (for example, to the extent that it greatly deviates from MBT and fuel consumption, drivability, and exhaust characteristics deteriorate). In this case, the ignition timing can be fixed to a predetermined value and the air-fuel ratio can be corrected to the rich side.
It is possible to reliably prevent the fuel efficiency, drivability, and exhaust characteristics from deteriorating significantly from the above.

[Brief description of drawings]

FIG. 1 is a block diagram according to the invention described in claim 1.

FIG. 2 is a block diagram according to the invention of claim 3;

FIG. 3 is an overall configuration diagram according to a first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a fuel injection amount setting routine of the above embodiment.

FIG. 5 is a flowchart illustrating an ignition timing setting routine during lean control according to the embodiment.

FIG. 6 is a flowchart illustrating a feedback control routine for stabilizing the engine during lean control according to the embodiment.

FIG. 7 is a flowchart illustrating a feedback control routine for stabilizing the engine during lean control according to the second embodiment of the present invention.

FIG. 8 is a diagram illustrating feedback control for engine stabilization during lean control according to the first embodiment of this invention.

FIG. 9 is a diagram illustrating feedback control for stabilizing the engine during lean control according to the second embodiment of the present invention.

FIG. 10 is a diagram for explaining the relationship between the air-fuel ratio and the ignition timing, the relationship between the air-fuel ratio and the exhaust harmful components, and the relationship between the ignition timing and the exhaust temperature.

[Explanation of symbols]

 1 engine 3 air flow meter 6 fuel injection valve 7 spark plug 8 combustion pressure sensor 10 oxygen sensor 11 three-way catalyst 12 crank angle sensor 13 water temperature sensor 50 control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02D 41/06 305 43/00 301 BE 45/00 301G

Claims (5)

[Claims] Claim: What is claimed is: 1. An internal combustion engine, comprising engine stability detecting means for detecting engine stability, wherein the air-fuel ratio of the engine intake air-fuel mixture is made lean within a predetermined engine stability limit within a predetermined time after the engine is started. In the engine control device, when the current air-fuel ratio is richer than a predetermined lean air-fuel ratio, the ignition timing is fixed to a predetermined ignition timing and the air-fuel ratio is changed so that a predetermined engine stability is obtained. When the air-fuel ratio becomes leaner than the predetermined lean air-fuel ratio due to the change of the air-fuel ratio by the first feedback control means and the first feedback control means, a predetermined engine stability is obtained so as to obtain a predetermined engine stability. A second feedback control means for fixing the fuel ratio to the predetermined lean air-fuel ratio and changing the ignition timing, and a control device for an internal combustion engine. 2. The second feedback control means stops the feedback control of the ignition timing by the second feedback control means when the predetermined engine stability cannot be obtained even if the ignition timing is advanced to a predetermined value or more. The control device for an internal combustion engine according to claim 1, further comprising sixth feedback control means for changing the air-fuel ratio so that a predetermined engine stability is obtained. 3. An internal combustion engine, comprising engine stability detection means for detecting engine stability, wherein the air-fuel ratio of the engine intake air-fuel mixture is made lean within a predetermined engine stability limit within a predetermined time after engine startup. In the engine control device, when the current air-fuel ratio is richer than the first target lean air-fuel ratio, the ignition timing is fixed to a predetermined ignition timing and the air-fuel ratio is changed so that a predetermined engine stability is obtained. An air-fuel ratio of the first target lean air-fuel ratio and a second target lean air-fuel ratio set leaner than the first target lean air-fuel ratio by changing the air-fuel ratio by the third feedback control means. In the case of a gap, in order to obtain the prescribed engine stability,
The fourth feedback control means for simultaneously changing the control amount of the air-fuel ratio and the ignition timing, and the change of the air-fuel ratio by the fourth feedback control means make the air-fuel ratio leaner than the second target lean air-fuel ratio. In order to obtain the desired engine stability,
A fifth feedback control means for fixing the air-fuel ratio to the second target lean air-fuel ratio and changing the ignition timing, and a control device for an internal combustion engine, comprising: 4. The feedback of air-fuel ratio and ignition timing by the fourth feedback control means when the predetermined engine stability cannot be obtained even if the fourth feedback control means advances the ignition timing beyond a predetermined value. The control device for an internal combustion engine according to claim 2, further comprising: a seventh feedback control unit that stops the control and changes the air-fuel ratio so that a predetermined engine stability is obtained. 5. The fifth feedback control means stops the feedback control of the ignition timing by the fifth feedback control means when the predetermined engine stability cannot be obtained even if the ignition timing is advanced to a predetermined value or more. The control device for an internal combustion engine according to claim 3 or 4, further comprising an eighth feedback control means for changing at least the air-fuel ratio so as to obtain a predetermined engine stability.