JP3612785B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a control device for an internal combustion engine, and more particularly to a technique for suppressing deterioration in drivability due to overshoot of air-fuel ratio feedback control.
[0002]
[Prior art]
As a technique for feedback-controlling the air-fuel ratio of the intake air-fuel mixture in the internal combustion engine to the target air-fuel ratio, there has been conventionally one disclosed in Japanese Patent Application Laid-Open No. 63-21342.
In this system, when shifting from engine start to air-fuel ratio feedback control, leaning is achieved by making the integral constant larger than the normal value until the air-fuel ratio enriched to ensure startability reverses to lean. The control speed in the direction is increased, and the rich air-fuel ratio at the start is returned to the target air-fuel ratio with good response.
[0003]
[Problems to be solved by the invention]
By the way, if the control speed in the leaning direction is increased immediately after the start of the air-fuel ratio feedback control after the start as described above, the rich state is quickly eliminated, and the exhaust properties and fuel consumption can be improved.
However, if the control speed in the direction of leaning the air-fuel ratio is large, the actual air-fuel ratio overshoots to the lean side exceeding the target air-fuel ratio (see FIG. 6), and accompanying this overshoot to the lean side There was a risk that the combustion would become unstable, causing a surge or a drop in output torque.
[0004]
The overshoot to the lean side can be sufficiently reduced by slowing the control speed, but if the control speed is slowed, the time from the start of the air-fuel ratio feedback control to returning to the vicinity of the target air-fuel ratio becomes long, While avoiding deterioration in drivability due to overshooting to the lean side, the return to the target air-fuel ratio could not be made sufficiently early.
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to suppress deterioration in drivability due to overshooting to the lean side while increasing the return speed to the target air-fuel ratio.
[0006]
[Means for Solving the Problems]
Therefore, the control apparatus for an internal combustion engine according to the invention of claim 1 is configured as shown in FIG.
In FIG. 1, the air-fuel ratio feedback control means feedback-controls the fuel supply to the engine so that the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detection means approaches the target air-fuel ratio.
[0007]
On the other hand, the control speed switching means switches the control speed in the air-fuel ratio feedback control means according to the engine operating conditions. The ignition advance means is configured so that when the control speed for controlling the air-fuel ratio in the lean direction by the air-fuel ratio feedback control means is a predetermined value or more,Based on the advance correction value corresponding to the control speed in the lean directionCorrect the ignition timing.
[0008]
In the control device for an internal combustion engine according to the invention of claim 2, the ignition advance means is:When the control speed at which the air-fuel ratio is controlled in the lean direction by the air-fuel ratio feedback control means is greater than or equal to a predetermined value, the control speed is once reversed to the control state in the rich direction, and the control speed is less than the predetermined value in the lean direction. Until the control starts,The ignition timing is corrected to advance. In the control apparatus for an internal combustion engine according to the third aspect of the present invention, the ignition advance means once controls the air-fuel ratio in the lean direction by the air-fuel ratio feedback control means once the control speed is equal to or higher than a predetermined value, and then once in the rich direction. Until the control state in the lean direction in which the control speed is less than the predetermined value is started.Based on the advance correction value corresponding to the control speed in the lean direction that is equal to or greater than the predetermined valueThe ignition timing is corrected to advance.
[0009]
In the control apparatus for an internal combustion engine according to a fourth aspect of the present invention, the ignition advance means gradually increases the advance correction value after the control speed in the lean direction by the air-fuel ratio feedback control means becomes less than the predetermined value. It was set as the structure which returns to zero.
In the control device for an internal combustion engine according to the fifth aspect of the invention, the control speed switching means may be configured such that the air-fuel ratio feedback control means immediately after the engine is started until the first air-fuel ratio reversal is started from the start of feedback control. The control speed by the fuel ratio feedback control means is set to be faster than the normal value.
[0010]
[Action]
According to the control apparatus for an internal combustion engine of the first aspect, when the control speed when the air-fuel ratio is controlled in the lean direction by the air-fuel ratio feedback control is equal to or higher than a predetermined value, the ignition timing is corrected to advance. Stabilize the combustion and avoid the occurrence of surge and drop in output torque due to unstable combustion even if overshooting to the lean side.
[0011]
In other words, if the air-fuel ratio overshoots to the lean side, the fuel density in the combustion chamber decreases and the flame propagation time becomes longer, so that the ignition timing is advanced accordingly and combustion stability is maintained. It is a thing.
here,As the control speed in the lean direction increases, the overshoot to the lean side increases, so by adjusting the ignition timing with the advance correction value corresponding to the control speed, the advance angle increases as the overshoot increases. The configuration can be corrected.
[0012]
Claim2According to the control device for an internal combustion engine according to the invention, not only the state in which the control is performed in the lean direction at a control speed higher than a predetermined speed, but also the advance angle correction is performed after the state is once reversed to the control state in the rich direction. The ignition timing advance correction is continued until it is confirmed that the control in the lean direction is started again and the control speed at that time is smaller than the predetermined value, and the combustion stability is reliably maintained by the advance correction. It was made to be.
According to the control device for an internal combustion engine according to the invention of claim 3, since the overshoot to the lean side increases as the control speed in the lean direction increases, the ignition timing is set with an advance correction value corresponding to the control speed. In addition to the state in which the advance angle is corrected, and in addition to the state in which the control is performed in the lean direction at a control speed greater than or equal to the predetermined speed, the advance angle correction is continued even after reversing from this state to the control state in the rich direction The advance correction of the ignition timing is continued until it is confirmed that the control in the lean direction is started again and the control speed at that time is smaller than the predetermined value.
[0013]
According to the control apparatus for an internal combustion engine of the fourth aspect, the ignition advance correction value is gradually returned to zero, thereby avoiding deterioration in drivability due to a sudden change in the ignition timing.
According to the control apparatus for an internal combustion engine of the fifth aspect of the present invention, the rich state at the time of start-up can be obtained by increasing the control speed during the period from the start of the air-fuel ratio feedback control immediately after the engine start to the inversion of the first air-fuel ratio. It becomes possible to quickly converge near the target air-fuel ratio.
[0014]
【Example】
Examples of the present invention will be described below.
In FIG. 2 showing one embodiment, the air whose flow rate is adjusted by the throttle valve 2 is sucked into the internal combustion engine 1 through the intake collector 3 and the intake manifold 4.
[0015]
The branch portion of the intake manifold 4 is provided with an electromagnetic fuel injection valve 5 for each cylinder, and injects fuel supplied from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator.
Further, each cylinder of the internal combustion engine 1 is provided with a spark plug 6, to which a high voltage generated in the ignition coil 7 is sequentially applied via a distributor 8, thereby spark ignition. The mixture is ignited and burned. Here, the ignition coil 7 is configured to control the generation timing of the high voltage, that is, the ignition timing, via the attached power transistor 9.
[0016]
The throttle valve 2 is provided with a throttle sensor 10 for detecting the opening degree TVO by a potentiometer, and a detection signal is output at every predetermined crank angle from the crank angle sensor 11 built in the distributor 8. It has come to be.
Further, the coolant jacket of the engine 1 is provided with a water temperature sensor 12 that detects a coolant temperature Tw that is representative of the engine temperature. An oxygen sensor 14 for detecting the oxygen concentration in the exhaust gas that is closely related to the air-fuel ratio is provided.
[0017]
The oxygen sensor 14 is an oxygen concentration cell that outputs a signal corresponding to the ratio of the partial pressure of oxygen in the atmosphere to the partial pressure of oxygen in the exhaust gas. When the oxygen concentration in the exhaust gas changes abruptly in the vicinity of the theoretical air-fuel ratio. This sensor is capable of detecting the theoretical air-fuel ratio when its output changes suddenly near the theoretical air-fuel ratio. The oxygen sensor 14 corresponds to the air-fuel ratio detection means in this embodiment.
[0018]
Further, the engine 1 is provided with an evaporative gas processing device 16 for the fuel tank 15. The evaporative gas treatment device 16 causes the adsorbent such as activated carbon filled in the canister 17 to adsorb and collect the fuel evaporative gas generated in the fuel tank 15 and purges the fuel adsorbed on the adsorbent. The purge air is supplied into the intake collector 3 downstream of the throttle valve 4 via the purge passage 18.
[0019]
Evaporated gas in the fuel tank 15 is introduced into the canister 17 via an evaporative gas passage 20 provided with a check valve 19 that opens when the positive pressure in the fuel tank 15 exceeds a predetermined value. It has become. The purge passage 18 is provided with a diaphragm valve 21 into which a throttle negative pressure is introduced, and an electromagnetic on-off valve 22 is provided in the middle of the passage, and the diaphragm valve 21 and the electromagnetic on-off valve 22 are provided. In this configuration, purge air is supplied via
[0020]
A control unit 23 for controlling fuel injection by the fuel injection valve 5, ignition timing by the spark plug 6, opening and closing of the electromagnetic on-off valve 22, and the like includes a microcomputer, and includes the throttle sensor 10, the crank angle sensor 11, While detection signals from the water temperature sensor 12, the oxygen sensor 14 and the like are input, a detection signal from an air flow meter 24 that detects the intake air flow rate Q of the engine is input.
[0021]
In FIG. 2, 25 is a three-way catalyst, and this three-way catalyst 25 exhibits the highest conversion efficiency when the air-fuel ratio of the engine intake air-fuel mixture is near the stoichiometric air-fuel ratio. Therefore, when the predetermined feedback control condition is satisfied, the control unit 23 feedback-controls the fuel injection amount so that the air-fuel ratio detected by the oxygen sensor 14 approaches the theoretical air-fuel ratio as the target air-fuel ratio. It is like that.
[0022]
Here, the fuel injection control by the control unit 23 will be described with reference to the flowcharts of FIGS. In this embodiment, the functions as the air-fuel ratio feedback control means and the control speed switching means are provided in software by the control unit 23 as shown in the flowcharts of FIGS.
[0023]
The flowchart of FIG. 3 shows a routine for calculating the fuel injection amount Ti (injection pulse width) by the fuel injection valve 5.
First, in step 1 (indicated as S1 in the figure, the same applies hereinafter), the detection signal of the air flow meter 24 is A / D converted and read to obtain the intake air flow rate Qa.
In step 2, the basic fuel injection amount Tp is calculated as Tp = K × Qa / Ne (K) based on the engine speed Ne calculated based on the detection signal from the crank angle sensor 11 and the intake air flow rate Qa. Is a constant).
[0024]
In the next step 3, the basic fuel injection amount Tp is corrected and set by various correction coefficients COEF, air-fuel ratio feedback correction coefficient α, air-fuel ratio learning correction coefficient αm, voltage correction amount Ts, and final fuel injection amount Ti. (Ti = Tp × COEF × α × αm + Ts) is set.
The air-fuel ratio feedback correction coefficient α is a value that is proportionally and integratedly controlled according to the output of the oxygen sensor 14 in accordance with the flowcharts of FIGS. 4 and 5 described later (see FIG. 6). The air-fuel ratio learning correction coefficient αm is The air-fuel ratio feedback correction coefficient α is a value learned for each operation region divided into a plurality of values depending on the basic fuel injection amount Tp representing the engine load and the engine speed.
[0025]
The various correction factors COEF are water temperature increase correction factors K for increasing the amount of fuel as the coolant temperature is lower._TwAlso, the post-startup increase correction coefficient K for correcting the increase in fuel as the coolant temperature is lower at the start._ASEtc.
Further, the voltage correction amount Ts is an addition correction term for dealing with a change in the operation delay time of the fuel injection valve due to the battery voltage.
[0026]
The control unit 23 controls the fuel injection by the fuel injection valve 5 by outputting to the fuel injection valve 5 an injection pulse signal having a pulse width corresponding to the latest fuel injection amount Ti calculated at a predetermined injection timing.
4 and 5 show a routine for performing proportional / integral control on the air-fuel ratio feedback correction coefficient α.
[0027]
In step 11, it is determined whether or not a predetermined air-fuel ratio feedback control condition is satisfied.
For example, the stop condition of air-fuel ratio feedback control is at start, at low water temperature, at idle, at high engine load, at deceleration, etc., and the condition that does not correspond to any of these stop conditions is satisfied What is necessary is just to be the structure judged to be in a state.
[0028]
If the control condition is not satisfied, the routine proceeds to step 12, where the air-fuel ratio feedback correction coefficient α is set to 100% of the initial value, and at the next step 13, a flag F4 described later is set to 1.
On the other hand, if the control condition is satisfied, the routine proceeds to step 14, where it is determined whether or not the first feedback control is started after the engine is started.
[0029]
Then, when it is time to start the feedback control immediately after starting, the routine proceeds to step 15 where 1 is set in the flag F1, and otherwise, the routine bypasses step 15 and proceeds to step 16.
In step 16, the output VO of the oxygen sensor 14.₂Is compared with a determination value SL corresponding to the theoretical air-fuel ratio, which is the target air-fuel ratio, to determine whether the actual air-fuel ratio is richer or leaner than the theoretical air-fuel ratio.
[0030]
The output VO₂Is larger than the judgment value SL, and when it is considered that the actual air-fuel ratio is richer than the stoichiometric air-fuel ratio, the routine proceeds to step 17 where φ is set in the flag F2, and conversely, the output VO₂Is equal to or less than the determination value SL, and when it is considered that the actual air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the routine proceeds to step 18 where 1 is set in the flag F2.
[0031]
Therefore, by determining the flag F2, it can be detected whether the current air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio.
In step 19, it is determined whether or not the flag F2 has been reversed from the previous state of this routine by the processing of step 17 or 18. That is, in step 19, it is determined whether the flag F2 is inverted from 1 to φ or from φ to 1. Since 1 and φ of the flag F2 indicate the rich / lean of the air-fuel ratio, this is necessary. Inversion determination is to determine rich / lean inversion of the air-fuel ratio to the stoichiometric air-fuel ratio.
[0032]
If the flag F2 is continuously held at a constant value, the process proceeds to step 20 to determine the flag F1.
If 1 is set in the flag F1, the routine proceeds to step 21 where the flag F2 is determined to determine whether the current air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio.
[0033]
When the flag F2 is φ and rich, the routine proceeds to step 22 where a value obtained by subtracting a predetermined integral constant IR2 from the previous value of the air-fuel ratio feedback correction coefficient α is set as the current correction coefficient α.
In the next step 23, 1 is set to the flag F3 indicating execution of the integration control in the lean direction.
[0034]
On the other hand, when it is determined in step 21 that the flag F2 is 1 and lean, the routine proceeds to step 24, where a value obtained by adding a predetermined integral constant IL2 to the correction coefficient α is set as the current correction coefficient α, and the next step In 25, φ is set in the flag F3.
At the start of the air-fuel ratio feedback control immediately after the start, the air-fuel ratio is in a rich state. Therefore, normally, the lean control by the step 22 is continued until the air-fuel ratio is reversed to lean. Become.
[0035]
When the air-fuel ratio is reversed, this is determined as the reversal of the flag F2 at step 19, and the routine proceeds to step 26 where the flag F1 is reset to zero. Therefore, when the air-fuel ratio feedback control is started immediately after starting, the flag F1 is held at 1 until the air-fuel ratio is first reversed.
In the next step 27, rich / lean determination is performed by determining the flag F2, and when the flag F2 is rich with φ, in other words, when the flag F2 is reversed from lean to rich, the routine proceeds to step 28, where the air-fuel ratio feedback correction coefficient A value obtained by subtracting a predetermined proportionality constant PR from the previous value of α is set as the current correction coefficient α.
[0036]
In the next step 29, the flag F3 is reset to zero.
On the other hand, when it is determined in step 27 that the flag F2 is 1 and lean, the routine proceeds to step 30, where a value obtained by adding a predetermined proportional constant PL to the correction coefficient α is set as the current correction coefficient α, and the next step At 31, the flag F3 is reset to zero.
Thereafter, the process proceeds from step 19 to step 20 until it is determined in step 19 that the reversal of the air-fuel ratio is the reversal of the flag F2, but the flag F1 is reset to zero at the first reversal. Proceed to step 32.
[0037]
In step 32, rich / lean determination is performed based on the flag F2. If the flag F2 is rich with φ, the process proceeds to step 33, and a value obtained by subtracting a predetermined integral constant IR1 from the previous value of the air-fuel ratio feedback correction coefficient α is calculated. Is set as the correction coefficient α.
In the next step 34, 1 is set in the flag F3, and it is determined by the flag F3 that the control state is in the lean direction.
[0038]
On the other hand, when it is determined in step 32 that the flag F2 is 1 and lean, the routine proceeds to step 35, where a value obtained by adding a predetermined proportional constant IL1 to the correction coefficient α is set as the current correction coefficient α, and the next step In 36, the flag F3 is reset to zero. Here, the integral constants IR1 and IL1 used in the integral control in steps 33 and 35 are set in advance as values smaller than the integral constants IR2 and IL2 used in the integral control in steps 22 and 24. Therefore, from the start of the air-fuel ratio feedback control immediately after start-up until the air-fuel ratio is first reversed, the air-fuel ratio feedback control is performed at a fast control speed with integral constants IR2, IL2 larger than the normal values (IR1, IL1). Is the target air / fuel ratioTo the theoretical air-fuel ratioIt can be converged quickly.
[0039]
Since the air-fuel ratio is rich during normal starting, if the control speed is increased using the relatively large integration constants IR2 and IL2 until the first reversal as described above, the control speed in the lean direction increases (see FIG. 6), the rich state can be quickly resolved and converged to the vicinity of the target air-fuel ratio, so that the exhaust properties and the like immediately after starting can be improved.
[0040]
However, if the control speed (integral constant IR) in the lean direction is increased, the overshoot of the air-fuel ratio to the lean side increases accordingly, and combustion stability is impaired (see FIG. 7).
Therefore, the ignition timing is advanced by the control shown in the flowcharts of FIGS. 8 and 9 in order to prevent the combustion stability from deteriorating while accelerating the convergence from the rich state immediately after the start to the stoichiometric air-fuel ratio. In this embodiment, the function as the ignition advance means is provided in software by the control unit 23 as shown in the flowcharts of FIGS.
[0041]
In the flowchart of FIG. 8, in step 41, the flag F3 is determined. As described above, the flag F3 is set to 1 when the integral control in the lean direction is performed, and it is determined in step 41 that 1 is set to the flag F3. If yes, go to Step 42.
In step 42, it is determined whether or not the integral constant IR used for the integral control in the lean direction is equal to or greater than a predetermined value IRSET.
[0042]
In the present embodiment, two large and small IR1 and IR2 (> IR1) are used as integral constant IR used for integral control in the lean direction. Correspondingly, in step 42The predetermined value IRSET is, Which is an intermediate value between IR1 and IR2, and the determination in step 42 substantially determines whether or not the integral constant IR2 is used.
[0043]
When the flag F3 is 1 and the integral constant IR used at that time is equal to or greater than a predetermined value IRSET, that is, the control speed is increased as compared with the normal state, the leaning at the beginning of the control immediately after the start At the time of control, the process proceeds to step 43, and an advance correction value IADVSET for correcting the advance of the ignition timing is set according to the integration constant IR (actually, the integration constant IR2) at that time.
[0044]
The advance angle correction value IADVSET is set as a larger value as the integral constant IR is larger, and the advance angle is corrected as the integral constant IR is larger (see FIG. 10). This is because, as the integral constant IR is larger during the integral control in the lean direction, the overshoot toward the lean side becomes larger (see FIG. 7), and the advance correction value required for maintaining combustion stability becomes smaller. This is because it becomes larger (see FIG. 11).
[0045]
In step 44, the advance angle correction value IADVSET set in step 43 is compared with the correction value IADV actually used for the advance angle correction last time.
If the previous value IADV is not equal to or greater than the advance angle correction value IADVSET, the process proceeds to step 45 where the predetermined value IIADV1 is added to the previous value IADV so as to approach the currently set advance angle correction value IADVSET.
[0046]
In step 46, the flag F4 is reset to zero.
When the lean control is performed at the beginning of the control immediately after the start by the processing of steps 43 to 45 and the integration control in the lean direction is performed with the integration constant IR2 larger than the normal value, the progress corresponding to the integration constant is performed. The angle is raised to the angle correction value (see FIG. 6). If the advance angle correction value IADV is not promptly raised, the advance angle correction amount is insufficient and combustion stability cannot be maintained when overshooting in the lean direction. Therefore, the predetermined value IIADV1 is It is set as a relatively large value.
[0047]
The advance angle correction by the advance angle correction value IADV is performed according to the flowchart of FIG.
First, in step 61, the current Tp is referred to by referring to a map in which basic ignition timing (basic advance value) is stored in advance for each operation region divided into a plurality by the basic fuel injection amount Tp and the engine speed Ne. , Ne is searched for basic ignition timing.
[0048]
In the next step 62, the result of the advance correction by adding the advance correction value IADV to the basic ignition timing is set as the final ignition timing, and the ignition timing by the spark plug 6 based on the ignition timing. To control.
Returning to the flowchart of FIG. 8, the description will be continued. When the integration control in the lean direction is performed with the integral constant IR2 larger than the normal value as described above, the advance correction value IADV depends on the integral constant IR2. However, when the air-fuel ratio reverses lean and shifts to the rich control state from this state, the flag F3 is reset to zero and the routine proceeds from step 41 to step 47.
[0049]
In step 47, it is determined whether or not 1 is set in the flag F4. When the integration control in the lean direction is performed with the integral constant IR2 larger than the normal value, the flag F4 is subjected to φ in the process of step 46. Is set, the routine is terminated while the advance angle correction value IADV is held. Accordingly, the ignition timing continues to be corrected in advance even after the control state in the rich direction is shifted to the control state in the rich direction following the control state in the first lean direction (see FIG. 6).
[0050]
When the control state in the rich direction is shifted to the control state in the lean direction again, 1 is set in the flag F3 (step 34), and the process proceeds from step 41 to step 42.
However, at the time of the second control in the lean direction, the normal value IR1 is used as the integral constant, so the routine proceeds from step 42 to step 48.
[0051]
In step 48, it is determined whether or not the advance angle correction value IADV is φ. If it is not zero, the process proceeds to step 49, where the advance angle correction value IADV is set to decrease by a predetermined value IIADV2, and in the next step 50, the advance angle is advanced. 1 is set in the flag F4 to indicate that the shift to the reduction control of the correction value IADV is made.
That is, the advance correction value IADV corresponding to the integration constant IR2 is held from the start of control until the second air-fuel ratio reversal, and then gradually decreased (see FIG. 6).
[0052]
As described above, if the ignition timing is corrected to advance while controlling in the lean direction with an integral constant IR2 larger than the normal value, combustion stability is increased even if the air-fuel ratio overshoots to the lean side. Deterioration can be avoided, and hence deterioration in drivability due to the overshoot can be suppressed. If the air-fuel ratio overshoots to the lean side, the fuel density in the combustion chamber will decrease and the flame propagation time will become longer.Accordingly, the ignition timing is advanced to maintain combustion stability. It is. Further, by continuing the advance angle correction even during the control in the rich direction following the control in the lean direction by the integral constant IR2, it is possible to more reliably avoid the deterioration in drivability due to the overshoot.
[0053]
The predetermined value IIADV2 is set as a value sufficiently smaller than IIADV1 used when the advance angle correction value IADV is raised, and the advance angle correction value IADV gradually decreases at a slow speed. Therefore, it is possible to avoid deterioration in drivability due to returning the advance correction value IADV to φ.
When reduction control of the advance correction value IADV is started, it is determined in step 47 that the flag F4 is 1 even if the flag F3 is not 1, that is, in the integration control state in the rich direction. Accordingly, the routine proceeds to step 48, where the advance angle correction value IADV is continuously reduced.
[0054]
When the advance angle correction value IADV decreases to φ, the process proceeds from step 48 to step 51, the flag F4 is reset to zero, and the advance angle correction is terminated.
Even when the air-fuel ratio feedback control condition is removed, 1 is set in the flag F4 (step 13). If the air-fuel ratio feedback control condition is removed during the advance angle correction, From this, the advance correction value IADV is controlled to decrease gradually.
[0055]
In the above embodiment, the air-fuel ratio feedback correction coefficient α is configured to perform proportional / integral control. However, the present invention is not limited to this, and a configuration using only integral control or proportional / integral / derivative control may be used.
[0056]
【The invention's effect】
Claims as described above1,3According to the control device for an internal combustion engine according to the invention, the ignition timing is corrected to advance when the control speed when the air-fuel ratio is feedback controlled in the lean direction is equal to or greater than a predetermined value. Even if the engine overshoots to the lean side, combustion can become unstable and surge and output torque drop can be avoided.At the same time, since the ignition timing is corrected with an advance correction value corresponding to the control speed in the lean direction, the advance angle can be corrected more greatly as the overshoot is larger, thereby maintaining combustion stability. Appropriate advance angle correction can be performedThere is an effect.
[0057]
According to the control device for an internal combustion engine according to the inventions of claims 2 and 3,Not only is the feedback control in the lean direction at a control speed higher than the specified value, but also the advance angle correction is continued after the state is once reversed to the control state in the rich direction, and the control in the lean direction is started again. Since the advance correction of the ignition timing is continued until it is confirmed that the control speed at that time is smaller than the predetermined value, the combustion stability can be reliably maintained by the advance correction. is there.
[0058]
According to the control apparatus for an internal combustion engine of the fourth aspect of the invention, there is an effect that deterioration in drivability due to a sudden change in the ignition timing can be avoided by gradually returning the ignition advance correction value to zero.
According to the control apparatus for an internal combustion engine of the fifth aspect of the invention, the rich state at the time of start-up can be quickly achieved by increasing the control speed between the start of the air-fuel ratio feedback control immediately after the engine start and the inversion of the first air-fuel ratio. As a result, it is possible to converge to the vicinity of the target air-fuel ratio and to avoid deterioration of combustion stability due to overshoot to the lean side by the advance angle correction at this time.
[Brief description of the drawings]
FIG. 1 is a block diagram of a basic configuration of a control device according to the invention of claim 1;
FIG. 2 is a system configuration diagram of the internal combustion engine in the embodiment.
FIG. 3 is a flowchart showing calculation of a fuel injection amount in the embodiment.
FIG. 4 is a flowchart showing calculation of an air-fuel ratio feedback correction coefficient in the embodiment.
FIG. 5 is a flowchart showing calculation of an air-fuel ratio feedback correction coefficient in the embodiment.
FIG. 6 is a time chart showing the correlation between the air-fuel ratio feedback correction coefficient and the advance correction value in the embodiment.
FIG. 7 is a diagram showing a correlation between an integral constant (control speed) and an air-fuel ratio overshoot amount.
FIG. 8 is a flowchart showing calculation of an advance correction value in the embodiment.
FIG. 9 is a flowchart showing calculation of ignition timing in the embodiment.
FIG. 10 is a diagram showing a correlation between an integration constant and an advance correction value in the embodiment.
FIG. 11 is a diagram showing a change in ignition advance required to maintain drivability with respect to a change in air-fuel ratio.
[Explanation of symbols]
1 Internal combustion engine
5 Fuel injection valve
6 Spark plug
11 Crank angle sensor
12 Water temperature sensor
14 Oxygen sensor
23 Control unit
24 Air flow meter

Claims (5)

Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture;
Air-fuel ratio feedback control means for feedback-controlling fuel supply to the engine so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio;
Control speed switching means for switching the control speed in the air-fuel ratio feedback control means according to engine operating conditions;
When the control speed for controlling the air-fuel ratio in the lean direction by the air-fuel ratio feedback control means is equal to or greater than a predetermined value, the ignition timing is advanced based on the advance correction value corresponding to the control speed in the lean direction. Ignition advance means,
A control device for an internal combustion engine, comprising: Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture;
Air-fuel ratio feedback control means for feedback-controlling fuel supply to the engine so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio;
Control speed switching means for switching the control speed in the air-fuel ratio feedback control means according to engine operating conditions;
When the control speed at which the air-fuel ratio is controlled in the lean direction by the air-fuel ratio feedback control means is greater than or equal to a predetermined value, the control speed is once reversed to the rich control state, and the control speed is less than the predetermined value in the lean direction. Ignition advance means for correcting the advance of the ignition timing to advance the ignition timing until the control is started ,
A control device for an internal combustion engine, comprising: Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture;
Air-fuel ratio feedback control means for feedback-controlling fuel supply to the engine so that the air-fuel ratio detected by the air-fuel ratio detection means approaches the target air-fuel ratio;
Control speed switching means for switching the control speed in the air-fuel ratio feedback control means according to engine operating conditions;
When the control speed at which the air-fuel ratio is controlled in the lean direction by the air-fuel ratio feedback control means is greater than or equal to a predetermined value, the control speed is once reversed to the rich control state, and the control speed is less than the predetermined value in the lean direction. Ignition advance means for advancing the ignition timing for advancing the ignition timing based on the advance correction value corresponding to the control speed in the lean direction that is equal to or greater than the predetermined value until the control is started When,
A control device for an internal combustion engine, comprising: 4. The ignition advance means gradually returns the advance correction value to zero after the control speed in the lean direction by the air-fuel ratio feedback control means becomes less than the predetermined value. The control apparatus for an internal combustion engine according to any one of the above. The control speed switching means increases the control speed by the air-fuel ratio feedback control means from a normal value between the start of the feedback control by the air-fuel ratio feedback control means immediately after the engine start and the reversal of the first air-fuel ratio. The control device for an internal combustion engine according to any one of claims 1 to 4.

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