JP2822804B2 - Control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine in which secondary air is supplied to an exhaust passage of the engine.

[0002]

2. Description of the Related Art In some internal combustion engines, secondary air is supplied to an exhaust passage to re-combust and reduce harmful components of exhaust gas such as CO and HC. Also, since the secondary air is usually supplied to the upstream side of the exhaust gas purification catalyst, C
The exhaust gas whose temperature has risen due to the reburning of O and HC flows into the exhaust gas purification catalyst and the catalyst temperature can be raised, so that the catalyst is activated early and the exhaust gas purification performance can be greatly improved.

[0003] It is to be noted that the continuous supply of the secondary air overheats the exhaust gas purification catalyst and rather impairs its function or is accompanied by deterioration due to high heat. (For example, at the time of steady idling when the mixture ratio is enriched)
3-9663). By the way, in the region where the secondary air is supplied, even if the supply amount of the secondary air is larger than the amount required for the re-combustion of CO and HC, the cooling effect by the air is more effective, and the re-combustion function by the exhaust gas is not effective. Be impaired.

For this reason, an exhaust gas temperature sensor for detecting the exhaust gas temperature is provided upstream of the exhaust gas purification catalyst, and when the exhaust gas temperature detected by the temperature sensor is lower than the lower limit temperature of the catalyst activation temperature, the ignition timing is retarded. In order to increase the exhaust gas temperature and compensate for the decrease in engine output when the ignition timing is retarded, the fuel injection amount is corrected in accordance with the cooling water temperature (Japanese Patent Laid-Open No. 3-164549).
Reference).

[0005]

However, if the ignition timing is excessively retarded, a misfire occurs and the engine becomes unstable. Therefore, the retard amount is set with a margin with respect to the stability limit of the engine. If the correction amount of the fuel injection amount is too large, a misfire will occur.

That is, the harmful components of exhaust gas, such as CO and HC
In order to greatly enhance the reduction performance of the catalyst, it is necessary to raise the temperature of the catalyst and activate it quickly, but in the case of the conventional internal combustion engine, it is also necessary to ensure good operability. Therefore, there is a problem that prompt responses cannot be taken. The present invention has been made in view of the above problems, and by monitoring the stability of the engine, retarding the ignition timing and increasing the fuel amount as close to the stability limit as possible to ensure good operability. Another object of the present invention is to greatly enhance the performance of reducing harmful components in exhaust gas.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention provides a first method.
As shown in FIG. 1, an engine operating state detecting means for detecting an engine operating state including at least an intake air flow rate and an engine rotation speed, and based on the detected intake air flow rate and the engine rotation speed, as shown in FIG. Basic fuel supply amount setting means for setting a basic fuel supply amount; fuel injection amount correction amount setting means for increasing or decreasing the correction amount of the basic fuel supply amount according to the detected operating state; and the set fuel injection Fuel supply amount setting means for correcting the set basic fuel injection amount based on the amount of correction to set a final fuel supply amount,
A fuel supply control unit for supplying fuel to the engine based on the set final fuel supply amount, an idle operation state detection unit for detecting an idle operation state of the engine, and a temperature of the engine. Temperature detection means for detecting the temperature of the engine and a secondary for supplying secondary air to an exhaust passage upstream of a catalyst which is interposed in an exhaust passage of the engine and purifies exhaust when the engine is in an idle operation state and the engine temperature is low. Air supply means, stability detection means for detecting the stability of the engine when secondary air is supplied, and a correction amount of the fuel supply amount when the stability is high based on the detected stability of the engine. And a fuel increase correction means for setting the fuel increase.

Further, as second technical means, as shown in FIG. 2, an engine operating state detecting means for detecting an engine operating state including at least an intake air flow rate and an engine rotational speed; Basic fuel supply amount setting means for setting a basic fuel supply amount based on the engine rotational speed, basic ignition timing setting means for setting a basic ignition timing based on the detected engine rotational speed and the basic fuel supply amount, An ignition timing correction value setting means for increasing or decreasing the correction value of the basic ignition timing according to the detected operating state; and correcting the set basic ignition timing based on the correction value of the set ignition timing. An internal combustion engine comprising: ignition timing setting means for setting a final ignition timing; and ignition signal output means for outputting an ignition signal to an ignition device based on the set final ignition timing. An idle operating state detecting means for detecting an idle operating state of the engine, an engine temperature detecting means for detecting the temperature of the engine, and an exhaust gas passage of the engine when the engine is in an idle operating state and the engine temperature is low. To supply secondary air to the exhaust passage upstream of the catalyst for purifying exhaust gas
Secondary air supply means, stability detection means for detecting the stability of the engine when secondary air is supplied, and a correction value for the ignition timing when the stability is high based on the detected stability of the engine. And ignition timing retard correction means for retarding the ignition timing.

Further, the stability detecting means in the first technical means and the second technical means is adapted to detect a change in the engine speed detected by the engine operating state detecting means or a change in the in-cylinder pressure of each cylinder. A configuration may be adopted in which the stability of the engine is detected by using this.

[0010]

According to the first technical means, when the engine is idling and the engine temperature is low, the secondary air is supplied to the exhaust passage of the engine, and based on the stability of the engine at that time. The temperature increase of the catalyst can be accelerated while ensuring the stability by setting the fuel supply amount to be increased.

According to the second technical means, the secondary air is supplied to the exhaust passage of the engine when the engine is idling and the engine temperature is low, based on the stability of the engine at that time. Thus, the ignition timing is corrected, and the stability can be ensured, and the temperature of the catalyst can be quickly increased. That is, since the exhaust temperature is positively increased only at the time of idling when the exhaust temperature is reduced without the influence of the deterioration of the operability due to the torque fluctuation of the engine, the inlet temperature of the catalyst interposed in the exhaust passage increases. Thus, the catalyst can be activated more quickly.

Further, when the engine becomes unstable, the maximum rotation speed during the explosion cycle in each cylinder varies, and the rotation fluctuation increases, so that the stability of the engine can be detected from the rotation fluctuation. Further, since the in-cylinder pressure of each cylinder also varies according to the stability of the engine in the same manner as the engine speed, the stability of the engine can be detected from the fluctuation in the in-cylinder pressure.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3 showing a system configuration of an embodiment, air is sucked into an internal combustion engine 1 via an air cleaner 2, an intake duct 3, a throttle chamber 4 and an intake manifold 5.

The intake duct 3 is provided with an air flow meter 6 for detecting an intake air flow rate Q. The throttle chamber 4 is provided with a throttle valve 7 interlocked with an accelerator pedal (not shown), and controls the intake air flow rate Q. The throttle valve 7 has a throttle sensor
A function of an idle switch for outputting a voltage signal corresponding to the opening TVO of the throttle valve 7 and outputting a fully closed position signal of the throttle valve 7 is provided.

An idle switch may be provided, and the idle switch may be turned on when the throttle valve 7 is fully closed. The intake manifold 5 is provided with an electromagnetic fuel injection valve 8 for each cylinder, and injects and supplies to the engine 1 fuel controlled at a predetermined pressure by a pressure regulator sent from a fuel pump (not shown).

The control of the fuel injection amount by the fuel injection valve 8 is performed by a control unit 9 with a built-in microcomputer, which controls a flow rate of an intake air flow Q detected by an air flow meter 6 and a crank angle sensor 10 built in a distributor 13. From the engine speed N calculated based on the signal, the basic fuel injection amount Tp = K × Q / N (K
Is a constant), and various corrections are made to the basic fuel injection amount Tp to set a final fuel injection amount Ti, and a drive pulse signal having a pulse width corresponding to the fuel injection amount Ti is transmitted to the engine. By outputting the fuel to the fuel injection valve 8 in synchronization with the rotation, the fuel injection valve 8 is opened for a predetermined time and a predetermined amount of fuel is injected and supplied to the engine 1.

Here, the correction amount for correcting the basic fuel injection amount Tp includes various correction coefficients including a start-up increase correction based on a cooling water temperature Tw representing the engine temperature detected by the water temperature sensor 14. COEF, an air-fuel ratio feedback correction coefficient α for feedback-correcting the actual air-fuel ratio to a target air-fuel ratio (for example, a stoichiometric air-fuel ratio), and a correction for correcting a change in the invalid injection time of the fuel injector 8 due to the battery voltage. Minutes Ts.

The air-fuel ratio feedback correction coefficient α is
Based on the oxygen concentration in the exhaust gas detected by the oxygen sensor 16 interposed in the exhaust passage 20, rich / lean with respect to the actual air-fuel ratio of the actual engine intake air-fuel mixture is determined, and the actual air-fuel ratio becomes the target air-fuel ratio. It is set and controlled by, for example, proportional integral control so as to approach. Incidentally, the downstream exhaust passage 20 of the oxygen sensor 16, CO in the exhaust gas, HC, along with the three-way catalyst 17 for purifying by oxidation and reduction of NO _X is provided downstream of the three-way catalyst 17 A muffler 18 is provided.

Each cylinder of the engine 1 is provided with an ignition plug 11 to which a high voltage generated by an ignition coil 12 is sequentially applied via a distributor 13, thereby spark-igniting and mixing. Ignition and burning. here,
The ignition coil 12 has a power transistor 12 attached to it.
The generation timing of the high voltage is controlled via a. Therefore, the ignition timing (ignition advance value) ADV is controlled by controlling the ON / OFF timing of the power transistor 12a by the ignition signal from the control unit 9. In this embodiment, the ignition device includes the above-described ignition plug 11, ignition coil 12, power transistor 12a, and distributor 13. Note that the ignition device may include an ignition coil 12 and a power transistor 12a for each cylinder, and do not perform power distribution by the distributor 13.

That is, in the control unit 9,
An arithmetic processing is performed based on various input signals to determine an optimal ignition timing (ignition advance value) ADV.
The ignition signal is sent to the power transistor 12a for driving the ignition coil 12 so that the ignition is performed by the control signal. More specifically, the basic ignition timing ADV ₀ of the corresponding operating condition is searched from a map of the basic ignition timing set in advance according to the operating condition of the engine speed N and the basic fuel injection amount Tp representing the engine load. while seeking Te, it sets the final ignition timing ADV to decrease correcting the correction value of the basic ignition timing ADV ₀ by occurrence of knocking of the engine.

Then, energization of the primary side of the ignition coil 12 is started so that sufficient ignition energy can be obtained by the ignition timing ADV. When the ignition timing ADV is detected based on the detection signal of the crank angle sensor 10, A high voltage is generated on the secondary side by shutting off the current, and a high voltage is supplied to the spark plug 11 for spark ignition. The correction value is a correction term that is added to the basic ignition timing ADV ₀ with the initial value being zero. If knocking is not detected, the correction value is increased by a predetermined value (advance correction), and conversely, knocking is detected. Then, the ignition angle is reduced by a predetermined value (retarded), and ignition is performed at the most advanced value as long as knocking does not occur.

In this embodiment, an electric air pump 19 is interposed in a secondary air supply pipe for supplying secondary air to an exhaust passage 20 upstream of the three-way catalyst 17, and is operated by a command from the control unit 9. On / off control is performed, and the supply of secondary air is on / off controlled. Further, an in-cylinder pressure sensor 21 for detecting an in-cylinder pressure (combustion chamber pressure) for each cylinder is provided on a seat surface of an ignition plug 11 provided for each cylinder of the engine 1, and an in-cylinder pressure for each cylinder is provided. Are output to the control unit 9.

Here, the fuel supply control and the ignition timing control performed by the control unit 9 according to the programs shown in the flowcharts of FIGS. 4 to 7 will be described. The routine shown in the flowchart of FIG. 4 is a fuel supply control program according to the first embodiment of the present invention, and is executed every 10 msec. At P1, a fully closed position signal of the throttle valve 7 is read from the throttle sensor 15.

At P 2, the intake air flow rate Q is measured by the air flow meter 6, the engine speed N based on the signal from the crank angle sensor 10, and the cooling water temperature T is calculated by the water temperature sensor 14.
w are respectively detected. That is, the air flow meter 6, the crank angle sensor 10 and the like constitute engine operating state detecting means, and the water temperature sensor 14 constitutes engine temperature detecting means.

At P3, a basic fuel injection amount Tp = K × Q / N (K is a constant) is calculated from the intake air flow rate Q and the engine speed N. That is, this step has the function of the basic fuel supply amount setting means. At P4, a basic increase coefficient K _Tw based on the cooling water temperature _Tw is set. In P5,
By reading the fully closed position signal of the throttle valve 7 from the throttle sensor 15, it is determined whether or not the throttle valve 7 is in the idle position. Only when it is determined that the throttle valve 7 is in the idle state, the process proceeds to P6.

That is, this step has the function of the idling operation state detecting means. At P6, it is determined whether or not the cooling water temperature Tw is equal to or lower than a predetermined temperature. If the cooling water temperature Tw is equal to or lower than the predetermined temperature, it is considered that the cooling water temperature Tw is low and the three-way catalyst 17 is also in an inactive state. Proceeding to the following, the control according to the present invention is performed. At P7, the electric air pump 19 is turned on to supply secondary air to the exhaust passage upstream of the three-way catalyst 17.

That is, this step has the function of the secondary air supply means. In P8, detecting the engine rotational speed omega _n of each cycle based on signals from the crank angle sensor 10. Here, the rotational speed ω _n is defined as the maximum rotational speed during the explosion cycle of each cylinder ω _n . That is, as shown in FIG. 8, the maximum rotational speed of each cylinder (four cylinders in this embodiment) during the explosion cycle changes as shown by ω ₁ to ω ₄ , and Detected as the maximum rotation speed during the cylinder explosion cycle.

[0028] In P9, calculating the standard deviation Yuomega _n of the rotational speed omega _n detected at P8 according to the following equation.

[0029]

(Equation 1)

[0030] In P10, compares the standard deviation Yuomega _n predetermined value (10 in this embodiment). And the standard deviation Uω
_{When n} is larger than a predetermined value, the fuel injection amount T set by performing various corrections on the basic fuel injection amount Tp is set.
i becomes too large, and the air-fuel ratio (A / F) becomes too rich, so that the stability is deemed to be poor, and the process proceeds to P11, where the stability limit correction coefficient K _SA is reduced by the minute value ΔK.

Here, the operation related to the step will be described. When the engine becomes unstable, the maximum rotational speed ω _n during the explosion cycle in each cylinder fluctuates, the fluctuation of the generated torque also increases, and the maximum rotational speed ω _n is the standard deviation Yuomega _n is greater than the predetermined value varies. FIG.
As shown in, when the air-fuel ratio is too rich, it varies the maximum rotational speed omega _n is the standard deviation Yuomega _n becomes larger than a predetermined value, has been stability is to exceed the stability limit.

On the other hand, at P10, the standard deviation Uω _n
If it is determined that is not larger than the predetermined value, it is determined that the stability is good and the stability is sufficient, the process proceeds to P12, and a large amount of unburned CO and HC is discharged to the exhaust passage 20 upstream of the catalyst 17. In order to increase the amount of heat generated by re-combustion with the secondary air, the stability limit correction coefficient K _SA is increased by a small value ΔK so as to increase the fuel injection amount, thereby enriching the air-fuel ratio. To approach the rich limit.

That is, the function of the stability detecting means is achieved by P9 and P10, and the function of the fuel increase correction means is exhibited by P12. In P13, the fuel injection amount Tp is determined based on the basic fuel injection amount Tp based on the basic increase coefficient K _Tw set in P4 and the stability limit correction coefficient K _SA set in P11 or P12.
i is calculated by the following equation.

Ti = Tp × (1 + K _Tw + K _SA ) + Ts Then, the routine is terminated, and the fuel injection amount Ti is set in the output register. As a result, a signal having a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 8, and fuel injection is performed. That is, a series of operations up to this point is performed as fuel supply control means.

On the other hand, if it is determined in P5 that the vehicle is not in the idle state, the secondary air is not supplied and the combustion control associated with the supply of the secondary air is not performed.
P6 to P13 jump and proceed to P14. At P14, the basic fuel injection amount Tp is corrected based on the basic increase coefficient K _Tw set at P4, and the fuel injection amount Ti is calculated by the following equation.

Ti = Tp × (1 + K _Tw ) + Ts Then, the routine is terminated, and the fuel injection amount Ti is set in the output register. That is, the function of the fuel supply amount setting means is achieved by P13 and P14. Accordingly, it is possible to correct the fuel injection amount without greatly changing the stability of the engine, and as shown in FIG. 10, by bringing the air-fuel ratio close to the rich limit only at the time of idling when the exhaust gas temperature decreases. In addition, while minimizing deterioration of fuel economy, the unburned CO and HC are positively discharged, and the secondary air is reburned to raise the exhaust gas temperature. It becomes possible to activate the catalyst by raising the catalyst temperature.

Further, since the stability of the engine is determined based on the engine speed N, there is no need to provide a special sensor for detecting the engine speed N, and it is possible to suppress an increase in cost. There is also an effect. Furthermore, it is possible to perform the increase correction of the fuel injection amount to near the stability limit without greatly changing the stability of the engine.
There is also an effect that it is possible to operate the engine 1 while suppressing a decrease in output when the exhaust gas temperature is increased.

Next, referring to the flowchart of FIG.
The ignition timing control according to the second embodiment of the present invention will be described. In the description of FIG. 5, steps having the same functions as those in FIG. 4 are denoted by the same step numbers, and description thereof is omitted. After calculating the basic fuel injection amount Tp in P3, the process proceeds to P21.

At P21, the basic ignition timing ADV ₀ of the corresponding operating condition is obtained from a map of the basic ignition timing previously set according to the operating condition of the engine speed N and the basic fuel injection amount Tp representing the engine load. Search for and ask. In P10, it compares the standard deviation Yuomega _n predetermined value (10 in this embodiment). Then, if the standard deviation Yuomega _n is greater than the predetermined value, the process proceeds to P22 as a bad stability because too much more retard correction to the basic ignition timing ADV _0, small angle stability limit correction angular coefficient A _SA The value is increased by ΔA, and as a result, the angle is advanced by the minute angle ΔA.

Here, the operation related to the step will be described. When the engine becomes unstable, the maximum rotational speed ω _n during the explosion cycle in each cylinder varies, and the fluctuation of the generated torque also increases. _n is the standard deviation Yuomega _n is greater than the predetermined value varies. FIG. 11
As shown in, when the ignition timing ADV (described below) is too retarded, varies the maximum rotational speed omega _n becomes larger than the predetermined value is a standard deviation Yuomega _n, has been stability can exceed the stability limit Becomes

On the other hand, at P10, the standard deviation Uω _n
Is not larger than the predetermined value, it is determined that the stability is good and the stability is sufficient, the process proceeds to P23, and the ignition timing ADV is increased in order to further increase the exhaust gas temperature.
The so slower, the stability limit correction angular coefficient A _SA by reducing small angle .DELTA.A, small angle .DELTA.A to further retard the result.

At P24, the basic ignition timing ADV _{0 is set} to P
22 or corrected based on the stable limit correction angular coefficient A _SA set in P23, the ignition timing ADV is calculated by the following equation. ADV = ADV ₀ + A _SA Then, the routine is terminated, and the ignition coil is set so that sufficient ignition energy is obtained by the ignition timing ADV.
The energization to the primary side is started, and when the ignition timing ADV is detected based on the detection signal of the crank angle sensor 10, the energization is cut off to generate a high voltage on the secondary side, and the ignition plug 11
Is supplied with a high voltage for spark ignition.

On the other hand, if it is determined in P5 that the vehicle is not in the idle state, the secondary air is not supplied and the ignition control accompanying the secondary air supply is not performed.
P6 to P24 jump and proceed to P25. Then, in P25, without correcting the basic ignition timing ADV _0, the ignition timing ADV. Accordingly, it is possible to correct the ignition timing without greatly changing the stability of the engine, and as shown in FIG. 12, the ignition timing is corrected to the vicinity of the retard limit only during the idle time when the exhaust gas temperature decreases. By doing so, the unburned C
Since O and HC are discharged and the secondary air is reburned to raise the exhaust gas temperature, the temperature at the inlet of the catalyst rises, and the catalyst temperature can be raised and activated more quickly.

Also, in the second embodiment, since the stability of the engine is determined based on the engine rotation speed N, there is an effect that an increase in cost can be suppressed. Further, in the second embodiment, it is not necessary to increase the fuel injection amount in order to secure the stability of the engine, so that there is an effect that the fuel efficiency can be improved. Next, fuel supply control according to a third embodiment of the present invention will be described with reference to the flowchart of FIG. This routine is also executed every 10 msec.

In the description of FIG. 6, steps having the same functions as those in FIG. 4 are denoted by the same step numbers, and the description thereof is omitted. In P4, a basic increase coefficient K _Tw based on the cooling water temperature _Tw is set, and the program proceeds to P31. At P31, the in-cylinder pressure (combustion chamber pressure) Pn of each cylinder of the engine 1 is detected by the in-cylinder pressure sensor 21.

At P5, by reading the fully closed position signal of the throttle valve 7 from the throttle sensor 15, it is determined whether or not the throttle valve 7 is at the idle position.
The process proceeds to P6 only when it is determined that the vehicle is in the idle state. In P7, the electric air pump 19 is turned on to supply secondary air to the exhaust passage upstream of the three-way catalyst 17, and then the process proceeds to P32.

At P32, the in-cylinder pressure P of each cylinder is determined based on signals from the in-cylinder pressure sensor 21 and the crank angle sensor 10.
crank angle theta] p _max when n represents the maximum pressure P _max
Is detected (see FIG. 13). In P33, we calculate the standard deviation Yushita _n crank angle theta] p _max detected in P32 according to the following equation.

[0048]

(Equation 2)

[0049] In P34, compares the standard deviation Yushita _n predetermined value (10 in this embodiment). And the standard deviation Uθ
_{When n} is larger than a predetermined value, the fuel injection amount T set by performing various corrections on the basic fuel injection amount Tp is set.
The control proceeds to P11 on the assumption that the stability is poor because i becomes too large and becomes too rich, and the stability limit correction coefficient K _SA is reduced by a small value ΔK.

Here, the operation of this step will be described. When the engine becomes unstable, the in-cylinder pressure P
crank angle theta] p _max when n represents the maximum pressure P _max
But variations, has also increased variation of torque, the standard deviation Yushita _n is greater than the predetermined value varies the crank angle theta] p _max. Further, as shown in FIG. 9, when the air-fuel ratio (A / F) is too rich, the crank angle θp _max varies and the standard deviation Uθ _n becomes larger than a predetermined value, so that the stability exceeds the stability limit. It will be.

On the other hand, at P34, the standard deviation Uθ _n
If it is determined that is not larger than the predetermined value, it is determined that the stability is good and the stability is sufficient, the process proceeds to P12, and a large amount of unburned CO and HC is discharged to the exhaust passage 20 upstream of the catalyst 17. to re-combustion by the secondary air is, so as to increase the amount of fuel injection, to increase the stability limit correction coefficient K _SA by a small value [Delta] K, enriching.

Therefore, it is possible to correct the fuel injection amount without greatly changing the stability of the engine.
As shown in FIG. 10, only at the time of idling when the exhaust gas temperature decreases, the air-fuel ratio is brought close to the vicinity of the rich limit so that the unburned CO and HC are positively discharged, and the exhaust gas is raised by reburning with the secondary air. Therefore, the inlet temperature of the catalyst rises, and the catalyst temperature can be raised and activated earlier.

Further, since the degree of stability of the engine is determined based on the in-cylinder pressure Pn of each cylinder, the combustion state of the engine 1 can be immediately detected. Can be performed with high accuracy. Further, it is possible to perform the increase correction of the fuel injection amount up to the vicinity of the stability limit without largely changing the stability of the engine, and there is also an effect that it is possible to operate the engine 1 while suppressing a decrease in the output. .

Next, referring to the flowchart of FIG.
The ignition timing control according to the fourth embodiment of the present invention will be described. In the description of FIG. 7, steps having the same functions as those in FIGS. 5 and 6 are denoted by the same step numbers,
The description will be simplified. At P21, the basic ignition timing ADV ₀ of the corresponding operating condition is searched for and obtained.

At P31, the in-cylinder pressure Pn of each cylinder is detected. When the secondary air is supplied in the idle state, at P32, the in-cylinder pressure Pn of each cylinder becomes the maximum pressure _Pmax based on the signals from the in-cylinder pressure sensor 21 and the crank angle sensor 10. detecting the crank angle theta] p _max when indicated, at P33, to calculate the standard deviation Yushita _n crank angle theta] p _max was detected at P32.

[0056] In P34, compares the standard deviation Yushita _n predetermined value (10 in this embodiment). And the standard deviation Uθ
_{If n} is larger than a predetermined value, the basic ignition timing ADV ₀
And the program proceeds to P22 because the stability is poor because too much retard correction has been performed, and the stability limit correction angle coefficient A _{SA is changed} to a small angle Δ
A is increased by a small angle ΔA.

Here, the operation of this step will be described. When the engine becomes unstable, the in-cylinder pressure P
crank angle theta] p _max when n represents the maximum pressure P _max
But variations, has also increased variation of torque, the standard deviation Yushita _n is greater than the predetermined value varies the crank angle theta] p _max. Further, as shown in FIG. 11, when the ignition timing ADV (described below) is too retarded, the crank angle theta] p _max and the varied standard deviation Yushita _n becomes larger than the predetermined value, with the stability in the stability limit Will be exceeded.

On the other hand, at P34, the standard deviation Uθ _n
Is not larger than the predetermined value, it is determined that the stability is good and the stability is sufficient, the process proceeds to P23, and the ignition timing ADV is increased in order to further increase the exhaust gas temperature.
The so slower, the stability limit correction angular coefficient A _SA by reducing small angle .DELTA.A, small angle .DELTA.A to further retard the result.

At P24, the basic ignition timing ADV _{0 is set} to P
22 or corrected based on the stable limit correction angular coefficient A _SA set in P23, the ignition timing ADV is calculated by the following equation. ADV = ADV ₀ + A _SA Then, the routine is terminated, and the ignition coil is set so that sufficient ignition energy is obtained by the ignition timing ADV.
The energization to the primary side is started, and when the ignition timing ADV is detected based on the detection signal of the crank angle sensor 10, the energization is cut off to generate a high voltage on the secondary side, and the ignition plug 11
Is supplied with a high voltage for spark ignition.

On the other hand, if it is determined in P5 that the vehicle is not in the idle state, the supply of the secondary air is not performed, and the ignition control associated with the supply of the secondary air is not performed.
P6 to P24 jump and proceed to P25. Then, in P25, without correcting the basic ignition timing ADV _0, the ignition timing ADV. Therefore, it is possible to correct the ignition timing without greatly changing the stability of the engine, and as shown in FIG. 12, the ignition timing is corrected to the vicinity of the retard limit only during the idle time when the exhaust gas temperature decreases. By doing so, the unburned CO and HC are positively discharged and the exhaust air temperature is raised by reburning with the secondary air, so that the temperature at the inlet of the catalyst rises and the catalyst can be activated earlier. It becomes possible.

Also, in the fourth embodiment, since the stability of the engine is determined based on the fluctuation of the in-cylinder pressure Pn of each cylinder, the combustion state of the engine 1 can be immediately detected. Therefore, control within the stability limit can be performed accurately. Further, also in the fourth embodiment, it is not necessary to increase the fuel injection amount in order to secure the stability of the engine, so that there is an effect that the fuel efficiency can be improved.

[0062]

As described above, according to the present invention, when the engine is idling and the engine temperature is low, the secondary air is supplied to the exhaust passage of the engine and the secondary air is supplied. When the stability is high based on the stability of the engine at the time, the correction amount of the fuel supply amount is set to be increased or the correction value of the ignition timing is set to be retarded, so that the drivability is deteriorated due to torque fluctuation. The exhaust temperature is positively increased only during idle time when there is no influence and the exhaust temperature is reduced, the catalyst inlet temperature is increased, the catalyst temperature is increased more quickly, and the catalyst is activated. Become.

Further, without greatly changing the stability of the engine detected based on the fluctuation of the engine rotation speed or the in-cylinder pressure of each cylinder, the fuel injection amount is increased or the ignition timing is delayed until the stability limit is reached. Angle correction can be performed, and there is also an effect that it is possible to operate the engine 1 while suppressing a decrease in output.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration according to claim 1 of the present invention.

FIG. 2 is a block diagram illustrating a configuration according to claim 2 of the present invention.

FIG. 3 is a schematic diagram showing a system configuration according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a fuel supply control operation according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing an ignition timing control operation according to a second embodiment of the present invention.

FIG. 6 is a flowchart showing a fuel supply control operation according to a third embodiment of the present invention.

FIG. 7 is a flowchart showing an ignition timing control operation according to a fourth embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a change in rotation speed during an explosion cycle of each cylinder.

FIG. 9 is a characteristic diagram showing a relationship between an air-fuel ratio and stability.

FIG. 10 is a temperature characteristic diagram showing the effect of the present embodiment.

FIG. 11 is a characteristic diagram showing a relationship between ignition advance and stability.

FIG. 12 is a temperature characteristic diagram showing the effect of the present embodiment.

FIG. 13 is a characteristic diagram showing a relationship between a maximum in-cylinder pressure _Pmax and a crank angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Air flow meter 7 Throttle valve 8 Fuel injection valve 9 Control unit 10 Crank angle sensor 11 Spark plug 14 Water temperature sensor 15 Throttle sensor 17 Three-way catalyst 19 Electric air pump 20 Exhaust passage 21 In-cylinder pressure sensor

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301H 301T 45/00 314 45/00 314Q 362 362J F02P 5/15 F02P 5/15 E

Claims (3)

(57) [Claims] An engine operating state detecting means for detecting an engine operating state including at least an intake air flow rate and an engine rotational speed;
Basic fuel supply amount setting means for setting a basic fuel supply amount based on the detected intake air flow rate and engine rotation speed, and a fuel for increasing or decreasing the correction amount of the basic fuel supply amount in accordance with the detected operation state An injection amount correction amount setting unit, a fuel supply amount setting unit that corrects the set basic fuel injection amount based on the set correction amount of the fuel injection amount and sets a final fuel supply amount, A fuel supply control unit for supplying fuel to the engine based on the set final fuel supply amount, an idle operation state detection unit for detecting an idle operation state of the engine, and a temperature of the engine. Engine temperature detecting means for detecting,
Secondary air supply means interposed in an exhaust passage of the engine to supply secondary air to an exhaust passage upstream of a catalyst for purifying exhaust when the engine is in an idle operation state and the engine temperature is low;
A stability detecting means for detecting the stability of the engine when the next air is supplied, and a fuel increase for setting a correction amount of the fuel supply amount when the stability is high based on the detected stability of the engine. A control device for an internal combustion engine, comprising: a correction unit. 2. An engine operating state detecting means for detecting an engine operating state including at least an intake air flow rate and an engine speed.
Basic fuel supply amount setting means for setting a basic fuel supply amount based on the detected intake air flow rate and the engine rotation speed, and setting a basic ignition timing based on the detected engine rotation speed and the basic fuel supply amount. Basic ignition timing setting means, ignition timing correction value setting means for increasing or decreasing the correction value of the basic ignition timing according to the detected operating state, and the ignition timing correction value set based on the set ignition timing correction value. An internal combustion engine comprising: ignition timing setting means for correcting a basic ignition timing to set a final ignition timing; and ignition signal output means for outputting an ignition signal to an ignition device based on the set final ignition timing. In the engine, idle operating state detecting means for detecting an idle operating state of the engine, engine temperature detecting means for detecting the temperature of the engine,
Secondary air supply means interposed in an exhaust passage of the engine to supply secondary air to an exhaust passage upstream of a catalyst for purifying exhaust when the engine is in an idle operation state and the engine temperature is low;
A stability detection means for detecting the stability of the engine when the next air is supplied, and an ignition timing for delay setting the correction value of the ignition timing when the stability is high based on the detected stability of the engine. A control device for an internal combustion engine, comprising: a retard correction means. 3. The system according to claim 1, wherein the stability detecting means detects the stability of the engine based on the fluctuation of the engine speed detected by the engine operating state detecting means or the fluctuation of the in-cylinder pressure of each cylinder. 3. The control device for an internal combustion engine according to 1 or 2.