JPH0681696A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To substantially raise performance of reducing harmful component in the exhaust gas while maintaining a good operational property by carrying out retarding of ignition timing and increasing of fuel quantity as close as possible to its stability limit. CONSTITUTION:When the cooling water temperature Tw is low during idle operation of an internal combustion engine, an air pump 19 is switched on (P5 to P7), and when a standard deviation Uomegan of the a maximum engine speed omegan in the course of an explosion cycle of each cylinder is higher than the specified value (P10), a stability limit correction coefficient KSA is made lower by a minuteness value DELTAK and made lean by way of the engine being in an unstable condition. (P11). When the Uomegan is not higher than the specified value (P11), the stable limit correction coefficient KSA is made higher by a minuteness value DELTAK and made rich by way of the engine still being in a stable condition. (P12).

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 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 reburn the harmful components CO and HC in the exhaust gas to reduce the amount. Further, since the secondary air is normally supplied to the upstream side of the exhaust purification catalyst, C
Since the exhaust gas whose temperature has risen due to the re-combustion of O and HC flows into the exhaust gas purification catalyst and the catalyst temperature can be raised, the catalyst is activated early, and the exhaust gas purification performance can be greatly improved.

It is to be noted that, if the secondary air is constantly supplied, the exhaust purification catalyst is overheated and rather its function is impaired, or it is deteriorated by high heat, so operating conditions (for example, stability Therefore, it is performed only during steady idling when the mixing ratio is made rich (Japanese Patent Publication Sho 5).
3-9663). By the way, in the area where the secondary air is supplied, even if the amount of the secondary air supplied is more 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 performed. Be damaged.

For this reason, an exhaust temperature sensor for detecting the exhaust temperature is provided upstream of the exhaust purification catalyst, and when the exhaust 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 engine output drop when the ignition timing is retarded, the fuel injection amount is corrected corresponding to the cooling water temperature (Japanese Patent Laid-Open No. 3-164549).
(See the official gazette).

[0005]

However, if the ignition timing is retarded too much, 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. Further, if the correction amount of the fuel injection amount is too large, misfiring occurs, so that the stability limit is similarly set with a margin.

That is, CO and HC which are harmful components in the exhaust gas
Although it is necessary to raise the temperature of the catalyst and activate the catalyst in order to significantly improve the reduction performance of the engine, it is also necessary to ensure good drivability in the conventional internal combustion engine. Therefore, there is a problem that a prompt response cannot be taken. The present invention has been made in view of the above problems, by monitoring the stability of the engine, retarding the ignition timing and increasing the fuel amount as close to the stability limit as possible, while ensuring good drivability. The purpose is to greatly improve the performance of reducing harmful components in exhaust gas.

[0007]

Therefore, the present invention provides the first aspect of the present invention.
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 a technical means for detecting the intake air flow rate and the engine rotation speed are used. Basic fuel supply amount setting means for setting the 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 correction amount of the amount and setting a final fuel supply amount,
In an internal combustion engine comprising: a fuel supply control means for supplying fuel to an engine based on the set final fuel supply amount, an idle operation state detection means for detecting an idle operation state of the engine, and an engine temperature. For detecting the engine temperature and a secondary air for supplying secondary air to the exhaust passage upstream of the catalyst which is interposed in the exhaust passage of the engine and purifies the exhaust when the engine is in the idle operation state and the engine temperature is low. Air supply means, stability detection means for detecting stability of the engine when secondary air is supplied, and 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 increasing and setting.

As a second technical means, as shown in FIG. 2, an engine operating state detecting means for detecting an engine operating state including at least the intake air flow rate and the engine rotation speed, and the detected intake air flow rate. Basic fuel supply amount setting means for setting a basic fuel supply amount based on the engine rotation speed, and basic ignition timing setting means for setting a basic ignition timing based on the detected engine rotation speed and the basic fuel supply amount, 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 including: 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 the idle operating state of the engine, an engine temperature detecting means for detecting the temperature of the engine, and an engine temperature detecting means for detecting the temperature of the engine, and an exhaust passage of the engine when the engine is in the idle operating state and the engine temperature is low. 2) Supply secondary air to the exhaust passage upstream of the catalyst
Secondary air supply means, stability detection means for detecting stability of the engine when secondary air is supplied, and correction value of the ignition timing when the stability is high based on the detected stability of the engine May be configured to include an ignition timing retard correction means for setting the retard angle.

Further, the stability detecting means in the first technical means and the second technical means is based on the fluctuation of the engine rotational speed detected by the engine operating state detecting means or the fluctuation of the cylinder pressure of each cylinder. Alternatively, the stability of the engine may be detected.

[0010]

According to the first technical means, the secondary air is supplied to the exhaust passage of the engine when the engine is idle and the engine temperature is low, and based on the stability of the engine at that time. It is possible to accelerate the temperature rise of the catalyst while ensuring the stability by increasing the fuel supply amount.

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, and based on the stability of the engine at that time. Thus, the ignition timing is corrected and the stability can be secured, and the temperature rise of the catalyst can be accelerated. That is, since there is no influence of deterioration of drivability due to torque fluctuation of the engine and the exhaust temperature is positively raised only during the idle time when the exhaust temperature falls, the inlet temperature of the catalyst interposed in the exhaust passage rises. It becomes possible to activate the catalyst earlier.

Further, when the engine becomes unstable, the maximum rotation speed in each cylinder during the explosion cycle varies, and the fluctuation in rotation increases, so that the stability of the engine can be detected from the fluctuation in rotation. Further, the in-cylinder pressure of each cylinder also varies depending on the stability of the engine similarly to the engine rotation speed, so that the stability of the engine can be detected by the fluctuation of the in-cylinder pressure.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3 showing the system configuration of one embodiment, air is drawn into the internal combustion engine 1 through 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 the intake air flow rate Q. The throttle chamber 4 is provided with a throttle valve 7 interlocking with an accelerator pedal (not shown) to control the intake air flow rate Q. The throttle valve 7 has a throttle sensor.
15 is additionally provided, and has a function of an idle switch that outputs a voltage signal according to the opening TVO of the throttle valve 7 and outputs a fully closed position signal of the throttle valve 7.

Further, an idle switch may be provided so that the idle switch is turned on at the fully closed position of the throttle valve 7. The intake manifold 5 is provided with an electromagnetic fuel injection valve 8 for each cylinder, and injects fuel, which is controlled to a predetermined pressure by a pressure regulator pressure-fed from a fuel pump (not shown), to the engine 1.

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, and an intake air flow rate 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 the final fuel injection amount Ti, and a drive pulse signal having a pulse width corresponding to this fuel injection amount Ti is set in 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, as the correction amount for correcting the basic fuel injection amount Tp, various correction coefficients including a startup increase correction based on the cooling water temperature Tw representing the engine temperature detected by the water temperature sensor 14 are included. COEF, an air-fuel ratio feedback correction coefficient α for feedback-correcting an actual air-fuel ratio to a target air-fuel ratio (for example, a theoretical air-fuel ratio), and a correction for correcting a change in the invalid injection time of the fuel injection valve 8 due to a battery voltage. There are minutes Ts and the like.

The air-fuel ratio feedback correction coefficient α is
On the basis of the oxygen concentration in the exhaust gas detected by the oxygen sensor 16 installed in the exhaust passage 20, rich / lean with respect to the target 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. The setting is controlled by, for example, proportional-plus-integral control so as to approach. In addition, in the exhaust passage 20 on the downstream side of the oxygen sensor 16, a three-way catalyst 17 for oxidizing and reducing CO, HC, and NO _x in the exhaust gas to purify it is provided, and the downstream side of the three-way catalyst 17 is provided. Is equipped with a muffler 18.

Further, each cylinder of the engine 1 is provided with a spark plug 11, to which high voltage generated in an ignition coil 12 is sequentially applied via a distributor 13, whereby spark ignition and mixing are performed. Ignite and burn the air. here,
The ignition coil 12 is 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 is composed of the above-mentioned spark plug 11, ignition coil 12, power transistor 12a and distributor 13. The ignition device may be provided with the ignition coil 12 and the power transistor 12a for each cylinder, and the power distribution by the distributor 13 may not be performed.

That is, in the control unit 9,
The optimum ignition timing (ignition advance value) ADV is determined by arithmetic processing based on various input signals, and the ignition timing ADV
An ignition signal is sent to the power transistor 12a for driving the ignition coil 12 so that the ignition is performed at. Specifically, the basic ignition timing ADV ₀ of the corresponding operating condition is searched from the map of the basic ignition timing which is set in advance according to the operating conditions of the engine speed N and the basic fuel injection amount Tp representing the engine load. On the other hand, the final ignition timing ADV is set by increasing / decreasing the correction value of the basic ignition timing ADV _{0 according} to the presence or absence of engine knocking.

When the primary side of the ignition coil 12 is energized so that sufficient ignition energy is obtained by the ignition timing ADV, and 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 cutting off the power supply to the spark plug 11, and the spark plug is ignited by supplying the high voltage to the spark plug 11. The correction value is a correction term that is added to the basic ignition timing ADV ₀ with an initial value of zero. If knocking occurrence is not detected, it is increased by a predetermined value (advance angle correction) and conversely, knocking occurrence is detected. Then, it is set to be decreased by a predetermined value (retarded angle correction), so that ignition is performed with the advance value just before knocking occurs.

Further, in the present embodiment, an electric air pump 19 is installed in the secondary air supply pipe for supplying the secondary air to the exhaust passage 20 upstream of the three-way catalyst 17, and in response to a command from the control unit 9. It is on / off controlled 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 portion of an ignition plug 11 provided for each cylinder of the engine 1, and an in-cylinder pressure for each cylinder is provided. The pressure signals respectively output according to the above are input to the control unit 9.

Here, the fuel supply control and ignition timing control performed by the control unit 9 will be described according to the programs shown in the flow charts of FIGS. 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, the fully closed position signal of the throttle valve 7 is read from the throttle sensor 15.

At P2, the intake air flow rate Q is measured by the air flow meter 6, the engine rotational speed N is determined based on the signal from the crank angle sensor 10, and the cooling water temperature T is determined by the water temperature sensor 14.
Each w is detected. That is, the air flow meter 6, the crank angle sensor 10 and the like constitute an engine operating state detecting means, and the water temperature sensor 14 constitutes an engine temperature detecting means.

At P3, the basic fuel injection amount Tp = K × Q / N (K is a constant) is calculated from the intake air flow rate Q and the engine rotation speed N. That is, the step has the function of the basic fuel supply amount setting means. At P4, the 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 functions as the idle operation state detecting means. At P6, it is determined whether or not the cooling water temperature Tw is lower than or equal to a predetermined temperature. If the cooling water temperature Tw is lower than or equal to the predetermined temperature, it is considered that the cooling water temperature Tw is low, and thus the three-way catalyst 17 is in an inactive state. Proceeding to the following, the control according to the present invention is implemented. At P7, the electric air pump 19 is turned on to supply the secondary air to the exhaust passage upstream of the three-way catalyst 17.

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

At P9, the standard deviation Uω _n of the rotation speed ω _n detected at P8 is calculated according to the following equation.

[0029]

[Equation 1]

At P10, the standard deviation Uω _n is compared with a predetermined value (10 in this embodiment). And the standard deviation Uω
_{When n} is larger than the predetermined value, the fuel injection amount Tp set by various corrections to the basic fuel injection amount Tp
Since i becomes too large and the air-fuel ratio (A / F) becomes too rich, the stability is considered to be poor, and the process proceeds to P11, where the stability limit correction coefficient K _SA is reduced by a minute value ΔK.

The operation of this step will now be described. When the engine becomes unstable, the maximum rotation speed ω _n in each cylinder during the explosion cycle varies, and the generated torque also fluctuates, and the maximum rotation speed ω increases. _{Since n} varies, the standard deviation Uω _n becomes larger than the predetermined value. Also in FIG.
As shown in, when the air-fuel ratio is too rich, the maximum rotation speed ω _n fluctuates and the standard deviation U ω _n becomes larger than a predetermined value, so that the stability exceeds the stability limit.

On the other hand, at P10, the standard deviation Uω _n
When it is determined that is not larger than the predetermined value, the stability is high and good, and there is a margin of stability, 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 heat generation amount by re-combusting with the secondary air, the stability limit correction coefficient K _SA is increased by a small value ΔK to increase the air-fuel ratio so that the fuel injection amount is increased. Approach the rich limit.

That is, P9 and P10 function as stability detection means, and P12 functions as fuel increase correction means. At P13, the fuel injection amount T is set based on the basic fuel increase amount K _Tw set at P4 and the stability limit correction coefficient K _SA set at P11 or P12 at P13.
i is calculated by the following equation.

Ti = Tp × (1 + K _Tw + K _SA ) + Ts Then, the routine is finished 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, the series of operations up to this point is performed as the fuel supply control means.

On the other hand, if it is determined in P5 that the engine is not in the idle state, neither the secondary air is supplied nor the combustion control associated with the secondary air supply is executed.
P6 to P13 jump and proceed to P14. Then, at P14, the basic fuel injection amount Tp is corrected based on the basic fuel 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 finished 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. Therefore, it becomes possible to correct the fuel injection amount without significantly changing the stability of the engine, and as shown in FIG. 10, by bringing the air-fuel ratio close to the rich limit only in the idling time when the exhaust temperature decreases. , The unburned CO and HC are positively discharged and the secondary air is re-combusted to raise the exhaust temperature while minimizing the deterioration of fuel efficiency, so that the inlet temperature of the catalyst rises and the It becomes possible to raise the catalyst temperature to activate the catalyst.

Further, since the stability of the engine is judged based on the engine speed N, it is not necessary to specially provide a sensor or the like for detecting the engine speed N, and the cost increase can be suppressed. There is also the effect. Furthermore, it becomes possible to perform the increase correction of the fuel injection amount near the stability limit without greatly changing the stability of the engine,
There is also an effect that it becomes possible to operate while suppressing the output reduction of the engine 1 when raising the exhaust gas temperature.

Next, referring to the flow chart of FIG.
The ignition timing control according to the second embodiment of the present invention will be described. Further, in the description of FIG. 5, steps having the same functions as those in FIG. 4 are designated by the same step numbers, and the description thereof will be 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 selected from the basic ignition timing map which is set in advance in accordance with the operating conditions of the engine speed N and the basic fuel injection amount Tp representing the engine load. Search for and ask. At P10, the standard deviation Uω _n is compared with a predetermined value (10 in this embodiment). When the standard deviation Uω _n is larger than the predetermined value, the retard angle correction is performed too much with respect to the basic ignition timing ADV ₀ , the stability is considered to be poor, and the process proceeds to P22 to set the stability limit correction angle coefficient A _SA to a small angle. Increase by ΔA, and as a result, advance by a minute angle ΔA.

The operation of this step will now be described. When the engine becomes unstable, the maximum rotation speed ω _n in each cylinder during the explosion cycle varies, and the generated torque also fluctuates, and the maximum rotation speed ω increases. _{Since n} varies, the standard deviation Uω _n becomes larger than the predetermined value. Fig. 11
As shown in FIG. 5, when the ignition timing ADV (described later) is retarded too much, the maximum rotation speed ω _n varies and the standard deviation U ω _n becomes larger than a predetermined value, so that the stability exceeds the stability limit. Becomes

On the other hand, at P10, the standard deviation Uω _n
If it is determined that is not greater than the predetermined value, the stability is high and good, and there is a margin in stability, the process proceeds to P23, and the ignition timing ADV is set in order to further raise the exhaust temperature.
The stability limit correction angle coefficient A _SA is made smaller by a minute angle ΔA so as to delay, and as a result, the angle is further retarded by a minute angle ΔA.

At P24, the basic ignition timing ADV _{0 is set} to P
22 or P23 is corrected based on the stability limit correction angle coefficient A _SA set, and 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 adjusted so that sufficient ignition energy can be obtained by the ignition timing ADV.
A high voltage is generated on the secondary side by starting energization to the primary side of 12 and interrupting the energization when the ignition timing ADV is detected based on the detection signal of the crank angle sensor 10, thereby generating a spark plug 11
A high voltage is supplied to spark ignition.

On the other hand, if it is determined in P5 that the engine is not in the idle state, neither the secondary air is supplied nor the ignition control associated with the secondary air supply is executed.
Jump from P6 to P24 and proceed to P25. Then, at P25, the basic ignition timing ADV ₀ is set to the ignition timing ADV without being corrected. Therefore, it becomes possible to correct the ignition timing without significantly changing the stability of the engine, and as shown in FIG. 12, the ignition timing is retarded near the retard limit only during the idle time when the exhaust temperature decreases. To reduce undesired C
Since O and HC are discharged and the secondary air is re-combusted to raise the exhaust temperature, the catalyst inlet temperature rises, and the catalyst temperature can be raised and activated more quickly.

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

In the description of FIG. 6, steps having the same functions as those in FIG. 4 are designated by the same step numbers, and the description thereof will be omitted. In P4, after setting the basic increase coefficient K _Tw based on the cooling water temperature Tw, the process proceeds to P31. At P31, the in-cylinder pressure sensor 21 detects the in-cylinder pressure (combustion chamber pressure) Pn for each cylinder of the engine 1.

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

At P32, based on the signals from the cylinder pressure sensor 21 and the crank angle sensor 10, the cylinder pressure P for each cylinder is set.
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]

At P34, the standard deviation Uθ _n is compared with a predetermined value (10 in this embodiment). And the standard deviation Uθ
_{When n} is larger than the predetermined value, the fuel injection amount Tp set by various corrections to the basic fuel injection amount Tp
Since i has become too large and has become too rich, the stability is considered to be poor, and the process proceeds to P11 to decrease the stability limit correction coefficient K _SA by a minute value ΔK.

The operation of this step will now be described. When the engine becomes unstable, the in-cylinder pressure P for each cylinder will be described.
crank angle theta] p _max when n represents the maximum pressure P _max
And the generated torque also fluctuates, and the crank angle θp _max fluctuates and the standard deviation Uθ _n becomes larger than a predetermined value. Further, as shown in FIG. 9, when the air-fuel ratio (A / F) is too rich, the crank angle θp _max fluctuates 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
When it is determined that is not greater than the predetermined value, the stability is high and good, and there is a margin of stability, 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 reburn the secondary air with the secondary air, the stability limit correction coefficient K _SA is increased by a minute value ΔK so as to increase the fuel injection amount, and the fuel is enriched.

Therefore, the fuel injection amount can be corrected without significantly changing the stability of the engine.
As shown in 10, the unburned CO and HC are positively discharged by bringing the air-fuel ratio close to the rich limit only during idle time when the exhaust temperature decreases, and the exhaust temperature is raised by recombusting with secondary air. Therefore, the catalyst inlet temperature rises, and the catalyst temperature can be raised and activated more quickly.

Further, since the stability of the engine is judged based on the in-cylinder pressure Pn for each cylinder, the combustion state of the engine 1 can be immediately detected, so that the control within the stability limit is possible. Can be performed accurately. Further, there is also an effect that the fuel injection amount can be increased and corrected to the vicinity of the stability limit without greatly changing the stability of the engine, and the engine 1 can be operated while suppressing the output reduction. .

Next, referring to the flow chart of FIG.
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 designated by the same step numbers,
The explanation will be simplified. At P21, the basic ignition timing ADV ₀ under the corresponding operating condition is searched and obtained.

At P31, the in-cylinder pressure Pn for each cylinder is detected. When the secondary air is supplied in the idle state, at P32, the cylinder pressure Pn of each cylinder is the maximum pressure _Pmax based on the signals from the cylinder pressure sensor 21 and the crank angle sensor 10. The crank angle θp _max at the time shown is detected, and in P33, the standard deviation Uθ _n of the crank angle θp _max detected in P32 is calculated.

At P34, the standard deviation Uθ _n is compared with a predetermined value (10 in this embodiment). And the standard deviation Uθ
_{When n} is larger than the predetermined value, the basic ignition timing ADV ₀
However, since the retard correction is performed too much, the stability is considered to be poor, and the process proceeds to P22, where the stability limit correction angle coefficient A _{SA is set} to a small angle Δ
It is increased by A, and as a result, it is advanced by a minute angle ΔA.

The operation of this step will now be described. When the engine becomes unstable, the cylinder pressure P for each cylinder will be described.
crank angle theta] p _max when n represents the maximum pressure P _max
And the generated torque also fluctuates, and the crank angle θp _max fluctuates and the standard deviation Uθ _n becomes larger than a predetermined value. Further, as shown in FIG. 11, when the ignition timing ADV (described later) is retarded too much, the crank angle θp _max varies and the standard deviation Uθ _n becomes larger than a predetermined value, so that the stability is stable. Will be exceeded.

On the other hand, at P34, the standard deviation Uθ _n
If it is determined that is not greater than the predetermined value, the stability is high and good, and there is a margin in stability, the process proceeds to P23, and the ignition timing ADV is set in order to further raise the exhaust temperature.
The stability limit correction angle coefficient A _SA is made smaller by a minute angle ΔA so as to delay, and as a result, the angle is further retarded by a minute angle ΔA.

At P24, the basic ignition timing ADV _{0 is set} to P
22 or P23 is corrected based on the stability limit correction angle coefficient A _SA set, and 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 adjusted so that sufficient ignition energy can be obtained by the ignition timing ADV.
A high voltage is generated on the secondary side by starting energization to the primary side of 12 and interrupting the energization when the ignition timing ADV is detected based on the detection signal of the crank angle sensor 10, thereby generating a spark plug 11
A high voltage is supplied to spark ignition.

On the other hand, if it is judged at P5 that the engine is not in the idle state, neither the secondary air is supplied nor the ignition control associated with the secondary air supply is executed.
Jump from P6 to P24 and proceed to P25. Then, at P25, the basic ignition timing ADV ₀ is set to the ignition timing ADV without being corrected. Therefore, it becomes possible to correct the ignition timing without significantly changing the stability of the engine, and as shown in FIG. 12, the ignition timing is retarded near the retard limit only during the idle time when the exhaust temperature decreases. By doing so, unburned CO and HC are positively discharged and re-combusted with secondary air to raise the exhaust temperature, so that the inlet temperature of the catalyst rises and the catalyst can be activated earlier. It will be possible.

Further, in the fourth embodiment as well, the stability of the engine is judged based on the fluctuation of the in-cylinder pressure Pn for each cylinder, so the combustion state of the engine 1 can be immediately detected. Therefore, it is possible to perform control within the stability limit with high accuracy. 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 consumption can be improved.

[0062]

As described above, according to the present invention, when the engine is idle 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 this time, the correction amount of the fuel supply amount is increased or the correction value of the ignition timing is retarded. Exhaust temperature is positively increased only during idle time when there is no effect and exhaust temperature decreases, and the catalyst inlet temperature rises and the catalyst temperature rises faster and is activated. Become.

Further, without significantly changing the stability of the engine detected based on the fluctuation of the engine rotation speed or the fluctuation of the cylinder pressure of each cylinder, the fuel injection amount increase correction and the ignition timing delay are performed to the vicinity of the stability limit. The angle correction can be performed, and the engine 1 can be operated while suppressing the output reduction.

[Brief description of 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 of an embodiment of the present invention.

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

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

FIG. 6 is a flowchart showing a fuel supply control operation according to the 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 changes in rotation speed of each cylinder during an explosion cycle.

FIG. 9 is a characteristic diagram showing the relationship between 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 the 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 the relationship between the maximum in-cylinder pressure P _max and the crank angle.

[Explanation 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 Cylinder Pressure Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display area F02D 43/00 H 7536-3G B 7536-3G 45/00 314 Q 7536-3G 362 J 7536-3G F02P 5/15 E

Claims (3)

[Claims] 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,
Basic fuel supply amount setting means for setting a basic fuel supply amount based on the detected intake air flow rate and engine speed, and fuel for increasing / decreasing a correction amount of the basic fuel supply amount according to the detected operating 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; In an internal combustion engine including: a fuel supply control unit that supplies fuel to the engine based on the final fuel supply amount that has been set, an idle operation state detection unit that detects an idle operation state of the engine, and a temperature of the engine. Engine temperature detecting means for detecting,
Secondary air supply means for supplying secondary air to the exhaust passage upstream of the catalyst which is interposed in the exhaust passage of the engine and purifies the exhaust when the engine is in the idle operation state and the engine temperature is low;
Stability detection means for detecting the stability of the engine when the next air is supplied, and fuel increase amount for increasing and setting the 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 rotation 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 basic ignition timing is set 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 / decreasing the correction value of the basic ignition timing according to the detected operating state, and the setting based on the correction value of the set ignition timing. An internal combustion engine comprising: an ignition timing setting means for correcting the basic ignition timing to set a final ignition timing; and an ignition signal output means for outputting an ignition signal to an ignition device based on the set final ignition timing. In the engine, an idle operating state detecting means for detecting an idle operating state of the engine, an engine temperature detecting means for detecting an engine temperature,
Secondary air supply means for supplying secondary air to the exhaust passage upstream of the catalyst which is interposed in the exhaust passage of the engine and purifies the exhaust when the engine is in the idle operation state and the engine temperature is low;
Stability detection means for detecting the stability of the engine when the next air is supplied, and ignition timing for retarding 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 unit. 3. The stability detecting means detects the stability of the engine on the basis of fluctuations in the engine speed detected by the engine operating state detecting means or fluctuations in the cylinder pressure of each cylinder. 1. The control device for an internal combustion engine according to 1 or 2.