JP2003328820A - Control device for in-cylinder injection spark ignition internal combustion engine - Google Patents

Abstract

(57) [Problem] To provide a control device for a direct injection type spark ignition type internal combustion engine capable of ensuring idle stability and preventing deterioration of fuel efficiency during idling operation. SOLUTION: In a control device for a direct injection type spark ignition type internal combustion engine, a fuel injection control means is provided during idle operation (S1
0), when operating at an air-fuel ratio equal to or lower than the predetermined air-fuel ratio (S1
8) The fuel is divided into an intake stroke and a compression stroke,
(Stage mixing operation) (S20).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a cylinder injection type spark ignition internal combustion engine, and more particularly to a fuel injection control technique during idle operation of a cylinder injection type spark ignition four cycle internal combustion engine. .

[0002]

2. Related Background Art In a cylinder injection type spark ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber, fuel is normally compressed so that the air-fuel ratio becomes a lean air-fuel ratio during idle operation. The injection is performed during the process to improve idle stability and fuel efficiency. On the other hand, even during the idle operation, when the internal combustion engine (engine) is in a cold state, the compressor of the air conditioner is operated by the driving force of the engine, or the lean air-fuel ratio operation continues for a predetermined period or longer. For example, the air-fuel ratio is set near the rich air-fuel ratio and the fuel is injected during the intake stroke to perform homogeneous mixed combustion, thereby warming up the engine, improving the output or securing the negative pressure of the brake booster. To meet the requirements of.

[0003]

Even when the air-fuel ratio is set to be close to the rich air-fuel ratio and uniform mixed combustion is performed as described above, the fuel injection amount is small and the intake air is low as in the idle operation. In operating areas where the amount is small,
Due to the small in-cylinder flow, a sufficient air-fuel mixture is not generated and idle stability is not ensured.

In particular, there is a case where exhaust gas recirculation (EGR including internal EGR) is performed for cleaning the exhaust gas at the time of idling operation. Will be things. Therefore, normally, when there is a request for warm-up or the like during idle operation or when EGR is performed, the idle rotation speed is set high to ensure idle stability.

However, if the idle speed is set to a high value in this way, the engine speed becomes high even during the idle operation, so that the idle feeling is deteriorated or the engine speed is reduced. This is not preferable because a new problem arises in that fuel consumption deteriorates because the fuel injection amount increases by the amount of increase.

The present invention has been made in order to solve such problems, and an object thereof is to in-cylinder injection type which can secure idle stability and prevent deterioration of fuel consumption during idle operation. An object of the present invention is to provide a control device for a spark ignition type internal combustion engine.

[0007]

In order to achieve the above-mentioned object, the invention of claim 1 has a fuel injection valve for directly injecting fuel into a combustion chamber, and controls fuel injection from the fuel injection valve. In a control device for a cylinder injection type spark ignition internal combustion engine equipped with a fuel injection control means, the fuel injection control means, during idle operation, when operating at an air-fuel ratio of a predetermined air-fuel ratio or less, the fuel to the intake stroke The feature is that the injection is performed separately in the compression stroke.

That is, during idle operation, the air-fuel ratio is normally made lean so that fuel is injected in the compression stroke to improve idle stability and fuel efficiency. When operating the internal combustion engine at an air-fuel ratio equal to or lower than the air-fuel ratio (for example, a rich air-fuel ratio), the fuel is injected by being divided into an intake stroke and a compression stroke, so that the air-fuel ratio is relatively rich as a whole. Also, it is possible to prevent the air-fuel mixture in the vicinity of the spark plug from being excessively rich by the fuel injected in the compression stroke.

As a result, during idle operation, even when the internal combustion engine is operated at an air-fuel ratio below a predetermined air-fuel ratio (for example, a rich air-fuel ratio), the fuel injection in the compression stroke is continued and stable stratification is achieved. Combustion is realized, and it becomes possible to maintain a low idle rotation speed, and idle stability is ensured while preventing deterioration of fuel efficiency. In addition, claim 2
According to another aspect of the present invention, there is provided a control device for a cylinder injection type spark ignition internal combustion engine, comprising: a fuel injection valve for directly injecting fuel into a combustion chamber; and a fuel injection control means for controlling fuel injection from the fuel injection valve. The fuel injection control means is at least any one of during idle operation, when the internal combustion engine is in a cold state, when an air conditioner operated by the driving force of the internal combustion engine is operated, and when lean air-fuel ratio operation continues for a predetermined period or longer. In such a case, the fuel is divided into the intake stroke and the compression stroke, and divided injection is performed.

That is, during idle operation, the air-fuel ratio is normally made to be a lean air-fuel ratio, and fuel is injected in the compression stroke to improve idle stability and fuel economy, but when the internal combustion engine is in a cold state. When the lean air-fuel ratio is limited, such as when the air conditioner operated by the driving force of the internal combustion engine is operated or when the lean air-fuel ratio operation continues for a predetermined period or longer, the fuel is divided into the intake stroke and the compression stroke. Therefore, even if the air-fuel ratio is relatively rich as a whole, the fuel injected in the compression stroke is prevented from excessively enriching the air-fuel mixture in the vicinity of the spark plug.

As a result, a stable stratified combustion is realized by continuing the fuel injection in the compression stroke even when the lean air-fuel ratio is limited during the idle operation, and the idle rotation speed is kept low. Is possible, and idle stability is secured while preventing deterioration of fuel efficiency. Also,
According to a third aspect of the present invention, there is provided a cylinder injection type spark ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber, and including fuel injection control means for controlling fuel injection from the fuel injection valve. The control device includes exhaust gas recirculation means for recirculating a part of exhaust gas from the internal combustion engine to the intake system, and the fuel injection control means recirculates a part of the exhaust gas to the intake system by the exhaust gas recirculation means during idle operation. In this case, the fuel is divided into the intake stroke and the compression stroke and injected separately.

That is, during idle operation, fuel is usually injected in the compression stroke so that the air-fuel ratio becomes lean air-fuel ratio, and idle stability and fuel economy are improved, but part of the exhaust gas (EGR gas) Is recirculated to the intake system, and when the fresh air amount is relatively small and the air-fuel ratio becomes rich as a whole, the fuel is injected separately in the intake stroke and the compression stroke, and is injected in the compression stroke. It is possible to prevent the air-fuel mixture in the vicinity of the spark plug from being excessively enriched by the fuel thus burned.

As a result, during idle operation, even when part of the exhaust gas (EGR gas) is recirculated to the intake system and the air-fuel ratio becomes rich, the fuel injection in the compression stroke is continued and stable stratification is achieved. Combustion is realized, and it becomes possible to maintain the idle rotation speed at a low value, and good idle stability is ensured while preventing deterioration of fuel efficiency. In addition, claim 4
In the invention, the split ratio between the intake stroke and the compression stroke of the split injection is approximately 6 to 4.

That is, according to the experiments by the inventor, in the case of the cylinder injection type spark ignition internal combustion engine, the fuel injection amount in the compression stroke is suppressed to a small amount, and the split ratio of the split injection in the intake stroke and the compression stroke is reduced. It was found that the fluctuation of the idle rotation can be minimized by setting it to about 6: 4 (see FIG. 4). Therefore, by setting the split ratio of the split injection in the intake stroke and the compression stroke to about 6: 4, Good idle stability is ensured while preventing deterioration of fuel efficiency.

Further, the invention of claim 5 is characterized in that the split ratio of the split injection is corrected according to the rotational fluctuation of the internal combustion engine. Therefore, the split ratio of the split injection in the intake stroke and the compression stroke is always appropriate, the fluctuation of the idle rotation is efficiently minimized, and the idle stability is well ensured while preventing the deterioration of fuel consumption. It

Further, in the invention of claim 6, the internal combustion engine has an exhaust gas purification catalytic converter in the exhaust passage, and the fuel injection control means is in idle operation, and when a temperature rise of the catalytic converter is required. In preference to the divided injection, the fuel is injected during the compression stroke so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio. That is, during idle operation, when the catalytic converter is not yet in the active state and the temperature increase of the catalytic converter is required, the temperature increase of the catalytic converter is preferentially performed without being hindered by the split injection, and the air-fuel ratio is Fuel is injected only during the compression stroke so that it becomes close to the stoichiometric air-fuel ratio, and CO and oxygen are simultaneously and satisfactorily discharged to the exhaust passage, and the catalytic converter is activated early by the heat of reaction between these CO and oxygen.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of a control device for a cylinder injection type spark ignition internal combustion engine according to the present invention, which is mounted on a vehicle. Hereinafter, the configuration of the control device will be described.

As the internal combustion engine (hereinafter, engine) 1,
For example, a cylinder injection type in which fuel injection in the intake stroke (intake stroke injection) and fuel injection in the compression stroke (compression stroke injection) can be performed by switching the fuel injection mode to the intake stroke injection mode or the compression stroke injection mode A spark ignition type 4-cycle 4-cylinder gasoline engine is adopted. This in-cylinder injection type engine 1 facilitates operation at a stoichiometric air-fuel ratio and operation at a rich air-fuel ratio (rich air-fuel ratio operation) by switching the fuel injection mode and controlling the air-fuel ratio. , Lean air-fuel ratio operation (lean air-fuel ratio operation)
Is feasible.

As shown in the figure, the cylinder head 2 of the engine 1 is equipped with an electromagnetic injector (fuel injection valve) 6 together with a spark plug 4 for each cylinder, whereby fuel is supplied to the combustion chamber. Can be directly injected into. An ignition coil 8 that outputs a high voltage is connected to the spark plug 4. A fuel supply device (not shown) having a fuel tank is connected to the injector 6 via a fuel pipe 7. More specifically, the fuel supply device is provided with a low-pressure fuel pump and a high-pressure fuel pump, whereby the fuel in the fuel tank is injected into the injector 6
In contrast, the fuel can be supplied at a low fuel pressure or a high fuel pressure, and the fuel can be injected from the injector 6 into the combustion chamber at a predetermined fuel pressure.

An intake port 9 is formed in the cylinder head 2 in a substantially upright direction for each cylinder.
The intake valve 11 that opens and closes on the combustion chamber 5 side following the cam 12a of the camshaft 12 that rotates according to the engine rotation, and that connects and disconnects each intake port 9 with the combustion chamber 5.
Are provided respectively. One end of an intake manifold 10 is connected to each intake port 9, and the intake manifold 10 is provided with an electromagnetic throttle valve 17 for adjusting the intake air amount. A throttle position sensor (TPS) 18 for detecting the throttle opening is provided near the throttle valve 17,
The PS18 is provided with an idle switch (idle SW).

Further, in a portion upstream of the throttle valve 17 of the intake manifold 10, a pressure-dependent Karman vortex type air flow sensor 19 is provided to detect the intake air amount.
Is provided. Further, the cylinder head 2 has an exhaust port 13 formed in a substantially horizontal direction for each cylinder.
An exhaust valve that opens and closes on the combustion chamber 5 side of each exhaust port 13 in accordance with a cam 16a of a camshaft 16 that rotates according to engine rotation, and that connects and disconnects each exhaust port 13 and the combustion chamber 5. 15 are provided respectively. One end of an exhaust manifold 14 is connected to each exhaust port 13.

The exhaust pipe 2 is provided at the other end of the exhaust manifold 14.
0 is connected, and the exhaust pipe 20 is provided with a three-way catalytic converter 30 capable of highly efficiently purifying HC, CO, and NOx in the vicinity of stoichio. Also, the exhaust pipe 2
An O ₂ sensor 2 for detecting the oxygen concentration in the exhaust gas, and thus the exhaust air-fuel ratio, is provided at the upstream portion of the three-way catalytic converter 30 of 0
2 is provided, and the three-way catalytic converter 30 is provided with a high temperature sensor 32 that detects the catalyst temperature.

The cylinder head 2 has a cam 12a.
The intake valve 1 is operated by advancing or retarding the cam 16a.
1, a variable valve timing mechanism 40 that changes the opening / closing timing of the exhaust valve 15 is provided. Furthermore, engine 1
An air conditioner compressor 5 for compressing a refrigerant of an air conditioner (not shown) is provided on the crankshaft 3 of
0 is connected via a drive belt 52.

The ECU 60 includes an input / output device, a storage device, a central processing unit (CPU), a timer counter, etc., and the ECU 60 controls the engine 1 as a whole. On the input side of the ECU 60, the TPS1
8. In addition to the air flow sensor 19, the O ₂ sensor 22, the high temperature sensor 32, etc., various sensors such as a water temperature sensor 62 for detecting the cooling water temperature Tw of the engine 1 and a crank angle sensor 64 for detecting the crank angle are connected. And the detection information from these sensors is input. The engine speed Ne is detected by the crank angle sensor 64.

On the other hand, various output devices such as the injector 6, the ignition coil 8, the throttle valve 17, the variable valve timing mechanism 40 and the air conditioner compressor 50 are connected to the output side of the ECU 60, and the injector 6 and the ignition coil 8 are connected. The throttle valve 17 has a fuel injection amount, a fuel injection timing, an ignition timing based on the fuel injection mode selected based on the above-mentioned various detection information and the combustion air-fuel ratio obtained according to the detection information from various sensors. , And throttle opening signals are output respectively. This allows
An appropriate amount of fuel is injected from the injector 6 at appropriate timing (fuel injection control means), spark ignition is performed at appropriate timing by the spark plug 4, and the throttle opening is controlled to an appropriate opening. Further, an appropriate valve timing command is supplied to the variable valve timing mechanism 40,
An air conditioner operation command is supplied to the air conditioner compressor 50 in response to an operation of an air conditioner switch (not shown).

The operation of the control apparatus for a cylinder injection type spark ignition internal combustion engine according to the present invention having the above-described structure will be described below. Referring to FIG. 2, a control routine of the idle operation control according to the present invention is shown in a flowchart, which will be described below based on the flowchart. Step S10
Then, it is determined whether or not the idle condition is satisfied. Here, based on the information from the idle SW, the idle SW
Detects whether or not is on (idle operation state). If the determination result is false (No) and the idle condition is not satisfied, the routine is exited without doing anything. On the other hand, if the determination result is true (Yes), the idle condition is satisfied, and it is determined that the engine 1 is in the idle operation state, the process proceeds to step S12.

In step S12, the combustion air-fuel ratio (target A / F) is set according to the operating state of the engine 1. Normally, in the in-cylinder injection type engine 1, when the engine 1 is in an idle operation state, compression stroke injection is performed in order to improve idle stability and fuel economy, and the target A / F is lean A / F. Set to F. On the other hand, when the engine 1 is in the cold state based on the information from the water temperature sensor 62, the target A / F is set to lean to the rich A / F so that the engine 1 is warmed up and leaning is restricted.
Further, even when the air conditioner compressor 50 is operating according to a command from the ECU 60, the target A /
F is leaner and is set closer to the rich A / F. Further, when the target A / F is lean A / F, the opening degree of the throttle valve 17 is greatly opened, the intake negative pressure approaches atmospheric pressure, and the negative pressure of a brake booster (not shown) that is an auxiliary brake device is set. Because pressure is not secured,
Even when the assist power of the brake booster is insufficient, such as when the period when the target A / F is lean A / F continues for a predetermined period or longer, the target A / F is leaned and leans toward the rich A / F. Is set to, and the opening degree of the throttle valve 17 is reduced.

When the target A / F is set, step S1
At 4, it is determined whether or not there is a request for raising the temperature of exhaust gas.
That is, the three-way catalytic converter 30 has an activation temperature (for example, 3
Since the purification performance cannot be sufficiently exhibited unless the temperature becomes 00 ° C), the activation of the three-way catalytic converter 30 is promoted by raising the temperature of the exhaust gas when the three-way catalytic converter 30 has not reached the activation temperature. Here, it is determined whether or not the exhaust gas temperature rise is required to activate the three-way catalytic converter 30. Specifically, based on the catalyst temperature information from the high temperature sensor 32, it is determined whether or not the catalyst temperature is lower than the activation temperature (for example, 300 ° C.).

The determination result of step S14 is false (No)
If the temperature of the three-way catalytic converter 30 is equal to or higher than the activation temperature (for example, 300 ° C.) and it is determined that it is not necessary to raise the temperature of exhaust gas, the process proceeds to step S16. In step S16, it is determined whether or not the target A / F set as described above is equal to or less than a predetermined air-fuel ratio (for example, value 18). Here, the predetermined air-fuel ratio (for example, the value 18) indicates the combustion limit (lower limit value) by the compression stroke injection. If the determination result is false (No), and the target A / F is a predetermined air-fuel ratio (for example,
If it is determined that the value is larger than the value 18), it is possible to perform the operation by the compression stroke injection. Therefore, the process proceeds to step S18, and the compression lean operation in which the fuel is injected by the compression stroke injection is performed. That is, the normal idle operation is performed. On the other hand, when the determination result is true (Yes) and it is determined that the target A / F is equal to or less than the predetermined air-fuel ratio (for example, the value 18), step S2
Go to 0.

The brake booster is used when the engine 1 is warmed up, when the air conditioner compressor 50 is operated, or when the target A / F is lean A / F for a predetermined period or longer. When the auxiliary power of is insufficient, the target A / F is normally set to a predetermined air-fuel ratio (for example, a value of 18) or less, so whether or not the engine 1 is warming up instead of the A / F determination. Whether the air conditioner compressor 50 is operating or the target A / F
It may be determined whether or not the period in which the lean A / F is continued for a predetermined period or more.

In step S20, the two-stage mixed operation is performed in response to the target A / F being equal to or less than the predetermined air-fuel ratio (for example, the value 18). That is, the fuel injection timing is divided into the intake stroke and the compression stroke, the fuel is divided into the intake stroke and the compression stroke, and the divided injection is performed, so that the fuel and the air are mixed in two stages. In this way, if the fuel is divided into the intake stroke and the compression stroke and the divided injection is performed, the air-fuel mixture around the ignition plug 4 becomes excessively rich in the combustion limit region only by the compression stroke injection, and combustion cannot be established. Even in such a case, by injecting a portion that cannot be injected in the compression stroke in the intake stroke, it is possible to perform the compression stroke injection as in the normal idle operation.

That is, when the fuel is injected in the compression stroke, the fuel undergoes stratified combustion, but this stratified combustion ensures stable combustion even when the amount of fuel is small compared to uniform mixing by intake stroke injection. Since it is feasible, by performing the compression stroke injection together with the intake stroke injection, it is possible to realize more stable idle operation than in the case where only uniform mixing is performed by only the intake stroke injection.

As a result, when only uniform mixing is performed by only intake stroke injection, the target idle rotation speed must be set high in order to stabilize the idle rotation speed.
The extra fuel will be consumed by that amount, but it is not necessary to supply such extra fuel,
Deterioration of fuel consumption is prevented by keeping the target idle speed relatively low.

Here, when performing the two-stage mixed operation, the split ratio of the fuel injected in each of the intake stroke and the compression stroke is the ratio of the intake stroke injection 6 to the compression stroke injection 4 (6: 4) in the vicinity of the compression stroke. It is better to keep the fuel injection amount at a low level. That is, referring to FIG. 4, the relationship between the split ratio of the split injection in the intake stroke and the compression stroke and the fluctuation of the idle rotation is shown based on the actual measurement value. Therefore, the fluctuation of the idle speed is minimized when the split ratio between the intake stroke and the compression stroke is approximately 6: 4. Therefore, the split ratio between the split injection in the intake stroke and the compression stroke is approximately 6: 4 here. Set to 4.

As a result, when the engine 1 is in a cold state, when the air conditioner compressor 50 is operating, or when the target A / F is lean A / F, the auxiliary force of the brake booster continues for a predetermined period or longer. Even when the lean A / F is limited and the target A / F is set to be close to the rich A / F, as in the case of shortage of
By performing the stage mixed operation, it is possible to ensure good idle stability while preventing deterioration of fuel efficiency.

When the two-stage mixed operation is carried out in this way,
Although the target idle speed is suppressed to a relatively low value, the target A / F at this time is equal to or less than the predetermined air-fuel ratio (for example, a value of 18), and therefore occurs when the fuel is injected during the intake stroke. The amount of heat is larger than during compression lean operation, and therefore, the engine 1 can be sufficiently warmed up when the engine 1 is cold, and sufficient output torque is secured when the air conditioner compressor 50 is operating. can do. In this case, when the amount of heat generated or the output torque is insufficient, the ratio of the fuel injected in the intake stroke may be appropriately increased within a range that does not impair idle stability.

After the two-stage mixed operation is carried out, next, at step S22, the rotation fluctuation ΔNe of the engine rotation speed Ne is set to a predetermined value X1 based on the information from the crank angle sensor 64.
It is determined whether or not it is larger. That is, as described above, it is determined whether or not the idle rotation is largely changed even though the fuel injection is performed with the split ratio between the intake stroke and the compression stroke being approximately 6: 4. If the determination result is false (No), nothing is done and the routine exits. On the other hand, when the determination result is true (Yes), that is, when the rotation fluctuation ΔNe is larger than the predetermined value X1 and the idle rotation greatly changes,
It is considered that the split ratio between the intake stroke and the compression stroke is not appropriate due to some factor, and the process proceeds to step S24.

In step S24, the division ratio between the intake stroke and the compression stroke is changed in order to suppress the fluctuation of the idle rotation. This change of the division ratio is performed until the rotation fluctuation ΔNe becomes equal to or less than the predetermined value X1 in the determination of step S22, the determination result becomes false (No), and the idle rotation is stabilized. As a result, the split ratio between the intake stroke and the compression stroke is always appropriate, and idle speed fluctuations can be efficiently and constantly minimized. The division ratio changed in step S22 is stored as a learning value for later use.

By the way, when the determination result of step S14 is true (Yes), the temperature of the three-way catalytic converter 30 is lower than the activation temperature (for example, 300 ° C.), and it is determined that the exhaust gas temperature raising request is made. In step S26, even if the target A / F is equal to or less than the predetermined air-fuel ratio (for example, value 18) and the two-stage mixed operation is to be performed,
The temperature of exhaust gas is raised in priority to the stage mixing operation. here,
Slight lean A / F (S which is slightly leaner than stoichio to the target A / F while performing compression stroke injection
/ L air-fuel ratio, near stoichiometric air-fuel ratio) and the compression S / L operation is performed.

When the compression S / L operation is performed, a large amount of CO is generated because the air-fuel ratio around the spark plug 4 is locally high, and the CO and oxygen on the periphery of the combustion chamber 5 are generated in the combustion chamber 5 and The reaction occurs in the exhaust port 13 and heat is generated, whereby the exhaust gas temperature rise is realized. As a result, the three-way catalytic converter 30 can be activated early without being hindered by the two-stage mixed operation.

Next, another embodiment will be described. It should be noted that in the other embodiment, step S16 is simply changed to step S16 'in the flowchart of FIG. 2 above, and only portions different from the flowchart of FIG. 2 will be described here. When the determination result of step S14 is false (No) and it is determined that the exhaust gas temperature raising request is not made, the closing timing of the exhaust valve 15 is set to the retard side by the variable valve timing mechanism 40 in step S16 ′. It is determined whether or not there is.

If the variable valve timing mechanism 40 sets the closing timing of the exhaust valve 15 to the retard side with respect to the exhaust top dead center, the period during which the exhaust valve 15 is open in the intake stroke becomes long, The exhaust gas once exhausted is returned to the inside of the combustion chamber 5 and functions as internal EGR gas (exhaust gas recirculation means). Therefore, here, the internal EGR gas is introduced into the combustion chamber 5 (intake system) by determining whether or not the closing timing of the exhaust valve 15 is set to the retard side from the exhaust top dead center. It is determined whether or not there is.

The determination result of step S16 'is false (No)
When the internal EGR gas is not introduced in step S3, the routine is exited without doing anything. On the other hand, when the determination result of step S16 ′ is true (Yes) and it is determined that the internal EGR gas is introduced, the process proceeds to step S20,
A two-stage mixed operation is carried out in the same manner as above. That is, the internal EG
When the R gas is introduced, the amount of fresh air taken into the combustion chamber 5 becomes relatively small, so that A /
It is known that F becomes thick, and therefore, the two-stage mixing operation is performed even when the internal EGR gas is introduced. As a result, even when the internal EGR gas is introduced, it is possible to ensure good idle stability while preventing deterioration of fuel efficiency.

Although the case where the closing timing of the exhaust valve 15 is set to the retard side and the internal EGR gas is introduced has been described here, the introduction of the internal EGR gas changes the opening timing of the intake valve 11 to the exhaust top dead center. The internal EGR gas may be introduced by setting it to a more advanced side than that, or the external EGR may be introduced without being limited to the internal EGR. Although the description of the embodiment has been completed, the present invention is not limited to the above embodiment.

For example, in the above-described embodiment, the temperature of the exhaust gas is raised by the compression S / L operation (step S1).
8) The compression stoichiometric operation with the target A / F set to stoichio may be performed, or the compression S / R operation may be performed to set the slightly rich A / F to a slightly rich A / F. Further, the ignition timing retard may be performed to raise the temperature of the exhaust gas, or the two-stage combustion operation in which the secondary injection is performed after the middle stage of the expansion stroke after the main injection is performed in the intake stroke or the compression stroke is performed. Good.

Further, in the above-described embodiment, when the engine 1 is warmed up, the air conditioner compressor 50 is operated, and the target A /
The description has been made by taking the case where the assisting force of the brake booster is insufficient for a period in which F is the lean A / F for a predetermined period of time or longer as an example. However, if the load of the engine 1 increases during idle operation, The invention can be applied.

Further, for example, in a system in which the exhaust pipe 20 is provided with a storage type NOx catalytic converter of a type that stores NOx in a lean atmosphere and releases and reduces the stored NOx in a rich atmosphere (NOx purge), NOx purge is performed. At this time, since the A / F is set to the rich A / F, the two-stage mixing may be performed when the NOx purge is performed during the idle operation.

[0048]

As described in detail above, according to the control apparatus for a cylinder injection type spark ignition type internal combustion engine of claim 1 of the present invention, a predetermined air-fuel ratio is used, such as during idle operation and during warm-up. When operating the internal combustion engine at the following air-fuel ratio (for example, rich air-fuel ratio), the fuel is divided into the intake stroke and the compression stroke and injected, so even if the air-fuel ratio is relatively rich as a whole, The fuel injected in the compression stroke can be prevented from excessively enriching the air-fuel mixture in the vicinity of the spark plug, and by continuing the fuel injection in the compression stroke, stable stratified combustion is achieved and the idle rotation speed is kept low. Can
It is possible to secure idle stability while preventing deterioration of fuel efficiency.

According to the control apparatus for a cylinder injection type spark ignition type internal combustion engine of claim 2, when the internal combustion engine is in a cold state during idle operation, the air conditioner which is operated by the driving force of the internal combustion engine is operated. When the lean air-fuel ratio is limited, such as when the lean air-fuel ratio operation continues for a predetermined period of time or longer, the fuel is divided into the intake stroke and the compression stroke and injected, so that the fuel is relatively rich as a whole. Even with an air-fuel ratio, the fuel injected in the compression stroke can be prevented from excessively enriching the air-fuel mixture in the vicinity of the spark plug, and by continuing the fuel injection in the compression stroke, stable stratified combustion is achieved and idle The rotation speed can be maintained low, and idle stability can be secured while preventing deterioration of fuel efficiency.

Further, according to the control device for a cylinder injection type spark ignition type internal combustion engine of claim 3, a part of the exhaust gas (EGR gas) is recirculated to the intake system during the idle operation, and the fresh air amount is relatively increased. When the air-fuel ratio becomes rich as a result of the decrease in fuel consumption, the fuel is divided into the intake stroke and the compression stroke for injection, so even if the air-fuel ratio is relatively rich as a whole, it is injected in the compression stroke. It is possible to prevent the air-fuel mixture near the spark plug from becoming excessively rich by the fuel, and by continuing the fuel injection in the compression stroke, stable stratified combustion can be realized and the idle rotation speed can be kept low, which reduces fuel consumption. Idle stability can be secured while preventing deterioration.

Further, according to the control device for a cylinder injection type spark ignition type internal combustion engine of claim 4, based on the experimental result, the split ratio of the intake stroke and the compression stroke of the split injection is set to approximately 6: 4. Since the fuel injection amount in the engine is suppressed to a small amount, it is possible to secure good idle stability while preventing deterioration of fuel efficiency. Further, according to the control device for a cylinder injection type spark ignition internal combustion engine of claim 5, since the split ratio of the split injection is corrected according to the rotational fluctuation of the internal combustion engine, the intake stroke and compression of the split injection are performed. It is possible to make the division ratio with the stroke always appropriate so that the fluctuation of the idle rotation can be efficiently minimized, and good idle stability can be ensured while preventing deterioration of fuel consumption.

Further, according to the control apparatus for a direct injection spark ignition internal combustion engine of claim 6, when the temperature rise of the catalytic converter is required during the idle operation, the air-fuel ratio is prioritized over the split injection. Since the fuel is injected during the compression stroke so as to be in the vicinity of the stoichiometric air-fuel ratio, CO and oxygen can be satisfactorily discharged into the exhaust passage at the same time without being hindered by the split injection, and the reaction heat of these CO and oxygen can be discharged. Thus, the catalytic converter can be activated quickly.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a control device for a cylinder injection type spark ignition internal combustion engine according to the present invention, which is mounted on a vehicle.

FIG. 2 is a flowchart showing a control routine of idle operation control according to the present invention.

FIG. 3 is a part of a flowchart showing a control routine of idle operation control according to another embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a split ratio of split injection and a fluctuation of idle rotation in an intake stroke and a compression stroke based on actual measurement values.

[Explanation of symbols]

1 engine (cylinder injection type spark ignition internal combustion engine) 5 Combustion chamber 6 Fuel injection valve 11 intake valve 14 Exhaust manifold 15 Exhaust valve 18 Throttle position sensor (TPS) 30 three way catalytic converter 40 Variable valve timing mechanism 50 air conditioner compressor 60 Electronic control unit (ECU) 62 Water temperature sensor 64 crank angle sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/06 335 F02D 41/06 335Z 41/34 41/34 H 43/00 301 43/00 301J 301N ( 72) Inventor Koujiro Okada 5-3-8, Shiba, Minato-ku, Tokyo F-term within Mitsubishi Motors Corporation (reference) 3G084 AA00 AA04 BA09 BA15 BA20 CA02 CA03 DA02 EA07 EA11 FA00 FA20 3G091 AA11 AA17 AA24 AA28 AB03 AB06 BA03 BA14 BA15 BA19 BA32 BA33 CB02 CB03 CB05 CB07 CB08 DA01 DA02 DB10 DC02 DC03 EA01 EA05 EA07 EA16 EA18 EA34 FA02 FA04 FA12 FA13 FB02 FB10 FB11 FB12 FC02 FC04 FC07 GA06 HA36 HB05 3G092 AA01 AA06 AA09 AA11 AA17 AB02 BA05 BA06 BB06 DA08 EA17 FA24 GA02 GA04 HA01Z HA06Z HA09Z HD02Z HD05Z HE08Z HF04Z 3G093 AB00 BA19 CA03 CA04 DA05 DA06 DA11 DB25 EA04 EA05 3G301 HA01 HA04 HA13 KA05 KA07 MA 01 MA19 MA23 MA26 NA08 NE23 PD04Z PE08Z PF13Z

Claims (6)

[Claims] 1. A control apparatus for a cylinder injection type spark ignition internal combustion engine, comprising a fuel injection valve for directly injecting fuel into a combustion chamber, and comprising fuel injection control means for controlling fuel injection from the fuel injection valve. In the in-cylinder injection type spark ignition, the fuel injection control means divides fuel into an intake stroke and a compression stroke in a divided manner when operating at an air-fuel ratio of a predetermined air-fuel ratio or less during idle operation. Control device for internal combustion engine. 2. A control device for a cylinder injection type spark ignition internal combustion engine, comprising a fuel injection valve for directly injecting fuel into a combustion chamber, and comprising fuel injection control means for controlling fuel injection from the fuel injection valve. In the fuel injection control means, at least during idle operation, when the internal combustion engine is in a cold state, when operating an air conditioner operated by the driving force of the internal combustion engine, and when lean air-fuel ratio operation continues for a predetermined period or more. In either case, the control device for a cylinder injection type spark ignition type internal combustion engine is characterized in that the fuel is divided into an intake stroke and a compression stroke and injected separately. 3. A control device for a cylinder injection type spark ignition internal combustion engine, comprising a fuel injection valve for directly injecting fuel into a combustion chamber, and comprising fuel injection control means for controlling fuel injection from the fuel injection valve. In exhaust gas recirculation means for recirculating a part of the exhaust gas from the internal combustion engine to the intake system, and the fuel injection control means, when idling, when a part of the exhaust gas is recirculated to the intake system by the exhaust gas recirculation means. A control device for a cylinder injection type spark ignition type internal combustion engine, characterized in that fuel is divided into an intake stroke and a compression stroke and injected separately. 4. The split ratio between the intake stroke and the compression stroke of the split injection is approximately 6 to 4.
4. A control device for a cylinder injection type spark ignition internal combustion engine according to any one of items 1 to 3. 5. The split ratio of the split injection is corrected according to the rotational fluctuation of the internal combustion engine.
4. A control device for a cylinder injection type spark ignition internal combustion engine according to any one of items 1 to 3. 6. The internal combustion engine has a catalytic converter for purifying exhaust gas in an exhaust passage, and the fuel injection control means gives priority to the split injection when a temperature rise of the catalytic converter is required during idle operation. 6. The fuel is injected during the compression stroke so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio.
13. A control device for a cylinder injection type spark ignition internal combustion engine according to any one of 1.