JPH1047126A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent misfire surely. SOLUTION: A device comprises a fuel injection correlation value computing means (S22) formed in such a constitution that load correlation value (Pe) or a target air-fuel ratio (a target A/F) is found out on the basis of either one of detected result of an acceleration operating condition detecting means and an intake air rate detecting means and a fuel injection correlation value (Tinj) which is a correlation relation with fuel injection quantity supplied to a combustion chamber on the basis of its load correlation value or the target air-fuel ratio, and means (S26) for applying restriction on the fuel injection correlation value when a compression stroke injection mode is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type spark ignition type internal combustion engine, and more particularly to a direct injection type spark ignition type internal combustion engine capable of injecting fuel in a compression stroke and an intake stroke.

[0002]

2. Related Background Art In recent years, in a spark ignition type internal combustion engine mounted on a vehicle, fuel is directly supplied to a combustion chamber in place of a conventional intake pipe injection type in order to reduce harmful exhaust gas components and improve fuel efficiency. Various direct injection gasoline engines have been proposed. In a cylinder injection type gasoline engine, for example, by injecting fuel from a fuel injection valve into a cavity provided at the top of the piston, an air-fuel mixture having an air-fuel ratio close to the stoichiometric air-fuel ratio is generated around the ignition plug at the time of ignition. Let me. This makes it possible to ignite even at a lean air-fuel ratio as a whole, thereby reducing CO and HC emissions and greatly improving fuel efficiency during idling and running under low load.

In such a gasoline engine,
The compression stroke injection mode (late injection mode) and the intake stroke injection mode (first injection mode) are switched according to the operating state of the engine, that is, the engine load.
As a result, during low-load operation, fuel can be injected during the compression stroke to form an air-fuel mixture having an air-fuel ratio close to the stoichiometric air-fuel ratio around the ignition plug or in the cavity. Good ignition can be realized even at a fuel ratio. On the other hand, during medium-high load operation, fuel can be injected during the intake stroke to form a mixture having a uniform air-fuel ratio in the combustion chamber, and thus, like the intake pipe injection type,
By burning a large amount of fuel, it is possible to secure the required output during acceleration or high-speed running.

[0004]

In the direct injection type gasoline engine, when a large amount of fuel is injected into the cavity when fuel is injected during the compression stroke, mixing around the spark plug is prevented. The air may exceed the stoichiometric air-fuel ratio and locally have a rich air-fuel ratio. When the air-fuel mixture around the spark plug is enriched in this way, ignition is not performed by the spark plug depending on the degree, and so-called misfire occurs even though the overall air-fuel ratio is a lean air-fuel ratio. There is a risk that the operating condition will deteriorate. When the operating state of the engine deteriorates in this way, the traveling property of the vehicle, that is, drivability is impaired, which is not preferable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an in-cylinder injection spark ignition type internal combustion engine capable of reliably preventing misfiring.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a fuel injection valve for directly injecting fuel into a combustion chamber is provided. Operating state detecting means for detecting an operating state of an acceleration operating member in an in-cylinder injection type spark ignition type internal combustion engine capable of selecting between an intake stroke injection mode for performing fuel injection and a compression stroke injection mode for mainly performing fuel injection in a compression stroke A load correlation value or a target air-fuel ratio based on a detection result of one of the intake air amount detection means for detecting an intake air amount guided to the combustion chamber, and the acceleration operation state detection means and the intake air amount detection means. And calculating a fuel injection correlation value correlated with the fuel injection amount supplied to the combustion chamber based on the load correlation value or the target air-fuel ratio. And means, when the compression stroke injection mode is selected, and characterized in that a regulating means to limit the fuel injection correlation value.

Therefore, in the compression stroke injection mode,
When the fuel is injected, the fuel is concentrated near the spark plug, and the air-fuel ratio around the spark plug is locally enriched.The fuel injection correlation value obtained from the load correlation value or the target air-fuel ratio, that is, the fuel injection amount Is subject to restrictions,
Injection of a large amount of fuel is suppressed, local enrichment of the air-fuel ratio around the ignition plug is regulated, and misfire of the internal combustion engine is suitably prevented.

Further, in the invention according to claim 2, the fuel injection correlation value is a fuel injection time, and the regulating means determines that the compression stroke injection mode is selected and the fuel injection time is longer than a first predetermined value. Then, the fuel injection time is set to the first predetermined value. Therefore, when the fuel injection time is equal to or longer than the first predetermined value in the compression stroke injection mode, the fuel injection time is maintained at the first predetermined value, so that a large amount of fuel is not injected around the spark plug. Is limited, and misfire of the internal combustion engine is suitably prevented.

Further, in the invention according to claim 3, when the compression stroke injection mode is selected and the target air-fuel ratio is equal to or less than a second predetermined value, the regulating means sets the target air-fuel ratio to the second predetermined value. Is set to a predetermined value to limit the fuel injection correlation value. Therefore, when the target air-fuel ratio is set to be equal to or less than the second predetermined value in the compression stroke injection mode, the target air-fuel ratio is maintained at the second predetermined value, so that the fuel injection correlation value is limited and a large amount of fuel is consumed. The local enrichment of the air-fuel ratio around the spark plug is regulated without being injected into the engine, and misfire of the internal combustion engine is suitably prevented.

[0010] In the invention of claim 4, a plurality of operating state detecting means for detecting an operating state of the internal combustion engine,
Correction coefficient calculation means for calculating an injection amount correction coefficient for correcting the fuel injection amount based on the detection results of the plurality of operating state detection means, and correction means for correcting the fuel injection correlation value based on the injection amount correction coefficient The regulating means sets the injection amount correction coefficient to the third predetermined value when the injection amount correction coefficient is equal to or more than a third predetermined value, thereby setting the fuel injection correlation value to It is characterized by adding restrictions.

Therefore, when the injection amount correction coefficient is equal to or more than the third predetermined value in the compression stroke injection mode, the fuel injection correlation value is restricted by maintaining the injection amount correction coefficient at the third predetermined value. Therefore, the local enrichment of the air-fuel ratio around the spark plug is regulated without injecting a large amount of fuel, and the misfire of the internal combustion engine is suitably prevented. Also,
The invention according to claim 5 is characterized in that the third predetermined value is variably set according to the load correlation value and the target air-fuel ratio.

Therefore, the injection amount correction coefficient normally varies according to the load correlation value and the target air-fuel ratio, and the third predetermined value is variably set accordingly. Therefore, the fuel injection correlation value to be regulated is prevented from fluctuating according to the load correlation value and the target air-fuel ratio, and misfire of the internal combustion engine is stably and more suitably prevented. Claim 6
The invention is characterized in that the regulation means is executed when the load correlation value becomes equal to or more than a fourth predetermined value.

Therefore, the regulating means is implemented only when the load correlation value is equal to or more than the fourth predetermined value,
That is, it can be suitably implemented only when the internal combustion engine is easily misfired. Further, the invention according to claim 7 is characterized in that the regulating means is executed when the target air-fuel ratio becomes equal to or less than a fifth predetermined value.

Therefore, the restricting means is implemented only when the target air-fuel ratio falls below the fifth predetermined value,
That is, it can be suitably implemented only when the internal combustion engine is easily misfired.

[0015]

An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of a control device for an internal combustion engine according to the present invention mounted on a vehicle. Hereinafter, the configuration of the control device for the internal combustion engine will be described with reference to FIG.

The engine 1 is capable of performing fuel injection in the compression stroke (late injection mode) together with fuel injection in the intake stroke (first injection mode), and combustion at a lean air-fuel ratio, that is, a lean air-fuel ratio. In-cylinder in-line four-cylinder gasoline engine is applicable. In the in-cylinder injection type engine 1, an EGR device (exhaust gas recirculation device) that performs an intake device and an exhaust gas recirculation (EGR) including a combustion chamber.
Are designed exclusively for in-cylinder injection, and can easily be operated at a rich air-fuel ratio, a stoichiometric air-fuel ratio (stoichio) AFS, and a lean air-fuel ratio.

The cylinder head 2 of the engine 1 is also provided with an electromagnetic fuel injection valve 4 together with an ignition plug 3 for each cylinder, so that fuel is directly injected into the combustion chamber 5. On the top surface of the piston 7 slidably held by the cylinder 6, a hemispherical depression, that is, a cavity 8 is formed at a position where the fuel spray from the fuel injection valve 4 reaches in the latter half of the compression stroke. ing. The compression ratio of the engine 1 is set higher (for example, about 12) than that of the intake pipe injection type. The DOHC4 valve type is adopted as the valve operating mechanism.
In the upper part of the table, to drive the intake and exhaust valves 9 and 10, respectively,
An intake camshaft 11 and an exhaust camshaft 12 are rotatably supported.

The cylinder head 2 has both camshafts 1
An intake port 13 is formed in a substantially upright direction so as to pass through between the intake ports 1 and 12, and an intake flow passing through the intake port 13 is tumbled in the combustion chamber 5 in a direction opposite to a normal tumble flow. A reverse tumble flow, which is a flow, can be generated. On the other hand, the exhaust port 14 is formed in a substantially horizontal direction similarly to a normal engine, but a large-diameter exhaust gas recirculation port, that is, an EGR port 15 is branched obliquely downward.

In the figure, reference numeral 16 denotes a water temperature sensor for detecting a cooling water temperature Tw. Reference numeral 17 denotes a vane type crank angle sensor that outputs a crank angle signal SGT at a predetermined crank position (for example, 5 ° BTDC and 75 ° BTDC) of each cylinder. The engine rotation speed Ne can be detected based on the Reference numeral 19 denotes an ignition coil that outputs a high voltage to the ignition plug 3. A camshaft that rotates at half the number of revolutions of the crankshaft is provided with a cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC. It is identifiable whether or not it is.

A throttle body 23, a stepper motor type # 1 ABV (first air bypass valve) 24, and an air flow sensor (intake air amount detecting means) 32 are connected to the intake port 13 via an intake manifold 21 having a surge tank 20. And an intake pipe 25 provided with an air cleaner 22. The intake pipe 25 has a throttle body 2
A large-diameter air bypass pipe 26 that bypasses 3 and sucks air into the intake manifold 21 is provided, and a large # 2 ABV (second air bypass valve) 27 of a linear solenoid type is provided in the pipeline. I have. The air bypass pipe 26 has a flow passage area similar to that of the intake pipe 25, and when the # 2 ABV 27 is fully opened, intake of an amount required in the low to medium speed range of the engine 1 is possible.

The throttle body 23 has a butterfly type throttle valve 28 for opening and closing the flow path, and a throttle position sensor (a throttle valve opening sensor as a throttle valve opening sensor for detecting the opening of the throttle valve 28, ie, the throttle opening θth. Acceleration operation state detection means,
The idle switch 30 detects the fully closed state of the throttle valve 28 and recognizes the idling state of the engine 1. Actually, from the TPS 29, the throttle opening θth
Is output, and the throttle opening θth is recognized based on the throttle voltage Vth.

The air flow sensor 32 detects the amount of intake air Qa, and for example, a Karman vortex flow sensor is used. The intake air amount Qa may be obtained from a boost pressure sensor attached to the surge tank 20 and from the intake pipe pressure detected by the boost pressure sensor. On the other hand, an exhaust pipe provided with a three-way catalyst 42 and a muffler (not shown) is connected to the exhaust port 14 via an exhaust manifold 41 provided with an O ₂ sensor 40 capable of detecting an actual air-fuel ratio (actual A / F). 43 are connected. The above-mentioned EGR port 15 is connected to the upstream of the intake manifold 21 via a large-diameter EGR pipe 44, and a stepper motor type EGR valve 45 is provided in the pipeline.

The fuel tank 50 is installed at the rear of the vehicle (not shown). The fuel stored in the fuel tank 50 is sucked up by an electric low-pressure fuel pump 51 and fed to the engine 1 via a low-pressure feed pipe 52. The fuel pressure in the low-pressure feed pipe 52 is regulated to a relatively low pressure (low fuel pressure) by a first fuel pressure regulator 54 interposed in the return pipe 53. Engine 1
Supplied to the high-pressure feed pipe 5 by a high-pressure fuel pump 55 attached to the cylinder head 2.
The fuel is supplied to each fuel injection valve 4 through the delivery pipe 6 and the delivery pipe 57.

The high-pressure fuel pump 55 is, for example, of a swash plate axial piston type, is driven by the exhaust-side camshaft 12, and has a 5M
A discharge pressure of Pa to 7 MPa or more can be generated. The fuel pressure in the delivery pipe 57 is adjusted to a relatively high pressure (high fuel pressure) by a second fuel pressure regulator 59 interposed in the return pipe 58.

In the figure, reference numeral 60 denotes the second fuel pressure regulator 5.
9 is an electromagnetic type fuel pressure switching valve attached to 9. The fuel pressure switching valve 60 is capable of relieving fuel in the ON state, thereby reducing the fuel pressure in the delivery pipe 57 to a low fuel pressure. Reference numeral 61 denotes a high-pressure fuel pump 55
A part of fuel used for lubrication and cooling of
This is a return pipe that returns to 0.

In the cabin of the vehicle, an input / output device, a storage device (RO) for storing control programs, control maps, and the like are provided.
M, RAM, BURAM, etc.), central processing unit (CP
U), an ECU (Electronic Control Unit) 70 including a timer counter and the like is installed, and the ECU 70 performs comprehensive control of the engine 1. ECU7
The various sensors described above are connected to the 0 input side, and detection information from the various sensors and the like is input. EC
U70 determines the fuel injection mode, the fuel injection amount, the ignition timing, the amount of EGR gas introduced, etc., based on the detected information, and determines the fuel injection valve 4, ignition coil 19, EG
The drive control of the R valve 45 and the like is performed. Although the description is omitted on the input side of the ECU 70, in addition to the above various sensors,
Many switches and sensors (not shown) are connected, and various warning lights and devices (not shown) are also connected to the output side.

Next, the engine 1 configured as described above
The operation of the control device, that is, the content of combustion control of the engine 1 will be described. When the engine 1 is cold,
When the driver turns on the ignition key, the ECU
70 turns on the low-pressure fuel pump 51 and the regulator bypass valve 60 to supply low-fuel pressure fuel to the fuel injection valve 4.

When the driver starts operating the ignition key, the engine 1 is cranked by a cell motor (not shown), and at the same time, the ECU 70 starts combustion control. At this time, the ECU 70 selects the first-stage injection mode (that is, the intake stroke injection mode) and injects fuel so as to have a relatively rich air-fuel ratio. This is based on the fact that since the fuel vaporization rate is low when the engine is cold, misfires and emission of unburned fuel (HC) cannot be avoided if the fuel is injected in the late injection mode (that is, the compression stroke injection mode). The ECU 70 closes the # 2ABV 27 at the time of such a start. Therefore, in this case, the intake air to the combustion chamber 5 is generated by the gap of the throttle valve 28 or the # 1 ABV
24. Note that # 1ABV24 and # 2A
The BV 27 is centrally managed by the ECU 70,
The respective valve opening amounts are determined according to the required amount of intake air (bypass air) bypassing the throttle valve 28.

When the start of the engine 1 is completed as described above and the engine 1 starts idling, the high-pressure fuel pump 55 starts the rated discharge operation, and the EC
U70 supplies high-pressure fuel to the fuel injection valve 4 by turning off the regulator bypass valve 60. At this time, the required fuel injection amount is obtained from the discharge pressure of the high-pressure fuel pump 55 and the valve opening time of the fuel injection valve 4, that is, the fuel injection time.

Until the cooling water temperature Tw rises to a predetermined value, the ECU 70 selects the first injection mode and injects fuel so as to obtain a rich air-fuel ratio as in the case of starting, and continues to # 2ABV27. Closed state. The control of the idle speed according to the increase or decrease of the load on the auxiliary equipment such as the air conditioner is performed by the # 1 ABV 24 in the same manner as in the case of the intake pipe injection type engine.

As described above, when the engine is cold, substantially the same fuel injection control as in the case of the intake pipe injection type engine is performed. In this case, the fuel droplets adhere to the wall of the intake pipe 13. Since there is no control, the response and accuracy of the control are high.
When the engine 1 is warmed up, the ECU 70
Based on the target average effective pressure (load correlation value) Pe obtained from the throttle opening information θth based on the throttle voltage Vth from 29 and the engine speed Ne, the current fuel injection mode area is obtained from the fuel injection control map of FIG. Search for. Thereby, the fuel injection mode is set. Then, the fuel injection amount is determined according to the fuel injection mode, and the drive of the fuel injection valve 4 is controlled. At the same time, open / close control of the # 2 ABV 27 and the EGR valve 45 is also performed.

For example, when the engine 1 is in a low-load / low-speed range, such as during idling or low-speed running, the fuel injection mode is set to the late injection lean mode based on FIG. 2, and fuel injection is performed during the compression stroke. As well as
The fuel injection amount is determined so as to become a lean target air-fuel ratio based on the target average effective pressure Pe, that is, a target A / F (for example, A / F = about 30 to 40).
The ignition timing Sa and the EGR amount Legr are set based on
Good combustion control is performed.

The combustion in the late injection lean mode will be described in more detail. In the in-cylinder injection type engine 1, the cavity 8 is formed on the upper surface of the piston 7 as described above. From this, the intake port 13
Of the fuel and the intake air, that is, the fuel spray is injected into the ignition plug 3
Good concentration in the vicinity. As a result, a mixture near the stoichiometric air-fuel ratio AFS is always formed in a layer around the spark plug 3 at the time of ignition. Therefore, in the latter-stage injection mode, good ignitability is ensured even at a lean air-fuel ratio as a whole.

When the engine 1 is in the middle load range, for example, at the time of traveling at a constant speed, the fuel injection mode is set to the first injection lean mode or the stoichiometric feedback mode based on FIG. In the first injection lean mode, fuel injection is performed in the intake stroke. In the first injection lean mode, the target A / F is calculated based on the volume efficiency Ev calculated based on the intake air amount Qa from the air flow sensor 32, for example, instead of the target average effective pressure Pe. Therefore, here, the fuel injection amount is determined so as to be a relatively lean target A / F (for example, A / F = about 20 to 23) based on the volume efficiency Ev, and the ignition timing is also determined based on the volume efficiency Ev. Sa and the EGR amount Legr are set, and good combustion control is performed.

On the other hand, in the stoichiometric feedback mode, fuel injection is also performed during the intake stroke, and the volumetric efficiency Ev
The ignition timing Sa and the EGR amount Legr are set on the basis of the air-fuel ratio feedback control based on the output voltage of the O ₂ sensor 40. Is controlled to become the stoichiometric air-fuel ratio AFS.

Also, for example, when the engine 1 is in a high load range such as during rapid acceleration or high-speed running, the fuel injection mode is set to the open loop mode based on FIG. While the selected fuel injection is performed in the intake stroke, the target A / F is set to a relatively rich air-fuel ratio based on the volumetric efficiency Ev as described above, and the ignition timing Sa, E
The GR amount Legr is set, and good combustion control is performed.

When coasting during middle-to-high speed running, etc.,
The fuel injection mode is a fuel cut mode as shown in FIG. 2, in which case the fuel injection is stopped. This fuel cut is immediately stopped when the engine rotation speed Ne falls below the return rotation speed or when the driver depresses the accelerator pedal. By the way, in the latter-stage injection lean mode, as described above, the mixture of the fuel injected from the fuel injection valve 4 and the intake air, that is, the fuel spray, is favorably concentrated in the vicinity of the ignition plug 3 by the cavity 8. . Therefore, normally, good ignitability is ensured even at a lean air-fuel ratio as a whole.

However, when the fuel injection amount is increased and the fuel amount sprayed in the vicinity of the ignition plug 3 is increased, the ignition plug 3 has a lean air-fuel ratio as a whole.
The concentration of the fuel in the vicinity increases, and the engine 1 may cause misfire. For example, based on an experiment or the like, the overall actual air-fuel ratio, that is, the actual A / F is the rich limit air-fuel ratio AF1.
It has been confirmed that the engine 1 causes a misfire when it becomes less than (for example, AF1 = 18). Therefore, in the engine 1 of the present invention, the actual A / F is prevented from being equal to or less than the predetermined air-fuel ratio AF1, thereby preventing the engine 1 from misfiring.

Referring to FIG. 3, there is shown a flowchart of a fuel injection amount setting routine executed by the ECU 70 in the latter injection mode, that is, the latter injection lean mode. The misfire prevention control procedure of the engine 1 will be described together with the setting procedure. In step S10 of FIG. 3, TPS2
9. Read detection values from various sensors such as the crank angle sensor 17 and the air flow sensor 32.

Then, in step S12, the TPS 29
Throttle opening information θth based on the throttle voltage Vth of
And engine speed information N from the crank angle sensor 17
Map target average effective pressure Pe based on e (not shown)
Ask from. Next, in step S14, the target A / F is calculated from the engine speed information Ne and the target average effective pressure Pe.
Is calculated. Actually, a target A / F setting map is provided in advance based on the engine speed information Ne and the target average effective pressure Pe, and the target A / F is read from this map.

In step S16, a reference fuel injection time TB is set by the following equation (1) based on the intake air amount Qa and the target A / F. TB = Qa / (target A / F) · K (1) where K is a coefficient. Then, the next step S18
In, various correction coefficients for correcting the reference fuel injection time TB are set based on detection values from various sensors (operating state detecting means). As various correction coefficients,
Intake temperature correction coefficient KAT, atmospheric pressure correction coefficient KAP, warm-up correction coefficient KTW, correction coefficient KAS immediately after starting, learning correction coefficient KLRN,
Idle correction coefficient KFI, A / F enrichment correction coefficient KAFr
And an A / F map correction coefficient KAF. Actually, these various correction coefficients are read from a map set in advance according to detection signals from the corresponding sensors.

In the next step S20, the A / F map correction coefficient KAF among the various correction coefficients obtained as described above
Except for the intake temperature correction coefficient KAT, atmospheric pressure correction coefficient KAP, warm-up correction coefficient KTW, correction coefficient KAS immediately after starting, learning correction coefficient K
An integrated value of the LRN, the idle correction coefficient KFI, and the A / F enrichment correction coefficient KAFr, that is, a correction coefficient value KETC other than the A / F map correction coefficient KAF is obtained from the following equation (2) (correction coefficient calculation means).

KETC = KAT, KAP, KTW, KAS, KLRN, KFI, KAFr (2) Then, in the next step S22, taking into account various correction coefficients and the invalid time correction value Td (correction means), the fuel injection time is calculated. That is, the fuel injection time (fuel injection correlation value) Tinj is obtained from the following equation (3) (fuel injection correlation value calculation means). Tinj = TB.KETC.KAF + Td (3) After the fuel injection time Tinj is calculated in this way, in the next step S24, the target A / F is set to a predetermined value (fifth value).
Is less than AF3 (for example, AF3 = 20) or the target average effective pressure Pe is a predetermined value (fourth predetermined value) Pe
It is determined whether or not 1 (for example, Pe1 = 2KPa) or more. This determination is made in the next step S26.
This is a determination of whether or not to perform the inj limit control, which means that the engine 1 is likely to be misfired and that it is necessary to perform the misfire prevention control of the engine 1.

The determination result of step S24 is false (No)
When the target A / F is larger than the predetermined value AF3 and the target average effective pressure Pe is smaller than the predetermined value Pe1, the reference fuel injection time TB, that is, the fuel injection time Tinj leads to misfire of the engine 1. It will not be as long. That is,
Although the fuel injection amount that affects the actual A / F is set based on the fuel injection time Tinj obtained by the above equation (3), the fuel injection amount is not so large with such a short fuel injection time Tinj. No, therefore, the actual A / F is engine 1
Does not become rich enough to lead to a misfire. Therefore, in this case, the process exits the routine without doing anything. That is, in this case, the fuel injection amount is set based on the fuel injection time Tinj obtained in step S22, and the combustion control is performed.

On the other hand, if the decision result in the step S24 is true (Y
In es), when the target A / F is equal to or less than the predetermined value AF3 or the target average effective pressure Pe is equal to or more than the predetermined value Pe1, the process proceeds to step S26, and the limit control of the fuel injection time Tinj is performed. The restriction control of the fuel injection time Tinj means the misfire prevention control of the engine 1 (restriction means).
Hereinafter, misfire prevention control of the engine 1 will be described.

Here, one of the flowcharts of the control routine of the fuel injection time Tinj shown in FIGS. 4 to 6 (Embodiments 1 to 3) is executed. Hereinafter, each embodiment will be described with reference to FIGS. First, the case of the first embodiment will be described with reference to FIG. Step S30
Then, the fuel injection time Tinj is set to a predetermined value (first predetermined value) T1.
It is determined whether or not this is the case. Here, the predetermined value T1
Is a clip value, and is the rich limit air-fuel ratio AF1
(For example, AF1 = 18)
F, that is, a value corresponding to a predetermined air-fuel ratio AF2 (for example, AF2 = 19).

If the determination result in step S30 is false and the fuel injection time Tinj has not reached the predetermined value T1, the actual A / F is set to the predetermined air-fuel ratio AF2 (for example, AF2 = 1).
9), it can be determined that the engine 1 will not be misfired. In this case, the routine exits without performing anything. On the other hand, if the determination result of step S30 is true and the fuel injection time Tinj is equal to or longer than the predetermined value T1, the actual A / F is set to the predetermined air-fuel ratio AF2 (for example, AF2 = 1).
9), it can be determined that the engine 1 has a risk of misfiring. In this case,
Next, the process proceeds to step S32.

In step S32, the fuel injection time Tinj is set to a predetermined value T1 so that the engine 1 does not misfire. That is, in step S32, the fuel injection time Tinj is fixed at the predetermined value T1, regardless of the fuel injection time Tinj calculated by the operation in step S22 in FIG. As a result, the fuel injection amount is not injected more than the amount corresponding to the predetermined value T1, which is the clip value, and the misfire of the engine 1 is prevented.

Next, the case of the second embodiment will be described with reference to FIG. In step S40 of FIG. 5, the target A / F is set to the predetermined air-fuel ratio (second predetermined value) AF2 (for example, AF2 = 1).
9) Determine whether or not: If the determination result is false, the process exits the routine without doing anything. On the other hand, when the result of the determination is true, the process proceeds to step S42.

In step S42, the target A / F is set to a predetermined air-fuel ratio AF2 (for example, AF2 = 19) which is a clip value. Thereby, in the next step S44,
A predetermined reference fuel injection time TB based on the predetermined air-fuel ratio AF2
1 is obtained and set as a reference fuel injection time TB. And
In step S46, the fuel injection time Tinj is newly calculated by the following equation (4) based on the predetermined reference fuel injection time TB1.

Tinj = TB1 · KETC · KAF + Td (4) As described above, the target A / F is set to the predetermined air-fuel ratio AF2 (for example,
AF2 = 19), the fuel injection time Ti
The increase in nj is limited, that is, the fuel injection amount is regulated, and the misfire of the engine 1 is also prevented. Next, a case of the third embodiment will be described with reference to FIG.

In step S50 of FIG. 6, it is determined whether or not the correction coefficient value KETC other than the A / F map correction coefficient KAF is equal to or larger than the clip value, that is, a predetermined value (third predetermined value) K1. If the determination result is false, the process exits the routine without doing anything. On the other hand, when the result of the determination is true, the process proceeds to step S52. In step S52, the correction coefficient value KETC is set to a predetermined value K1. Then, step S5
In 4, the fuel injection time Tinj is calculated again by the following equation (5) based on the predetermined value K1.

Tinj = TB ・ K1 ・ KAF + Td (5) As described above, by fixing the correction coefficient value KETC to the predetermined value K1, even if the correction coefficient value KETC is increased, the correction coefficient It is limited that the numerical value KETC is increased to a predetermined value K1 or more. As a result, the fuel injection time T
The increase in inj is limited, and the fuel injection amount is regulated, thereby preventing the engine 1 from misfiring.

Since the A / F map correction coefficient KAF is a coefficient directly related to the target A / F, it is left as it is without setting a limit value. Actually, the correction coefficient value KETC is equal to the reference fuel injection time TB, that is, the target A /
It fluctuates according to F and the target average effective pressure Pe.
Therefore, the predetermined value K1 which is the clip value of the correction coefficient value KETC
Is preferably variably set in accordance with the target A / F and the target average effective pressure Pe. As a result, the variation in the fuel injection time Tinj when the correction coefficient value KETC is set to the predetermined value K1 is reduced, and the increase in the fuel injection time Tinj is more appropriately restricted, and the fuel injection amount is regulated. Therefore, Engine 1
Misfire is more reliably prevented.

As described above, in the in-cylinder injection type spark ignition type internal combustion engine of the present invention, when the engine 1 is in a low load range such as during idling operation or low-speed running.
The late injection lean mode, which is the latter injection mode, is selected as the fuel injection mode. In the latter injection mode, the fuel is injected as described in the first to third embodiments (see FIGS. 4 to 6). A clip value is provided for the injection time Tinj itself, the target A / F, or the correction coefficient value KETC so that the fuel injection time Tinj does not become too long. Therefore, it is possible to limit the fuel injection amount so that the actual A / F does not become lower than the rich limit air-fuel ratio AF1 (for example, AF1 = 18). Even if the fuel injection mode is the late injection mode, the engine 1 Misfire can be reliably prevented.

In the above-described embodiment, it is determined in step S24 in FIG. 3 whether or not the engine 1 is in a state of easily misfiring, that is, whether or not it is necessary to perform the misfire prevention control of the engine 1. However, this step S
The control for limiting the fuel injection time Tinj in step S26, that is, the control for preventing the misfire of the engine 1 may be performed directly without performing the determination in step S24.

[0057]

As described in detail above, claim 1 is as follows.
According to the in-cylinder injection type spark ignition type internal combustion engine, when the compression stroke injection mode is selected, the fuel injection correlation value is provided with a restricting means, so that in the compression stroke injection mode, the load correlation value Alternatively, it is possible to limit the fuel injection correlation value obtained from the target air-fuel ratio, that is, the fuel injection amount, and thus suppress the injection of a large amount of fuel to restrict the local air-fuel ratio enrichment around the spark plug. Thus, misfire of the internal combustion engine can be suitably prevented. Therefore, when the internal combustion engine is mounted on a vehicle, drivability can be improved.

Further, according to the in-cylinder injection type spark ignition type internal combustion engine of the second aspect, when the fuel injection time is set to the first predetermined value or more in the compression stroke injection mode, the fuel injection time is set to the first predetermined value. It is possible to prevent the injection of a large amount of fuel by maintaining the value at a value, and therefore, it is possible to preferably limit the local enrichment of the air-fuel ratio around the ignition plug and appropriately prevent the misfire of the internal combustion engine.

According to the third aspect of the present invention, when the target air-fuel ratio is set to the second predetermined value or less in the compression stroke injection mode, the target air-fuel ratio is set to the second predetermined value. It is possible to limit the fuel injection correlation value by holding the value at a value, so that it is possible to restrict the local air-fuel ratio enrichment around the ignition plug by not injecting a large amount of fuel, and it is preferable to misfire the internal combustion engine. Can be prevented.

According to the fourth aspect of the present invention, when the injection amount correction coefficient is set to a third predetermined value or more in the compression stroke injection mode, the injection amount correction coefficient is set to the third predetermined value. The fuel injection correlation value can be limited by maintaining the predetermined value of the internal combustion engine. Therefore, the local air-fuel ratio enrichment around the spark plug can be restricted by preventing the injection of a large amount of fuel, and the misfire of the internal combustion engine can be prevented. Can be suitably prevented.

According to the cylinder injection type spark ignition type internal combustion engine of the fifth aspect, the load correlation value and the target air-fuel ratio are adjusted in accordance with the load correlation value and the injection amount correction coefficient which varies according to the target air-fuel ratio. The third predetermined value can be variably set in accordance with
Therefore, it is possible to prevent the fuel injection correlation value to be regulated from fluctuating according to the load correlation value and the target air-fuel ratio,
A misfire of the internal combustion engine can be stably and more suitably prevented.

According to the in-cylinder injection spark ignition type internal combustion engine of the sixth aspect, the restricting means can be implemented only when the load correlation value becomes equal to or more than the fourth predetermined value. In other words, the restricting means can be suitably implemented only when the internal combustion engine is easily misfired. Thus, in a situation where it is not necessary to limit the fuel injection correlation value, the restricting means can be prevented from being meaninglessly implemented.

Further, according to the in-cylinder injection spark ignition type internal combustion engine of the seventh aspect, the restricting means can be implemented only when the target air-fuel ratio becomes equal to or less than the fifth predetermined value. In other words, the restricting means can be suitably implemented only when the internal combustion engine is easily misfired. Thus, in a situation where it is not necessary to limit the fuel injection correlation value, the restricting means can be prevented from being meaninglessly implemented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a direct injection type spark ignition type internal combustion engine of the present invention.

FIG. 2 is a diagram showing a determination map of a fuel injection mode.

FIG. 3 is a flowchart illustrating a fuel injection amount setting routine in a late injection mode.

FIG. 4 is a flowchart showing a control routine as a first embodiment of the Tinj limit control in FIG. 3;

FIG. 5 is a flowchart showing a control routine as a second embodiment of the Tinj limit control in FIG. 3;

FIG. 6 is a flowchart showing a control routine as a third embodiment of the Tinj limit control in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 3 Spark plug 4 Fuel injection valve 17 Crank angle sensor 19 Ignition coil 24 # 1ABV (first air bypass valve) 27 # 2ABV (second air bypass valve) 29 TPS (acceleration operation state detecting means) 32 Air flow sensor (suction) Air amount detecting means) 70 Electronic control unit (ECU)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation

Claims (7)

[Claims] 1. An intake stroke injection mode having a fuel injection valve for directly injecting fuel into a combustion chamber and performing fuel injection mainly in an intake stroke according to an operation state, and a compression stroke injection mainly performing fuel injection in a compression stroke In a direct injection type spark ignition type internal combustion engine capable of selecting a mode, an acceleration operation state detection means for detecting an operation state of an acceleration operation member, and an intake air amount detection means for detecting an intake air amount guided to the combustion chamber A load correlation value or a target air-fuel ratio is determined based on a detection result of one of the acceleration operation state detection means and the intake air amount detection means, and is supplied to the combustion chamber based on the load correlation value or the target air-fuel ratio. Fuel injection correlation value calculation means for calculating a fuel injection correlation value that is correlated with the fuel injection amount; and when the compression stroke injection mode is selected, the fuel Cylinder injection type spark ignition internal combustion engine, wherein the regulating means to restrict the correlation value morphism, further comprising a. 2. The fuel injection correlation value is a fuel injection time, and the restricting means is configured to: when the compression stroke injection mode is selected and the fuel injection time is equal to or longer than a first predetermined value.
The in-cylinder injection spark ignition type internal combustion engine according to claim 1, wherein the fuel injection time is set to the first predetermined value. 3. The control means sets the target air-fuel ratio to the second predetermined value when the compression stroke injection mode is selected and the target air-fuel ratio is equal to or less than a second predetermined value. The in-cylinder injection spark ignition type internal combustion engine according to claim 1, wherein the fuel injection correlation value is limited. 4. A plurality of operating state detecting means for detecting an operating state of the internal combustion engine, and a correction for calculating an injection amount correction coefficient for correcting the fuel injection amount in accordance with a detection result of the plurality of operating state detecting means. A coefficient calculating unit, and a correcting unit that corrects the fuel injection correlation value based on the injection amount correction coefficient. The regulating unit, when the injection amount correction coefficient is equal to or more than a third predetermined value, 2. The direct injection spark ignition type internal combustion engine according to claim 1, wherein the fuel injection correlation value is limited by setting an injection amount correction coefficient to the third predetermined value. 5. The in-cylinder injection spark ignition internal combustion engine according to claim 4, wherein the third predetermined value is variably set according to the load correlation value and the target air-fuel ratio. 6. The regulating means according to claim 4, wherein said load correlation value is a fourth value.
The in-cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 5, wherein the internal combustion engine is executed when the predetermined value is equal to or more than a predetermined value. 7. The regulating means, wherein the target air-fuel ratio is set to a fifth value.
The in-cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 5, wherein the internal combustion engine is executed when the predetermined value is equal to or less than a predetermined value.