JP2004360539A - Direct cylinder injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform stratified charge combustion operation excellent in fuel economy or exhaust emission , in a wide operation range. <P>SOLUTION: A fuel injection valve is disposed at an approximately center position of an upper face of a combustion chamber, and an ignition plug is disposed adjacently to the fuel injection valve. An approximately cylindrical cavity is formed at a center position of the crown surface of a piston. Two stratified charge combustion modes are provided as follows: a first stratified charge operation mode (mode 1) igniting fuel during fuel injection or immediately after the completion of the fuel injection and before a collision with a piston; and a second stratified charge operation mode (mode 2) igniting the fuel after the completion of the fuel injection and has passed through the piston. In the first stratified charge mode, when a smoke emission amount or a CO emission amount exceeds a switching level, the first stratified mode is switched to the second stratified charge mode (mode 2). In the second stratified charge mode, when combustion stability exceeds a switching level, the second stratified charge mode is switched to the first stratified charge mode (mode 1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in an in-cylinder direct injection type internal combustion engine which realizes stratified combustion by injecting fuel into a cylinder.
[0002]
[Prior art]
Patent Literature 1 discloses an example of a direct injection internal combustion engine. In the internal combustion engine of Patent Document 1, a cavity, that is, a piston bowl is recessed in a piston crown surface, a fuel injection valve is disposed immediately above the piston bowl, and fuel spray collides with a peripheral surface of the piston bowl. By forming a spray circulation flow toward the center, an appropriate stratified mixture is formed in the cylinder, thereby reducing fuel consumption.
[0003]
[Patent Document 1]
JP-A-11-82028
[Problems to be solved by the invention]
However, in the above configuration, the size of the stratified mixture formed via the piston (in other words, colliding with the piston) is substantially determined by the shape of the piston cavity, that is, the cavity volume.
[0005]
In this case, in order to perform stable combustion and achieve good fuel efficiency and exhaust emission under a certain stratified operation condition, good combustion is established under another stratified operation condition having different engine speeds and loads. Otherwise, there is a concern that so-called bouncing may occur.
[0006]
For example, when the engine rotation speed is high, the progress of the crank angle (piston rise) with respect to the mixture formation time becomes relatively faster than when the engine rotation speed is low, and the same fuel injection timing and fuel injection period are used. In this case (which is proportional to the engine load), a predetermined ignition timing is reached before the combustible mixture reaches the vicinity of the ignition plug. It is conceivable to avoid the above problem by setting the injection timing to the advanced side as the engine rotational speed becomes higher. However, in early injection, it becomes difficult to receive fuel spray by the piston cavity. In particular, in consideration of performing combustion with a uniform air-fuel mixture by intake stroke injection in the full load region, it is necessary to use fuel spray injected at a spray angle (a bevel angle) of a certain degree or more. It is not possible to set a proper injection timing.
[0007]
In addition, if the cavity is made to have a large opening so as to easily receive the fuel spray, the depth of the cavity is restricted from the viewpoint of the compression ratio. It becomes difficult.
[0008]
That is, in the configuration in which the fuel passing through the piston cavity is always ignited during stratified combustion as in the above-described conventional art, it is difficult to perform stable and good fuel economy and exhaust operation with respect to the engine speed. .
[0009]
On the other hand, when examining the level of the engine load, the stratified mixture near the spark plug tends to be lean in the stratified operation at a low load, and the stratified mixture tends to be lean, the combustion stability is deteriorated, and the fuel efficiency is deteriorated in the same mixture formation process. It becomes a tendency. Further, in the stratified operation under a high load, the stratified mixture in the vicinity of the ignition plug becomes excessively rich, and there is a concern that smoke and HC increase.
[0010]
[Means for Solving the Problems]
In the present invention, in order to solve the above-mentioned problem, switching is made between two types of combustion systems under stratified operation conditions.
[0011]
That is, the direct injection type internal combustion engine of the present invention has an ignition plug and a fuel injection valve in the upper part of the combustion chamber, and has a substantially cylindrical cavity near the center of the piston crown. As the operation mode for performing stratified combustion, a first stratified operation mode for igniting fuel before colliding with the piston during fuel injection or immediately after the end of fuel injection, and igniting fuel passing through the piston after ending fuel injection. A second stratified operation mode.
[0012]
Here, the air-fuel mixture formed via the piston after the end of fuel injection as the second stratified operation mode passes through the cavity, and after being sufficiently vaporized and mixed, a relatively uniform mixture is formed above the cavity. Form a mixture distribution. Accordingly, there is no fear of smoke and CO emission from the rich mixture, and there is an advantage that the mixture is less likely to be affected by the cycle fluctuation.
[0013]
However, there is a concern that, as the engine rotation speed increases, time is insufficient to sufficiently form a uniform air-fuel mixture. Also, as the in-cylinder flow becomes stronger with an increase in the engine rotation speed, the air-fuel mixture becomes overdiffused, and the vicinity of the ignition plug may become too thin.
[0014]
Furthermore, when the engine load is low, the relatively uniform mixture formed above the cavity becomes thinner than the combustible air-fuel ratio, and there is a risk of misfiring.
[0015]
On the other hand, in the first stratified operation mode, during the fuel injection or during the flight before the fuel collides with the piston immediately after the end of the fuel injection, the fuel spray during the flight, immediately after the injection, mixes the air-fuel mixture with the surrounding air by mixing and vaporizing from the surrounding air. Form. The air-fuel mixture that does not pass through the piston is quickly formed as a compact air-fuel mixture immediately below the fuel injection valve regardless of the engine speed, so that stable stratified combustion can be performed regardless of the engine speed.
[0016]
In addition, even when the engine load is low, the fuel (air-fuel mixture) can be reliably disposed near the spark gap, so that stable combustion can be realized.
[0017]
However, fuel during or immediately after the injection has a large distribution, and in a high load region where the fuel injection amount is large, the mixture concentration around the spark gap becomes rich beyond the combustible air-fuel ratio, deteriorating the combustion stability. In addition, CO or smoke may be emitted from the rich mixture.
[0018]
The invention of claim 1 is characterized in that these two stratified operation modes are switched according to the combustion state of the internal combustion engine. That is, even if the two stratified operation modes are switched in accordance with the engine speed and load, in a multi-cylinder internal combustion engine, there are cylinder variations due to individual differences of the fuel injection valves, and deterioration over time of the fuel injection valves, spark plugs, etc. In order to cope with these, it is necessary to select an appropriate combustion mode from the two stratified operation modes according to the combustion state during operation. The parameters indicating the combustion state of the internal combustion engine include, for example, the combustion stability of the internal combustion engine, the amount of smoke emission, the amount of CO emission, and the like.
[0019]
【The invention's effect】
According to the present invention, the first stratification operation mode in which fuel is ignited before colliding with the piston during fuel injection or immediately after the end of fuel injection, and the second stratification mode in which fuel is ignited through the piston after fuel injection is completed By switching between the operation mode and the actual combustion state of the internal combustion engine, it is possible to always perform stable stratified combustion regardless of the engine speed or load and without being affected by deterioration over time. In a wide operating range, fuel efficiency and exhaust emissions can be improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a mechanical configuration of one embodiment of a direct injection internal combustion engine according to the present invention. As shown, a combustion chamber 5 is formed by the cylinder head 1, the cylinder 3 of the cylinder block 2, and the piston 4. The combustion chamber 5 communicates with an intake port 7 via an intake valve 6 and communicates with an exhaust port 9 via an exhaust valve 8. The intake valve 6 is driven to open and close by an intake valve camshaft (not shown), and the exhaust valve 8 is driven to open and close by an exhaust valve camshaft (not shown).
[0021]
A fuel injection valve 11 for injecting fuel toward the piston 4 is provided on the upper surface of the combustion chamber 5, that is, substantially at the center of the ceiling surface on the cylinder head 1 side. The spray center line of the fuel injection valve 11 substantially coincides with the cylinder center line. An ignition plug 12 is arranged adjacent to the fuel injection valve 11, and a spark gap 12 a thereof is located near the center of the combustion chamber 5. The fuel injection valve 11 and the spark plug 12 are controlled based on a signal from an engine control unit (ECU) 10 and perform fuel injection and ignition at a timing according to the engine operating conditions.
[0022]
A substantially cylindrical cavity 13 is formed at the center of the crown of the piston 4 so as to face the fuel injection valve 11. The cavity 13 is, for example, of a reentrant type, and a stratified mixture is formed mainly in and above the cavity 13 during stratified combustion.
[0023]
As shown in the enlarged view of FIG. 2, an optical fiber 14 is embedded in the ignition plug 12 substantially in parallel with the center electrode, and the tip of the optical fiber 14 has a viewing angle θ toward the combustion chamber 5. It is open at. As shown in FIG. 1, the base end of the optical fiber 14 is connected to a light intensity detector 15 so as to irradiate the light intensity detector 15 with light emitted from the combustion chamber 5. The detection signal of the light intensity detector 15 is input to the engine control unit 10.
[0024]
The light intensity detector 15 detects only light emission called a bright flame between a wavelength of 500 nm and 600 nm, which is observed when a rich mixture such as smoke or CO is present, among combustion flames. A filter corresponding to the band is provided on the front or inside, and the emission amount of CO or smoke is calculated based on the signal light intensity from the light intensity detector 15. Therefore, the optical fiber 14, the light intensity detector 15, and the like constitute smoke emission amount detecting means or CO emission amount detecting means.
[0025]
The above filter may be set to detect only light emission from a C2 radical having a wavelength of 516.5 nm, which is observed when a rich mixture that emits smoke or CO is present.
[0026]
FIG. 3 shows a relationship between the amount of smoke emission (or the amount of CO emission) and the emission intensity of the bright flame (C2 radical).
[0027]
Further, a crank angle sensor 16 is used as the combustion stability detecting means, and the engine control unit 10 calculates the combustion stability based on the fluctuation of the angular velocity obtained from the crank angle sensor 16. ing.
[0028]
In the internal combustion engine of the present invention configured as described above, as a combustion mode, a stratified charge combustion mode that realizes a lean operation by performing fuel injection mainly during the compression stroke (particularly, the latter half of the compression stroke) and improves fuel efficiency is provided. And a homogeneous combustion mode for realizing a stoichiometric air-fuel ratio operation by performing fuel injection during the intake stroke (particularly in the first half of the intake stroke), and is selected according to the operation state.
[0029]
Further, in the above-described stratified combustion mode, a first stratified operation mode (mode 1) in which fuel is ignited before colliding with the piston 4 during fuel injection or immediately after the end of the fuel injection, and the piston 4 after the end of the fuel injection is set. And a second stratified combustion mode (mode 2) in which the fuel that has passed through is ignited. The optimum combustion mode is determined based on the combustion stability, smoke emission, or CO emission. The selected fuel injection timing and ignition timing are set. That is, the control of the engine is performed so as to switch between the two.
[0030]
First, the outline of the mixture formation process in the two stratified operation modes of the present invention will be described.
[0031]
FIG. 4 shows the mixture formation process in the first stratified operation mode, that is, the stratified operation mode in which the fuel is ignited before the collision with the piston 4 during the fuel injection or immediately after the end of the fuel injection. In the first stratified operation mode, the fuel injection timing is set near the compression top dead center. The spark gap 12a is installed near the tip of the fuel injection valve 11, and ignites immediately after the start of fuel injection or immediately after the end of fuel injection. This is to ignite the fuel in flight before colliding with the piston 4 among the injected fuel. Here, as shown in the order of (a), (b), and (c) in FIG. 2, the injected fuel spray forms an air-fuel mixture from the tip and periphery of the spray shaft by mixing with ambient air. By setting the injection timing relatively late near the compression top dead center, the in-cylinder temperature during fuel injection is high, and the fuel after injection is quickly vaporized and mixed. In the first stratified operation mode, during or immediately after fuel injection, in the course of rapid vaporization and mixing, fuel is ignited around the spray shaft where a combustible mixture is formed. Thereby, stable combustion is realized.
[0032]
Next, the formation of an air-fuel mixture in the second stratified operation mode, that is, in the stratified operation mode in which fuel is ignited via the piston 4 after fuel injection is completed, will be described with reference to FIG. In FIG. 5, the mixture formation process proceeds in the order of (a) → (b) → (c) → (d). Further, (d1) shows a state when the load is high in the last step (d), and (d2) shows a state when the load is low.
[0033]
In the second stratified operation mode, the fuel injection timing is set so that the fuel spray is received by the piston cavity 13, and the injected fuel spray collides with the bottom surface of the cavity 13. After that, the spray proceeds along the bottom surface of the piston cavity 13 due to the penetration force of the spray as shown in FIG. Thereafter, a relatively homogeneous stratified mixture is generated above the cavity 13 near the ignition plug 12 while swirling the surrounding air while swirling over the combustion chamber 5.
[0034]
When the engine load is high, a relatively dense homogeneous mixture is formed above the cavity 13 as shown in FIG. (D1), and as the engine load becomes lower, the mixture is formed above the cavity 13 as shown in FIG. The concentration decreases.
[0035]
Then, by igniting the relatively homogeneous mixture formed in this way, it is less susceptible to cycle fluctuations, and the stratified combustion is stabilized while suppressing the deterioration of the exhaust emission due to the concentration of the mixture. Is realized.
[0036]
Next, based on FIGS. 6 and 7, the relationship between the combustion stability, the CO emission amount, and the smoke emission amount in the two stratified operation modes with respect to the engine load and the engine rotation speed will be described. In the figure, M1 indicates the characteristic in the first stratified operation mode, and M2 indicates the characteristic in the second stratified operation mode.
[0037]
In the first stratified operation mode (abbreviated as mode 1 in the figure), a compact air-fuel mixture is formed immediately below the fuel injection valve 11, so that even when the engine load is low, the fuel is reliably located near the spark gap 12a. (Air-fuel mixture) can be provided, and stable combustion can be realized. On the other hand, when the engine load is high, the mixture concentration around the spark gap 12a becomes higher than the flammable air-fuel ratio, and the combustion stability deteriorates. When the load increases, CO and smoke are emitted from the rich mixture.
[0038]
On the other hand, in the case of the second stratified operation mode (abbreviated as mode 2 in the figure), the stratified gas mixture formed via the piston 4 is relatively formed after sufficiently vaporized and mixed. Since it is homogeneous, good combustion can be realized without deterioration of exhaust emission in a high load region. On the other hand, when the engine load is reduced, the homogeneous air-fuel mixture becomes thinner than the combustible air-fuel ratio, so that the air-fuel mixture concentration becomes too low and the combustion stability deteriorates.
[0039]
With respect to the engine speed, in the first stratified operation mode, a compact air-fuel mixture can be quickly formed even at a relatively high engine speed, so that stable stratified combustion can be performed.
[0040]
However, in the first stratified operation mode, the fuel during injection or immediately after the end of injection has a large concentration distribution. Therefore, when the diffusion and mixing of the fuel does not sufficiently proceed in the low engine speed region where the in-cylinder flow is weak, excessive fuel mixing occurs. The presence of a rich mixture causes deterioration of exhaust emissions such as smoke and CO.
[0041]
Further, when the fuel injection period for injecting the fuel injection amount corresponding to the engine load becomes relatively long with respect to the engine speed, a large amount of HC is discharged due to the diffusion of the initially injected fuel, and the heat generation amount is reduced. Large fluctuations between cycles degrade combustion stability.
[0042]
On the other hand, in the second stratified operation mode, as the engine rotation speed increases, time is apt to be insufficient to sufficiently form a uniform air-fuel mixture. Over diffusion occurs, and the vicinity of the ignition plug becomes too thin, and the combustion stability deteriorates.
[0043]
In the present invention, as shown in FIGS. 6 and 7, the operation mode is switched based on the combustion stability and the amount of CO emissions or smoke emissions. Specifically, switching from the first stratified operation mode (mode 1) to the second stratified operation mode (mode 2) is performed by switching either the smoke emission amount or the CO emission amount under the first stratified operation mode. Is performed when a predetermined switching level is exceeded (a in the figure), and switching from the second stratified operation mode (mode 2) to the first stratified operation mode (mode 1) is performed in the second stratified operation mode (mode 1). This is performed when the combustion stability under the stratified operation mode exceeds a predetermined switching level (b in the figure).
[0044]
FIG. 8 shows a basic combustion mode switching map corresponding to the engine speed and the engine load. Basically, in the region where the engine speed is low and the engine load is high, the operation in the second stratified operation mode (mode 2) is performed, and in the region where the engine speed is high and the engine load is low, the first operation is performed. Operation in the stratified operation mode (mode 1) is performed. It should be noted that in a high-load region equal to or higher than a predetermined engine load and a high-speed region equal to or higher than a predetermined engine rotation speed, homogeneous combustion is performed by the intake stroke injection.
[0045]
The switching between the first stratified operation mode and the second stratified operation mode is set such that the higher the engine load, the higher the engine speed at which the operation mode is switched.
[0046]
When parameters such as the combustion stability cannot be detected, for example, when the engine is started, the first and second stratified operation modes are selected based on the map shown in FIG. Then, when the detection of the combustion stability, the amount of smoke, and the amount of emitted CO is started, the optimal combustion method is selected for each cylinder and each cycle based on the detection.
[0047]
In addition, as for switching between the first and second stratified operation modes in the stratified combustion region, both are switched based on only the parameters such as the above-described combustion stability without having a switching map. You can also. FIG. 9 shows a switching map in such a case, and as shown, stratified combustion and homogeneous combustion are determined from operating conditions, and within the stratified combustion region, parameters such as combustion stability are used as described above. Based on this, switching between the first and second stratified operation modes is performed. This is because, as exemplified in FIGS. 6 and 7, the switching region (dead zone) between the first stratified operation mode (mode 1) and the second stratified operation mode (mode 2) based on each parameter is wide, and This is suitable when the combustion performance in the switching region does not differ between the two, and by performing the switching control based on the determination of the combustion state, a favorable stratified combustion operation can always be performed.
[0048]
Next, FIGS. 10 and 11 show another embodiment of the CO emission detecting means. This is because a pair of windows are formed facing each other across the exhaust pipe 21 of each cylinder, and the first light is transmitted from one of the windows so that infrared light including the vibration mode frequency of CO molecules crosses the exhaust flow. The infrared light is projected through the fiber 22, the transmitted light is received from the other window through the second optical fiber 23, and the transmitted light is guided to the photodetector for each cylinder. It is what was constituted. The optical fibers 22 and 23 are attached to windows of the exhaust pipe 21 by connectors 24 and 25, respectively.
[0049]
In such a configuration, the amount of CO emission and the transmittance of infrared light have a relationship as shown in FIG. 12, whereby the amount of CO emission is detected. In the method of the present embodiment, measurement having a time resolution for each cycle can be performed by a pair of light sources and a photodetector.
[0050]
Hereinafter, the operation and effect unique to each claim that embodies the present invention will be described together.
[0051]
The invention according to claim 2 has means for detecting the combustion stability of the internal combustion engine as a parameter indicating the combustion state of the internal combustion engine. Based on a signal from the combustion stability detection means, the two stratified operation modes are set. Switching was performed. According to a more specific aspect of the present invention, when it is determined during the operation in one of the stratified operation modes that the combustion stability has become worse than a predetermined level based on the signal of the combustion stability detection means, , To switch to the other stratified operation mode. Therefore, regardless of the operating conditions of the engine, it is possible to always improve fuel economy by stratified combustion without causing deterioration of drivability due to deterioration of combustion.
[0052]
In addition, the mixture during stratified combustion has a large density distribution depending on the fuel injection amount, the time interval between the fuel injection timing and the ignition timing, and the magnitude of the interaction with the gas flow, and the combustion stability deteriorates. Even when not performed, smoke may be generated and discharged by the rich mixture.
[0053]
Therefore, the invention of claim 4 has means for detecting the amount of smoke emission of the internal combustion engine as a parameter indicating the combustion state of the internal combustion engine. Based on the signal of the smoke emission amount detection means, two stratified operation modes are provided. Is switched. According to a more specific aspect of the present invention, when the smoke emission amount is equal to or more than a predetermined value based on a signal of the smoke emission amount detection means during operation in one stratification operation mode, the other stratification operation mode Switched to Therefore, the fuel efficiency can be improved by the stable stratified combustion irrespective of the operating conditions without the emission of smoke.
[0054]
In addition, even if smoke is not discharged from a mixture having a large concentration distribution during stratified combustion, even if smoke is not discharged by the mixture, combustion efficiency may be deteriorated due to CO emissions.
[0055]
Therefore, the invention according to claim 6 has means for detecting the amount of CO emission of the internal combustion engine as a parameter indicating the combustion state of the internal combustion engine. Is switched. According to a more specific aspect of the present invention, during operation in one of the stratified operation modes, if the CO emission is equal to or more than a predetermined value based on a signal from the CO emission detection means, the other stratified operation mode Switched to Therefore, the fuel efficiency can be improved by the stratified combustion without causing the deterioration of the combustion efficiency due to the increase of the CO emission.
[0056]
In the second stratified operation mode, the air-fuel mixture formed via the piston after the end of the fuel injection passes through the cavity, and after being sufficiently vaporized and mixed, a relatively uniform mixture is formed above the cavity. Form a mixture distribution. Accordingly, there is no fear of smoke and CO emission from the rich mixture, and there is an advantage that the mixture is less likely to be affected by the cycle fluctuation.
[0057]
However, there is a concern that time will be insufficient to sufficiently form a uniform air-fuel mixture with an increase in the engine rotation speed. Also, as the in-cylinder flow becomes stronger with an increase in the engine rotation speed, the air-fuel mixture becomes overdiffused, and the vicinity of the ignition plug may become too thin.
[0058]
Furthermore, especially when the engine load is low, the relatively uniform mixture formed above the cavity becomes thinner than the combustible air-fuel ratio, and there is a risk of misfiring.
[0059]
On the other hand, in the first stratified operation mode, the fuel spray during the flight before the collision with the piston during the fuel injection or immediately after the end of the fuel injection is immediately mixed with the surrounding air from around the spray axis and vaporized. A mixture is formed. Since the air-fuel mixture that does not pass through the piston is formed as a compact air-fuel mixture immediately below the fuel injection valve regardless of the engine speed, stable stratified combustion can be performed regardless of the engine speed.
[0060]
In addition, even when the engine load is low, the fuel (air-fuel mixture) can be reliably disposed near the spark gap, so that stable combustion can be realized.
[0061]
However, in the first stratified operation mode, the fuel during or immediately after the injection has a large concentration distribution, and in the high load operation region where the combustion injection amount is large, the mixture concentration around the spark gap decreases the combustible air-fuel ratio. When the mixture becomes too rich, the combustion stability is deteriorated, and CO or smoke may be emitted from the rich mixture.
[0062]
In view of this, the invention according to claim 8 includes means for detecting smoke emission of the internal combustion engine or means for detecting CO emission of the internal combustion engine as parameters indicating the combustion state of the internal combustion engine; Means for detecting, wherein the switching from the first stratified operation mode to the second stratified operation mode is performed based on the smoke emission amount or the CO emission amount in the first stratified operation mode, Switching from the second stratified operation mode to the first stratified operation mode is performed based on the combustion stability in the second stratified operation mode.
[0063]
That is, in the second stratified operation mode in which the stratified combustion may not be realized due to the deterioration of the combustion stability, it is determined whether or not the combustion mode is possible by detecting the combustion stability, and the smoke or CO emission is reduced rather than the combustion stability. In the first stratified operation mode in which there is a risk, the determination of the feasibility of the combustion mode based on the smoke emission amount or the CO emission amount allows the stratified combustion in which smoke and CO emissions are suppressed without impairing combustion stability. realizable.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a direct injection internal combustion engine according to the present invention.
FIG. 2 is an enlarged view of a spark plug provided with an optical fiber.
FIG. 3 is a characteristic diagram showing a relationship between a smoke emission amount (or a CO emission amount) and a luminous intensity of a bright flame.
FIG. 4 is an explanatory diagram showing a mixture formation process in a first stratified operation mode.
FIG. 5 is an explanatory diagram showing a mixture formation process in a second stratified operation mode.
FIG. 6 is a characteristic diagram showing a change in combustion stability and the like with respect to an engine load and mode switching.
FIG. 7 is a characteristic diagram showing a change in combustion stability and the like with respect to an engine rotation speed and mode switching.
FIG. 8 is a characteristic diagram showing a map of a combustion mode with respect to operating conditions.
FIG. 9 is a characteristic diagram showing a different example of a map of a combustion mode with respect to operating conditions.
FIG. 10 is an explanatory view showing an embodiment in which an optical fiber is provided in an exhaust pipe as CO emission detecting means.
FIG. 11 is an explanatory sectional view of the exhaust pipe.
FIG. 12 is a characteristic diagram showing a relationship between a CO emission amount and an infrared light transmittance in this embodiment.
[Explanation of symbols]
4 Piston 5 Combustion chamber 10 Engine control unit 11 Fuel injector 12 Spark plug 13 Cavity 14 Optical fiber 15 Light intensity detector 16 Crank angle sensor

Claims (8)

An in-cylinder direct injection internal combustion engine having an ignition plug and a fuel injection valve in the upper part of the combustion chamber, and having a substantially cylindrical cavity near the center of the piston crown,
There is a first stratified operation mode in which fuel is ignited before colliding with the piston during or immediately after the end of fuel injection, and a second stratified operation mode in which fuel is ignited through the piston after fuel injection is completed. And
An in-cylinder direct injection internal combustion engine characterized by switching between these two stratified operation modes according to the combustion state of the internal combustion engine. 2. The direct in-cylinder according to claim 1, further comprising means for detecting the combustion stability of the internal combustion engine, and switching between the two stratified operation modes based on a signal from the combustion stability detection means. Injection type internal combustion engine. During the operation in one stratified operation mode, if it is determined that the combustion stability has become worse than a predetermined level based on the signal of the combustion stability detection means, the operation is switched to the other stratified operation mode. The direct injection internal combustion engine according to claim 2, wherein: 2. The direct injection in a cylinder according to claim 1, further comprising means for detecting a smoke emission amount of the internal combustion engine, and switching between two stratified operation modes based on a signal from the smoke emission amount detection means. Type internal combustion engine. The method according to claim 4, wherein, during operation in one of the stratified operation modes, based on a signal from the smoke emission amount detection means, when the smoke emission amount is equal to or more than a predetermined value, the mode is switched to the other stratified operation mode. An in-cylinder direct injection internal combustion engine according to claim 1. 2. The direct injection in a cylinder according to claim 1, further comprising means for detecting a CO emission amount of the internal combustion engine, and switching between two stratified operation modes based on a signal from the CO emission detection means. Type internal combustion engine. The method according to claim 6, wherein during operation in one stratified operation mode, based on a signal from the CO emission amount detection means, when the CO emission amount is equal to or more than a predetermined value, the operation mode is switched to the other stratified operation mode. An in-cylinder direct injection internal combustion engine according to claim 1. Means for detecting smoke emission of the internal combustion engine or means for detecting CO emission of the internal combustion engine, and means for detecting the combustion stability of the internal combustion engine,
The switching from the first stratified operation mode to the second stratified operation mode is performed based on the amount of smoke emission or the amount of CO emission in the first stratified operation mode,
The in-cylinder direct injection according to claim 1, wherein the switching from the second stratified operation mode to the first stratified operation mode is performed based on the combustion stability in the second stratified operation mode. Type internal combustion engine.

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