JP2007198324A - Cylinder direct-injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly activate a catalyst when an engine is cool and avoid the deterioration of the primary peak of HC. <P>SOLUTION: When the internal combustion engine for which the early increase in the temperature of a catalytic converter is requested is started in a cool state, the ignition timing ADV is largely retarded, a first fuel injection I1 is performed during the compression stroke at a rather low fuel pressure, and a second fuel injection I2 is performed at the time 10 to 20° CA before the ignition timing ADV during the expansion stroke. A compact air-fuel mixture lump is formed near an ignition plug by the first spray, and a richer air-fuel mixture lump is locally formed on the inside thereof by the second spray and ignited. Robustness against variations for each cycle is increased and the occurrence of HC in a quench area and a clevis is reduced. A fuel injection valve is disposed on the exhaust valve side and injects a fuel to the intake valve side. Since the unburned HC produced near the exhaust valve is reduced, the primary peak of HC the instant the exhaust valve is opened is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an in-cylinder direct injection type spark ignition internal combustion engine that directly injects fuel into a cylinder, and in particular, at a cold start in which early temperature rise (early activation) of an exhaust system catalytic converter is required. It relates to control of injection timing and ignition timing.

  In Patent Document 1, as a catalyst warm-up method for a direct injection spark-ignition internal combustion engine, a period from the intake stroke to the ignition timing when the exhaust gas catalytic converter is in an unwarmed state lower than the activation temperature. In this case, it is possible to spread the fuel by the late injection in which the air-fuel mixture having a partial air-fuel ratio concentration is formed in the combustion chamber, the fuel is injected before this late injection, and the fuel of the late injection and the combustion of the late injection And at least two split injections of early injection for generating an air-fuel mixture leaner than the stoichiometric air-fuel ratio in the combustion chamber, and retarding the ignition timing by a predetermined amount from the MBT point, and no engine load A technique is described in which the ignition timing is set before the compression top dead center in the region, and the ignition timing is retarded until the compression top dead center in the low speed and low load region excluding the no-load region. The latter-stage injection is performed, for example, at 120 ° BTDC to 45 ° BTDC after the middle of the compression stroke.

Further, Patent Document 2 was previously proposed by the present applicant, and uses combustion in the cylinder due to the spray energy of high-pressure fuel injection to retard the ignition timing until after compression top dead center. As an example, it is disclosed that the first fuel injection is performed in the latter half of the compression stroke, and the second fuel injection is performed immediately before the ignition of the expansion stroke. ing.
Japanese Patent No. 3325230 Japanese Patent Laid-Open No. 2005-214039

  However, in Patent Document 1, the first fuel injection (early injection) is performed during the intake stroke, and the second fuel injection (late injection) is performed from 120 ° BTDC to 45 ° BTDC during the compression stroke. Therefore, the combustion stability is low. In particular, in the no-load region, the ignition timing is set to before compression top dead center (BTDC ignition). Therefore, the exhaust temperature rise and the HC reduction due to the ignition timing retard cannot be sufficiently achieved.

  In addition, if the first injection is performed during the intake stroke, the fuel enters the quench region and the clevis in the combustion chamber and becomes a source of HC generation.

  Further, in the above prior art, since the combustion becomes unstable, a large amount of HC is generated in the combustion chamber, and when the exhaust valve is opened, the HC concentration at the so-called primary peak that flows out to the exhaust port increases. is there. In particular, the amount of HC at the primary peak is increased as the fuel injection timing is retarded, so that the amount of fuel adhering to the wall surface increases because the fuel is injected with the combustion chamber volume being reduced. It tends to increase. That is, even if the exhaust gas temperature increases due to the retard of the ignition timing, there is a possibility that HC increases conversely.

  On the other hand, in Patent Document 2, the first fuel injection is performed in the latter half of the compression stroke, and the second fuel injection is performed immediately before the ignition of the expansion stroke. However, depending on the in-cylinder turbulence due to the second fuel injection, Since combustion is established, a high fuel pressure is required. As a result, combustion is relatively fast (compared to the case where the fuel pressure is low), and there is still room for improvement in terms of an increase in exhaust temperature and a reduction in HC associated therewith.

  The present invention is based on such a situation, and aims to improve combustion stability in superretarded combustion for early activation of the catalyst and reduction of HC and to suppress the primary peak of HC.

The present invention includes a fuel injection valve and a spark plug for directly injecting fuel into a cylinder, and in a predetermined operation state, for example, when it is necessary to raise the exhaust gas temperature, such as when the catalytic converter is cold, In the in-cylinder direct injection spark ignition internal combustion engine that performs super retard combustion with the ignition timing set after compression top dead center,
During super retard combustion, the first fuel injection is performed during the compression stroke to form a rich air-fuel mixture in a part of the combustion chamber near the spark plug,
A second fuel injection is performed during the expansion stroke at a timing preceding the ignition timing by a predetermined period so that a locally richer air-fuel mixture reaches the ignition plug at the ignition timing,
The ignition is performed in a state where a two-stage stratified mixture is formed in a part of the combustion chamber in the vicinity of the spark plug.

  Further, the fuel / air mixture by the injected fuel is configured to be relatively unevenly distributed closer to the intake valve in the combustion chamber.

  That is, in the present invention, a compact stratified mixture is formed in the combustion chamber by two fuel injections at a relatively low fuel pressure without depending on the spray energy of the fuel injection. In particular, at the ignition timing, a locally rich air-fuel mixture is present in the vicinity of the spark plug due to the spray of the second fuel injection, and surrounds the periphery of the spark plug rather than the stoichiometric air-fuel ratio by the first fuel injection. A rich and lean air-fuel mixture exists near the spark plug. That is, a compact stratified mixture having two different concentrations is formed, and ignition is performed in this state. It is desirable that the air-fuel mixture produced by the first fuel injection does not diffuse throughout the combustion chamber.

  According to such a combustion method, stable combustion is possible with respect to a minute change in rotational speed or a minute load change for each cycle. Since both fuel injections are performed at a relatively low fuel pressure in a place where the in-cylinder pressure is high, the spray becomes compact and hardly enters the quench region or the clevis, thus suppressing the generation of HC. In addition, since a relatively low fuel pressure can be used, the combustion speed can be suppressed, which is advantageous in increasing the exhaust temperature and reducing HC.

  FIG. 17 shows the characteristics of the HC emission concentration (concentration at the exhaust port) in a general direct injection spark-ignition internal combustion engine and its exhaust mechanism. As shown in FIG. The HC concentration has a primary peak at the beginning of the exhaust stroke (beginning to open the exhaust valve) and a secondary peak at the end of the exhaust stroke (just before the exhaust valve is closed). As shown in FIG. 1A, the primary peak is that unburned HC existing in the vicinity of the exhaust valve in the combustion chamber flows out to the exhaust port side at the moment when the exhaust valve is opened. As shown in Fig. 2 (b), the secondary peak increases the HC concentration when unburned components in the piston crown and bore walls and unburned components in the clevis are pushed out by the piston. is there.

  In the present invention, since the air-fuel mixture due to the injected fuel is relatively unevenly distributed near the intake valve in the combustion chamber, unburned HC near the exhaust valve at the end of the expansion stroke is reduced, and the exhaust valve starts to open. Is suppressed.

  A relatively large amount of injected fuel near the intake valve in the combustion chamber can be achieved by various means such as the position of the fuel injection valve, the direction of fuel spray, or the configuration of the piston top.

  According to the present invention, the combustion stability of the super retard combustion in which the ignition timing is set after the compression top dead center is improved. For example, at the time of cold start, early activation of the catalyst and reduction of HC are achieved by increasing the exhaust temperature. can do. In particular, since the air-fuel mixture due to the injected fuel is unevenly distributed closer to the intake valve, the primary peak of the HC concentration at the start of opening of the exhaust valve can be suppressed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration explanatory view showing a system configuration of a direct injection type spark ignition internal combustion engine to which the present invention is applied.

  An intake passage 4 is connected to the combustion chamber 3 formed by the piston 2 of the internal combustion engine 1 via an intake valve (not shown), and an exhaust passage 5 is connected via an exhaust valve (not shown). Has been. The intake passage 4 is provided with an air flow meter 6 for detecting the amount of intake air, and an electronically controlled throttle valve 7 whose opening degree is controlled via an actuator 8 by a control signal. The exhaust passage 5 is provided with a catalytic converter 10 for purifying exhaust gas, and air-fuel ratio sensors 11 and 12 are provided on the upstream side and the downstream side, respectively. Further, the upstream air-fuel ratio sensor 11 is provided. Is provided with an exhaust gas temperature sensor 13 for detecting the exhaust gas temperature at the inlet side of the catalytic converter 10.

  A spark plug 14 is disposed at the central top of the combustion chamber 3. A fuel injection valve 15 that directly injects fuel into the combustion chamber 3 is disposed on the side of the combustion chamber 3 on the exhaust passage 5 side. The fuel that has been regulated to a predetermined pressure by the high-pressure fuel pump 16 and the pressure regulator 17 is supplied to the fuel injection valve 15 via the high-pressure fuel passage 18. Therefore, when the fuel injection valve 15 of each cylinder is opened by the control pulse, an amount of fuel corresponding to the valve opening period is injected. Reference numeral 19 denotes a fuel pressure sensor that detects the fuel pressure, and 20 denotes a low-pressure fuel pump that sends fuel to the high-pressure fuel pump 16.

  In addition, the internal combustion engine 1 is provided with a water temperature sensor 21 for detecting the engine cooling water temperature and a crank angle sensor 22 for detecting a crank angle. Further, an accelerator opening sensor 23 is provided for detecting the amount of depression of the accelerator pedal by the driver.

  The fuel injection amount, injection timing, ignition timing, etc. of the internal combustion engine 1 are controlled by the control unit 25. The control unit 25 receives detection signals from the various sensors described above. The control unit 25 determines the combustion method, that is, the homogeneous combustion or the stratified combustion, in accordance with the engine operating conditions detected by these input signals, and according to this, the electronic control throttle valve 7 is opened. The fuel injection timing and fuel injection amount of the fuel injection valve 15, the ignition timing of the spark plug 14, and the like are controlled.

  After completion of warm-up, normal stratified combustion operation or homogeneous combustion operation is performed. For example, in a predetermined region on the low speed and low load side, as normal stratified combustion operation, fuel injection is performed at an appropriate time in the compression stroke, and ignition is performed at a time before the compression top dead center. The fuel spray is collected in a layered manner in the vicinity of the spark plug 14, thereby realizing, for example, stratified combustion with a lean air-fuel ratio. Further, in a predetermined region on the high speed and high load side, as normal homogeneous combustion operation, fuel injection is performed during the intake stroke, and ignition is performed in the vicinity of the MBT point before the compression top dead center. In this case, the fuel becomes a homogeneous mixture in the cylinder.

  The present invention performs super retard combustion so that the exhaust gas temperature becomes high at the time of cold start of the internal combustion engine 1 where early temperature rise of the catalytic converter 10 is required. The fuel injection timing and ignition timing will be described with reference to FIG.

  FIG. 2 shows an example of the fuel injection timing and ignition timing during super retard combustion, and the ignition timing ADV is set to 10 ° to 50 ° ATDC in order to obtain a sufficiently high exhaust temperature. . That is, the period B is 10 ° to 50 ° CA. Further, the first fuel injection I1 is performed during the compression stroke, and the second fuel injection I2 is performed during the expansion stroke. The first fuel injection I1 is for forming a rich air-fuel mixture that spreads in a part of the combustion chamber 3 in the vicinity of the spark plug 14, and from the fuel injection timing (specifically, the fuel injection start timing) to the ignition timing. The period C until ADV is set to 50 ° to 140 ° CA, for example. In other words, the fuel injection timing is set so that the fuel spray by the first fuel injection I1 diffuses in the combustion chamber 3 to some extent but does not diffuse excessively. When the period C is excessively long, the fuel spray is excessively diffused, and the fuel component enters the quench region or the clevis.

  Then, the second fuel injection I2 during the expansion stroke is performed at a timing preceding the ignition timing ADV by a predetermined period A so that a locally richer air-fuel mixture reaches the ignition plug 14 at the ignition timing ADV. Done. The period A from the fuel injection timing (specifically, the fuel injection start timing) to the ignition timing ADV basically correlates with the distance from the fuel injection valve 15 to the spark plug 14, for example, 10 ° to 20 ° CA. is there.

  At this time, the air-fuel ratio (the average air-fuel ratio of the entire combustion chamber by two injections) is set to the stoichiometric air-fuel ratio or slightly lean (about 16 to 17). Thereby, a necessary and sufficient amount of oxygen necessary for the afterburning of HC is ensured.

  Further, since combustion is performed without depending on the disturbance due to the energy of the fuel spray, a relatively low fuel pressure is used as the fuel pressure within a range where combustion is established as will be described later.

  By performing the fuel injection as described above, at the ignition timing ADV, as shown in FIG. 3, a compact stratified air-fuel mixture having a two-stage concentration surrounding the spark plug 14 is formed. That is, by the first fuel injection I1, a first air-fuel mixture richer than the stoichiometric air-fuel ratio is formed in a part of the combustion chamber 3 in the vicinity of the spark plug 14 as indicated by reference numeral 31, and 2 A richer second air-fuel mixture resulting from the second fuel injection I2 is locally formed in the vicinity of the spark plug 14 as indicated by reference numeral 32. Both fuel injections are performed toward a field where the in-cylinder pressure in the vicinity of the top dead center is high and the fuel pressure is relatively low. The outside is basically a fresh air layer where fuel is not diffused. Then, in this state of stratification, the second air-fuel mixture 32 is ignited by the spark plug 14 and combustion is performed relatively slowly.

  In the retarded combustion according to the method of the present invention, the injection timing of the first fuel injection I1 hardly affects the combustion stability, that is, the misfire rate and torque fluctuation, and the fluctuation of the injection timing of the second fuel injection I2 is misfired. The effect on the rate and torque fluctuation is small.

  FIG. 4 shows the change in misfire rate and torque fluctuation when the expansion stroke injection, that is, the injection timing of the second fuel injection I2 is changed from the optimal injection timing. In the characteristics of the embodiment, the injection timing slightly changes. However, the misfire rate and torque fluctuation do not deteriorate rapidly. On the other hand, in the characteristics of the reference example in which the entire amount is injected at a time during the expansion stroke, if the injection timing changes even slightly from the optimal injection timing, the misfire rate and torque fluctuation are rapidly deteriorated.

  Therefore, in the present invention, even if the optimum value of the injection timing of the second fuel injection I2 changes due to a minute change in the rotational speed or a minute load for each cycle, the misfire rate and torque fluctuation increase. Stable combustion can be obtained. In other words, the robustness against cycle changes is high.

  Further, in the present invention, the air-fuel mixture becomes compact and the fuel component does not enter the quench region or the clevis, so that HC generated from these portions is reduced.

  Further, as shown in FIG. 5 (a), in the combustion method of the present invention, even if the fuel pressure is lowered, the deterioration of combustion (for example, torque fluctuation) is small, and on the other hand, by reducing the fuel pressure, As shown in the figure, the exhaust gas temperature is higher, and accordingly, as shown in (c), the HC emission amount is reduced. This is because by lowering the fuel pressure, the combustion becomes slower and the combustion is performed later. Therefore, in the present invention, it is desirable to reduce the fuel pressure within a range where combustion is established. As a result, the exhaust temperature can be increased and HC can be further reduced.

  On the other hand, the unburned HC flows out into the exhaust port at the moment when the exhaust valve is opened after the end of the combustion, and becomes a so-called primary peak. In the configuration of the above embodiment, the side portion of the combustion chamber 3 on the exhaust valve side Since the fuel is injected from the fuel injection valve 15 provided in the engine toward the intake valve side, as shown in FIG. 3, the air-fuel mixture is relatively unevenly distributed on the intake valve side and exists on the exhaust valve side. The proportion of fuel is relatively low. Therefore, a large amount of unburned HC generated in the combustion chamber 3 at the end of the expansion stroke exists near the intake valve, and the exhaust valve side is relatively small. Accordingly, the unburned HC flowing out to the exhaust port side at the moment when the exhaust valve is opened is reduced, and the primary peak of the HC concentration is reduced.

  Next, embodiments in which the fuel injection valve 15 and the like are arranged differently so that the air-fuel mixture is largely distributed on the intake valve side as described above will be described.

  In the embodiment of FIG. 6, a pair of intake valves 41 and a pair of exhaust valves 42 are provided for one cylinder, and in the center of the ceiling surface of the combustion chamber 3 surrounded by these four valves, A fuel injection valve 15 is disposed, and a spark plug 14 is disposed adjacent to the fuel injection valve 15. From the fuel injection valve 15, fuel is injected along the cylinder axis toward the top of the piston 2. More specifically, on the combustion chamber ceiling, the tip of the fuel injection valve 15 is located closer to the pair of exhaust valves 42 than the cylinder axis c, and the spark plug 14 is located closer to the pair of intake valves 41. To do. The fuel injection valve 15 has a general configuration in which a conical spray is formed coaxially with the center axis m thereof, and the center axis m so that the base end side is closer to the exhaust valve 42 with respect to the tip position. Is attached to the cylinder head 4 in a posture inclined with respect to the cylinder axis c. Therefore, the fuel injection direction is inclined toward the intake valve 41 side, and the fuel injected near the compression top dead center when the engine is cold as described above is relatively close to the intake valve 41 in the combustion chamber 3. The ratio of the fuel present on the exhaust valve 42 side is relatively small.

  Therefore, as in the above-described embodiment, unburned HC flowing out to the exhaust port 43 side at the moment when the exhaust valve 42 is opened is reduced, and the primary peak of the HC concentration is reduced.

  In the above configuration, since the tip of the fuel injection valve 15 is biased toward the exhaust valve 42, the fuel spray is injected when the fuel is injected during the intake stroke in which the intake valve 41 is open as a homogeneous combustion operation. There is no collision with the valve head of the intake valve 41. Therefore, the deterioration of HC during the homogeneous combustion operation due to the fuel adhering to the intake valve 41 is avoided.

  Next, in the embodiment shown in FIG. 7, the tip position of the fuel injection valve 15 facing the combustion chamber 3 is located on the cylinder axis c. The central axis m of the fuel injection valve 15 is inclined in the same manner as in the embodiment of FIG. 6, so that the fuel injected near the compression top dead center is unevenly distributed closer to the intake valve 41 as in the above embodiment. To do. In this case, the position of the ignition plug 14 may be arranged closer to the intake valve 41 than the fuel injection valve 15 as shown, or may be arranged closer to the exhaust valve 42 than the fuel injection valve 15. Also good.

  Next, in the embodiment shown in FIG. 8, the tip position of the fuel injection valve 15 attached in an inclined posture is arranged closer to the intake valve 41 than the cylinder axis c in the same manner as the embodiments of FIGS. Is. In this case, the spark plug 14 is disposed closer to the exhaust valve 42 than the fuel injection valve 15.

  Further, in the embodiment shown in FIG. 9, the fuel injection valve 15 is arranged perpendicularly to the center of the combustion chamber 3 so that the center axis m of the fuel injection valve 15 coincides with the cylinder axis c, and the fuel is taken into the intake air. The spray center axis f is inclined toward the intake valve 41 side with respect to the center axis m of the fuel injection valve 15 so as to be unevenly distributed closer to the valve 41. That is, the conical spray is injected obliquely with respect to the fuel injection valve 15 itself. In this case, although not shown, the spark plug 14 may be disposed closer to the intake valve 41 than the fuel injection valve 15 or may be disposed closer to the exhaust valve 42.

  In the embodiment shown in FIG. 10, as in the embodiment of FIG. 9, the fuel injection valve 15 is arranged perpendicularly to the center of the combustion chamber 3 so that the center axis m of the fuel injection valve 15 coincides with the cylinder axis c. In particular, a fuel injection valve 15 of a type in which the fuel distribution in the spray is non-uniform is used, and by using this, fuel is unevenly distributed closer to the intake valve 41. .

  As an example, as shown in FIGS. 11 (a) and 11 (b), a known multi-hole type fuel injection valve in which a large number of fine injection holes 15b are arranged on the front end surface 15a is used. By arranging a large amount on one side, the distribution of the fuel composed of the fine spray F can be biased.

  As another example, as shown in FIGS. 12 (a) and 12 (b), a known fuel injection in which a spray F having a C-shaped cross section is formed by making the shape of the injection hole portion irregular. A valve 15 can be used. In this case, the fuel distribution in the cross section of the spray on the plane bb orthogonal to the central axis m of the fuel injection valve 15 is largely biased toward the C-shaped central portion. Therefore, a large amount of fuel can be biased toward the intake valve 41.

  Next, in the embodiment of FIG. 13, the fuel injection valve 15 is arranged so that the center axis m thereof is parallel to the cylinder axis c and is offset from the cylinder axis c to the exhaust valve 42 side. Is. Then, by using the fuel injection valve 15 having the configuration described with reference to FIG. 11 or FIG. 12, a large amount of fuel is unevenly distributed near the intake valve 41. In this embodiment, since the fuel injection valve 15 is located away from the intake valve 41, the spray collides with the valve head of the intake valve 41 during the intake stroke injection as described in the embodiment of FIG. There is nothing.

  Next, in the embodiment of FIG. 14, the fuel injection valve 15 is arranged so that the center axis m thereof is parallel to the cylinder axis c and is offset from the cylinder axis c toward the intake valve 41. Is. The spray center axis coincides with the center axis m of the fuel injection valve 15. Therefore, a large amount of fuel is unevenly distributed closer to the intake valve 41.

  Next, an embodiment in which the fuel injected after the compression top dead center is relatively unevenly distributed closer to the intake valve 41 by devising the shape of the top of the piston 2 will be described.

  In the embodiment of FIG. 15, a cavity 45 is formed on the top side of the piston 2 on the intake valve 41 side, and a convex portion 46 close to the exhaust valve 42 is formed on the exhaust valve 42 side. In particular, a relatively large gap 47 is provided between the top surface of the convex portion 46 and the ceiling surface of the combustion chamber 3 on the exhaust valve 42 side so as not to cause a spray drawing effect by squish. In this embodiment, the fuel spray injected vertically from the fuel injection valve 15 located at the center of the combustion chamber 3 collides with the bottom surface of the cavity 45 and is reflected to the intake valve 41 side. Thereby, many are unevenly distributed in the intake valve 41 side.

  In the embodiment of FIG. 16, a cavity 45 is formed in the substantially central portion of the top of the piston 2, and the top surface of the convex portion 46 located on the intake valve 41 side is the ceiling of the combustion chamber 3 on the intake valve 41 side. It is the structure which mutually adjoins so that a squish area may be comprised between surfaces. In this embodiment, when the piston 2 descends from the top dead center, a pulling effect is produced by the squish area on the intake valve 41 side, and the fuel spray injected toward the cavity 45 after the top dead center moves to the intake valve 41 side. Gravitate. Thereby, a relatively large amount of fuel is unevenly distributed on the intake valve 41 side.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. The characteristic view which shows the fuel injection timing and ignition timing of the super retard combustion of this invention. Explanatory drawing which shows the state of the stratified mixture formed in a combustion chamber. The characteristic view which shows the relationship between the injection timing of expansion stroke injection, (a) torque fluctuation, and (b) misfire rate. The characteristic view which shows the relationship between a fuel pressure, (a) torque fluctuation, (b) exhaust temperature, (c) HC discharge | emission amount. Sectional drawing which shows the Example from which arrangement | positioning of a fuel injection valve and a spark plug differs. Sectional drawing of the Example which made the fuel injection valve front-end | tip position the cylinder axis line c. Sectional drawing of the Example which made the fuel injection valve front-end | tip position close to the intake valve. Sectional drawing of the Example which the spray center axis line inclined with respect to the center axis line of a fuel injection valve. Sectional drawing of the Example which made the fuel distribution in spray non-uniform | heterogenous. It is explanatory drawing of an example of the fuel injection valve from which fuel distribution becomes non-uniform | heterogenous, (a) is explanatory drawing which looked at the spray from the side, (b) is explanatory drawing seen from the front. It is explanatory drawing of the other example of the fuel injection valve from which fuel distribution becomes non-uniform | heterogenous, (a) is explanatory drawing which looked at the spray from the side, (b) is sectional drawing of the spray along the bb line. Sectional drawing of the Example which has arrange | positioned the fuel injection valve near the exhaust valve. Sectional drawing of the Example which has arrange | positioned the fuel injection valve near the intake valve. FIG. 3 is a cross-sectional view showing an embodiment in which a large amount of fuel is unevenly distributed closer to the intake valve depending on the shape of the piston top. Sectional drawing which shows the other Example which made it unevenly distribute fuel near the intake valve by the shape of the piston top part. The characteristic view which showed the characteristic of HC discharge concentration in the general direct injection type spark ignition internal combustion engine with the discharge mechanism.

Explanation of symbols

3 ... Combustion chamber 10 ... Catalytic converter 14 ... Spark plug 15 ... Fuel injection valve 25 ... Control unit

Claims (11)

An in-cylinder direct injection spark ignition internal combustion engine that includes a fuel injection valve that directly injects fuel into a cylinder and an ignition plug, and performs super retard combustion with ignition timing set after compression top dead center in a predetermined operating state ,
During super retard combustion, the first fuel injection is performed during the compression stroke to form a rich air-fuel mixture in a part of the combustion chamber near the spark plug,
A second fuel injection is performed during the expansion stroke at a timing preceding the ignition timing by a predetermined period so that a locally richer air-fuel mixture reaches the ignition plug at the ignition timing,
It is configured to ignite in a state where a two-stage stratified mixture is formed in a part of the combustion chamber near the spark plug,
Further, the direct injection type spark ignition internal combustion engine is characterized in that the air-fuel mixture by the injected fuel is configured to be relatively unevenly distributed closer to the intake valve in the combustion chamber.   The in-cylinder direct injection spark ignition internal combustion engine according to claim 1, wherein the ignition timing in the super retard combustion is 10 ° to 50 ° CA after compression top dead center.   The in-cylinder direct injection spark ignition internal combustion engine according to claim 1 or 2, wherein a period from an injection start timing of the second fuel injection to an ignition timing is 10 ° to 20 ° CA.   The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 3, wherein a period from an injection start timing to an ignition timing of the first fuel injection is 50 ° to 140 ° CA.   The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 4, wherein the air-fuel ratio in super retarded combustion is a stoichiometric air-fuel ratio or slightly lean.   The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 5, wherein the super retard combustion is executed when a temperature increase of the exhaust gas is required as a predetermined operation state. organ.   The direct injection spark ignition internal combustion engine according to any one of claims 1 to 6, wherein a low fuel pressure is used within a range where combustion is established.   The in-cylinder direct according to any one of claims 1 to 7, wherein the fuel injection valve is disposed on a side of the combustion chamber on the exhaust valve side and injects fuel toward the intake valve side. Injection spark ignition internal combustion engine.   The fuel injection valve is disposed at the center of the combustion chamber ceiling surface and injects fuel toward the top of the piston, and the central axis of the fuel injection valve is a cylinder axis so that the fuel injection direction is toward the intake valve. The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 7, wherein the internal combustion engine is inclined with respect to the cylinder.   The fuel injection valve is disposed at the center of the combustion chamber ceiling surface, and injects fuel toward the top of the piston, and sprays with respect to the central axis of the fuel injection valve so that the fuel injection direction is toward the intake valve. The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 7, wherein a central axis is inclined. The fuel injection valve is disposed at the center of the combustion chamber ceiling surface, and injects fuel toward the piston top, and sprays orthogonal to the central axis of the fuel injection valve so that the fuel is unevenly distributed closer to the intake valve. The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 7, wherein the fuel distribution in the cross section is non-uniform.

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