JP2007278257A - Direct injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly attain stabilization of combustion, improvement of fuel consumption and reduction of exhaust gas in a spray guide combustion system. <P>SOLUTION: A direct injection type spark ignition internal combustion engine comprises a fuel injection valve for directly injecting fuel into a combustion chamber and an ignition plug and is characterized in that the ignition plug is provided to situate an ignition electrode part inside a fuel spray injected from the fuel injection valve or near a ridge line of the spray and ignites the fuel after injection to generate flame, and at least one or more sprays are newly and diffusively burned by the generated flame after the ignition time and ignition is newly made at least one or more times after completion of all injections in a combustion stroke. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a direct injection type spark ignition internal combustion engine.

  Conventionally, an in-cylinder direct injection spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber by a fuel injection valve is known. A fuel injection valve is provided in the center of the upper wall of the combustion chamber, and the electrode part of the spark plug is laid out so that it is located inside the fuel spray from the fuel injection valve or in the vicinity of the fuel spray ridge line, and directly to the fuel spray during or immediately after fuel injection A so-called spray guide method for performing ignition is known. (Patent Document 1) According to this spray guide system, leaner and more stable combustion without misfire can be achieved in a low load operating region than other types of in-cylinder injection type spark ignition type internal combustion engines. Effects such as reduction of gas HC components and suppression of smoke can be obtained.

However, as the load increases, the fuel injection amount also increases, resulting in a rich bias in the mixture distribution, resulting in smoke, etc., or in the worst case, misfires cause an increase in unburned exhaust gas and fuel consumption. There was a problem of inviting.
In order to solve this problem, in the publicly known document shown in Patent Document 2, injection is performed twice during the compression stroke. By the way, as a method of the second injection, in addition to the method of Patent Document 2, a method in which the first time is a fire type and the second time is a main injection can be considered.
JP 2002-539365 A JP 2003-49679 A

  In the case of the method in which the fuel from the second additional fuel injection is ignited by the flame of the main combustion by the combustion flame by the first injection and burned, the first half of the injection amount is reduced in the operation region where the load is relatively small. Therefore, combustion becomes unstable due to variations due to changes over time and parts manufacturing timing, and disturbances due to changes in the surrounding environment. In the worst case, misfiring occurs, improving fuel efficiency and reducing emissions. Therefore, there is a problem that the stabilization of the combustion by diluting the air-fuel mixture which is effective for the above and the increase of the exhaust gas recirculation (EGR) amount for reducing the soot and NOx components cannot be achieved.

  The present invention has been made to solve the above-described problem. In the spray guide combustion system, at least new fuel ignition is performed after directly igniting the fuel spray during or immediately after injection from the fuel injection valve. In order to improve the fuel consumption and reduce exhaust gas, the combustion of the mixture is reduced by diffusing and burning one or more sprays at a time, and igniting at least once after all the injections in the combustion stroke are completed. An object of the present invention is to provide an apparatus that achieves both stabilization and an increase in the amount of exhaust gas recirculation (EGR) for reducing soot and NOx components.

In order to solve the above-mentioned problems of the prior art, the invention of claim 1 is an in-cylinder direct injection spark ignition internal combustion engine comprising a fuel injection valve for directly injecting fuel into a combustion chamber and an ignition plug. ,
An ignition plug is provided so that an ignition electrode portion is positioned during spraying of the fuel injected from the fuel injection valve or in the vicinity of the spray ridge line, and the fuel is ignited after injection to generate a flame. Thereafter, it is characterized in that at least one new spray is diffused and burned at least once, and after all injections during the combustion stroke are completed, at least one new ignition is performed.

  The invention according to claim 2 is characterized in that all injections are performed in the compression stroke, and the ignition timing after completion of all injections is after the compression top dead center.

  The invention according to claim 3 is characterized in that the control is performed when the load region of the internal combustion engine is within a predetermined range.

  According to a fourth aspect of the present invention, each cylinder is provided with an intake valve and an exhaust valve. In addition to the spark plug, at least one or more is provided on the combustion chamber wall surface and between the intake valve and the exhaust valve. The spark plug is characterized in that the spark plug is ignited simultaneously with the spark plug after completion of all the injections in one combustion stroke.

  According to a fifth aspect of the present invention, each cylinder is provided with an intake valve and an exhaust valve. In addition to the ignition plug, at least one or more is provided on the combustion chamber wall surface and between the intake valve and the exhaust valve. The spark plug is characterized in that the spark plug is ignited after a predetermined time elapses after the ignition plug is ignited after completion of all the injections in one combustion stroke.

  According to the present invention, reliable ignition can be performed by igniting again in the vicinity of the compression top dead center where the air-fuel mixture becomes relatively homogenous, so that combustion is stable and misfire due to extinguishing of the flame can be prevented. As a result, a reduction in torque generated by combustion can be prevented, and unburned HC components in the combustion chamber outer periphery quench zone can be reduced.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Example 1]
FIG. 1 is a schematic configuration diagram of a first embodiment of a control device for a direct injection spark ignition type internal combustion engine of the present invention, and FIG. 2 is a plan view of the combustion chamber of FIG. 1 as viewed from above. . FIG. 3 shows a time chart in which the injection timing and the ignition timing are simplified. Hereinafter, a description will be given with reference to FIGS.

  In FIG. 1, a cylinder head 1 constitutes a pent roof-like combustion chamber 2 having a roof inclined in the drawing, and an intake port 3 for introducing intake air to the left and right roof portions also discharges the gas after combustion. The exhaust ports 4 are open. A cylinder 6 is formed in the cylinder block 5 in the vertical direction in the figure, and a piston 7 slides in the vertical direction in the cylinder 6. The intake valve 8 and the exhaust valve 9 open and close the ports 3 and 4 in accordance with the movement of the piston 7.

  In the present embodiment, the electrode portion 11a of the spark plug 11 is laid out so as to be located in or near the fuel spray ridge line F from the fuel injection valve 10 disposed on the upper wall portion of the combustion chamber 2, and fuel injection is being performed or Immediately after that, a so-called spray guide system in which the fuel spray is directly ignited is assumed. Particularly in the present embodiment, the arrangement of the fuel injection valve 10 and the spark plug 11 and the shape of the cavity 7a formed on the piston crown surface are devised. That is, a fuel injection valve 10 having an injection hole directed downward in the exhaust valve direction is provided at a substantially central position of the ceiling of the combustion chamber 2, and an ignition plug 11 is provided on the exhaust side in the immediate vicinity thereof. A cavity 7 a that can hold fuel spray from the fuel injection valve 10 is formed on the piston crown surface. Specifically, the cavity shape, the position of the fuel injection valve, and the spray direction are determined so that the fuel spray injected from the fuel injection valve 10 is contained in the piston cavity 7a.

  In the spray guide system, it is common to ignite and burn almost the entire amount of spray injected from the fuel injection valve 10 in the combustion chamber 2 when it reaches the spark plug 11, but the engine load is high. As a result, the intake air amount per cycle increases, and if the necessary injection amount corresponding to the intake air amount increases, a rich bias may occur in the mixture distribution in the combustion chamber. In this case, the rich portion is discharged as unburned HC gas, leading to an increase in exhaust gas and deterioration in fuel consumption. Therefore, as a solution to this problem, a method of dividing the injection into two times and igniting when the last spray reaches the spark plug to prevent the vicinity of the spark plug from being rich is taken. This method is particularly effective when the engine is heavily loaded. The total number of injections is not limited to two, and the number of injections can be increased according to the fuel injection valve performance and the required injection amount.

  By the way, in a state where the engine load is in a predetermined range relatively lower than the high load (medium load state), the first injection is performed with a small injection amount (minimum injection amount) that can be ignited but not torque. The spray formed by the injection is ignited when it passes through the vicinity of the ignition plug, and immediately after that, the second injection is performed. The fuel mixture generated by the first injection and ignition is ignited and the second fuel is ignited. A method is known in which the second injection is burned while generating torque. It has also been clarified by the inventors that this method can stabilize combustion so that the amount of exhaust gas recirculation (EGR) can be increased more than before, and as a result, NOx emissions can be reduced.

Hereinafter, the operation of the in-cylinder injection spark ignition type internal combustion engine according to the first embodiment configured as described above will be described.
In the in-cylinder injection engine, it can only be ignited by the spark plug 11 during combustion from the bottom dead center of intake to the top dead center of compression, that is, during the period when the piston 7 is approaching the fuel injection valve 10 (compression stroke). The fuel is injected from the fuel injection valve 10 at a timing when a small amount of fuel enters the piston cavity 7a.

  Next, when the injected fuel spray reaches the vicinity of the spark plug 11, the spark plug 11 is ignited, and the air-fuel mixture formed by the spray becomes a flame and burns. Further, when the flame remains in the combustion chamber, particularly in the cavity 7a of the piston 7, a second spray is performed from the fuel injection valve 10, and the air-fuel mixture formed by the spray is ignited by the residual flame and burned. Let

  By the way, if the fuel injected from the fuel injection valve 10 for the first time differs from the amount intended by the designer due to secular change, manufacturing variation, injection-specific variation, temperature or atmospheric pressure environmental change, misfiring or unnecessary There is a risk of engine output torque. In other words, if the amount of fuel is too large, the fuel that does not contribute to combustion becomes an unburned HC gas component that is discharged, the explosive power increases, and the engine output torque increases. May cause the driver to feel uncomfortable by increasing the longitudinal vibration of the vehicle. On the other hand, if the amount of fuel is too small, an air-fuel mixture that can be ignited is not formed around the spark plug 11, and even if it is ignited, it is not burned and is discharged as unburned HC gas components. In the worst case, the temperature of the catalyst may be melted and melted.

  In this embodiment, even when such a variation exists, by performing the second ignition at a timing after the compression top dead center, until the air-fuel mixture by the last injection in the cycle is homogenized. Therefore, it is no longer possible to ignite while the air-fuel mixture is inhomogeneous, and misfire can be prevented and combustion can be stabilized.

[Example 2]
Next, a second embodiment will be described.
Referring to FIG. 4, there is shown a plan view of a combustion chamber of a direct injection spark ignition type internal combustion engine according to the second embodiment of the present invention as viewed from above. Referring to FIG. A time chart according to the second embodiment is shown. Hereinafter, a description will be given with reference to FIGS. In addition, the same code | symbol is used about the component and site | part same as the said Example 1, and description is abbreviate | omitted about the same function.

  In an engine that injects fuel directly into the cylinder, the fuel injected into the combustion chamber spreads as a spray, but part of it protrudes out of the combustion chamber and is called a quenching zone (piston is top dead center). , It will enter a flat gap between the piston upper surface and the cylinder head. This oversprayed spray extinguishes heat without being deprived of heat by the cylinder wall surface or satisfying the condition of burning due to temporary oxygen shortage. For this reason, the fuel that has entered the quenching zone is discharged without burning, causing exhaust gases such as HC and PM (particulate matter).

In the second embodiment, the position of the fuel injection valve and the position of the spark plug 11 are located at the center of the top surface as in the first embodiment, but the second spark plug 12 is connected to the intake valve 8 and the exhaust valve. 9 and the combustion chamber upper wall peripheral portion 13 are newly disposed. Further, as shown in FIG. 5, the second spark plug 12 is ignited simultaneously with the first spark plug igniting for the second time.
As a result, the same effects as in the first embodiment can be obtained, and in addition, the unburned HC emission amount in the quenching zone can be reduced.

Example 3
Next, a third embodiment will be described.
A plan view of the combustion chamber of the direct injection type spark ignition type internal combustion engine according to the third embodiment of the present invention viewed from above is as shown in FIG. 4 as in the second embodiment. Referring to FIG. 6, there is shown a time chart according to the third embodiment of the present invention. This will be described below with reference to FIGS. In addition, the same code | symbol is used about the component and site | part same as the said Example 1 or the said Example 2, and description is abbreviate | omitted about the same function.

In the third embodiment, as shown in FIG. 6, the second spark plug 12 is ignited for a predetermined time before the first spark plug 11 is ignited for the second time.
As a result, the same effects as those of the first and second embodiments can be obtained. In addition, the ignition by the second spark plug 12 is far more effective than the torque generated by the ignition of the first spark plug 11. Therefore, the combustion chamber temperature and the combustion chamber pressure can be set near the top dead center, and as a result, the stable combustion without misfire and the effect of reducing the quenching zone HC can be more reliably performed.

  By the way, in Embodiment 1 thru | or 3 mentioned above, although the piston 7 is limited to the thing by which the cavity 7a is formed in the piston crown surface, this invention is not limited to this. That is, the shape of the piston 7 may be, for example, a so-called flat piston having no cavity in the piston.

Further, in the first to third embodiments described above, the direction in which fuel is sprayed from the fuel injection valve 10 disposed in the center of the upper wall of the combustion chamber 2 is limited to the spray method in which the fuel is sprayed downward on the exhaust side. However, the present invention is not limited to this. That is, as a spraying method, for example, center injection in which fuel is sprayed concentrically from the center of the upper wall of the combustion chamber 2 to the center of the piston, or the injector is slightly offset from the center of the combustion chamber 2 instead of the center of the top It may be a spray system arranged in the form of

1 is a schematic longitudinal sectional view showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention. It is the schematic sectional drawing which looked at the internal combustion engine combustion chamber in a 1st embodiment from the upper part. It is a time chart which shows the relationship between the injection timing per cycle and ignition timing in 1st Embodiment. It is the schematic sectional drawing which looked at the internal combustion engine combustion chamber in the 2nd and 3rd embodiments from the upper part. It is a time chart which shows the relationship between the injection timing per cycle and ignition timing in 2nd Embodiment. It is a time chart which shows the relationship between the injection timing per cycle and ignition timing in 3rd Embodiment.

Explanation of symbols

2 Combustion chamber 7 Piston 7a Cavity 8 Intake valve 9 Exhaust valve 10 Fuel injection valve 11 Spark plug 11a Electrode portion 12 Second spark plug 13 Combustion chamber upper wall peripheral portion F Spray ridge line

Claims (5)

  An in-cylinder direct injection type spark ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber and an ignition plug, and an ignition electrode portion in or near the spray ridge line of fuel injected from the fuel injection valve When the internal combustion engine is in a predetermined operating range, the fuel is ignited after being injected to generate a flame, and the generated flame is used as a fire type to be at least 1 injected after the ignition. An in-cylinder direct injection spark ignition internal combustion engine characterized in that at least one spray is burned, and after all injections during the combustion stroke are completed, at least one new ignition is performed.   2. An in-cylinder direct injection spark ignition internal combustion engine according to claim 1, wherein all injections are performed in a compression stroke, and an ignition timing after completion of all injections is after compression top dead center.   The in-cylinder direct injection spark ignition internal combustion engine according to claim 1 or 2, wherein the predetermined operating range of the internal combustion engine is an intermediate load range.   Each cylinder is provided with an intake valve and an exhaust valve. In addition to the ignition plug, at least one additional ignition plug is provided on the combustion chamber wall surface and between the intake valve and the exhaust valve. The in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 3, wherein the additional ignition plug is ignited simultaneously with the ignition plug after completion of all injections in one combustion stroke. Each cylinder is provided with an intake valve and an exhaust valve. In addition to the ignition plug, at least one additional ignition plug is provided on the combustion chamber wall surface and between the intake valve and the exhaust valve. The in-cylinder direct injection according to any one of claims 1 to 3, wherein the additional ignition plug is ignited after a predetermined time elapses after the ignition plug ignites after completion of all injections in one combustion stroke. Type spark ignition internal combustion engine.

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