JPH051826U - In-cylinder direct injection engine combustion chamber - Google Patents

Abstract

(57) [Summary] [Purpose] A combustion chamber of a direct injection type internal combustion engine that achieves both stable stratified combustion and good uniform combustion without increasing preignition, increasing HC generation, or deteriorating fuel efficiency. I will provide a. A squish area 8b is smoothly continuous around the center dome 8a to prevent heat spotting, and an injection port 8d facing the fuel injection hole of the injector 10 is formed at the top of the center dome 8a to form a fuel injection hole. And keep the distance from the piston. Further, the mounting boss 8e of the spark plug 11 is bulged into the center dome 8a along the outer edge of the fuel spray of the injector 10 in parallel therewith, whereby the projection amount of the plug gap of the spark plug 11 can be reduced and the preignition is performed. While avoiding
Avoiding collision of injected fuel and avoiding increase of HC generation and deterioration of fuel consumption.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 INDUSTRIAL APPLICABILITY The present invention has been improved in a cylinder direct injection engine in which an injector and an ignition plug are installed facing the combustion chamber so that both stable stratified combustion at low load and good uniform combustion at high load are compatible. Regarding the combustion chamber.

[0002]

[Prior Art]

 An in-cylinder direct injection engine in which the injector and the spark plug are installed facing the combustion chamber is known in which the plug gap of the spark plug is located in front of the injector in the fuel injection direction (Japanese Patent Laid-Open No. 62- 58013). In this type of in-cylinder direct injection engine, the combustion method can be switched between stratified combustion and uniform combustion by controlling the fuel injection timing.

Stratified combustion is a combustion method in which the fuel injection timing of the injector is controlled immediately before the ignition timing to generate a rich mixture near the plug gap of the ignition plug, which is ignited to propagate the flame. It is suitable as a combustion method in the low and medium load operating range of the engine because stable combustion can be obtained. Uniform combustion is a combustion method in which the fuel injection timing is advanced by a relatively large amount relative to the ignition timing, a mixture of uniform concentration is generated in the combustion chamber, and the mixture is ignited. It is suitable as a combustion method in the high load operation range.

Here, in order to stably and reliably perform the stratified charge combustion, the positional relationship between the injector and the ignition plug greatly affects the ignitability, which is an important factor. Therefore, in Japanese Patent Publication No. 1-273824, atomized fuel is supplied from an injector to a plug gap of an ignition plug located on the axis of a combustion chamber to achieve stable ignition and flame propagation. ..

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The arrangement of injectors and spark plugs largely depends on the shape of the engine combustion chamber, and the shape of the engine combustion chamber depends on the flame propagation characteristics during stratified combustion and uniform combustion It directly affects the burning rate. For this reason, it is largely dependent on the shape of the combustion chamber of the engine to achieve both stable stratified combustion and good uniform combustion. However, each of the conventional combustion chamber shapes has advantages and disadvantages as described below.

For example, the shell-type combustion chamber a shown in FIGS. 4 and 5 and the offset-type combustion chamber b shown in FIGS. 6 and 7 are suitable for stratified combustion, but on the other hand, because the combustion speed during uniform combustion is slow, There was a problem of low output. On the other hand, the squish dome type combustion chamber c shown in FIGS. 8 and 9 has good uniform combustion characteristics at high speed and high load, but in order to obtain stable stratified combustion, the plug gap e of the ignition plug d is burned. It is necessary to make it largely protrude into the chamber c, which may cause preignition during uniform combustion under high load and damage the engine. Further, in this squish dome type combustion chamber c, it is difficult to secure a sufficient distance from the fuel injection hole g of the injector f to the piston top surface, and the fuel spray collides with the piston top surface to generate HC (hydrocarbon). There is a problem that fuel consumption increases or fuel efficiency deteriorates. As described above, the conventional combustion chamber has advantages and disadvantages, and it is difficult to achieve both stable stratified combustion and good uniform combustion.

Accordingly, the present invention provides a combustion chamber for a direct injection type cylinder engine capable of achieving both stable stratified combustion and good uniform combustion without causing preignition, increase in HC generation, or deterioration in fuel efficiency. The purpose is to provide.

[0008]

[Means for Solving the Problems]

 For this purpose, the present invention is a combustion chamber of a direct injection type cylinder engine in which a squish area is smoothly continuous around the center dome, and an injection port facing the fuel injection hole of the injector is formed at the top of the center dome. The boss of the spark plug is bulged in the center dome along the outer edge of the fuel spray of the injector in parallel with it.

[0009]

[Action]

 With such means, the injector is installed with its fuel injection hole facing the injection port at the top of the center dome, and the spark plug is installed on the mounting boss with its plug gap facing forward in the fuel injection direction of the injector. To be done. Then, the fuel injected from the injector becomes fuel spray having an outer edge parallel to the mounting boss of the spark plug, and produces a rich mixture near the plug gap of the spark plug. By doing so, stratified combustion with flame propagation is stably performed. In addition, the fuel spray injected from the injector is well agitated in the center dome that is continuous with the squish area to form a uniform air-fuel mixture. Be seen.

Here, since the mounting boss of the spark plug bulges into the center dome, it is not necessary to make the plug gap of the spark plug largely project into the center dome, and the occurrence of pre-ignition, which has been a problem in the past, does not occur. It can be avoided.

Further, the mounting boss of the spark plug is parallel to and along the outer edge of the fuel spray injected from the injector, and in addition, the fuel injection hole of the injector faces the injection port at the top of the center dome and A sufficient distance from the top surface is secured. Therefore, the fuel spray injected from the injector does not directly collide with the mounting boss of the ignition plug or the top surface of the piston, and thus the generation of HC (hydrocarbon) and the deterioration of fuel consumption are not accompanied.

Further, since the center dome and the squish area are smoothly continuous, this continuous portion does not become a heat spot and carbon does not deposit on the continuous portion.

[0013]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a direct injection type engine with a combustion chamber according to an embodiment. This engine is a two-cycle gasoline engine that is forcibly scavenged by a scavenging pump (not shown). A cylinder bore 4 is formed in the cylinder block 1 in which a scavenging port 2 and an exhaust port 3 are opened, and a piston 5 is formed in the cylinder bore 4. Is reciprocally slidably inserted. An oil pan 7 is attached to the lower portion of the crank case 6 joined to the cylinder block 1.

A cylinder head 9 forming a combustion chamber 8 is connected to the cylinder block 1, and an injector 10 for injecting fuel into the combustion chamber 8 and an injector 10 for injecting fuel into the cylinder head 9 are connected to the cylinder head 9. A spark plug 11 for igniting is installed. A fuel passage 12 extending from a fuel tank (not shown) via a fuel pump, a filter, and a regulator communicates with the injector 10 described above. In addition, the fuel injection signal and the ignition signal from the control unit 13 are input to the injector 10 and the spark plug 11.

In the combustion chamber 8, the squish area 8b is continuous with the peripheral portion of the center dome 8a, and the joint portion 8c is formed in a smooth R shape. An injection port 8d facing the fuel injection hole 10a of the injector 10 is formed on the top of the center dome 8a as shown in an enlarged view in FIG. Here, the injector 10 injects fuel in a cone shape from the fuel injection hole 10a, and the injection port 8d is formed in a tapered hole shape corresponding to the shape of the fuel spray, and the fuel injection is made in the inner portion thereof. The hole 10a faces.

Further, as shown in FIG. 3, a mounting boss 8e of the spark plug 11 is bulged in the center dome 8a of the combustion chamber 8. The mounting boss 8e has a bulging surface 8f that is an inclined surface that is continuous with the tapered surface of the injection port 8d, and is parallel to the outer edge of the cone-shaped fuel spray injected from the injector 10. .. The spark plug 11 mounted on the mounting boss 8e has a plug gap facing the front of the injector 10 in the fuel injection direction at the substantially central portion of the center dome 8a.

In the combustion chamber 8 of the in-cylinder direct injection type engine configured as described above, the fuel injected from the injector 10 is a cone-shaped fuel spray along the bulging surface 8f of the mounting boss 8e of the spark plug 11. Thus, a rich mixture is generated near the plug gap of the spark plug 11. If it is not ignited at this point, the generated rich air-fuel mixture is well agitated and mixed with air in the center dome 8a continuous with the squish area 8b, and eventually becomes a homogeneous air-fuel mixture capable of rapid combustion.

Therefore, by appropriately controlling the fuel injection timing of the injector 10 with respect to the ignition timing of the spark plug 11 by the control unit 13, it is possible to switch between stratified combustion that ignites the rich mixture and uniform combustion that ignites the homogeneous mixture. It is possible. For example, by controlling ignition so that a rich air-fuel mixture is generated near the plug gap of the ignition plug 11, stratified combustion with flame propagation is stably performed. Further, by controlling to ignite when a uniform air-fuel mixture is generated in the center dome 8a, good uniform combustion is performed.

Here, in particular, since the mounting boss 8e of the ignition plug 11 bulges into the center dome 8a, the amount of the plug gap of the ignition plug 11 protruding into the center dome 8a is short. Therefore, it is possible to avoid the occurrence of pre-ignition, which has been a problem in the past.

The boss 8e of the spark plug 11 has a bulging surface 8f parallel to and along the outer edge of the fuel spray injected from the injector 10. In addition, the fuel injection hole 10a of the injector 10 has a center. It faces the injection port 8d at the top of the dome 8a, and a sufficient distance from the piston top surface is secured. Therefore, the fuel spray injected from the injector 10 does not directly collide with the mounting boss 8e of the ignition plug 11 or the top surface of the piston, which causes increase in generation of HC (hydrocarbon) and deterioration of fuel consumption. There is no.

Further, in the combustion chamber 8, since the center dome 8a and the squish area 8b are connected by a smooth R-shaped continuous portion 8c, the continuous portion 8c serves as a heat spot, and the continuous portion 8c is covered with carbon. Will not be deposited.

The present invention is not limited to a 2-cycle gasoline engine, but can be applied to a 4-cycle engine or an engine using alcohol as a fuel.

[0023]

[Effect of the device]

 As described above, according to the present invention, the injector is installed with its fuel injection hole facing the injection port at the top of the center dome, and the spark plug is installed with its plug gap facing forward in the fuel injection direction of the injector. Is installed in. Then, the fuel injected from the injector becomes a fuel spray having an outer edge parallel to the mounting boss of the spark plug, and produces a rich mixture near the plug gap of the spark plug. By igniting, the stratified combustion with flame propagation is stably performed. In addition, the fuel spray injected from the injector is well agitated in the center dome continuous with the squish area to form a uniform air-fuel mixture. Done.

Here, since the mounting boss of the spark plug bulges into the center dome, it is not necessary to make the plug gap of the spark plug largely protrude into the center dome, and the occurrence of preignition, which has been a problem in the past, does not occur. It can be avoided.

The attachment boss of the spark plug is parallel to and along the outer edge of the fuel spray injected from the injector, and in addition, the fuel injection hole of the injector faces the injection port at the top of the center dome and A sufficient distance from the top surface is secured. Therefore, the fuel spray injected from the injector does not directly collide with the mounting boss of the ignition plug or the top surface of the piston, and thus the generation of HC (hydrocarbon) and the deterioration of fuel consumption are not accompanied.

Further, since the center dome and the squish area are smoothly continuous, this continuous portion does not become a heat spot and carbon does not deposit on the continuous portion.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a combustion chamber of a direct injection type cylinder engine according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a II part in FIG.

3 is a sectional view taken along the line III-III of FIG.

FIG. 4 is a sectional view of a shell-type combustion chamber according to a conventional example.

FIG. 5 is a view on arrow V in FIG.

FIG. 6 is a sectional view of an offset type combustion chamber according to a conventional example.

FIG. 7 is a view on arrow VII in FIG.

FIG. 8 is a sectional view of a squish dome type combustion chamber according to a conventional example.

9 is a view on arrow IX in FIG.

[Explanation of symbols] 1 cylinder block 2 scavenging port 3 exhaust port 4 cylinder bore 5 piston 6 crankcase 7 oil pan 8 combustion chamber 8a center dome 8b squish area 8c joint 8d injection port 8e mounting boss 8f bulge surface 9 cylinder head 9a mounting Boss 10 Injector 10a Fuel injection hole 11 Spark plug 12 Fuel passage 13 Control unit

Claims (1)

[Claims for utility model registration] [Claim 1] A combustion chamber of a direct injection engine in a cylinder in which a squish area is smoothly connected to a peripheral portion of a center dome, and an injection port facing a fuel injection hole of an injector is used as a center. A combustion chamber of a direct injection type internal combustion engine, characterized in that a mounting boss for a spark plug is formed at the top of the dome and bulges along the outer edge of the fuel spray of the injector in parallel with the center dome.