JPH10141062A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel consumption by reducing an amount of discharging black smoke and HC in spite of the generation of NOx being suppressed. SOLUTION: A combustion chamber 2 is recessed in the top surface of a piston 1 and a squish area 3 is arranged at the peripheral edge of the combustion chamber 2. A dome 5 positioned opposite to the combustion chamber 2 is recessed in a cylinder head 4. An injection nozzle 6 having a nozzle hole 7 opened toward the side wall surface of the dome 5 is attached to the central part of the dome 5 and by forming the dome such that the outside diameter of the dome 5 is approximately equal to the bore of the combustion chamber 2, as fuel is injected toward the side wall surface of the dome 5 and a spray- through force of fuel spray 8 is rendered ineffective, the fuel spray 8 is effectively induced to a combustion chamber 3 by a squish flow to generate excellent air-fuel mixture. Further, strong squish is generated and highefficient combustion is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine and, more particularly, to a black smoke and H2 gas while suppressing the generation of NOx.
The present invention relates to a diesel engine capable of improving fuel efficiency by reducing C emission.

[0002]

2. Description of the Related Art In order to reduce NOx contained in exhaust gas of a diesel engine, it is effective to perform a timing retard that suppresses the generation of NOx by delaying a fuel injection timing. In order to reduce the emission, it has been considered effective to increase the fuel injection pressure or to employ a reentrant combustion chamber.

However, when timing retardation is performed to reduce NOx contained in exhaust gas, black smoke and H
There is a concern that fuel consumption will deteriorate as the amount of C emission increases. Further, in the high-pressure injection, although the atomization of fuel is improved, the emission of black smoke and HC can be improved, but the combustion temperature rises and the emission of NOx increases. Therefore, it has been considered extremely difficult to improve fuel efficiency by reducing the emission of black smoke and HC while suppressing the generation of NOx in a diesel engine.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in spite of being able to suppress the generation of NOx, it is possible to reduce the amount of black smoke and HC emissions and to reduce fuel consumption. It is an object of the present invention to provide a diesel engine that can improve the performance.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a combustion chamber having a recess provided on a top surface thereof and a piston provided with a squish area on the periphery of the combustion chamber. Opposing domes are recessed in the cylinder head. In addition, an injection nozzle having an injection opening that opens toward the side wall surface of the dome is attached to the center of the dome, and the outer diameter of the dome is formed to be substantially the same as the diameter of the combustion chamber.

Further, according to the present invention, by forming the dome into a hemispherical or conical shape, the fuel spray injected from the injection nozzle can be efficiently introduced into the combustion chamber to perform efficient combustion.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing a state of fuel injection showing one embodiment of a diesel engine according to the present invention, and FIG. 2 is a sectional view showing a relationship between a dome and a combustion chamber at a compression top dead center.

In these figures, a combustion chamber 2 is provided at the center of the top surface of a piston 1 connected to a crankshaft (not shown).
And a squish area 3 is formed at the opening edge of the combustion chamber 2. The lower surface of the cylinder head 4 facing the top surface of the piston 1 has the combustion chamber 2
The dome 5 is formed opposite to the dome 5.

The dome 5 is formed in a hemispherical shape having an outer diameter substantially the same as the diameter of the combustion chamber 2, and an injection nozzle 6 is attached to the center of the bottom wall of the dome 5. The injection nozzle 6 is constituted by a hole nozzle provided with a plurality of injection ports 7 opening toward the side wall surface of the dome 5, and injects fuel delivered from an injection pump (not shown) toward the side wall surface of the dome 5. I am trying to do it. 8 is fuel spray,
Reference numeral 9 denotes a valve which surrounds the dome 5 and is attached to a cylinder head.

In the above-structured diesel engine, during the intake stroke in which the piston 1 descends, the valve 9 opens to draw air into the cylinder,
Swirl occurs in the cylinder as in the conventional case. Piston 1
In the compression stroke, the swirl generated in the cylinder is gradually strengthened, and a squish flow is generated in which the air in the squish area 3 is pushed into the combustion chamber 2. When the piston 1 rises to the vicinity of the compression top dead center and reaches the injection timing, the fuel delivered from the injection pump (not shown) is injected from the injection nozzle 6.

At this time, the injection port 7 provided in the injection nozzle 6 is open toward the side wall surface of the dome 5. Therefore, the fuel spray 8 by the fuel injected from the injection port 7 collides with the side wall surface of the dome 5 as shown in FIG. 1, loses penetration force, is atomized, and diffuses downward.

By the way, at such an injection timing, a squish flow having a sufficient strength is generated so that the piston 1 further approaches the compression top dead center, and the diameter of the combustion chamber 2 is substantially equal to the outer diameter of the dome 5. They are the same. For this reason, almost the entire amount of the fuel spray 8 diffused downward as described above reliably flows into the combustion chamber 2 with the help of the squish flow, and the fuel spray 8 comes into contact with the air in the combustion chamber 2 so that the air While being swirled, it is sufficiently mixed with air by the diffusion effect of swirl (see FIG. 2). Then, the pre-oxidation reaction proceeds in the heated air-fuel mixture, and self-ignition is performed in a portion where the reaction has progressed most, and combustion is started.

Further, the fuel injected from the injection port 7 loses penetration force due to collision with the side wall surface of the dome 5, and is reflected downward and diffused gradually. Therefore, a premixed compression ignition system in which fuel is injected by the middle stage of the suction stroke or the compression stroke, the injected fuel is vaporized and mixed, and ignited and burns by spontaneous ignition at the end of the compression stroke, and a very small amount is used in the early to middle stages of the suction stroke. A partially lean premixed compression ignition system in which the remaining fuel is injected at the end of the compression stroke to perform more reliable ignition combustion while injecting fuel to compress the lean mixture,
Alternatively, even when the pilot injection is performed early to suppress the generation of NOx, the fuel spray 8 does not adhere to the cylinder liner, and problems such as an increase in HC and damage to the oil film are prevented.

On the other hand, when the process proceeds to the expansion stroke with the start of combustion, the piston 1 starts to descend. Then, the combustion flame previously sealed in the combustion chamber 2 becomes a strong reverse squish flow and flows out of the combustion chamber 2 and comes into contact with new air, so that active combustion is performed and fuel efficiency is improved. And does not emit black smoke and HC. Therefore, even when exhaust gas recirculation is performed to effectively suppress the generation of NOx, the amount of black smoke emitted does not increase.

In the above embodiment, a squish area 3 having a sufficient size is provided by providing a reentrant combustion chamber 2.
And a strong reverse squish is obtained. However, when the opening area of the combustion chamber 2 occupying the entire top surface of the piston 1 is small, for example, an open chamber type combustion chamber may be provided.

In the above embodiment, the hemispherical dome 5 is used.
However, the dome 5 is not limited to a hemispherical one, but a conical or deep dish-shaped dome can be provided. If necessary, a ceramic coat may be applied to the surface of the dome 5. In addition, by embedding a dissimilar metal having excellent heat resistance and abrasion resistance into the surface of the dome 5, it is possible to suppress the abrasion of the side wall surface due to collision with the fuel spray 8 and to embed the ceramic coat or dissimilar metal. It is also possible to promote the vaporization of fuel to further reduce HC.

[0017]

As is apparent from the above description, according to the present invention, the fuel is injected toward the side wall surface of the dome provided on the cylinder head so that the fuel spray penetrates and the peripheral edge of the combustion chamber is lost. The squish area provided in the squish area effectively guides the fuel spray into the combustion chamber together with the air, and obtains a strong reverse squish for efficient combustion. Lean premixed compression ignition or early pilot injection
Although the generation of Ox can be suppressed, the amount of black smoke and HC emissions can be reduced, and the fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state of fuel injection showing one embodiment of a diesel engine according to the present invention.

FIG. 2 is a sectional view showing a relationship between a dome and a combustion chamber at a compression top dead center.

[Explanation of symbols]

 Reference Signs List 1 piston 2 combustion chamber 3 squish area 4 cylinder head 5 dome 6 injection nozzle 7 injection port 8 fuel spray 9 valve

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 61/14 310 F02M 61/14 310D 61/18 360 61/18 360J

Claims (2)

[Claims] A piston provided with a squish area on the periphery of the combustion chamber and a dome facing the combustion chamber;
A diesel nozzle having an injection nozzle attached to a central portion of the dome and having an injection opening opening toward a side wall surface of the dome, wherein an outer diameter of the dome is formed to be substantially the same as a diameter of a combustion chamber. engine. 2. The diesel engine according to claim 1, wherein the dome has a hemispherical or conical configuration.