JPH10184364A - Combustion chamber structure of direct-type diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress exhaust of unburned HC under a low load, and suppress generation of smoke due to combustion failure under a high load by forming guide fins or guide grooves on a side wall inside a combustion chamber containing a projected collision base, so as to obliquely extend upward from the bottom wall to the side of an opening of the combustion chamber. SOLUTION: In a compression process, a piston 1 reaches a top dead center and fuel is sprayed from an injection nozzle 3. The fuel is struck against a collision surface 9a on the top of a collision base 9, and diffused horizontally inside a combustion chamber 7. The fuel is then ignited and burned by the heat of the piston 1. Since air swirl is generated inside the combustion chamber 7 accompanied with the compression process, frame F generated inside the combustion chamber 7 is turned clockwise. In an expansion process, the piston 1 is lowered and an opening 10 of the combustion chamber 7 is opened. The frame F is guided by, for instance, four guide fins 11 which are obliquely formed on a side wall 7a of the combustion chamber, and flowed to the outside as ascending current, and mixed satisfactorily with air for perfect combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure of a direct-type diesel engine used as an internal combustion engine for an automobile.

[0002]

2. Description of the Related Art Conventionally, combustion types of automobile diesel engines are roughly classified into a direct injection type (direct injection type, DI) and an indirect injection type (sub chamber type, IDI) due to a difference in a method of forming an air-fuel mixture. Can be. Among them, in the direct injection type diesel engine, atomization of the spray and atomization of the spray and air are achieved by arranging the injection nozzle with a plurality of injection holes radially at the approximate center of the combustion chamber on the piston crown surface. Those that promote the mixing with the water are becoming mainstream.

However, in such a structure, when the injection pressure is increased to promote atomization, the penetration force of the spray is increased, the flight distance is increased, and the spray adheres to the side wall of the combustion chamber, and the unburned fuel is unburned. There is a problem that HC is easily discharged. In particular, the unburned HC is easily generated remarkably in a small engine in which the diameter of the combustion chamber cannot be made large or in a low load in which the injection amount is small and the temperature in the cylinder is relatively low.

On the other hand, a collision table is provided in the combustion chamber, and the fuel is directly collided with the collision table to disperse (diffuse) so as to atomize the spray. In Japanese Patent Application Laid-Open No. 62-63121), since the penetration force of the spray is weakened by the collision, the spray does not adhere to the side wall of the combustion chamber even in a small engine having a small diameter of the combustion chamber. The emission of unburned HC can be greatly reduced.

[0005]

By the way, in the OSKA type combustion chamber in which the fuel collides with the collision table so as to weaken the penetration force of the spray, the emission of unburned HC at a low load is suppressed. However, at the time of a high load in which the injection amount is large, a large amount of fuel is burned only in the combustion chamber, so that there is a disadvantage that rich combustion occurs and a large amount of smoke is generated.

That is, in the conventional combustion chamber structure using a multi-injection nozzle, the flame after ignition flows out of the combustion chamber due to the penetration force of the spray itself, and this flows into the lower surface of the cylinder head formed as the piston descends. While it mixes well with air existing in the space above the piston and burns it, OS
This is because, in the KA type combustion chamber, since the penetration force of the spray is weak, almost no flame flow out of the combustion chamber is seen, and poor combustion occurs due to insufficient air.

The present invention has been devised in order to effectively solve such disadvantages. The object of the present invention is to suppress the discharge of unburned HC at low load and, of course, at high load. It is an object of the present invention to provide a novel direct-injection diesel engine combustion chamber structure capable of effectively suppressing the generation of smoke due to poor combustion.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a combustion chamber formed on a piston crown surface with:
In a combustion chamber structure of a direct-radiation type diesel engine provided with a convex collision table for causing fuel injected from an injection nozzle to collide and diffuse into the combustion chamber, a combustion chamber opening is formed on a side wall in the combustion chamber from a bottom wall of the combustion chamber. It is provided with at least one or more guide fins or guide grooves extending obliquely upward toward the part side.

As a result, when the piston rises (compression stroke), an oblique swirling flow is formed in the combustion chamber. When the piston descends (expansion stroke), the swirling flow flows out of the combustion chamber. Becomes

Therefore, even if the combustion flame is generated by the collision diffusion spray, the outflow to the outside of the combustion chamber is promoted, and the air existing in the space between the lower surface of the cylinder head and the upper surface of the piston can be effectively used. Smoke reduction under load can be achieved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a combustion chamber structure of a direct-injection diesel engine according to the present invention. In FIG. 1, reference numeral 1 denotes a piston which reciprocates in a cylinder 2; The injection nozzles 5 and 6 are provided on the cylinder head 4, and the intake and exhaust ports 5a and 6a are valves for opening and closing the intake port 5 and the exhaust port 6, respectively.

A reentrant combustion chamber 7 having a narrowed opening 10 is formed on the crown surface of the piston 1, and a projecting collision table 9 is formed at the center of the bottom wall 8 of the combustion chamber 7. Are formed to protrude in a mountain shape. The top of the collision table 9 is formed with a collision surface 9a which is cut out horizontally, and is arranged so as to face the injection hole 3a of the injection nozzle 3 provided substantially at the center of the cylinder head 4. .

As shown in FIGS. 1 to 3, the side wall 7a of the combustion chamber 7 extends from the bottom wall 8 of the combustion chamber to the opening 10 side of the combustion chamber 7 and at the center of the combustion chamber 7. The four raised guide fins 11, 11, 11, 11 are formed at substantially equal intervals.
11, 11, 11 are disposed so as to be inclined in the same direction. Specifically, the swirl is provided to be inclined obliquely upward in the forward direction of the swirl so as to guide the swirl (swirl) swirling clockwise in the combustion chamber 7 toward the opening 10.

In the above, first, as shown in FIG. 2, the piston 1 reaches the top dead center in the compression stroke and the injection nozzle 3
When the fuel is sprayed from the injection hole 3a, the fuel collides with the collision surface 9a on the top of the collision table 9 to weaken the penetration force of the spray and diffuse in the combustion chamber 7 in the horizontal direction.
It is ignited by the heat of the water and starts burning. At this time, since the swirl of air (clockwise in the present embodiment) is generated in the combustion chamber 7 during the compression stroke, the flame F generated in the combustion chamber 7 burns along the side wall 7a. In the room 7,
It starts to flow clockwise around the collision table 9.

Next, as shown in FIG. 3, when the expansion stroke starts and the piston 1 descends, and the opening 10 of the combustion chamber 7 is opened, the combustion chamber 7 turns clockwise. The flame is guided by guide fins 11, 11, 11, 11 formed on the side wall 7a of the combustion chamber 7 to form an obliquely rising flow, and from the opening 10 of the combustion chamber 7, the space between the cylinder head 4 and the piston 1 is formed. After flowing out to the S side, complete combustion is performed by further mixing well with the air in the space S.

That is, even if the combustion flame has a low penetration force due to the impingement diffusion spray, the guide fins 11 formed in the combustion chamber 7 promote the flow of the flame out of the combustion chamber 7, resulting in insufficient air. It is possible to effectively avoid poor combustion due to the above.

Therefore, according to the combustion chamber structure of the present invention, it is possible not only to reduce the generation of unburned HC at a low load, but also to effectively suppress the generation of smoke at a high load.

Since the combustion chamber of a normal direct-radiation diesel engine has a collision diffusion spray area diameter of about 30 mm at the time of ignition, the combustion chamber diameter in the horizontal direction of the collision part is larger than the collision diffusion spray area diameter. For example, by forming it to be about 35 mm, the air in the combustion chamber 7 can be effectively used. Further, in the present embodiment, as the combustion chamber 7,
Although an example using a reentrant type with the opening 10 narrowed has been described, the same effect as described above can be obtained even when a toroidal type combustion chamber without a throttle is used. Further, the number of guide fins is not limited to four, and the number and interval may be increased or decreased as needed.

[0020]

In summary, according to the present invention, even in the case of a combustion flame having a low penetration force due to impingement diffusion spray, the flow of the flame to the outside of the combustion chamber is promoted, and poor combustion due to a shortage of air can be prevented. In addition, it is possible to exhibit excellent effects such as not only reducing the generation of unburned HC at a low load, but also effectively suppressing the generation of smoke at a high load.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrows AA in FIG.

FIG. 3 is a view taken in the direction of arrows BB in FIG. 1;

FIG. 4 is a cross-sectional view showing the flow of air and the like during compression.

FIG. 5 is a cross-sectional view showing a flow of a flame during expansion.

[Explanation of symbols]

 Reference Signs List 1 piston 3 injection nozzle 7 combustion chamber 7a side wall 8 bottom wall 9 collision table 10 opening 11 guide fin

Claims (2)

[Claims] 1. A combustion chamber structure of a direct-radiation diesel engine having a convex collision table for impinging fuel injected from an injection nozzle on a bottom wall of a combustion chamber formed on a piston crown surface and diffusing the fuel into the combustion chamber. , Wherein at least one or more guide fins extending obliquely upward from the bottom wall of the combustion chamber to the opening side of the combustion chamber are provided on a side wall of the combustion chamber. . 2. The combustion chamber is of a reentrant type,
The combustion chamber structure of a direct-radiation diesel engine according to claim 1, wherein the inner diameter is 27 to 35 mm.