JPH04276125A - Piston for diesel engine - Google Patents

Abstract

PURPOSE:To improve the probation of a fire in a diesel engine by shortening delay duration in an ignition timing at the time of the burning of injected fuel. CONSTITUTION:A combustion chamber 8 which opens on the top surface 4 of a crown 2 has the same number of pockets 11 at the injection port of a fuel injection nozzle, and the fuel injection axis 21 of the injection port is set to the wall surface 12 of the pocket 11 which is located in a range 15 from incurving start 13 to incurving center 14 at a fuel injection shaft 21 of the injection port in a swirl direction 20. Fuel is injected to a part which is on the upstream side in a swirl direction 20 in the wall surface 12 of the pocket 11, the mixture of fuel and air is activated with swirl and expedited by the pocket 11, and at the same time the fuel is distributed in the combustion chamber 8 uniformly with the outer peripheral air flow in the combustion chamber 8 and the turbulence of outer peripheral air flow which is generated at the pocket 11. It is thus possible to shorten delay duration in an ignition timing and make fire propagation uniform, improving the combustion efficiency and the performance of a diesel engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a piston for a direct injection diesel engine.

0002

[Prior Art] Usually, in direct injection diesel engines, Japanese Patent Laid-Open No. 58-185921 and Japanese Patent Laid-Open No. 63-170
No. 521, Japanese Patent Application Publication No. 1-9641, and Utility Model Application No. 1986-
Publication No. 148731 and Japanese Unexamined Patent Publication No. 186912/1986
No., JP-A No. 195315-1983, and JP-A No. 64-
As disclosed in Publication No. 15424, the combustion chamber opened at the top surface of the piston is formed in a shape having a plurality of pockets gouged in the side wall surface or a shape having a plurality of protrusions protruding from the inner wall surface. The aim is to improve combustion efficiency by improving the mixing of injected fuel and compressed intake air, shortening the ignition delay period, and improving combustion efficiency.

However, in such a combustion chamber, when the injected fuel is combusted, the fire propagation is affected by swirl, which deteriorates the combustion and degrades the performance of the diesel engine.

0004

SUMMARY OF THE INVENTION It is an object of the present invention to improve the combustion efficiency and performance of a diesel engine by reducing the ignition delay period and improving fire propagation when the injected fuel is combusted.

[0005]

[Means for the Problem] This invention provides a combustion chamber having the same number of pockets as the nozzle of the fuel injection nozzle and opening on the top surface of the crown, and the pockets extending from the start of gouging to the center of gouging in the swirl direction. The wall surface within the range of is set as the fuel injection axis of the nozzle.

[0006]

[Operation] From the nozzle of the fuel injection nozzle, fuel is injected onto the wall surface of the pocket in the range from the start of gouging to the center of gouging in the swirl direction, and mixing of the fuel with air is promoted in the pocket by the cooperation of the swirl. The fire is then propagated uniformly within the combustion chamber as the fuel is evenly distributed within the combustion chamber by the turbulence of the circumferential airflow created in the pocket.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 show a specific example 1 of a diesel engine piston of the present invention applied to a direct injection type diesel engine of an automobile. In particular, since the diesel engine is a central injection type that uses a fuel injection nozzle (not shown) having six injection ports, the piston 1 has a combustion chamber 8 whose opening center is aligned with the piston axis, and a crown 2. The top surface 4 was opened. The opening of the combustion chamber 8 is limited by a lip 10 projecting from the side wall 9 at the position of the top surface 4 thereof.

Further, the combustion chamber 8 is formed with six pockets 11, which are the same number as the nozzle of the fuel injection nozzle. The surface was gouged out into small circular arcs at equal intervals in the direction. And that pocket 1 that was gouged out into a small arc surface like that
In the swirl direction 20, the wall surface 12 of No. 1 has a range 15 from the gouging start 13 to the gouging center 14 set as the fuel injection axis 21 of the nozzle. In other words, the pockets 11 are set at a place where the wall surface 12 in the swirl direction 20 positions the fuel injection axis 21 of the nozzle in the range 15 from the gouge start 13 to the gouge center 14, and Gouged out by side wall 9. The depth of gouging of these pockets 11 was set to 3 mm, which is the recess from the side wall 9 of the combustion chamber 8 to the small arc wall surface 12 at the center 14 of the gouge. Of course, that pocket 1
The depth of gouging 1 varies depending on the size of the piston 1, and is set to 5 mm or less, but is usually 3 m.
m to 4 mm. Also, this pocket 11
The width, the so-called gouging width, was set to about 1.5 times its height, but is preferably set to approximately the same or greater than its height.

Further, in this piston 1, 3 is a skirt, 5 is a land and ring zone, 6 is a pin boss, and 7 is a pin hole.

From the nozzle of the fuel injection nozzle, fuel is injected into the pocket 11 onto the small circular arc wall surface 12 on the upstream side in the swirl direction 20, and the mixture of fuel and air is cooperated with the swirl. In this case, the fuel is distributed uniformly in the combustion chamber 8 by being carried by the peripheral air flow in the combustion chamber 8 and the turbulence of the peripheral air flow generated in the pocket 11. As a result, the ignition delay period for combustion was shortened and the fire was spread uniformly within the combustion chamber 8. Thus, combustion efficiency and performance were improved in the automobile diesel engine using this piston 1.

FIG. 4 partially shows another specific embodiment 41 of the diesel engine piston of the present invention, which is applied to a direct injection type diesel engine of an automobile. In this piston 41, a pocket 34 formed in the combustion chamber 32 has a wall surface 35 formed by combining a flat surface 36, a small circular arc surface 37, and a flat surface 38, and is gouged into the side wall 33 of the combustion chamber 32.

0012

Benefits of the Invention As understood from the above, the diesel engine piston of the present invention has a combustion chamber having the same number of pockets as the nozzle of the fuel injection nozzle and opening at the top surface of the crown. In the swirl direction, the wall surface in the range from the start of gouging to the center of gouging is set as the fuel injection axis of the nozzle, so in a diesel engine, the fuel from the nozzle of the fuel injection nozzle is directed to the wall surface of the pocket. In the combustion chamber, the fuel is injected into the upstream part of the combustion chamber, and mixing of fuel and air is promoted in the pocket by the swirl. It is evenly distributed within the combustion chamber by riding on the turbulence of the peripheral airflow generated in the pocket, and during combustion, the ignition delay period is shortened and the fire propagation is uniform.
As a result, the combustion efficiency and performance of diesel engines are improved, and it is very useful and practical for diesel engines.

As mentioned above, from the specific examples of the present invention described with reference to the drawings, various design modifications and changes will be easily made by those having ordinary knowledge in the technical field to which this invention pertains. Furthermore, the content of the invention is essential to the establishment of the invention that accomplishes the task of the invention, and originates from the technical essence of the invention, which is the nature of the invention, and If it is internalized, it can be easily replaced with an objectively recognized aspect.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view, partially cut away, of a specific example of a diesel engine piston of the present invention applied to a direct injection diesel engine for an automobile.

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view of a part of FIG. 2;

FIG. 4 is a partial sectional view showing another specific example of the diesel engine piston of the present invention applied to a direct injection type diesel engine of an automobile.

[Explanation of symbols]

1 Piston 8 Combustion chamber 11 Pocket 31 Piston 32 Combustion chamber 34 Pocket

Claims (1)

[Claims] [Claim 1] The combustion chamber has the same number of pockets as the nozzle of the fuel injection nozzle and is opened on the top surface of the crown, and the pockets are located in a range from the start of gouging to the center of gouging in the swirl direction. The piston of a diesel engine whose wall is set at the fuel injection axis of its nozzle.