JP2565516Y2 - Combustion chamber of a swirl chamber type diesel engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a combustion chamber of a vortex chamber type diesel engine, and more particularly to an improvement in a piston side cavity structure.

[0002]

2. Description of the Related Art In a swirl chamber type diesel engine, a groove-shaped trench extending from the lower part of the injection port toward the center of the piston is provided on the top surface of the piston, and a pair of large cavities is continuously formed at the tip of the trench. In general, a so-called cloverleaf-type cavity is formed in a concave shape, and further, a base portion of the trench portion, that is, a position below the injection port is formed partially deep (for example, Japanese Patent Application Laid-Open No. Sho 53-2570).
No. 9) is also known.

[0003]

However, in the above-mentioned conventional structure, the jet jetting out from the injection port smoothly goes straight along the trench portion, so that the jet jet and the surroundings in the initial stage of combustion on the main combustion chamber side. Mixing with air tends to be insufficient, and there is a problem that a large amount of HC and smoke is emitted. Even if the lower part of the injection port is locally deeply recessed, the air in the concave portion is effectively used at the very early stage when the jet starts to be ejected from the injection port, but if the jet continues to be ejected, Since the gas stagnates in a state where the air is insufficient in the concave portion and the diffusion to the large cavity portion side is hindered, the effect of reducing HC and smoke cannot be expected so much.

[0004]

The combustion chamber of the swirl chamber type diesel engine according to the present invention is open to the periphery of the main combustion chamber and is inclined so that the jet from the swirl chamber is directed toward the center of the main combustion chamber. And a pair of large cavities, which are recessed on the piston top surface and extend to the right and left respectively across the center line of the jet flow, and are continuous with each other at the center, and the position of the piston top surface below the nozzle And having substantially the same depth as the large cavity portion, and a jet introduction portion continuous with the large cavity portion, and a jet flow passage from the jet introduction portion to the large cavity portion in the middle of the flow path of the jet flow. A large cavity portion and a jet diffusion portion formed deeper than the jet introduction portion.

[0005]

The jet containing unburned fuel ejected from the swirl chamber through the nozzle near the top dead center of the compression collides with the bottom of the jet introduction part,
And it flows toward a large cavity part. Then, when the jet passes over the jet diffusion part, the fresh air remaining in the jet diffusion part is entrained, and the mixing of the unburned fuel and the air is promoted. In other words, at the same time as quickly diffusing to the large cavity portion side, fresh air is taken in the middle of the diffusion and good initial combustion is performed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention, in which 1 denotes a cylinder block, 2 denotes a cylinder head, and 3 denotes a piston. The lower surface of the cylinder head 2 that covers the upper surface of the cylinder bore 4 is formed as a flat surface, and the main combustion chamber 5 is formed between the lower surface and the top surface of the piston 3.

The swirl chamber 6 is located along the side of the cylinder head 2, and an injection port 7 extending from the swirl chamber 6 opens to the periphery of the main combustion chamber 5. The injection port 7 has a flat passage section with a slightly wide width direction, and is inclined so that the jet from the vortex chamber 6 is directed toward the center of the main combustion chamber 5. In FIG. 1, the center line of the above-mentioned jet on the plane of the piston 3 is indicated by a symbol L.

On the top surface of the piston 3 defining the main combustion chamber 5, a pair of large cavities 8 having a substantially circular shape are recessed at a constant depth near the center of the piston 3. The large cavity portion 8 extends right and left with the center line L interposed therebetween, and has a figure-eight shape as a whole, and central portions along the center line L are continuously integrated with each other. The outer shell on the center line L on the opposite side to the injection port 7 serving as a connection portion extends in a tongue shape toward the injection port 7 and forms an opposing wall portion 9 that partitions the large cavity portions 8. ing.
The large cavity 8 also serves as a valve recess for the intake and exhaust valves.

At a position below the injection port 7 on the top surface of the piston 3, a jet introduction section 10 is formed in a substantially rectangular groove shape corresponding to the opening shape of the injection port 7. The jet introduction portion 10 has the same depth as the large cavity portion 8, extends toward the center of the piston 3 along the jet center line L, and smoothly continues to the large cavity portion 8. I have. Incidentally, the wall surface of the outer shell forming the large cavity portion 8 and the jet flow introducing portion 10 is perpendicular to the top surface of the piston 3.

[0011] At the connection between the jet introduction portion 10 and the large cavity portion 8, a jet diffusion portion 11 having a groove shape deeper than that of the large cavity portion 8 or the like is provided. The jet diffusing section 11 is located at the outlet of the jet introducing section 10, that is, at the end on the center side of the piston 3, has substantially the same width as the jet introducing section 10, and extends to near the center of the piston 3. The wall surface of the end 11a on the side of the jet introduction part 10 is perpendicular to the top surface of the piston 3 so that a distinct step is formed between the end part 11a and the jet introduction part 10.
On the center side, the bottom surface forms an inclined surface so that the depth gradually becomes shallow, and smoothly continues to the bottom surface of the large cavity portion 8.

Next, the operation of the above embodiment will be described.

The fuel injected into the swirl chamber 6 before the compression top dead center is ignited and burns in the swirl chamber 6, and becomes a flame containing unburned fuel near the compression top dead center, from the injection port 7 to the main combustion chamber 5. Spout to the side. The jet of the combustion gas first collides with the bottom surface of the jet introduction part 10 where the injection port 7 faces, and tries to go straight along the jet center line L. Then, it passes over the jet diffusion portion 11 and collides with the opposing wall portion 9, and is smoothly diverted right and left along the outer shell. As a result, a strong swirling flow as shown by an arrow is generated in the large cavity portion 8.

Here, when the above-mentioned jet flows over the jet diffusion part 11, the fresh air remaining in the jet diffusion part 11 is gradually caught in the jet and mixed with the unburned fuel and air. Is promoted. In addition, fine turbulence occurs with the entrainment of the air, and combustion is promoted. It should be noted that the jet basically passes over the jet diffusion portion 11 and passes through the large cavity portion 8.
Therefore, the air in the jet diffusion portion 11 is kept in an excessively long state for a relatively long time, and the unburned fuel does not stagnate and does not cause smoke or the like. Therefore, the main combustion chamber 5
The relatively early combustion on the side can be made good, and the reduction of HC and smoke can be achieved.

Next, FIGS. 3 and 4 show the second embodiment of the present invention.
An example is shown. In this embodiment, a side cavity portion 21 extending left and right along the periphery of the piston 3 from below the injection hole 7 is added to the side of the injection hole 7 on the top surface of the piston 3, and the jet flow is dispersed to the side cavity portion 21. Is provided with a dispersing table 22. The side cavity portion 21 has the same depth as the jet flow introduction portion 10 below the injection port 7 and is continuous with each other, so that the side cavity portion 21 also substantially serves as the jet flow introduction portion 10. The outer shell 21a of the side cavity portion 21 on the rear side of the injection port 7 has an arc shape along the periphery of the piston 3. Outer shell 2 on both sides
1b is smoothly curved and extends obliquely toward the center of the piston 3, and guides the jet flowing out of the side cavity portion 21 in a substantially tangential direction of the swirling flow generated in the large cavity portion 8. ing. The dispersion table 22 includes the piston 3
It is raised in the shape of an island to the same height as the top surface, and is located on the jet center line L so as to face the injection port 7 and has a substantially rhombic shape so as to form part of the outer shell of the large cavity portion 8. It has a planar shape.

On both sides of the dispersion table 22 through which the jet flowing out of the jet port 7 passes, there are provided jet diffusing portions 23 which are deeper than the large cavity portion 8 and the side cavity portion 21. The jet diffusion portion 23 is formed in a groove shape that connects the protruding outer shells 21 b on both sides of the side cavity portion 21 and the side edge of the dispersion table 14 near the injection port 7, and faces the dispersion table 14. The width is gradually increasing.

In this embodiment, the jet flowing out of the injection port 7 and going straight ahead collides with the dispersion table 22 and is widely dispersed to the left and right side cavities 21. That is, the air near the side cavity portion 21 is quickly taken in and the initial combustion is performed. Then, the jet flows into the large cavity portion 8 through both sides of the dispersion table 22, and generates a swirling flow in the large cavity portion 8. At this time, since the jet traverses the jet diffusing section 23, the air remaining in the jet diffusing section 23 is caught in the jet similarly to the above-described embodiment, and the mixing of the unburned fuel and the air is promoted. At the same time, a minute turbulence is generated to promote combustion. Therefore, the initial combustion is further improved in combination with the dispersion of the jet flow into the side cavity portion 21. Since the jet flowing toward the side cavity portion 21 joins the swirling flow in the large cavity portion 8 from the substantially tangential direction along the outer shells 21b on both sides, the swirling flow in the large cavity portion 8 is strengthened. You. Further, since the straight traveling velocity component of the jet is weakened by the collision with the dispersion table 22, the opposed wall portion 9 is formed.
, And collides with the cylinder bore 4 to extinguish the flame. Therefore, the air utilization rate in the entire main combustion chamber 5 is further improved.

[0018]

As is apparent from the above description, according to the combustion chamber of the swirl chamber type diesel engine according to the present invention, the air in the jet diffusion portion is generated while the jet ejected from the nozzle goes toward the large cavity portion. Entrained in the jet, the mixing of unburned fuel and air is promoted, and fine turbulence is generated, so that the initial combustion on the main combustion chamber side is good and the emission of HC and smoke is reduced. Reduce.

[Brief description of the drawings]

FIG. 1 is a plan view of a piston top surface showing a first embodiment of a combustion chamber according to the present invention.

FIG. 2 is a cross-sectional view of a main part of the combustion chamber along the line AA in FIG. 1;

FIG. 3 is a plan view of a piston top surface showing a second embodiment of the combustion chamber according to the present invention.

FIG. 4 is a sectional view of the top of the piston taken along line BB of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Piston 5 ... Main combustion chamber 6 ... Swirl chamber 7 ... Injection port 8 ... Large cavity part 9 ... Opposing wall part 10 ... Jet introduction part 11 ... Jet diffusion part 21 ... Side cavity part 22 ... Dispersion table 23 ... Jet diffusion part

Claims (1)

(57) [Scope of request for utility model registration] 1. An injection opening which is open to a peripheral portion of a main combustion chamber and is inclined so that a jet from the vortex flow chamber is directed toward a center of the main combustion chamber, and a recess provided on a piston top surface and a center line of the jet. A pair of large cavities continuous with each other at the center, and are recessed below the injection port on the top surface of the piston, and have substantially the same depth as the large cavities. A jet introduction portion continuous with the large cavity portion, and a jet flow located in the middle of the flow path of the jet from the jet introduction portion to the large cavity portion and formed deeper than the large cavity portion and the jet introduction portion. A combustion chamber for a swirl chamber type diesel engine, comprising: a diffusion section.