JP2510170Y2 - Combustion chamber of internal combustion engine - Google Patents

Description

The present invention relates to a combustion chamber of an internal combustion engine, and more particularly to a combustion chamber of an internal combustion engine provided with means for locally generating a small vortex in the combustion chamber.

[Prior Art] In a combustion chamber of an internal combustion engine configured to evaporate a supplied fuel by heat of compressed air to cause spontaneous combustion, that is, in a combustion chamber of a diesel engine, a vertical cross section is formed at a center of a bottom wall of the combustion chamber. A chevron-shaped protrusion is formed to positively generate a swirl in the combustion chamber to promote evaporation of the fuel spray and effective mixing of air in the combustion chamber and vapor of the fuel.

However, since the swirl formed by the protrusion becomes a swirl that swirls around the protrusion and cannot locally generate a small vortex that disturbs the generation of the air-fuel mixture, it conventionally corresponds to the skirt of the protrusion. Proposed that vertical pins are erected on the part to generate a small vortex flow around the pins and that fuel spray is supplied between the pins that are in the circumferentially adjacent relationship (Shokai Sho 56-127326). [Problems to be Solved by the Invention] When the pin is erected as in the above proposal, it becomes possible to locally atomize and vaporize the fuel spray by a small vortex flow, while the pin is provided. Soot adheres to and is discharged as graphite during the exhaust stroke, and the pin is erected at the proposed position to prevent the growth of flame propagation. As a result, combustion unburned matter is likely to be generated, HC increases, output may decrease, and the swirl strength weakens because the small vortex flow generation position is closer to the center of the combustion chamber. In some cases, fuel may adhere to the side wall, and as a result, a large amount of HC (white smoke) may be discharged.

That is, it is necessary to reexamine the formation means and the formation position of the small vortex flow.

[Means for Solving the Problems] The present invention is intended to solve the above problems, and a combustion chamber recessed to accommodate a swirl at the top of the piston and a bottom wall of the combustion chamber located near the side wall. Formed in a small circular shape, a horizontal portion formed on the bottom wall radially inward of the depression, and spraying fuel toward the swirl upstream side of the depression. And an injection nozzle.

[Operation] According to the above configuration, the swirl circulating in the combustion chamber is
While the flow (main swirl) is held by the horizontal portion formed radially inward of the bottom wall of the combustion chamber, the micro swirl is generated above the recessed portion located near the outer side wall.

The main swirl acts not only to generate the microswirl in the depression, but also to maintain the strength of the microswirl once generated. Because the horizontal part around the main swirl is located inward in the radial direction, and the hollow part where the microswirl is generated is located outward in the radial direction (near the side wall). Because it works to assist the micro swirl.

Therefore, by spraying fuel just upstream of the swirl (main swirl) of this micro swirl,
Good mixing can be obtained even when the swirl speed is low at the time of starting.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 2, a combustion chamber 3 is formed in the top portion 2 of the piston 1 by being recessed along the axial direction. The combustion chamber 3 has four linear side walls 4 and a corner wall 5 having a predetermined curvature.
And are connected smoothly to form a quadrangular horizontal section.

A recess 7 having a small circular cross section is formed in the bottom wall 6 of the combustion chamber 3 at a position near the side wall 4 along the axial direction, and the ring 7 is positioned radially inward of the recess 7. The horizontal portion 6a is formed in the shape of a circle. In the embodiment, the recessed portion 7 is formed at a position substantially central to the side wall 4. On the other hand, an injection nozzle 9 is provided substantially in the axial center of the combustion chamber 3 with the fuel injection portion 8 facing the inside of the combustion chamber 3.

On the other hand, the injection nozzle 9 is composed of a well-known Hall type injection nozzle, and a plurality of injection holes 11 and 12 for atomizing and injecting fuel are provided in a hole portion 10 having a volume for collecting fuel. , 13, 14 ... Are formed at intervals in the circumferential direction. These injection ports 11, 12, 13, 14, ... Are respectively formed at positions where the combustion spray is supplied toward the immediately upstream side of each of the depressions 7.

 Next, the operation of the embodiment will be described.

As shown in FIGS. 1 and 2, during the compression stroke, the combustion chamber 3
A swirl S having a strength depending on the rising speed of the piston and the ratio of the diameter of the piston to the opening diameter of the combustion chamber 3 is generated therein. The swirl S is separated at the connecting portion between the side wall 4 and the corner wall 5 to correct the direction inward from the side wall 4 inward in the radial direction, and collides with the side wall 4 immediately downstream, and again the side wall 4 immediately downstream. The process of being swung along is repeated, and as a result, the microswirl S1 is generated in the vicinity of the corner wall 5 and is appropriately damped in order to fluidize the inside of the combustion chamber 3. That is, the swirl S that circulates in the combustion chamber 3 has its flow (main swirl) held by the horizontal portion 6a formed radially inward of the bottom wall 6 of the combustion chamber 3, and the swirl S
Orbit inside.

At the same time, the swirl S flows into the depression 7 and generates a strong small vortex S2 on the depression 7. That is, combustion chamber 3
Based on the same principle as generating the swirl S inside, each recess 7 is formed with a circular cross section open to the combustion chamber 3,
Moreover, by making the diameter of the recess 7 small, a stronger small vortex S2 can be formed. That is, the swirl S that circulates in the combustion chamber 3 retains its flow (main swirl S) by the horizontal portion 6a that is formed radially inward of the bottom wall 6 of the combustion chamber wall, and the dent located outside thereof. Part 7
A micro-swirl (small vortex) S2 is generated above. The swirl S produces | generates this small vortex flow S2, and it always works so that the intensity | strength of the small vortex flow S2 produced | generated may be maintained at least. Because the horizontal portion 6a around which the main swirl circulates is located inward in the radial direction, and the depression 7 in which the microswirl is generated is located radially outward (near the side wall), so the flow of the main swirl S This is because some of them work to assist the Micro Swirl S2.

At the end of the compression stroke, each of the injection holes 11, 12,
The fuel sprays f _{1,2,3,4, ...} Are injected from 13, 14, .. As a result, the amount of fuel attached to the side wall 4 is extremely reduced. The total amount of the air-fuel mixture generated by the small vortex S2 and the air-fuel mixture evaporated by the heat of the compressed air while being carried downstream by the swirl S during the injection is sufficient for the combustion chamber 3 The rate is greatly improved, and combustion with less combustion noise with a shorter ignition delay period is realized. As a result of reducing the amount of fuel attached to the side wall 4, graphite, bluish white smoke, smoke, and HC are reduced.

It should be noted that instead of the above-mentioned depression, a small circular groove as shown in FIG.
Even if the recess 7a is formed, a small vortex S2 can be generated similarly to the recess 7, and the same effect can be produced. Further, in the description of the embodiment, the recess 7 is formed substantially at the center of the side wall in the circumferential direction and near the side wall 4, but the recess 7 (or the groove 7a) is located near the side wall 4 and swirl. It is also possible to form a large number of air-fuel mixtures in positions close to each other along the direction and distribute the mixture in a band shape along the swirl direction to perform reliable flame propagation combustion. The horizontal cross section of the combustion chamber 3 is not limited to the polygonal combustion chamber such as the above-mentioned square, but the circular combustion chamber or the combustion bottom having a shelf-like step on the upper side wall or the shelf-like step as described above. Of course, it is also possible to provide the recess 7 (or the groove 7a). Further, as the fuel used in the above-mentioned combustion chamber 3, not only light oil, but also volatile low cetane number fuel such as alcohol can be used.

[Effects of the Invention] As is apparent from the above description, the present invention exhibits the following excellent effects.

(1) Main swirl can be maintained by the horizontal part formed on the bottom wall of the combustion chamber, and micro swirl can be generated by the recessed part, so black smoke can be generated even when the aural speed is slow at the time of starting. , Blue-white smoke, smoke,
It is possible to perform reliable flame propagation combustion with reduced HC and without misfire.

[Brief description of drawings]

FIG. 1 is a plan view showing a preferred embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is an enlarged sectional view of an essential part of a groove according to the present invention. In the figure, 1 is a piston, 2 is the top of the piston, 3 is a combustion chamber,
4 is a side wall, 6 is a bottom wall, 6a is a horizontal part, 7 is a hollow part, 9 is an injection nozzle, S is a swirl, and S2 is a small vortex.

Claims (1)

(57) [Scope of utility model registration request] Claim: What is claimed is: 1. A combustion chamber which is recessed to accommodate a swirl at the top of the piston, a small circular recess formed in the bottom wall of the combustion chamber near the side wall, and a diameter smaller than the recess. A combustion chamber of an internal combustion engine, comprising: a horizontal portion located inward in the direction and formed on the bottom wall; and an injection nozzle that sprays fuel toward the upstream side of the swirl of the recess.