JPH0343619A - Combustion chamber of vortex chamber diesel engine - Google Patents

Abstract

PURPOSE:To improve combustion efficiency by letting one part of jet from a vortex chamber pass over a dispersion board and flow into large cavities and by letting the other part thereof collide with the dispersion board flow into side cavities that communicate with the large cavities. CONSTITUTION:A nozzle hole 6 by which a fuel jet is blown out of a vortex chamber 5 of a cylinder head 4, is opened to a periphery of a main combustion chamber 9 on the upper part of a piston 3. In the vicinity of a nozzle hole 6 on a jet center line 1 directed to the center of the main combustion chamber 9, a dispersion board 13 is arranged. In front of the dispersion board 13, a pair of large cavities 12 is formed out of arc outer shells 17 arranged symmetrically around the jet center line 1. Before the dispersion board 13, a pair of right and left side cavities 14 communicating with each other is formed, and is communicated to the large cavities 12. On an outer shell 18 that forms the side cavities 14, a guiding part 18A is formed so as for a curvature to be gradually smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the shape of the combustion chamber of a swirl chamber type diesel engine.

(Prior art) In order to improve the combustion of swirl chamber type diesel engines, Fig. 6,
There is a proposal in which a combustion chamber is formed as shown in FIG. 7 (Japanese Utility Model Application No. 63-79435).

A swirl chamber 5 provided in the cylinder head 4 communicates with the main combustion chamber above the piston 3 via a nozzle 6, and a jet from the nozzle 6 of the swirl chamber 5 is provided on the top surface of the piston 3. For guiding, a groove-shaped trench portion 11 extending radially from the lower surface toward the center, and a pair of approximately circular shallow cavity portions 10 extending from the tip of the trench portion 11 to both sides are recessed. This forms a so-called cloverleaf type piston cavity.

As the fuel injected into the swirl chamber 5 is ignited near compression top dead center, combustion flame is ejected from the nozzle port 6 into the main combustion chamber 9. This jet flow is transmitted to the main combustion chamber 9 by the trench portion 11 of the piston 3.
is guided to the center of the combustion chamber 10, and further diffuses as a swirling flow along the inner periphery of both cavity parts 10 as shown by arrow a, and while mixing with the air in the main combustion chamber 9, mainly the air in FIG. Burns in the area indicated by the dashed line.

(Problem to be Solved by the Invention) However, in such a piston cavity, the force of the straight jet flow directly from the nozzle 6 toward the center along the trench portion 11 is too strong, so that both cavity portions 1
The force of the swirling flow that disperses toward zero becomes weaker, and the combustion flame spreads over a wide area of the main combustion chamber 9. As a result, the air utilization rate decreases, and depending on the operating conditions, smoke and HC
, C0 increases.

The present invention aims to solve such problems.

(Means for Solving the Problems) Therefore, the present invention provides a swirl chamber type diesel engine in which a jet nozzle from the swirl chamber is opened at the periphery of the main combustion chamber so that the jet flow is directed toward the center of the main combustion chamber. A dispersion table is raised on the surface so as to be located on the center line of the jet stream and closer to the nozzle, and on both sides of the dispersion table, the dispersion table is connected to each other and spreads out in a substantially circular shape, and the outer shell increases as it moves left and right away from the center line of the jet stream. A large cavity portion whose curvature gradually decreases is recessed, and lateral cavity portions that communicate with each other are recessed on both sides in front of the dispersion table. A guide part is formed in a part of the outer shell that connects each side cavity part and defines each side cavity part to guide the jet flow from the side cavity part in the tangential direction of the swirling flow generated in the large cavity part. did.

(Function) Part of the jet of combustion gas containing fuel from the swirl chamber passes over the dispersion table and flows into the left and right large cavities, creating a swirling flow along the inner circumference of the cavity. The flow is split into the left and right side cavities due to the collision with the flow, and flows into the large cavity ahead of the dispersion table from the tangential direction of the swirling flow while being guided by the guide section.

The curvature of the outer shell that defines the left and right large cavities that spread approximately circularly at the tip of the dispersion table gradually decreases as it moves away from the center line of the jet, so the outer edge of the piston crosses the cavity and collides with the cylinder bore. The jet component that was previously generated is reduced, and the swirling flow generated in the large cavity portion is strengthened accordingly, promoting the mixing of fuel and air within the cavity.

By reinforcing the swirling flow in the large cavity in this way, combustion is spread over a wide area of the main combustion chamber while drawing in air.

(Example) Embodiments of the present invention will be described below based on the drawings.

In the first embodiment shown in the first [Z, second plot], the jet nozzle 6 for jetting out the jet containing fuel from the swirl chamber 5 of the cylinder head 4 is opened in the periphery of the main combustion chamber 9 above the piston 3. On the plane, a dispersing table 13 is formed on the top surface 8 of the piston 3 at a position close to the nozzle 6, located on the jet flow center line l toward the center of the main combustion chamber 9.

A pair of substantially circular large cavity portions 12 are defined by arc-shaped outer shells 17 arranged symmetrically across the jet flow center line l at the forward end of the dispersion table 13 which is formed by protruding into a substantially diamond shape. Ru.

The curvature of the outer shell 17 that defines the substantially circular large cavity part 12 is set to gradually become smaller as it moves away from the center line l of the jet flow, thereby strengthening the swirling flow generated in the large cavity part 12 and This reduces the amount of acid in the four jets that collide with the cylinder bore.

Further, an opposing wall portion 17A is formed in a portion of the outer shell 17 and is located on the jet flow center line l and protrudes in a substantially V-shape.

Further, in front of the dispersing table 13, a side cavity part 14 is formed which communicates with each other in the left and right directions, and this side cavity part 14 also communicates with the large cavity part 12 on both sides of the dispersing table 13.

The outer shell 18 defining the side cavity part 14 has an arcuate shape on the back side of the nozzle 6 along the outer periphery of the piston 3, and its curvature gradually decreases on the side connected to the large cavity part 12. Guide portion 18A curved as shown in FIG.
is formed, and the dispersing table 1 is arranged so that the jet gas flowing into the large cavity part 12 from the side cavity part 14 joins from the tangential direction of the swirling flow generated in the large cavity part 12.
I will guide you towards the destination of 3.

The structure is as described above, and the same parts as in FIGS. 6 and 7 are given the same reference numerals, and the operation will be explained next.

As it moves from the compression top dead center to the expansion stroke, a part of the flame jet containing unburned fuel ejected from the vortex chamber 5 into the main combustion chamber 9 via the jet nozzle 6 is transferred to the dispersion table 13 located immediately in front of the jet.
As shown by the arrows in FIG. 1, the flow is divided into the left and right side cavities 14, and after passing over the dispersing table 13, a part of the jet flows into the opposite wall of the substantially ■-shaped shape on the center line of the jet. A swirling flow as shown by arrow C is generated in the left and right large cavity portions 12 with 17A as the boundary.

In this case, the outer shell 17 that defines the substantially circular large cavity part 12 has a curvature that gradually decreases as it moves away from the center line l of the jet, and in order to suppress the swirling jet from spreading excessively, the outer shell 17 and collides with the cylinder bore, reducing the number of combustion flames to be extinguished. This also prevents the swirling flow generated in the large cavity portion 12 from attenuating and sufficiently promotes the mixing of fuel and air.

Further, the jet flow branched from the front side of the dispersion table 13 to the side cavity part 14 as indicated by the arrow is directed toward the jet center line l ahead of the dispersion table 13 by the guide section 18A continuous from the arc-shaped outer shell 18. By being guided inward and tangentially joining the swirling flow in the large cavity portion 12, the swirling flow can be further strengthened without reducing the inflow speed and without causing stagnation at the merging portion.

In this way, the jet stream containing unburned fuel components generates a strong swirling flow in the large cavity part 12 and diffuses combustion outward while entrapping air. The flame propagates and spreads over a wide area of the combustion chamber 9.

As a result, good combustion with a high air utilization rate is ensured throughout the entire area of the main combustion chamber 9, and the unburned fuel (HC) at low load is ensured.
, SOF, etc.) and smoke emissions during high loads can be significantly reduced.

Next, the embodiment shown in FIG. 3 will be explained. This is because the curvature of the outer shell 17 defining the substantially circular large cavity part 12 is made smaller as it moves left and right away from the center line l of the jet.
At the portion connecting the large cavity part 12 and the side cavity part 14, the back surface of the guide part 18A is curved and protruded inward of the large cavity part 12, and this protruding surface 18B directs the swirling flow toward the center of the cavity. .

This also prevents the swirling flow from dispersing in the large cavity portion 12, thereby strengthening the swirling flow and reducing the jet component that collides with the cylinder bore.

Next, the embodiment shown in FIGS. 4 and 5 will be explained. In this embodiment, a part of the outer shell 17 of the left and right large cavity parts 12, especially the part facing the center line e of the jet flow, is raised from the top surface 8 of the piston. , the cylinder head 4 corresponds to this raised portion 1'7C.
A recess 4A is formed on the lower surface of the nozzle 6 to guide the jet flow from the nozzle 6 to rotate along the inner circumference of the large cavity part 12 without going over the cavity when it collides with the jet flow. It is possible to further strengthen the swirling flow caused by this.

By thus strengthening the swirling flow in the large cavity part (2), the mixing of unburned fuel and air is further promoted, and even more efficient combustion can be achieved.

(Effects of the Invention) As described above, according to the present invention, a part of the jet from the nozzle is diverted from in front of the dispersion table to the shallow measuring cavity, diffused, and accelerates the initial combustion rate, and further passes over the dispersion table. The outer shell, which is formed so that the curvature gradually decreases, generates a swirling flow in the jet flow that flows into the large cavity part, and the jet flow from the square cavity part joins in the tangential direction of the outer shell. The curvature of the outer shell of the large cavity part that swirls the jet is made smaller as it moves left and right away from the center line of the jet to further promote the mixing of fuel and air. The quenching of the combustion flame is reduced by suppressing the impinging jets, and as a result, good combustion with high air utilization is ensured throughout the main combustion chamber, and unburned fuel (HC, SOF, etc.) is reduced at low loads. ) and the amount of smoke emitted during high loads can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a plan view of the first embodiment of the present invention, and FIG. 2 is a plan view of the first embodiment of the present invention.
3 is a plan view of the second embodiment,
FIG. 4 is a sectional view of the third embodiment, FIG. 5 is an explanatory view of the protrusion, FIG. 6 is a plan view of the conventional example, and FIG. 7 is a sectional view. 3... Piston, 3B... Bottom surface, 4... Cylinder head, 5... Swirl chamber, 6... Nozzle port, 9... Main combustion chamber, 12... Large cavity part 213... Distributing table, 1
4... Side cavity part, 18A... Guide part.

Claims (1)

[Claims] In a swirl chamber type diesel engine in which the jet from the swirl chamber is opened at the periphery of the main combustion chamber so that the jet flows toward the center of the main combustion chamber, the jet is located on the top surface of the piston on the center line of the jet and close to the jet. As well as raising the dispersion table,
A large cavity portion is recessed on both sides of the front side of the dispersion table, and the curvature of the outer shell gradually decreases as the distance from the center line of the jet stream increases to the left and right, and the curvature of the shell gradually decreases as the distance from the center line of the jet stream increases to the left and right. A part of the outer shell that is recessed with side cavity portions that communicate with each other on both sides of the dispersing table, and that communicates each side cavity portion with each large cavity portion on both sides of the dispersion table, and that defines each side cavity portion. A combustion chamber for a swirl chamber type diesel engine, characterized in that a guide part is formed to guide a jet flow from a side cavity part in a tangential direction of a swirling flow generated in a large cavity part.