JPH0711959A - Combustion chamber device for diesel engine - Google Patents

Abstract

PURPOSE:To promote mixture of air and fuel by a method wherein a re-entrant ring serving as a squish guard is protruded from the under surface of a cylinder head in a state to surround a fuel injection nozzle therewith and a compression flow is forced into collision with fuel spray through the gap of a cavity. CONSTITUTION:A re-entrant ring 2 is protruded from the under surface of a cylinder head 1 in a state to surround a fuel injection nozzle 3 therewith. A gap 7 is provided between the lip part 6 of a cavity 5 formed in the top surface of a piston 4 and the outer surface of the re-entrant ring 2. In which case, when the piston 4 is raised to a top dead center, a squish flow F1 is caused to flow through the gap 7 and injected in the cavity 5. The injection of the squish flow causes joining together of the squish flow F1 and a swirl flow F2 to promote a turbulence, improves mixture of it with fuel spray injected through the fuel injection nozzle 3 and in turn also causes improvement of NOx in exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention intends to promote the fuel / air mixture necessary for improving combustion in a direct injection type diesel engine.

[0002]

2. Description of the Related Art Timing retardation for improving exhaust gas (reducing NOx) has already reached its limit (misfire), and in order to solve this problem, promote mixing of fuel and air required for combustion improvement. In order to achieve this, efforts have been made to reduce the top clearance of the piston, but interference with the top surface of the piston with the cylinder head has already become a problem, and the structure has reached its limit.

Further, in order to effectively use the skip flow at the top dead center of the piston, JP-A-56-1060 is used.
The combustion chamber device described in Japanese Patent No. 21 has been proposed, and an attempt has been made to collide the skip flow with the swirl flow in the cavity.

[0004]

DISCLOSURE OF THE INVENTION The present invention is an improvement of the device described in the above publication to provide a fuel / fuel required for improving combustion.
The purpose is to promote the mixing of air more effectively.

[0005]

According to a first aspect of the present invention, there is provided a reentrant ring as a skip guide on the lower surface of the cylinder head so as to surround the fuel injection nozzle, and the top dead center of the piston. The structure is characterized in that the compressed flow generated on the top surface of the piston and the lower surface of the cylinder head at the point of time is introduced into the gap of the cavity and the flow is forcibly collided with the fuel spray.

According to a second aspect of the present invention, in the apparatus according to the first aspect, the lower surface of the reentrant ring is an inclined surface that faces upward toward the center of the ring.

According to the third aspect of the present invention, the same number of pier-shaped protrusions as the number of injection holes are provided on the lower surface of the cylinder head in correspondence with the direction of the fuel injection holes from the fuel injection nozzle.
By providing recesses on the top surface of the piston in which these protrusions can be loosely fitted, and opening these recesses in the inner wall of the cavity, the skip flow at the piston top dead center is ejected into the cavity, and fuel spray is performed. It is characterized in that it has a structure to forcibly collide with.

According to the fourth aspect of the present invention, the ridge portion of the piston is provided with the same number of skip guide grooves as the injection holes from the fuel injection nozzle in correspondence with the direction of the fuel injection holes from the fuel injection nozzle. It is characterized in that the swash flow at the dead point is focused on these swash guide grooves, merges with the swirl flow in the cavity, and is forced to collide with the fuel spray.

[0009]

With the device having the above-mentioned structure, at the top dead center of the piston, the skip flow forcibly collides with the swirl flow in the cavity to promote the mixing of fuel and air, thereby improving the exhaust gas. It is possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in the first embodiment shown in FIGS. 1 to 4, 1 is a cylinder head, and the lower surface of the cylinder head 1 is cast with a reentrant ring 2 surrounding a fuel injection nozzle 3. Alternatively, the protrusion is provided by friction welding.

A gap 7 is formed between the lip portion 6 of the cavity 5 formed on the top surface of the piston 4 and the outer surface of the reentrant ring 2, and the piston 4 moves upward to reach the top dead center. When it reaches, the skip flow (shown by arrow F1 in FIG. 2; the same applies hereinafter) is injected into the cavity 5 through this gap 7 and swirl flow (arrow F2 in FIG. 2).
Indicate. same as below. ), To promote the disturbance,
Mixing with the fuel spray from the fuel injection nozzle 3 is further improved.

FIG. 3 showing the effect in this example, in order to improve the black smoke deterioration in the NOx reduction by the timing retard, in the diffusion combustion region, the combustion in the latter stage is promoted by the air-fuel mixture promotion according to the present invention. Shows the state of
FIG. 4 shows the state of improvement of smoke and NOx of the present invention in a state where the engine speed is constant.

The second embodiment shown in FIGS. 5 to 7 is different from the above-mentioned embodiment in that the lower surface of the reentrant ring 2 is an inclined surface 8 which is directed upward toward the center of the ring 2. Since the other points are the same, the same portions are denoted by the same reference numerals and the description thereof will be omitted. The same applies to each of the following embodiments.

According to this embodiment, the fuel spray from the fuel injection nozzle 3 at the top dead center of the piston 4 is generated by the inclined surface 8
Along with the swash flow F2 which is injected through the gap, and when the piston 4 descends, combustion gas flows through the inclined surface 8 as shown by an arrow F3 in FIG. About the liner 9
It does not turn to the side and is kept in a high temperature combustion chamber, so that the effect of reburning the black smoke is obtained.

Next, in the third embodiment shown in FIGS. 8 to 10, the fuel injection nozzle 3 is provided on the lower surface of the cylinder head 1.
Corresponding to the number of fuel injection ports 10 (6 in the illustrated embodiment), the same number of pier-shaped projections 11 as the fuel injection ports 10 are provided by casting or friction welding.

On the other hand, the recesses 12 that can be loosely fitted to the protrusions 11 are provided on the top surface of the piston 4, and the recesses 12 are opened in the inner wall 13 of the cavity 5 through the communication port 14 to allow the piston 4 to move. When the compression rises (FIG. 10), the air flowing from the head space 15 through the recess 12 and the communication port 14 into the cavity 5 reaches the top dead center of the piston 4, and the projection portion Gap 16 between 11 and recess 12
As a skip flow F2 compressed and passing through, is jetted into the cavity 5 through the communication port 14, where it collides with the fuel spray from each fuel injection port 10 and splits the fuel spray to promote mixing. is there. In this case, the communication effect is further enhanced by forming the communication port 14 upward toward the fuel injection port 10 as shown in the drawing.

Further, in the fourth embodiment shown in FIGS. 11 to 15, the lip portion 6 of the cavity 5 of the piston 4 is used.
At the top dead center of the piston 4, by providing the same number of skip guide grooves 17 as the number of the nozzles 10 (6 in this embodiment) corresponding to the direction of the fuel nozzles 10 from the fuel injection nozzle 3. The skip flow F2 is focused on these skip guide grooves 17 and swirled in the cavity 5.
The turbulent flow is generated by merging with the fuel flow F1 and collides with the fuel spray.

The aim and effect of this embodiment are as follows. That is, there is a problem that black smoke is deteriorated in NOx reduction by the timing retard. Therefore, by concentrating the strongly generated swash flow F2, which is the top dead center of the piston, it is disturbed by the confluence with the swirl flow F1. As a result, the fuel spray mixes well, the black smoke is improved, and the fuel consumption is improved by promoting combustion and shortening the combustion period.
15 and FIG.

[0019]

By adopting the above-mentioned device of the present invention, the swash flow generated at the top dead center of the piston is merged with the swirl flow in the cavity to force fuel spray. It is possible to improve the atomization of the fuel spray and the mixing with the air, and consequently to improve the NOx in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a first embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a graph showing a relationship between a crank surface and a heat generation rate.

FIG. 4 is a graph showing a state of improvement of black smoke and NOx of the present invention and a conventional example when the engine speed is constant.

FIG. 5 is a vertical sectional view of a second embodiment of the present invention.

FIG. 6 is a plan view of FIG.

FIG. 7 is a cross-sectional view showing a state when the piston is descending.

FIG. 8 is a vertical sectional view of a third embodiment of the present invention.

9 is a plan view of FIG. 8. FIG.

FIG. 10 is a vertical cross-sectional view showing a state when the piston is compressed.

FIG. 11 is a vertical cross-sectional view of the fourth embodiment of the present invention.

FIG. 12 is a plan view of FIG. 11.

FIG. 13 is an enlarged perspective view of a main part of the present invention.

FIG. 14 is a graph showing a relationship between a crank surface and a reheating rate.

FIG. 15 is a graph showing the relationship between crank surface and turbulence.

[Explanation of symbols]

 1 Cylinder Head 2 Reentrant Ring 3 Fuel Injection Nozzle 4 Piston 5 Cavity 6 Rip Part 7 Clearance 8 Sloping Surface 10 Fuel Injection Port 11 Projection 12 Recess 13 Inner Wall 16 Clearance 17 Skip Guide Slot

Claims (4)

[Claims] 1. A reentrant ring as a skip guide is provided on the lower surface of the cylinder head so as to surround the fuel injection nozzle, so that at the top dead center of the piston, the reentrant ring is generated on the top surface of the piston and the lower surface of the cylinder head. A fuel chamber device for a diesel engine having a structure in which a compressed flow is guided into a cavity and the flow is forcibly collided with a fuel spray. 2. The fuel chamber device for a diesel engine according to claim 1, wherein the lower surface of the reentrant ring is an inclined surface that is upward toward the center of the ring. 3. The cylinder head has a plurality of pierce-like protrusions protruding from the lower surface of the cylinder head in correspondence with the directions of the fuel injection nozzles from the fuel injection nozzle, and these protrusions can be loosely fitted. By providing such recesses on the top surface of the piston and opening these recesses on the inner wall of the cavity, a skip flow at the piston top dead center is ejected into the cavity,
A combustion chamber device for a diesel engine, which has a structure for forcibly colliding with a fuel spray. 4. A skip flow at the top dead center of the piston is provided by providing, in the cavity portion of the piston, the same number of skip guide grooves as the number of the nozzles corresponding to the direction of the fuel injection ports from the fuel injection nozzle. A combustion chamber device of a diesel engine having a structure in which the swirl flow in the cavity is converged and merged with the swirl flow in the cavity to forcefully collide with the fuel spray.