JPH0131005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a swirl combustion chamber structure for a diesel engine.

(Prior Art) The present applicant eccentrically centers the central axes of the front and rear chambers of the pre-combustion chamber in opposite directions with respect to the central axis of the fuel injection valve, and creates a jet impingement surface between the front and rear chambers. We have already proposed a pre-combustion chamber for a diesel engine that has a stepped section (Utility Model Publication No. 51-50893). Its structure makes it easy to start, but the combustion noise immediately after starting is a little loud. In addition, since the vortex velocity is reduced by the jet impingement surface, carbon tends to adhere to the tip of the fuel injector, and when carbon adheres, the angle of the spray changes, which tends to increase noise during low idle and cold conditions. . On the other hand, in order to increase the vortex velocity, the vortex combustion chamber is made into a long spherical, oval, or similar smooth shape along the cylinder centerline, and the cross-sectional shape of the nozzle is improved to make the nozzle the main part. It is formed by a round hole and a pair of side passages connected to the round hole and extending laterally.The side passages are deep on the main combustion chamber side and small on the vortex combustion chamber side, and the side passages are the main combustion chamber. A fan-shaped design that expands toward the room has already been proposed (Tokuko Sho 57-).
59410). However, according to this structure, during the compression process in which air flows from the main combustion chamber into the vortex combustion chamber, the air from the round hole in the nozzle and the air from the side passages come into contact with the main jet so that they converge to one point in the vortex combustion chamber. In order to merge, a cavity phenomenon occurs on both the left and right sides of the main jet, and it becomes difficult for not only the main jet but also the auxiliary jet that has flowed into the vortex combustion chamber via the side passage to reach this cavity, and it becomes difficult for the main jet to reach the vortex combustion chamber. Mixing of the spray with air becomes insufficient. As described above, since complete air-fuel mixture formation cannot be obtained in the swirl combustion chamber, combustion performance tends to deteriorate.

(Objective of the Invention) The present invention improves the velocity distribution of the air flowing from the main combustion chamber into the vortex combustion chamber in the direction of inflow of the sub-jet so that the velocity distribution of the air flowing into the vortex combustion chamber becomes gentler as it moves from the central part of the main jet to the left and right sides. , the aim is to ensure that a complete mixture formation is obtained within the vortex combustion chamber.

(Structure of the Invention) The present invention provides an injection valve with an injection direction directed at the center of a vortex combustion chamber having a long spherical shape, an egg shape, or an elongated shape similar to the shape along the cylinder center line, and a main combustion chamber and a vortex combustion chamber. The nozzle connecting the injector is angled toward the center of the main combustion chamber as it moves toward the main combustion chamber with respect to the center line of the injection valve, and the center of the opening on the swirl combustion chamber side is on the center line of the injection valve passing through the center of the swirl combustion chamber. In the case where the spout is a main part of the round hole
A pair of parallel groove-like slits with a substantially rectangular uniform cross section and a semicircular bottom extend in both directions perpendicular to the plane containing the injector center line and the nozzle axis. This is a vortex combustion chamber of a diesel engine, which is characterized by the following:

(Example) In FIG. 1 showing the longitudinal section, the vortex combustion chamber 1
(the whirlpool chamber) has an elongated spherical shape in the direction along the center line O ₁ - O ₁ of the cylinder 2, and the center line of the whirlpool combustion chamber 1
O ₂ −O ₂ is parallel to the cylinder center line O ₁ −O ₁ . The shape of the swirl combustion chamber 1 can also be an oval shape extending in the direction along the cylinder center line O ₁ -O ₁ or a similar smooth shape.
The vortex combustion chamber 1 is formed by a cylinder head 3 and a mouthpiece 4, and the combustion chamber 1 is formed at the upper end of the combustion chamber 1.
A fuel injection valve 5 is installed with the injection direction directed toward the center _P1 . The center line O ₃ -O ₃ of the injection valve 5 passes through the combustion chamber center P ₁ and further passes through the opening center P ₂ of the injection port 6 on the combustion chamber 1 side. The nozzle 6 connects the combustion chamber 1 and the main combustion chamber 7, and the main combustion chamber 7 is formed by the cylinder head 3, the piston 8, and the gasket 9. In addition, the center line O ₄ -O ₄ (axis line) of the nozzle 6 tilts toward the center of the main combustion chamber 7 (left side in Figure 1) as it goes from the swirl combustion chamber 1 side to the main combustion chamber 7 side. There is.

As shown in FIG. 2, the nozzle 6 has a uniform cross section consisting of a central round hole 6a serving as the main part and a pair of parallel groove-like slits 6b connected to the round hole 6a. As is clear from FIG. 1, the slit portion 6b protrudes in both directions perpendicular to a plane (the paper plane of FIG. 1) including the injection valve center line O ₃ -O ₃ and the nozzle axis O ₄ -O ₄ . That is, one slit portion 6b protrudes toward the front side of the paper in FIG. 1, and the other slit portion 6b
is overhanging the back side of the paper. Slit part 6b
has a substantially rectangular cross section with a semicircular bottom, and therefore a ridge-like protrusion 6c with an uneven cross-sectional shape is formed at the boundary between the slit portion 6b and the round hole 6a. In FIG. 1, reference numeral 10 denotes a glow plug, which is provided near the injection valve between the injection valve 5 and the cylinder center line O ₁ -O ₁ .

Next, the operation will be explained. During the compression stroke in which the piston 8 rises, the air in the main combustion chamber 7 flows into the combustion chamber 1 in the direction of arrow _A1 through the jet nozzle 6.
It performs a turning motion by curving along the inner surface as shown by arrows A ₂ and A ₃ . Fuel is injected from the injection valve 5 into the combustion chamber 1 at a predetermined time just before the piston 8 reaches top dead center, and the fuel spray mixes with the air jet within the combustion chamber 1 and self-ignites. The flame (combustion gas) generated in the combustion chamber 1 is ejected from the combustion chamber 1 through the nozzle 6 into the main combustion chamber 7 during the next expansion stroke, mixes with the air in the main combustion chamber 7, and burns, causing the piston 8 to move. Push down.

The air jet flowing from the main combustion chamber 7 into the vortex combustion chamber 1 via the nozzle 6 is transmitted through the combustion chamber 1 because the cross-sectional shape of the nozzle 6 is formed by a round hole 6a and a groove-like slit portion 6b as shown in FIG. As shown in FIG. 3, the velocity distribution within the jet is strong in the central part of the main jet supplied from the round hole 6a, and gentle in both sides of the secondary jet supplied from the slit part 6b. As a result, no hollow portions with thin air are created on both sides of the main air jet (the front side and the back side in FIG. 1). That is, the hollow portions on both sides of the main jet are eliminated by the sub jet supplied from the slit portion 6b. Therefore, the air-fuel mixture within the swirl combustion chamber 1 is quickly formed. Also, when the combustion gas in the swirl combustion chamber 1 flows into the main combustion chamber 7, a secondary combustion gas flow is created beside the main combustion gas flow by the slits 6b on both sides of the round hole 6a. A combustion gas flow is formed in which the flow velocity is high toward the center and becomes slower toward the outside, so that the combustion air within the main combustion chamber 7 is fully utilized. The fuel injection valve 5 has an angle θ of _{20 to}
It is installed in an inclined position at an angle of 25 degrees, and the injection is directed toward the center of the swirl combustion chamber 1. With such a structure, it becomes easier to spray into the main combustion chamber 7 at the time of starting, and ignition at the time of starting is improved. Use glow plug 10 at extremely low temperatures.

(Effects of the Invention) According to the present invention, since the cross section of the combustion chamber nozzle 6 has a special shape, the vortex flow into the vortex combustion chamber 1 is strong in the center and gentle on both sides, so that the mixture is formed quickly. be exposed. Even when the combustion gas in the swirl combustion chamber 1 flows into the main combustion chamber 7, secondary jet gas flows are generated on both sides of the main combustion gas flow by the slit portions 6b on both sides, and the distribution of the combustion gas flow is faster in the center. A gentle gas flow is formed on the outside, and the combustion air in the main combustion chamber 7 can be fully utilized, improving combustion performance. The noise during cold start is also improved.

Figure 4 is a graph showing the relationship between shaft output, shaft average effective pressure, fuel consumption rate, exhaust temperature, and exhaust concentration index.
The solid line indicates the combustion chamber of the present invention. Further, FIG. 5 shows the noise level with respect to the lubricating oil temperature at startup, and similarly to FIG. 4, the broken line shows the current combustion chamber, and the solid line shows the product of the present invention. As is clear from FIGS. 4 and 5, combustion performance is significantly improved according to the present invention. In short, in the present invention, a pair of parallel groove-like slits 6b are formed on both the left and right sides of the nozzle 6 (on the front side and the back side of the paper in FIG. 1), extending from the round hole 6a to the ridge-like projection 6c. Therefore, the main jet flow flows from the main combustion chamber 7 into the swirl combustion chamber 1 through the round hole 6a, and on both left and right sides (the front side and the back side in FIG. A jet is formed, and there are no thin air cavities on either side of the main jet. That is, the flow velocity V shown by the arrow in FIG. 3 is large in the round hole region 6a' where the flow flows through the round hole 6a, and is slow in the slit region 6b' where the flow flows through the slit portions 6b on both sides thereof. Compared to the case where the main jet flows only through the round hole 6a, it is possible to reliably prevent the formation of thin hollow portions that tend to occur on both sides of the hole. Similarly, when the combustion gas in the swirl combustion chamber 1 flows into the main combustion chamber 7, a secondary combustion gas flow is created beside the main combustion gas flow, and the flow velocity toward the center of the main combustion chamber 7 is fast. A combustion gas flow is formed that becomes gentler as it goes to both sides (the front side and the back side in Figure 1), and the main combustion chamber 7
The combustion air inside is fully utilized. Further, since the protrusion 6c is ridge-shaped, there is an advantage that a gentle sub-jet can be reliably formed.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional partial view of a combustion chamber according to the present invention;
Figure 2 is a partial view of the - cross section of Figure 1, Figure 3 is a schematic diagram of the flow velocity distribution in the - cross section of Figure 1, and Figure 4 is a schematic diagram of the flow velocity distribution in the - cross section of Figure 1.
FIG. 5 is a graph showing combustion performance. 1... vortex combustion chamber, 5... fuel injection valve, 6...
Nozzle, 6a...Round hole, 6b...Slit part, 7...
...Main combustion chamber.

Claims (1)

[Claims] 1. An injection valve is provided with the injection direction directed at the center of a whirlpool combustion chamber in the shape of a long sphere, an egg, or an elongated shape similar to this along the cylinder center line, and the nozzle that connects the main combustion chamber and the whirlpool combustion chamber is positioned at the center of the injection valve. In the case where the nozzle is installed so that it slopes toward the center of the main combustion chamber as it goes toward the main combustion chamber side with respect to the line, and the center of the opening on the swirl combustion chamber side is on the center line of the injection valve passing through the center of the swirl combustion chamber. , a pair of circular holes that are the main part, and a substantially rectangular uniform cross section with a semicircular bottom that extends in both directions perpendicular to the plane containing the injector center line and the nozzle axis, and extends from the round hole with a ridge-like protrusion. A vortex combustion chamber for a diesel engine, characterized in that it is formed by parallel groove-like slits.