JPH089376Y2 - Subchamber diesel engine combustion chamber structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a combustion chamber structure of a sub-chamber diesel engine in which the shape of a groove formed in the upper surface of a piston is improved.

(Prior Art) A sub-chamber diesel engine that has a main chamber and a sub-chamber and allows combustion gas in the sub-chamber to flow into the main chamber as a jet flow as the piston descends is generally effective for the combustion gas and air in the main chamber. For the purpose of effective circulation and mixing, as shown in FIG. 5, a substantially circular recess a is formed in the substantially central portion of the upper surface of the piston.
A groove having a shape in which a pair of circles are connected to each other is engraved and extends from the position corresponding to the auxiliary chamber injection hole portion toward the center of the main chamber to guide the combustion gas from the auxiliary chamber to the substantially circular recess a. The guide recess b is engraved. Then, the combustion gas flowing into the main chamber from the sub chamber spreads into the main chamber as a swirling flow (arrow in FIG. 5) flowing along the groove shape of the substantially circular recess a through the guide recess b.

(Problems to be solved by the invention) However, in the case of the cylinder having the guide recess having the above-described shape, the combustion gas and the air are effectively circulated in the central portion of the cylinder and the inflow facing portion of the combustion gas (chain line in FIG. 5). However, air is accumulated in both sides of the guide recess (broken line in FIG. 5), which makes it difficult to obtain effective combustion, and excess fuel is generated in a part of the main chamber, resulting in smoke in the exhaust. There is a problem that it occurs. In order to solve this, as shown in JP-A-58-138217, air intake grooves having a taper on both sides of a cavity handle (guide recess) are alternated at right angles and left and right with respect to the guide recess. Although there is one that is provided in a displaced manner, the air that stays on both sides of the guide recess in this configuration is
The combustion gas flowing from the air intake groove to the upper surface of the piston pushes the gas outward to the left and right, and a flow is generated that opposes the swirling flow indicated by the arrow in FIG. It does not lead to a solution.

Further, in the one provided with the guide recess and the substantially circular recess as described above, when the combustion gas is introduced into the circular recess from the guide recess, the jet flow of the combustion gas is accompanied by the sudden expansion of the jet flow passage. There is a problem that the turbulence of the combustion gas is generated around the continuous portion of the guide recess and the circular recess due to the disturbance, and there is a limit to improving the combustibility of the air-fuel mixture in the main chamber.

(Means for Solving the Problems) In view of the above problems, the present invention provides a guide recess extending from the position corresponding to the auxiliary chamber injection hole portion toward the center of the main chamber on the upper surface of the piston of the auxiliary chamber diesel engine, A substantially circular recess is formed on both sides of the guide recess that is continuous with the guide recess, and extends on both sides of the guide recess toward the center of the upper surface of the piston so as to form a predetermined angle with the extension direction of the guide recess. In addition, the present invention relates to a combustion chamber structure of a sub-chamber diesel engine in which an auxiliary guide groove having one end opened is formed in the vicinity of a continuous portion of the guide recess and the substantially circular recess.

(Operation) As an operation of the present invention having the above configuration, when the combustion gas in the sub chamber is introduced into the main chamber as the piston descends, the air on both sides of the guide recess is supplemented by the auxiliary guide groove formed on the upper surface of the piston. Is introduced into the substantially circular recess along with, merges and mixes with the combustion gas, becomes a swirling flow that flows along the groove shape of the substantially circular recess, spreads into the main chamber, and effective combustion is performed. Further, the air from the auxiliary guide groove guides the combustion gas introduced from the guide recess to the circular recess into the circular recess, thereby suppressing the turbulent flow of the combustion gas around the connecting portion between the guide recess and the circular recess. Will be done.

(Embodiment) Next, an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a plan view of a piston 1 of a sub-chamber diesel engine, in which a substantially circular recess 2 which is a groove having a shape in which a pair of circles are connected is carved in a substantially central portion, and a sub chamber (not shown). A guide recess 3 extending from a position corresponding to the auxiliary chamber injection hole portion toward the center of the main chamber is formed to guide the combustion gas from the chamber to the substantially circular recess 2. On both sides of the guide recess 3, as shown in FIG.
An auxiliary guide groove 4 that extends toward the center of the upper surface 1a of the piston 1 at a predetermined angle with respect to the extension direction of the piston 1 and has one end opening near the connecting portion between the guide recess 3 and the substantially circular recess 2. , 4 are engraved. The auxiliary guide groove 4
Is an inclined groove having side walls at angles α and β with respect to the side wall 3a of the guide recess 3 as shown in FIG. 1, and is formed so as to connect the upper surface 1a of the piston and the guide recess 3 to each other. is there. Further, as shown in FIG. 3, the guide recess 3 and the auxiliary guide groove 4 are partly partitioned by the partition wall 5 formed by the side wall 3a of the guide recess 3 and the side wall 4b of the auxiliary guide groove.

 Next, the operation of the present invention will be described.

The combustion gas exploded in the sub chamber becomes a jet flow into the main chamber through the injection holes of the sub chamber, and the combustion gas flows through the guide recess 3 along the groove shape of the substantially circular recess 2 (first (Figure arrow) and spreads into the main room. On the other hand, the air in both sides (the broken line in FIG. 1) of the guide recess 3 is guided to the auxiliary guide groove 4 by the jet negative pressure of the combustion gas and flows into the guide recess 3 along the inclined surface 4a of the auxiliary guide groove. The mixed gas is mixed and mixed with the combustion gas, introduced into the substantially circular recess, and spread into the main chamber as described above. Then, the combustion gas in the main chamber is sufficiently mixed with air, ideal combustion is performed, and smoke in the exhaust gas is reduced. The experimental results are shown in the graph of FIG. 4, where A is the structure of the present invention and the angle α is 40 ° and β is 10 °, 20 °, and 30 °. B is a conventional general circular recess and guide recess, and C is a structure in which the air intake groove is provided in the guide recess. Clearly smoke is reduced,
Particularly, it is effective to set the angle β to 20 °.

In addition, the air from the auxiliary guide groove 4 is guided by the guide recess 3
The combustion gas introduced into the substantially circular recess 2 from the inside is guided into the substantially circular recess 2, and the turbulent flow of the combustion gas in the vicinity of the connecting portion between the guide recess 3 and the substantially circular recess 2 is suppressed. The combustibility of the air-fuel mixture in the room is further improved.

Further, the shape of the auxiliary guide groove in the present invention is not limited to this embodiment, but may be changed appropriately.

(Effect of the Invention) As described above, according to the combustion chamber structure of the sub-chamber diesel engine of the present invention, the air on both sides of the guide recess can be mixed with the combustion gas, and the air necessary for combustion can be fully utilized. Therefore, there is an effect that ideal combustion can be performed and smoke generated in the exhaust gas due to excess fuel in a part of the main chamber can be reduced. Further, since the air from the auxiliary guide groove guides the combustion gas introduced from the guide recess to the substantially circular recess into the substantially circular recess, the combustion gas around the connecting portion between the guide recess and the substantially circular recess is Turbulence is suppressed, and the combustibility of the air-fuel mixture in the main chamber can be further improved.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a plan view of a piston, FIG. 2 is a perspective view of the upper surface of the piston, and FIG. 3 is a III-III line of FIG. 4 is a vertical cross-sectional view of FIG. 4, FIG. 4 is a graph comparing smoke generation amounts of the conventional structure and the present invention, and FIG. 5 is a plan view of a piston of a conventional subchamber diesel engine. 1 ... piston, 1a ... top surface, 2 ... substantially circular recess, 3
…… Guide recess, 4 …… Auxiliary guide groove.

Claims (2)

[Scope of utility model registration request] 1. A guide recess extending from the position corresponding to the injection hole portion of the auxiliary chamber toward the center of the main chamber on the upper surface of the piston of the auxiliary chamber diesel engine, and a guide recess formed on both sides of the guide recess. Circular recesses are formed on both sides of the guide recess, extending toward the center of the piston upper surface so as to form a predetermined angle with the extension direction of the guide recess, and substantially circular with the guide recess. A combustion chamber structure for a sub-chamber diesel engine, characterized in that an auxiliary guide groove, one end of which opens, is formed in the vicinity of the continuous portion with the recess. 2. The combustion chamber structure for a sub-chamber diesel engine according to claim 1, wherein the auxiliary guide groove is partly defined by a guide recess and a partition wall.