JPH0623714Y2 - Subchamber diesel engine combustion chamber structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a combustion chamber structure of a sub-chamber diesel engine including a sub-combustion chamber communicating with the main combustion chamber through a communication hole.

(Prior Art) Generally, an auxiliary chamber type diesel engine is provided with an auxiliary combustion chamber that communicates with the main combustion chamber through a communication hole, and jets from the auxiliary combustion chamber to the main combustion chamber through the communication hole on the upper surface of the piston. It is known that a cavity for diffusing a burning flame into the main combustion chamber is provided as a recess, and valve recesses (recesses) that are arranged in parallel in a direction perpendicular to the communication hole opening direction are arranged in the cylinder head when viewed from the top surface of the piston. (For example, JP-A-5
7-32009 gazette).

The shape of the cavity that is generally used is, as shown in FIG. 7, a communication hole (a nozzle) of the auxiliary combustion chamber.
Is a bilobal cavity d composed of a base portion a located below the base a and two enlarged portions b and c branched from the base portion a to the left and right. b and c are configured to have the same size, and one of the enlarged portions is below the intake valve and the other is below the exhaust valve due to the positional relationship with the auxiliary combustion chamber, the intake valve, and the exhaust valve provided in the cylinder head. The parts are arranged so as to partially overlap each other.

On the other hand, the intake / exhaust valve has its lower surface in the closed position in order to avoid hitting the piston f (see FIG. 8).
Valve recesses g and h communicating with the intake / exhaust port are formed below the intake / exhaust valve and have sizes corresponding to the diameters of the intake / exhaust valve, respectively, and are formed in the cylinder head between the valve recesses g and h. A valve bridge i is provided to prevent cracks between the valve recesses.

(Problems to be solved by the invention) However, in the conventional sub-chamber diesel engine as described above, as shown in FIG. 8, the space j between the cylinder head e and the piston f is narrow in the central portion thereof. ,
The flow direction of the vortex is regulated (see the arrow in FIG. 8), the air in the regions S ₁ and S ₂ of the valve recesses g and h separated from the cavity d with respect to the center of the piston f is not sufficiently used, and the fuel is not used. Smoke is generated in the high load area where the supply is large.

The present invention has been made in view of the above circumstances, and provides a combustion chamber structure of a sub-chamber diesel engine that can sufficiently use the air in the valve recess corresponding to the intake and exhaust ports and reduce smoke. The purpose is.

(Means for Solving the Problem) In order to achieve the above object, the present invention includes a sub combustion chamber communicating with a main combustion chamber through a communication hole, and a piston upper surface,
A cavity for diffusing a fire ejected from the sub-combustion chamber to the main combustion chamber through the communication hole into the main combustion chamber is provided as a recess, and a communication hole opening is formed in the cylinder head when viewed from above the piston. It is premised that a plurality of valve recesses arranged in a direction perpendicular to the direction are arranged at positions displaced from the communication hole opening side with respect to the cavity. The cylinder head between the valve recesses is provided with a recess for communicating the two valve recesses, and the opening edge of the recess on the communication hole opening side is positioned so that the recess overlaps with the cavity when viewed from the piston upper surface direction. , The opening end of the recess opposite to the communication hole opening side is configured to guide a part of the flame flow ejected into the cavity to the end of the valve recess opposite to the communication hole opening side. It is characterized in that it is smoothly connected to the edge of the communication hole opposite to the opening side.

(Operation) Accordingly, in the present invention, the combustion gas (combustion flame) ejected from the auxiliary combustion chamber into the cavity through the recess formed in the cylinder head between the valve recesses so as to overlap with the cavity on the upper surface of the piston is distributed over the entire valve recess. Expands and the air utilization rate increases.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, 1 is a cylinder block, 2
Is a cylinder formed by cutting or fitting a liner in the cylinder block 1, 3 is a piston arranged in the cylinder 2, and 4 is a cylinder head fixed to the upper part of the cylinder block 1.

Reference numeral 5 is a sub-combustion chamber serving as a substantially spherical swirl chamber.
The sub-combustion chamber 5 is facing the fuel injection nozzle (not shown).
Is communicated with a main combustion chamber 7 constituted by the upper surface 3a of the cylinder 2, the piston 3 and the lower surface 4a of the cylinder head 4 through a communication hole 6 as an injection port.

An intake / exhaust port (not shown) is arranged in the cylinder head 4 in parallel with a direction perpendicular to the opening direction of the communication hole 6 when viewed from the direction of the upper surface 3a of the piston 3, and the cylinder corresponds to the intake / exhaust port. Valve recesses 8 and 9 are formed as recesses that are recessed from the lower surface 4a of the head.

On the other hand, a cavity 10 having a certain depth is recessed in the upper surface 3a of the piston 3, and the cavity 10 includes a base portion 10a located below the opening of the communication hole 6 to the main combustion chamber 7, and the base portion 10a. It has a bilobal shape composed of two circular expanded portions 10b and 10c that branch to the left and right, that is, both valve recesses 8 and 9 and extend. The valve recesses 8 and 9 are provided at positions displaced from the cavity 10 on the side opposite to the opening side of the communication hole 6.

The enlarged portions 10b and 10c of the cavity 10 overlap with both valve recesses 8 and 9 when viewed from the upper surface direction of the piston 3, and the size thereof is such that the combustion gas ejected from the auxiliary combustion chamber 5 is enlarged portion 10b, It is preferable to make the size of the overlapping portion with both valve recesses 8 and 9 equal so that the flow is introduced into the valve recesses 8 and 9 substantially evenly through 10c.

Further, the cylinder head 4 between the valve recesses 8 and 9 is provided with a recess 11 which connects the valve recesses 8 and 9 with each other. The opening edge of the recess 11 on the opening side of the communication hole 6 is located so that the recess 11 overlaps with the cavity 10 when viewed from the upper surface direction of the piston 3,
The opening edge of the communication hole 6 opposite to the opening side is a part of the flame flow ejected into the cavity 10 and the valve recesses 8,
The valve recesses 8 and 9 are smoothly connected to the ends of the valve recesses 8 and 9 on the side opposite to the side where the communication hole 6 is opened so as to guide the end of the valve recess 9 to the side opposite to the side where the communication hole 6 is opened.

With the above configuration, the combustion gas (combustion flame) ejected from the sub-combustion chamber 5 is generated by the expanded portion 10 b of the cavity 10.
Since it is introduced into the entire area of the valve recesses 8 and 9 through the recess 10c and the recessed portion 11, air is sufficiently used throughout (see the arrow in FIG. 3).

That is, as shown in FIG. 4, the enlarged portions 10b, 10c
Since both sides of the valve overlap directly with the valve recesses 8 and 9, the combustion gas is expanded in the area where the combustion gas expands.
It directly flows into the regions of the valve recesses 8 and 9 near b and 10c. On the other hand, since the central portions of the enlarged portions 10b and 10c overlap the concave portion 11, the combustion gas flows into the region of the valve recesses 8 and 9 far from the enlarged portions 10b and 10c through the concave portion 11 in that portion. as a result,
The combustion gas spreads over the entire valve recesses 8 and 9.

Therefore, it is possible to sufficiently use the air in the region that could not be sufficiently used in the conventional configuration, improve the combustion in the main combustion chamber 7, and reduce the smoke.

Incidentally, FIG. 6 shows an example of the present invention and a conventional example (FIGS. 7 and 8).
The results of the tests compared with (see the figure) are shown.

The shape of the cavity 10 of the above embodiment is such that both enlarged portions 10b,
Although 10c has a bilobal shape that is a circular shape, both of the enlarged portions may have a polygonal shape, or the entire shape may have a heart shape.

(Effect of the Invention) Since the present invention is configured as described above, the entire air in the valve recess corresponding to the intake and exhaust ports can be fully utilized, the combustibility in the main combustion chamber is improved, and smoke is reduced. To be done.

[Brief description of drawings]

1 to 6 show an embodiment of the present invention, FIG. 1 is a bottom view of a main combustion chamber of a sub-chamber diesel engine, FIG. 2 is a sectional view taken along line II-II of FIG. 3 to 5 are explanatory views of the operation, FIG. 3 is a view similar to FIG. 1, FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3, and FIG. 5 is V- of FIG.
FIG. 6 is a sectional view taken along line V, showing the test results. 7 and 8 show a conventional example, FIG. 7 is a view similar to FIG. 1 for the conventional example, and FIG. 8 is a VIII-V of FIG.
It is a sectional view taken along the line III. 1 ... Cylinder block, 3 ... Piston, 4 ... Cylinder head, 5 ... Secondary combustion chamber, 6 ... Communication hole, 7 ... Main combustion chamber, 8, 9 ... Valve recess, 10 ... Cavity, 11 …… A recess.

Claims (1)

[Scope of utility model registration request] 1. A sub-combustion chamber communicating with the main combustion chamber through a communication hole, wherein a fire ejected from the sub-combustion chamber to the main combustion chamber through the communication hole is diffused to the upper surface of the piston. A cavity for allowing the cavity to be formed is provided in the cylinder head, and a plurality of valve recesses that are parallel to each other in the direction perpendicular to the opening direction of the communication hole when viewed from the top surface direction of the piston are opposite to the communication hole opening side with respect to the cavity. The cylinder head between the valve recesses is provided with a recessed portion that communicates with both valve recesses, and the opening edge on the communication hole opening side of the recessed portion is viewed from the piston upper surface direction. Is located so as to overlap with the cavity, and the opening edge of the recess on the side opposite to the communication hole opening side is used to open a part of the flame flow ejected into the cavity into the communication hole openings of both valve recesses. A combustion chamber structure of the pre-combustion chamber diesel engines, characterized in that it is smoothly connected to the opposite end edge and communicating hole opening side of the both valve recess to guide to the opposite side edge and.