JP2534248Y2 - Combustion chamber of vortex chamber diesel engine - Google Patents

Description

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

(Prior Art) As the main combustion chamber shape of a vortex chamber type diesel engine,
The one shown in FIGS. A and B is known. To explain this, a swirl chamber 5 provided in the cylinder head 4 is offset from the center of the cylinder and communicates with a main combustion chamber 9 through an injection port 6. A groove-shaped trench portion 26 extending radially from a region substantially directly below the opening of the injection port 6 on the main combustion chamber side;
A substantially circular cavity portion 10 extending to both sides from a region near the center of the piston 26 is formed, and these form a so-called cloverleaf cavity.

In this swirl chamber type combustion chamber structure, the air flowing from the main combustion chamber 9 to the swirl chamber 5 through the injection port 6 in the compression stroke forms a swirl (swirl). Combustion is started by injecting and supplying fuel to the vortex through an injection nozzle (not shown). With the start of fuel in the vortex chamber 5, the expansion gas and a part of the injected fuel are supplied through the injection port 6. It gushes into the main combustion chamber 9. The fuel in the ejected gas is guided toward the center of the main combustion chamber 9 along the trench 26 of the piston 3,
Further, as shown by the arrow a, the gas is diffused as a swirling flow into the cavity portions 10 on both sides. As a result, the fuel is mixed and burned with the air in the main combustion chamber substantially in the range indicated by the broken line in FIG. (Refer to, for example, Japanese Utility Model Laid-Open No. 57-174725 for a known example of this type of combustion chamber structure.) (Problems to be Solved by the Invention) However, such a conventional vortex chamber type combustion chamber has a problem. Since the trench 26 extends along the direction of the jet from the swirl chamber 5, the jet flowing radially from the injection port 6 along the trench 26 has a relatively large momentum, and the cavity 10 is Initially, the power of the jet diffusing to the side of the trench 26 becomes relatively weak. For this reason, especially near the base end of the trench portion 26 upstream of the jet and on both sides thereof, the mixing of fuel and air is insufficient, and the air utilization rate tends to decrease. This causes an increase in the concentration of the unburned fuel component in the exhaust during low load operation and an increase in the smoke concentration during high load operation.

The purpose of the present invention is to solve such conventional problems.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a vortex chamber type diesel engine in which an injection port from a vortex chamber is opened near a green portion of a main combustion chamber toward a substantially cylinder center direction. In the combustion chamber, the first diffusion promoting portion is raised on the piston top surface in an island shape so as to be located on the center line of the jet from the swirl chamber to the main combustion chamber when viewed from above, and the first A second diffusion enhancer having an outer shape whose vertex protrudes opposite to the jet is protruded at a position opposed to the injection port with the diffusion enhancer interposed therebetween, and a second diffusion enhancer is provided on the first diffusion enhancer. Forming a slope facing the portion.

(Function) In the above configuration, near the top dead center of the piston, the jet collides with the first diffusion promoting portion, diverges to the left and right with respect to the jetting direction of the jet, and diffuses in the main combustion chamber. The jet is sufficiently diffused to the side of.

As the piston descends, the jet flows onto the inclined surface formed in the first diffusion promoting section, collides with the second diffusion promoting section, and moves left and right with respect to the jet direction of the jet. Divide. Because the inclined surface is inclined to face the second diffusion promoting portion, without weakening the power of the jet,
The jet is sufficiently diffused to the side of the second diffusion promoting portion.

In this manner, the jet of the combustion gas containing the fuel is sufficiently diffused over a wide range of the main combustion chamber, so that the air in the main combustion chamber is effectively used and good combustion properties are obtained.

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing. Parts corresponding to FIGS. 2A and 2B are denoted by the same reference numerals as those in FIG.

In FIG. 1A or FIG. 1B, reference numeral 20 denotes a concave diffusion portion formed on the piston top surface 8, and in this case, from the trench portion 11 located immediately below the injection port 6, to the left and right substantially along the outline of the piston 3. It is surrounded by an upstream outer shell 20A that expands in a circle along the downstream side, and a downstream outer shell 20B that is symmetrically arranged with a circular arc across the center line 1 of the jet flow so as to face the upstream outer shell 20A.

Reference numeral 22 denotes a first diffusion promoting portion formed inside the concave diffusion portion 20 so as to be located on the jet center line l. As shown in FIG. 1B, the first diffusion promoting portion 22 has a shape protruding in an island shape from the bottom surface 20C of the diffusion portion 20 when viewed from the side, and The outer portion 22A has a substantially V-shaped and protruding shape.

Reference numeral 23 denotes a second diffusion promoting portion located on the side opposite to the injection port 6 with the first diffusion promoting portion 22 interposed therebetween.
The central portion of the downstream side outer shell 20B of the has a shape protruding in a substantially V-shape facing the injection port 6.

An inclined surface 22C facing the second diffusion promoting portion 23 is formed on the first diffusion promoting portion 22 without a step from the top surface 22B to the bottom surface 20C of the diffusion portion 20. The inclined surface 22C inclines the piston 3 at a predetermined angle so as to be parallel to the extension of the injection port 6 when viewed from the side.

Based on the above configuration, near the piston top dead center in the expansion stroke, the jet containing unburned fuel that has been ejected from the vortex chamber to the main combustion chamber via the injection port 6 first flows into the injection port 6 as indicated by the general arrow A. It collides with the V-shaped outer portion 22A of the first diffusion promoting portion 22 located immediately downstream, diverges in the left-right direction, and spreads in a swirl shape in the downstream region after the diversion. In addition, the jet flowing over the first diffusion promoting section 22 has a slope 22C.
, And is diffused in the left-right direction by the second diffusion promoting unit 23 without weakening the power.

When the piston 3 descends to some extent, the intersection of the extension of the injection port 6 and the top surface 8 of the piston moves toward the center of the piston, so that the jet ejected through the injection port 6 is mainly subjected to the first diffusion as indicated by a substantially arrow B. After jetting on the inclined surface 22C of the accelerating portion 22, it collides with the second diffusion accelerating portion and diverges right and left with respect to the jetting direction of the jet. Since the inclined surface 22C is inclined toward the second diffusion promoting portion 23, the turbulence imparted to the jet is reduced, and the jet is guided to the second diffusion promoting portion 23, without weakening the power thereof. The jet is sufficiently diffused to the side of the diffusion promoting portion 23 as well.

In this manner, the jet of gas containing fuel ejected from the swirl chamber through the injection port 6 is supplied to the first and second diffusion promoting portions 22 and 2.
3, the diffusion area of the jet is extremely widened, so that the air in the main combustion chamber 9 can be sufficiently utilized for efficient combustion.

(Effects of the Invention) As described above, according to the present invention, the first and second diffusion promoting portions are raised on the top surface of the piston along the direction of the jet from the vortex chamber in an island shape, and the first diffusion promoting portion is formed. Formed an inclined surface facing the second diffusion promoting portion, so that the jet flow is reliably diffused through the first and second diffusion promoting portions, thereby increasing the air utilization rate over the entire area of the main combustion chamber. Therefore, the amount of unburned fuel during low-load operation and the amount of smoke discharged during high-load operation are significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a longitudinal sectional view of an essential part of an embodiment of the present invention, and FIG. 1B is a plan view of the piston. FIG. 2A is a longitudinal sectional view of a main part of a conventional example, and FIG. 2B is a plan view of the piston. 3 ... Piston, 4 ... Cylinder head, 5 ... Swirl chamber, 6 ... Injector, 8 ... Piston top surface, 22 ... First diffusion promoting part, 22B ... Top surface, 22C ... Slope surface , 23..Second diffusion promotion part.

Claims (1)

(57) [Scope of request for utility model registration] In a combustion chamber of a vortex-chamber diesel engine in which an injection port from a vortex chamber is opened in the vicinity of a green portion of a main combustion chamber toward a substantially central direction of a cylinder, a vortex is formed on a piston top surface when viewed from above. The first diffusion promoting portion is raised in an island shape so as to be located on the center line of the jet from the chamber to the main combustion chamber, and the vertex is located at a position opposed to the injection port with the first diffusion promoting portion interposed therebetween. A vortex flow characterized by projecting a second diffusion promoting portion having an outer shape protruding opposite to the jet, and forming an inclined surface facing the second diffusion promoting portion in the first diffusion promoting portion. Combustion chamber of a room-type diesel engine.