JP2562600Y2 - Two-valve diesel engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-valve diesel engine in which a multi-hole nozzle is offset from a combustion chamber of a piston.

[0002]

2. Description of the Related Art In general, in a two-valve diesel engine in which intake and exhaust are covered by one intake valve and one exhaust valve, intake ports and exhaust ports are designed to maximize the volumetric efficiency of the intake and exhaust ports. However, in this case, the combustion chamber of the piston and the multi-injection nozzle must be provided at a position offset from the center axis of the cylinder. It must be installed at an angle to the combustion chamber.

[0003]

However, with the above construction, the inclination angle between the axis of the multi-hole nozzle and the injection hole and the distance between the injection hole and the cavity peripheral wall surface differ for each injection hole. Therefore, there is a problem that the speed of the fuel spray when colliding with the wall surface of the combustion chamber and the spatial fuel injection amount become non-uniform, so that the combustion is deteriorated, and the smoke and the fuel consumption are deteriorated.

[0004] A proposal has been made to improve the dispersion and distribution of fuel spray by forming the peripheral wall surface of the cavity at substantially the same distance from the center of the multi-injection nozzle ("Piston head structure of direct injection diesel engine"). (59-18225)
No.)) is made, but in order to make the concentration of the air-fuel mixture on the multi-nozzle nozzle side as uniform as the other parts, the depth of the cavity must be increased, but in this case, There was a problem of buffering with the connecting rod and it could not be easily adopted.

[0005] An object of the present invention is to make the distribution and distribution of fuel spray to the combustion chamber uniform in a two-valve diesel engine and to improve the mixing with air.

[0006]

In order to achieve the above object, the present invention relates to a diesel engine having a multi-hole nozzle provided with a multi-hole nozzle inclined with a nozzle opening facing a cavity formed in a piston top surface. The peripheral side wall portion of the cavity comprises a vertical surface portion along the axial direction of the piston, and a semicircular curved surface portion continuous with both ends of the vertical surface portion. It has a large number of injection holes for dispersing and spraying fuel spray only on the surface portion and is provided at the center position of the radius of the curved surface portion, and the radius of curvature of the curved surface portion is
The radius is set so that the flight distances of the fuel sprays ejected from the respective injection holes are equal to each other.

[0007]

With the above construction, the flight distance and the spray speed of the fuel spray between the injection hole and the curved surface portion are the same in each injection hole, and the spray angle is substantially the same. Therefore, the distribution and distribution of the fuel spray to the combustion chamber becomes uniform, and the smoke,
Fuel economy is greatly improved compared to conventional two-valve diesel engines.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a plan view of a combustion chamber of a direct injection diesel engine according to the present invention, and FIG. 2 is a sectional view taken along the line II-II of FIG.

In FIG. 1, reference numeral 1 denotes a large-diameter intake port formed in a cylinder head (not shown), and 2 denotes a large-diameter exhaust port formed in a cylinder head.
The combustion chamber 3 is defined by a cavity 6 formed by recessing the piston top surface 5 of the piston 4 downward in the axial direction. The cavity 6 has a peripheral wall portion formed of a vertical surface portion 7 along the axial direction of the piston 4 and a semicircular curved surface portion 8 continuous with both ends of the vertical surface portion 7.
The multi-hole nozzle 9 has its nozzle hole portion 10 positioned at the center O of the radius of the curved surface portion 8 and is attached to the cylinder head at an angle. By the way, the multi-hole nozzle is provided at the nozzle tip (injection portion) of the hole type nozzle with an interval in the circumferential direction for the purpose of making the distribution and distribution of the fuel spray to the cavity 6 uniform. In general, a fuel injection nozzle having a structure in which fuel spray is simultaneously ejected from a large number of injection holes in different directions in the combustion chamber 3 is used, such as a type in which a plurality of fuel injection nozzles are formed.
The configuration of the multi-hole nozzle 9 differs from that of a normal multi-hole nozzle in the following point. That is, the multi-injection nozzle 9 of the present invention has a large number of injection holes 11 provided in the injection hole portion 10 instead of a large number of injection holes 11 formed over the entire circumference as in the related art. In order to spray the fuel spray only to the curved surface portion 8 including the contact portion with the portion 8, the injection hole portion 1
The injection holes 11 are formed at intervals only in the half-circumferential portion on the side of the curved surface portion 8 (the position of the injection holes 11 with respect to the injection hole portion 10 is determined by swirling air or the like that stirs the inside of the combustion chamber 3). Determined in consideration of flow). For this multi-hole nozzle 9, the radius of curvature R of the curved surface portion 8 is set to a radius that makes the flight distances L of the fuel sprays F injected from the respective injection holes 11 equal to each other. Further, in the present invention, as shown in FIG. 1, in order to effectively utilize the air in the cavity 6 to generate a mixture having a uniform concentration in the entire combustion chamber 3,
The fuel spray F
To squirt. In such a case, unlike the case of injecting the fuel spray F into the other part of the cavity 6, the diffusivity of the fuel spray F itself is taken into consideration, and the HC
It is necessary to prevent the fuel spray F from excessively adhering to the vertical surface portion 7 as a liquid film in order to prevent the generation. For this reason, in the present invention, the concave portion 12 having a depth corresponding to the diffusion of the fuel spray F itself is formed in the vertical surface portion 7 so as to be divergent.

Therefore, the flight distance L and the spray speed of the fuel spray F between the injection hole 11 and the curved surface portion 8 are the same in each injection hole 11, and the spray angle is substantially the same in each injection hole 11, so that the combustion chamber The dispersion / distribution of the fuel spray F with respect to No. 3 is uniform, and the smoke and fuel consumption are greatly improved as compared with the conventional two-valve diesel engine.

In FIG. 1, a cavity 6a indicated by a chain line
FIG. 1 shows an example in which the vertical surface portion 7 is appropriately retracted radially outward with respect to the multi-injection nozzle 9 to form a combustion space for pilot injection, and a cavity 6 indicated by a two-dot chain line in FIG.
b shows an example in which the combustion space for pilot injection is fan-shaped.

[0013]

[Effects of the Invention] As is apparent from the above description, the present invention exerts the following excellent effects.

The flight distance, spray speed, and spray angle of the fuel spray are the same at each injection port, and the dispersion and distribution of the fuel spray to the combustion chamber become uniform. Therefore, smoke and fuel efficiency can be greatly improved as compared with the conventional two-valve diesel engine.

[Brief description of the drawings]

FIG. 1 is a plan view of a two-valve diesel engine according to the present invention.

2 is a II-II line cross-sectional view taken along FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

 Reference Signs List 4 piston 5 piston top surface 6 cavity 7 vertical surface portion 8 curved surface portion 9 multiple injection nozzle 11 injection hole F fuel spray O center of curved surface portion R radius of curvature

Claims (1)

(57) [Scope of request for utility model registration] In a diesel engine in which a multi-hole nozzle is provided with a nozzle opening facing a cavity formed in a top surface of a piston, a peripheral side wall portion of the cavity extends along the axial direction of the piston. The multi-injection nozzle has a large number of injection holes for dispersing the fuel spray only in the curved surface portion and comprising a semicircular curved surface portion continuous with both ends of the vertical surface portion. Is provided at the center position of the radius of the curved surface portion, the radius of curvature of the curved surface portion,
A two-valve diesel engine wherein the radii of fuel sprays ejected from the injection holes are set to be equal to each other.