JPH10318097A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further form fuel spray in the space part of the lower side of umbrella-like fuel sprays by composing a guiding surface for forming mushroom- like fuel spray out of a plurality of surfaces having different positions from one another in the axial direction of a nozzle. SOLUTION: A needle valve has a shaft part, and the protruded end part 3a of the shaft part is protruded from the tip part of a nozzle body. A guiding part 4 is provided in the protruded end part 3a. The height position of a guiding surface in the nozzle axial direction is made different by an amount equal to a level difference (h) and formed into two stage of a guiding surface 41a for forming an upper surface and a guiding surface 41b for forming a middle stage surface. The guiding surface 41a is formed to be inclined gently downward at an angle α, and the guiding surface 41b is formed to be inclined gently downward at an angle β smaller than the angle α. By the action of the guiding part 4, fuel is mixed with air well by forming the two stages of a mushroom-like fuel spray Fa and a fuel spray Fb radically expanded downward. Thus, an air utilization rate in a combustion chamber can be increased, and smoke is reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle for injecting fuel into a cylinder of an engine, and more particularly, to a fuel injection nozzle capable of spraying the injected fuel widely into a combustion space in an umbrella shape. Is what you do.

[0002]

2. Description of the Related Art In a multi-hole hole nozzle of a general engine, a plurality of injection holes are radially opened from the axis of the nozzle, so that it is impossible to spread the fuel spray in the combustion space as a whole. In addition, there is a problem that the distribution becomes uneven and the fuel spray and the air cannot be mixed well, so that the air utilization rate in the combustion chamber cannot be increased.

In order to make the spatial distribution of the fuel spray uniform, it is conceivable that the diameter of each injection hole is made smaller and the number of the injection holes is increased. Due to the above restrictions, the number of the injection holes is limited. Therefore, Japanese Patent Application Laid-Open No. 4-27875 proposes a fuel injection nozzle provided with a guide portion having a larger diameter than the injection hole at the tip of the needle valve. In the fuel injection nozzle described in this publication, the fuel injected from the injection hole forms an umbrella-shaped spray with the guide portion at the top, so that the cylinder circle is larger than a general multi-injection hole nozzle. The spatial distribution of the spray in the circumferential direction is improved.

Further, in recent years, according to Japanese Patent Application Laid-Open No. 7-317588, fuel is injected relatively early in the intake stroke or the compression stroke to form a mixture in the cylinder in advance, and the air-fuel mixture is simultaneously formed around the compression top dead center. A combustion-type diesel engine that ignites is studied. Also in this publication, a fuel injection nozzle provided with a guide portion at the tip of a needle valve is used as shown in FIG. 6 of the publication to uniformly form an air-fuel mixture in a cylinder.

[0005]

However, the above-mentioned Japanese Patent Application Laid-Open No.
In any of the fuel injection nozzles of Japanese Patent No. 27785 and Japanese Patent Application Laid-Open No. 7-317588, fuel injected from the main injection hole at the tip of the nozzle body collides with the guide portion and spreads in an umbrella shape in the circumferential direction in the cylinder. To form a fuel spray.

However, this fuel spray is merely an umbrella-shaped area that collides with and scatters on the upper surface of the guide portion, and no fuel is supplied to a lower portion thereof. There is a problem that it is not possible to widely disperse the fuel mixture in a space portion further below the fuel-air mixture, in other words, below the umbrella-shaped fuel spray, that is, in the longitudinal direction of the cylinder.

The present invention solves the problem that the conventional fuel injection nozzle can form an umbrella-shaped fuel spray but cannot form a fuel spray in a space below the fuel spray nozzle. It is an object to provide an injection nozzle.

[0008]

A fuel injection nozzle according to the present invention for achieving the above object has a nozzle body having an injection hole opened at a tip end in a nozzle axial direction, and a fuel injection nozzle for opening and closing the injection hole. A needle valve housed in the nozzle body so as to be liftable, the needle valve being inserted into the injection hole and protruding to the outside, and provided at a protruding end of the shaft portion; A guide portion formed with a larger diameter than the portion, and the guide portion further scatters fuel injected from the injection hole in an inner circumferential direction of the cylinder to form an umbrella-shaped fuel spray. The guide surface is configured by a plurality of surfaces having different positions in the nozzle axis direction, and by changing the position of the arc-shaped fuel spray radiated from each guide surface in the nozzle axis direction, Injects fuel in stages to spray fuel throughout the combustion chamber Kill.

A nozzle body having an injection hole opened at a tip end portion in a nozzle axial direction; and a needle valve housed in the nozzle body so as to be liftable to open and close the injection hole,
The needle valve has a shaft portion inserted into the injection hole and protruding to the outside, and a guide portion provided at a protruding end of the shaft portion and having a larger diameter than the shaft portion, Further, the guide portion has a guide surface that scatters the fuel injected from the injection hole in the inner circumferential direction of the cylinder to form an umbrella-shaped fuel spray, and the guide surface is different from the nozzle axial direction. It is constituted by a plurality of surfaces having an inclination angle. By changing the injection angle of the arc-shaped fuel spray radiated from each guide surface, it is possible to spray the fuel in the entire combustion chamber.

[0010] Alternatively, the plurality of surfaces constituting the guide surface are formed by connecting adjacent surfaces with a predetermined step.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a fuel injection nozzle according to the present invention, in which a needle valve 2 is inserted into a hole 6 of a cylindrical nozzle body 1 having a reduced end and a valve seat 5 formed at an intermediate portion. The needle valve 2 is lifted by the pressure of the high-pressure fuel supplied to the space between the nozzle body 1 and the needle valve 2, and the injection hole 7 opened at the reduced tip portion 1a The fuel is injected into the cylinder.

The needle valve 2 has a shaft portion 3 at a tip portion 2a reduced in a conical shape, and a projecting end portion 3a of the shaft portion 3 projects from a tip portion 1a of the nozzle body 1, and the projecting end portion 3a
Is provided with a guide portion 4 applied in the present invention. As shown in FIG. 2, the guide portion 4 has a larger diameter than the injection hole 7 and, with respect to a surface on the injection hole 7 side, a guide surface 41 formed by being divided in the circumferential direction at every angle θ, for example. The height of the guide surface 41a forming the upper surface and the guide surface 41b forming the middle surface are changed by changing the height position in the 1c direction by the step h.
Form in steps.

That is, the plurality of surfaces constituting the guide surface 41 are formed by connecting adjacent surfaces with a predetermined vertical interval, that is, a step h. The upper and lower steps may be provided stepwise or may be connected by a curved surface.
Further, the angle of the guide surface 41a with respect to the direction of the nozzle axis 1c is α and is formed to be gently inclined downward, and the angle of the guide surface 41b with respect to the direction of the nozzle axis 1c is an angle α.
It is formed to be gently inclined downward at a smaller angle β.

The periphery of the guide portion 4 is formed by a conically reduced side surface 4b extending in the direction of the axis 1c of the needle valve 2 from the periphery of the guide surface 41a. That is, the guide portion 4 is formed in a truncated cone shape having a smaller diameter toward the lower side in the drawing. The guide portion 4 is connected to the lower end of the protruding end portion 3a of the shaft portion 3 by brazing or the like. In this assembled state, the needle valve 2 cannot be pulled out of the nozzle body 1.

According to the fuel injection nozzle having the above configuration, the fuel F is injected from the tubular passage between the injection hole 7 and the shaft portion 3 in FIG. 1 as shown by a mark f in FIGS. Then, the fuel sprays Fa and Fb are changed in direction by colliding with the guide surfaces 41a and 41b of the guide portion 4 and spread in steps in the circumferential direction of the guide portion 4 to form umbrella-shaped fuel sprays Fa and Fb in the cylinder.

That is, a part of the fuel F injected into the tube from the injection hole 7 of the fuel F is reflected by the guide surface 41a forming the upper surface of the guide portion 4 and spreads in the cylinder in the circumferential direction to spread the fuel spray. Fa is formed in an umbrella shape at the angle α, and the remaining portion of the fuel F is ejected radially from the middle surface 41b at an angle β with respect to the axis 1c.

Accordingly, the fuel F is formed into two stages of an umbrella-shaped fuel spray Fa and a fuel spray Fb radially spreading below the fuel spray F by the action of the guide portion 4 provided at the tip of the needle valve 2 so that the fuel F is favorably combined with the air. As a result, when applied to a normal diesel engine, the air utilization rate in the combustion chamber can be increased, smoke can be reduced, and a uniform preheating method as disclosed in JP-A-7-317588 can be achieved. When applied to a mixed combustion diesel engine, stable ignition can be obtained.

The predetermined step h and the inclination angles α and β
Is determined by experiments and calculations so as to optimize the distribution of the fuel sprays Fa and Fb spreading in the cylinder. In addition,
In the above-described embodiment, the one in which one middle surface is formed on the side surface 4b of the guide portion 4 is shown. However, a larger number of middle surfaces may be formed. By changing only the distance in the direction of the axis 1c, a plurality of guide surfaces 4
1a, 41b, 41c and the like may be formed.

Alternatively, a plurality of guide surfaces 41 having different inclination angles α, β, γ, etc., with respect to the direction of the nozzle axis 1c, with the same position in the direction of the nozzle axis 1c.
a, 41b, 41c and the like.

[0020]

According to the fuel injection nozzle of the present invention, the fuel injected into the cylinder from the injection hole is reflected on the guide surface of the guide portion in the circumferential direction of the cylinder to form an umbrella-shaped fuel spray. I do. At this time, by changing the position and inclination angle of the guide surface in the nozzle axis direction, the direction and height of the fuel spray can be changed, so that substantially uniform fuel can be sprayed uniformly throughout the combustion chamber. Can be.

Therefore, the fuel injection nozzle of the present invention can spray fuel so as to be distributed throughout the combustion chamber and sufficiently mix it with air in the combustion chamber. The air utilization can be increased, and smoke can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a fuel injection nozzle.

FIGS. 2A and 2B are diagrams showing a shape of a guide portion and a fuel spray state, wherein FIG. 2A is a perspective view and FIG. 2B is a longitudinal sectional view.

3A and 3B are diagrams showing a shape of a guide portion and a fuel spray state according to another embodiment, wherein FIG. 3A is a perspective view, FIG. 3B is a plan view, and FIG. It is an XX sectional view enlarged view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Nozzle body 1a ... Tip part of nozzle body 1c ... Axis line 2 ... Needle valve 2a ... Tip part 3 ... Shaft part 3a ... Protruding end part 4 ... Guide part 4b ... Side surface 5 ... Valve seat 6 ... Hollow part 7 ... Injection hole 41, 41a, 42b, ... Guide surface F, Fa, Fb ... Fuel spray

Claims (3)

[Claims] 1. A nozzle body having an injection hole opened at a tip end in a nozzle axis direction, and a needle valve housed in the nozzle body so as to be liftable to open and close the injection hole, wherein the needle valve is A shaft portion inserted into the injection hole and protruding to the outside, and a guide portion provided at a protruding end of the shaft portion and having a larger diameter than the shaft portion, further comprising the guide portion Has a guide surface that scatters the fuel injected from the injection hole in the inner circumferential direction of the cylinder to form an umbrella-shaped fuel spray,
The fuel injection nozzle, wherein the guide surface includes a plurality of surfaces having different positions in the nozzle axis direction. 2. A nozzle body having an injection hole opened at a tip end portion in a nozzle axial direction, and a needle valve housed in the nozzle body so as to be liftable to open and close the injection hole, wherein the needle valve is A shaft portion inserted into the injection hole and protruding to the outside, and a guide portion provided at a protruding end of the shaft portion and having a larger diameter than the shaft portion, further comprising the guide portion Has a guide surface that scatters the fuel injected from the injection hole in the inner circumferential direction of the cylinder to form an umbrella-shaped fuel spray,
A fuel injection nozzle in which the guide surface is constituted by a plurality of surfaces having different inclination angles with respect to the nozzle axis direction. 3. The plurality of surfaces constituting the guide surface are connected such that adjacent surfaces have predetermined steps.
Or the fuel injection nozzle according to 2.