JPH04252861A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To adjust the decentering of a needle valve automatically, in a fuel injection nozzle. CONSTITUTION:A ring guide 9 being housed in a fuel chamber and fitting the midway of a needle valve slidably, is installed separately from a nozzle body 1, and a joining area 15, having one end face 34 of this guide 9 slidably joined to this nozzle body 1, while such a spring 5 as pressing the guide 9 to this joined area 15 by dint of its energizing force is installed as well.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel injection nozzle installed in a direct injection diesel engine or the like.

0002

[Prior art and its problems] This type of fuel injection nozzle is equipped with multiple fuel injection holes, and if variations occur in the fuel spray from each injection hole, fuel atomization and mixing with air will deteriorate. As a result, the amount of smoke, particulates, or unburned HC emissions increases.

[0003] As a countermeasure for this problem, there has conventionally been a fuel injection nozzle shown in FIG. 3 (see Japanese Utility Model Application No. 61-53566).

To explain this, the nozzle body 4
A needle valve 42 that is lifted by fuel pressure introduced into a fuel chamber 44 is housed in the fuel chamber 1 . The nozzle body 41 has a fuel chamber 44.
A guide surface 46 that slides into contact with the protrusion 45 of the needle valve 42 is formed in a cylindrical shape and guides the conical end surface 47 of the needle valve 42 concentrically with the seat surface 48 of the nozzle body 41.

[0005]

However, during engine operation, the nozzle body 41 is partially exposed to high-temperature combustion gas in the combustion chamber and heat is transferred from the cylinder head, so the nozzle body 41 suffers thermal distortion. As a result, the friction of the needle valve 42 may increase or the needle valve 42 may become eccentric with respect to the seat surface 48 of the nozzle body 41. For this reason, when the needle valve 42 shown in the figure is closed, the sealing performance against the seat surface 48 is deteriorated, and when the needle valve 42 is lifted, shown as a solid line in the figure, the needle valve 42 is against the seat surface 48. This causes a problem in that the fuel spray that is eccentrically injected into the combustion chamber from each nozzle hole 49 varies, and the amount of smoke, particulates, or unburned HC discharged increases.

The present invention aims to solve these conventional problems.

[0007]

[Means for Solving the Problems] The present invention forms a seal hole in which a needle valve is slidably fitted in a nozzle body, and also forms a seat surface on which a conical end surface of the needle valve is seated. In a fuel injection nozzle that defines a fuel chamber between a hole and a seating surface for storing fuel led from a fuel pump to a nozzle hole, an annular shaped valve is housed in the fuel chamber and slidably fits in the middle of the needle valve. A guide is provided separately from the nozzle body, and a joint surface is formed to slidably join one end surface of the guide to the nozzle body, and an elastic body is interposed to press and bias the guide against the joint surface.

[0008]

[Operation] The needle valve is centered during the valve closing operation when the tip conical surface of the needle valve sits on the seat surface. When a slight eccentricity occurs between the seat surface and the needle valve due to thermal distortion of the nozzle body, a radial load is applied from the needle valve to the guide, and the position of the guide is corrected. Even if the needle valve lifts and separates from the seat surface, it is held in the centering position by the guide, so that the annular cross-sectional fuel flow path formed between the needle valve and the seat surface is maintained evenly. The fuel spray injected into the combustion chamber from each injection hole of the injection nozzle is evenly dispersed, promoting atomization of the fuel and mixing with air. When the needle valve is closed, no gap is created between the needle valve and the seat surface, and fuel leakage from the nozzle hole is prevented. As a result, smoke, particulates, or unburned H
C can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a fuel injection nozzle for a direct injection diesel engine will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a hollow nozzle body;
2 is a needle valve housed within this nozzle body 1.

A conical surface 21 protruding conically is formed at the tip of the needle valve 2, while a seat surface 11 conically recessed is formed on the nozzle body 1. A plurality of nozzle holes 8 radially open in this seat surface 11 and communicate with the combustion chamber of the diesel engine.

A cylindrical main guide part 22 is formed at the base end of the needle valve 2, and this main guide part 22 is formed in the nozzle body 1.
A sealing hole 12 is formed into which the holder is slidably fitted. A fuel chamber 4 is defined within the nozzle body 1 between the seal hole 12 and the seat surface 11, and fuel introduced through a passage 3 from a fuel pump (not shown) is stored in the fuel chamber 4.

A return spring (not shown) is provided on the base end surface of the needle valve 2, and when the pressure of the fuel introduced into the fuel chamber 4 increases in synchronization with engine rotation, the needle valve 2 resists the return spring. The conical surface 21 is pushed up and separated from the seat surface 11, and this high-pressure fuel is pushed up between the conical surface 21 and the seat surface 1.
The fuel is ejected from each nozzle hole 8 into the combustion chamber through an annular flow path defined between the nozzle holes 8 and 1.

[0014] In the middle of the needle valve 2, there is an auxiliary guide part 2 in the shape of an arc surface.
3 is formed, while this auxiliary guide part 2 is formed in the fuel chamber 4.
An annular guide 9 into which the nozzle body 3 is slidably fitted is provided separately from the nozzle body 1. The inner circumferential surface 31 of the guide 9, together with the seal hole 12, performs a centering function for guiding the needle valve 2 concentrically with the seat surface 11 of the nozzle body 1.

A pair of notched surfaces 25 are formed in the auxiliary guide portion 23, and fuel flows through the gap between the notched surfaces 25 and the guide 9.

A hole 13 for accommodating the guide 9 is formed in the nozzle body 1, and a joint surface 15 is formed at the bottom of the hole 13 to slidably join the lower end surface 34 of the guide 9. An annular groove 19 is formed in the middle of the hole 13, a snap ring-shaped stopper 6 is fitted into the annular groove 19, and an annular disc spring 5 is interposed between the stopper 6 and the upper end surface 33 of the guide 9. be done. The lower end surface 34 of the guide 9 is pressed against the joint surface 15 by the biasing force of the disc spring 5, and is held by the frictional force acting between the two.

The joint surface 15 is formed perpendicularly to the center line O of the nozzle body 1, and is formed on the inner circumferential surface 1 of the hole 13.
4 and the outer circumferential surface 32 of the guide 9, a predetermined gap 7 is defined, allowing the guide 9 to be slightly displaced.

Next, the operation will be explained.

The needle valve 2 is centered during the valve closing operation when the conical end surface 21 of the needle valve 2 is seated on the seat surface 11. When a slight eccentricity occurs between the seat surface 11 and the needle valve 2 due to thermal distortion of the nozzle body 1, etc., a radial load is applied from the needle valve 2 to the guide 9, and the position of the guide 9 is corrected. Ru. Even if the needle valve 2 is lifted and separated from the seat surface 11, it is held in the centering position by the guide 9, so that the annular cross-sectional fuel flow path formed between the needle valve 2 and the seat surface 11 is evenly distributed. is maintained. Thereby, the fuel spray injected into the combustion chamber from each nozzle hole 8 is uniformly diffused, and atomization of the fuel and mixing with air are promoted. When the needle valve 2 is closed, there is no gap between the needle valve 2 and the seat surface 11, and the nozzle hole 8
This prevents fuel leakage from the As a result, smoke, particulates, or unburned HC discharged from the engine can be reduced.

Another embodiment shown in FIG.
0 is interposed between the guide 9 and the needle valve 2. A seat surface 36 for seating the lower end of the coil spring 10 is formed at the upper end of the guide 9, and a seat surface 36 for seating the lower end of the coil spring 10 is formed in the middle of the needle valve 2.
A seat surface 26 is formed on which the upper end of the seat is seated.

In this case as well, the needle valve 2 is centered during the valve closing operation when the conical end surface 21 of the needle valve 2 is seated on the seat surface 11. When a slight eccentricity occurs between the seat surface 11 and the needle valve 2 due to thermal distortion of the nozzle body 1, etc., a radial load is applied from the needle valve 2 to the guide 9, and the position of the guide 9 is corrected. Ru. Note that the opening characteristic of the needle valve 2 can be maintained by increasing the spring load of the return spring that urges the needle valve 2 in the valve-closing direction in accordance with the spring load of the coil spring 10.

Furthermore, in this embodiment, the guide 9 and the coil spring 10 can be assembled into the nozzle body 1 relatively easily.

[0023]

[Effects of the Invention] As explained above, the present invention forms a seal hole in which a needle valve is slidably fitted in a nozzle body, and also forms a seat surface on which a conical surface at the tip of the needle valve is seated. In a fuel injection nozzle that defines a fuel chamber between the seal hole and the seat surface to store fuel led from the fuel pump to the nozzle hole, the needle valve is housed in this fuel chamber and is slidably fitted in the middle of the needle valve. An annular guide is provided separately from the nozzle body,
Since a joint surface is formed on the nozzle body to slidably join one end surface of this guide, and an elastic body is inserted to press and bias the guide against this joint surface, thermal distortion of the nozzle body may cause the seat surface and needle to Even if a slight amount of eccentricity occurs between the needle valve and the valve, the centering action of the guide automatically adjusts the amount of eccentricity with respect to the seat surface during lift, preventing deterioration of the needle valve's sealing performance and friction. By uniformly diffusing the fuel spray injected into the combustion chamber from each nozzle hole, smoke, particulates, or unburned HC discharged from the engine can be reduced. It also makes it possible to reduce the processing precision required for the nozzle body.
Product costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a fuel injection nozzle showing an embodiment of the present invention.

FIG. 2 is a sectional view of a fuel injection nozzle showing another embodiment.

FIG. 3 is a sectional view of a conventional fuel injection nozzle.

[Explanation of symbols]

1 Nozzle body 2 Needle valve 4 Fuel chamber 5 Disc spring (elastic body) 9 Guide 11 Seat surface 12 Seal hole 15 Joint surface 21 Conical surface

Claims (1)

[Claims] Claim 1: A seal hole is formed in the nozzle body into which the needle valve is slidably fitted, and a seat surface is formed on which the conical end surface of the needle valve is seated, and a space between the seal hole and the seat surface is formed. A fuel chamber is defined to store fuel led from the fuel pump to the nozzle hole, and an annular guide is provided separately from the nozzle body to be housed in the fuel chamber and slidably fit in the middle of the needle valve. A fuel injection nozzle characterized in that a joint surface is formed on the nozzle body to slidably join one end surface of the guide, and an elastic body is interposed to press and bias the guide against the joint surface.