GB2104150A

GB2104150A - I.C. Engine fuel injection nozzles

Info

Publication number: GB2104150A
Application number: GB08220203A
Authority: GB
Inventors: Christopher John Ernest Moody; David Michael Harvey
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1981-07-22
Filing date: 1982-07-12
Publication date: 1983-03-02
Also published as: IT1152442B; FR2510197A1; DE3227173A1; IT8222535A0; JPS5825568A

Abstract

The nozzle bore defines a seating 17 adjacent the outlet 15 and the valve member 18 has a shaped portion 22 which extends from a conical portion 21 through the outlet. The shaped portion 22 defines a clearance with the outlet 15 and the conical portion 21 at or adjacent its end nearer to the outlet defines a seating edge for engagement with the seating 17. The increase in the area of the valve member which is exposed to fuel pressure, which occurs as the valve member is lifted from the seating is minimised as compared with known constructions in which the seating edge is disposed at the end of the conical portion remote from the outlet. <IMAGE>

Description

SPECIFICATION Fuel injection nozzles This invention relates to fuel injection nozzles for supplying fuel to internal combustion engines, the nozzles being of the kind comprising a nozzle body, a bore formed in the body and extending to a fuel outlet, a seating defined in the bore adjacent to the outlet, a valve member located within the bore, said valve member having a portion shaped to define a seating edge for engagement with said seating to prevent the flow of fuel through the outlet, resilient means for biasing the valve member into contact with said seating, the valve member mounting a shaped projection which extends through said outlet and the valve member also defining a surface against which fuel under pressure can act to lift the valve member from the seating, said shapedprnjection acting to modify the area of the flow path through which fuel can flow as the valve member is lifted from its seating.

Such nozzles are known in the art as "pintle" nozzles. In order to ensure stability at engine idling speeds, the overlap of the aforesaid projection and the portion of the wall of the bore which defines the outlet is of such length as to ensure the correct restriction to the flow of fuel.

When the valve member has to open to allow a larger flow of fuel as for example when the engine is operating on full load, a finite time is required for the projection to be withdrawn a sufficient amount to allow the increased flow of fuel and during this time the flow of fuel is at a restricted rate. In the past it has been the practice to arrange that the aforesaid seating edge is positioned at or adjacent the end of the conical portion remote from the outlet. As a result for a given pressure, as the valve member moves away from the seating there has been a substantial increase in the area of the valve member exposed to the pressure with the result that the force acting to open the valve member increases. The length of the overlap has been chosen to take this into account.

The object of the present invention is to provide a fuel injection nozzle of the kind specified in an improved form.

According to the invention a fuel injection nozzle of the kind specified is characterized in that the seating edge is positioned at or adjacent the end of the conical portion nearer to the outlet.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic sectional view of part of the nozzle and Figure 2 is a view to an enlarged scale of part of the nozzle seen in Figure 1.

Referring to the drawings the fuel injection nozzle comprises a nozzle body 10 in which is defined a cylindrical bore 11. The body 10 is adapted by the provision of a step 12, to be secured to a nozzle holder which is provided with a fuel inlet. The passage in the holder connects the fuel inlet with a supply passage 13 in the nozzle body 10 and the passage 13 communicates with a gallery 14 defined by an enlarged portion of the bore 11.

The bore communicates with an outlet 1 5 which as shown in Figure 2, has a wall 16 of right cylindrical form. Leading into the outlet 1 5 is a truncated conical seating 17.

Slidable within the bore 11 is a valve member 1 8 which at its end remote from the outlet 1 5 has a extension 1 9 of reduced diameter which is engaged by a spring abutment which is located in a chamber in the nozzle holder. The spring abutment is engaged by a coiled compression spring to urge the valve member 1 8 towards the seating.

At its lower end the valve member is of reduced diameter so as to define a surface 20 against which the fuel pressure in the supply gallery 14 can act to provide a force to move the valve member against the action of the spring.

The reduced portion of the valve member has a truncated conical portion 21 from which extends a projection generally indicated at 22. The projection defines a cylindrical portion 23 adjacent the conical portion 21 and this is followed by a first tapering portion 24, a second tapering portion 25 and a third tapering portion 26. The junction between the cylindrical portion 23 and the first tapered portion 24 coincides with the junction of the seating 1 7 and the right cylindrical wall 16. It will be noted that the cylindrical portion 23 is smaller in diameter than the diameter of the wall 16 so as to leave a clearance.

An important aspect of the nozzle is the fact that the truncated conical portion 21 of the valve member contacts the seating 1 7 at a position close to the junction of the seating with the cylindrical wall 1 6. In use, when fuel under pressure is supplied to the chamber 14 the fuel pressure acts upon the surfaces of the valve member in particular the surface 20 and substantially the whole of the surface of the truncated conical portion 21, to create a force which urges the valve member against the action of the spring.As the seating edge defined by the truncated conical portion 21 lifts from the seating, there is a slight increase in the area of the valve member which is exposed to the fuel pressure but this is less than in known nozzles of this type in which the seating edge is positioned at or adjacent the wider end of the truncated conical portion 21. As a result of this modification, as the valve member lifts from its seating the increase in force applied to the valve member will be very much less than in the case with known constructions. The overlap between the cylindrical wall 1 6 and the tapered portions of the valve member therefore does not have to be so great as with the known constructions in order to maintain the same control over the effective area of the clearance defined between the cylindrical wall 1 6 and the tapering portions in particular the portion 24. When the associated engine is operating at full load, the amount of lift of the valve member which is required to withdraw at least the tapering portion 24 from the outlet, is reduced and hence the time required is also reduced. This means thdt the time during which fuel is supplied by the nozzle at the restricted rate is also reduced.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising a nozzle body, a bore formed in the body and extending to a fuel outlet, a seating defined in the bore adjacent the outlet, a valve member located within the bore, said valve member having a portion shaped to define a seating edge for engagement with said seating to prevent the flow of fuel through the outlet, resilient means for biasing the valve member into contact with said seating, the valve member mounting a shaped projection which extends through said outlet and the valve member also defining a surface against which fuel under pressure can act to lift the valve member from the seating, said shaped projection acting to modify the area of the flow path through which fuel can flow as the valve member is lifted from its seating, characterized in that the seating edge is positioned at or adjacent the end of said portion nearer the outlet.

2. A nozzle according to claim 1 in which said portion is of conical form.

3. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described.