GB2215395A

GB2215395A - I.C. engine fuel injection nozzle

Info

Publication number: GB2215395A
Application number: GB8804508A
Authority: GB
Inventors: Edward Robert Lintott
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1988-02-26
Filing date: 1988-02-26
Publication date: 1989-09-20
Also published as: GB8804508D0

Abstract

A valve member 22 provided with a flange 24 is slidable in a sleeve 19 slidable in a nozzle body 10. When fuel under pressure is supplied to the nozzle the valve member and sleeve are acted upon by the fuel under pressure to move against the action of a spring. The movement of the sleeve is halted by a stop surface 16 and the further movement of the valve member is halted by the abutment of the flange 24 with a further stop surface 29. <IMAGE>

Description

"FUEL INJECTION NOZZLE" This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine the nozzle being of the kind comprising an axially movable valve member, resilient means for urging the valve member into contact with a seating to prevent flow of fuel from an inlet to an outlet, the valve member being slidable within a sleeve which itself is slidable in a nozzle body, the sleeve and valve member defining surfaces against which the fuel pressure at the inlet can act to lift the valve member from the seating, the nozzle body being clamped against a part which defines a surface which is engaged by the sleeve to limit the movement of the sleeve so that the continued movement of the valve member away from the seating is due to the fuel pressure acting on the valve member, and means for limiting the movement of the valve member away from the seating.

Such nozzles are well known in the art and provide for two stages of lift of the valve member using a single spring only. The first stage of lift which is determined by the engagement of the sleeve with the surface allows for restricted flow of fuel to the engine and it is essential that the extent of lift should be very carefully controlled.

The object of the present invention is to provide a fuel injection nozzle of the kind specified in a form in which adjustment of the lift of the valve member in the first and second stages can be readily effected.

According to the invention in a fuel injection nozzle of the kind specified the valve member is provided with a flange, the face of the flange directed towards the seating being engaged by said sleeve so that the force generated by the fuel pressure acting on the sleeve is transmitted to the valve member through the flange until the sleeve engages with said surface, and the face of the sleeve remote from said seating engaging with a second surface on said part to limit the movement of the valve member.

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 part sectional side elevation of part of a fuel injection nozzle in accordance with the invention, and Figure 2 is a view to an enlarged scale of a portion of the nozzle seen in Figure 1.

Referring to Figure 1 of the drawings there is provided a nozzle body 10 of stepped cylindrical form in which is formed a stepped bore 11. Intermediate the wider and narrower portions of the bore there is formed an enlargement 12 to which liquid fuel under pressure is supplied by way of a passage 13 in the body and a further passage 14 which is formed in a distance piece 15 the latter defining a surface 16 presented to the nozzle body and against which the nozzle body is clamped by a cap nut. The distance piece 15 is clamped in turn to a nozzle holder which defines a continuation of the passage 14 and which also is provided with a fuel inlet connection to an outlet of a high pressure fuel injection pump. At the end of the narrower portion of the bore there is defined a seating 17 which surrounds an outlet diagrammatically illustrated at 18.

The wider portion of the bore accommodates a sleeve 19 which at its end remote from the enlargement is provided with a peripheral flange 20 which is accommodated with clearance within a recess 21 in the nozzle body. The surface 16 in the assembled condition of the nozzle extends over the recess 21 and, as will be explained, can be engaged by the flange 20 of the sleeve.

Slidable axially within the sleeve is an elongated valve member 22 which extends with clearance within the narrower portion of the bore and within this portion of the bore, is of slightly reduced diameter to define an annular surface 23. Moreover, the valve member is shaped for co-operation with the seating 17. At its opposite end, the valve member is provided with a flange 24 from which extends an extension 25 engaged by a spring abutment 26 the latter being engaged by one end of a coiled compression spring 27 which is located within a chamber formed in the aforesaid holder.

Between the flange and the main portion of the valve member, the latter is of slightly reduced diameter.

The flange 24 is located within a recess 28 formed in the distance piece 15 and the recess 28 defines a stop surface 29. The sleeve 19 in known manner is provided with openings 30 so that the working clearances between the sleeve and the wider portion of the bore 11 and between the valve member and the sleeve are connected to each other at intervals along the length of the sleeve.

The valve member is shown in the closed position in the drawings with the valve member in engagement with the seating 17. When fuel under pressure is supplied from the injection pump, the fuel under pressure acts upon the surface 23 to generate a force acting to move the valve member away from the seating against the action of the spring 27. Moreover, the pressure of fuel acting on the end of the sleeve in the enlargement also generates a force which moves the sleeve into engagement with the flange so that the force is transmitted to the valve member. When the two forces generated by the fuel under pressure are sufficient to overcome the force exerted by the spring the valve member is lifted from its seating and this movement will continue until the flange 20 of the sleeve engages the surface 16.The valve member is therefore lifted a limited extent from its seating and fuel can flow at a restricted rate through the outlet 18. As the fuel pressure continues to increase, the pressure acting on the surface 23 will eventually produce sufficient force so that the valve member can move alone against the action of the spring 27. The valve member therefore is lifted further from the seating to allow full flow of fuel to the associated engine and the extent of movement of the valve member is limited by the abutment of the flange 24 with the surface 29.

When the pressure at the inlet of the nozzle falls the valve member and the sleeve will return to the positions shown in the drawing.

The extent of movement of the valve member particularly in the first stage of operation is critical and in the present construction the adjustment of the movement of the valve member in the first stage and also in the second stage is obtained by grinding the opposite faces of the flange 24. Thus in order to determine the movement of the valve member in the first stage of operation, the surface of the flange 24 which is directed towards the seating is ground to provide the required clearance between the end of the flange 20 of the sleeve and the surface 16. The opposite face of the flange 24 is ground to determine the total movement of the valve member and it will be appreciated that the gap- in the closed position of a valve member between the flange 20 and the surface 16 is less than the gap between the flange 24 and the surface 29.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising an axially movable valve member, resilient means for urging the valve member into contact with a seating to prevent flow of fuel from an inlet to an outlet, the valve member being slidable within a sleeve which itself is slidable in a nozzle body, the sleeve and valve member defining surfaces against which the fuel pressure at the inlet can act to lift the valve member from the seating, the nozzle body being clamped against a part which defines a surface which is engaged by the sleeve to limit the movement of the sleeve so that the continued movement of the valve member away from the seating is due to the fuel pressure acting on the valve member, means for limiting the movement of the valve member away from the seating, a flange on the valve member, the face of the flange directed towards the seating being engaged by said sleeve so that the force generated by the fuel pressure acting on the sleeve is transmitted to the valve member through the flange until the sleeve engages with said surface, and the face of the sleeve remote from said seating engaging with a second surface on said part to limit the movement of the valve member.

2. A nozzle according to Claim 1 in which said means for limiting the movement of the valve member away from the seating comprises a further surface defined by said part.

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