GB2215397A

GB2215397A - I.C. engine fuel injection nozzle

Info

Publication number: GB2215397A
Application number: GB8804510A
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: GB8804510D0

Abstract

A valve member 22 is slidable within a sleeve 19 which is slidable within a bore 11 formed in a nozzle body. The valve member terminates short of the end of the sleeve and within the sleeve and engageable with the valve member is a push piece 24 having a flange 29. The push piece transmits the force exerted by a spring to the valve member. When fuel under pressure is supplied to the nozzle the fuel pressure acts on the valve member and the sleeve to move them against the action of the spring. The movement of the sleeve is halted by its engagement with a stop surface 16 and the further movement of the valve member is halted by the engagement of the flange 29 with the stop surface. <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 terminates within the sleeve and there is mounted within the sleeve a flanged push piece which transmits the force exerted by the resilient means to the valve member, the sleeve defining an internal step for engagement with one side of the flange of the push piece, the other side of the flange being engageable with said surface 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. The opposite end of the valve member terminates within the sleeve and there is provided a flanged push piece 24 which is engageable by the valve member directly orthrough a shim 25. The push piece has an integral extension which is 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. The flange 29 of the push piece can engage with the surface 16 or with a step 30 defined on the sleeve.The sleeve 19 in known manner is provided with openings 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 step 30 of the sleeve into engagement with the flange 29 so that the force acting on the sleeve supplements the force acting on 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 29 with the surface 16.

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 the adjustment can be effected by grinding the face of the push piece 24 presented to the valve member or by providing the shim 25. With the valve member in the closed position the depth below the end surface of the body 10 which engages the surface 16 is measured and knowing the required lift of the valve member in the first stage of operation, the depth of the step 30 below the end surface of the sleeve and the length of the lower section of the push piece within the sleeve, the thickness of the shim can be calculated. If the shim is not to be used, the desired length of the lower section of the push piece can be calculated. Once the lift of the valve member in the first stage has been set the total lift of the valve member is adjusted by grinding the face of the flange 29 presented to the surface 16. The required thickness of the flange can be determined by calculation. Alternatively shims may be interposed between the surface 16 and the flange 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, said valve member terminating within the sleeve, a flanged push piece mounted within the sleeve, the push piece transmitting the force exerted by the resilient means to the valve member, and the sleeve defining an internal step for engagement with one side of the flange of the push piece, the other side of the flange being engageable with said surface to limit the movement of the valve member.

2. A nozzle according to Claim 1 in which said sleeve is provided with a flange which is located within a recess in the nozzle body.

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.