GB2200689A

GB2200689A - I. C. engine fuel injection nozzle

Info

Publication number: GB2200689A
Application number: GB08801571A
Authority: GB
Inventors: Godfrey Greeves; Robert James Fry
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-02-06
Filing date: 1988-01-25
Publication date: 1988-08-10
Also published as: GB8801571D0

Abstract

The machined rib 27 formed on a distance piece 26 which is positioned between the nozzle body 10 and a holder 31 in which the spring 25 is located determines the lift of sleeve 14 and subsequently valve member 18. <IMAGE>

Description

"FUEL INJECTION NOZZLE" This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a nozzle body, a valve member which is movable axially by fuel under pressure supplied through a nozzle inlet, away from a seating to permit fuel flow from the inlet to an outlet, resilient means biasing the valve member into contact with the seating and stop means for limiting the movement of the valve member by fuel under-pressure.

A nozzle of the aforesaid kind but including in addition a sleeve surrounding the valve member, is known from British specification 2145468B and the aforesaid stop means is constituted by an end face of a nozzle body holder to which the nozzle body is secured in well known manner by means of a cap nut. The holder also defines a chamber to accommodate the resilient means which in the particular example is a coiled compression spring. The action of the sleeve is to lower the nozzle opening pressure and to allow a small movement of the valve member so that fuel is supplied to the associated engine at a restricted rate. When the movement of the sleeve is prevented by the stop means, continued movement of the valve member will require an increased fuel pressure at the inlet, the maximum movement of the valve member being limited by its engagement with the stop means.

It is essential in this example to be able to set accurately the movement of the sleeve and the valve member and when the stop means is constituted by the end face of the holder, measurement of the movement of the sleeve and the valve member is difficult since they are in effect located at the distant end of the chamber in the holder.

The object of the present invention is to provide a fuel injection nozzle of the aforesaid kind in a simple and convenie-nt form.

According to the invention an injection nozzle of the kind specified comprises a nozzle holder, a distance piece located between an end face of the nozzle body and an end face of the holder, said distance piece being provided with a central aperture through which extends means connecting the resilient means and the valve member, the distance piece defining a machined rib which defines a stop surface for the valve member, the arrangement being such that adjustment of the travel of the valve member is effected by altering the dimensions of said rib.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing which shows part of the injection nozzle in sectional side elevation.

The nozzle comprises a stepped nozzle body 10 in which is defined a stepped bore 11 the narrower end of the bore communicating with an outlet opening 12 which extends to the exterior of the body. Defined at this end of the bore is a seating 13 and axially slidable within the wider portion of the bore is a sleeve 14 which at its end adjacent the other end of the bore 11 is provided with an enlarged portion 15 which limits the extent of movement of the sleeve into the bore, the bore being slightly enlarged to accommodate the enlarged portion of the sleeve. At its opposite end the sleeve is provided with an inwardly extending portion 16 which is shaped for engagement with a step 17 defined on a valve member which is slidable within the bore in the sleeve.

The portion of the valve member which extends from the sleeve in the direction of the seating 13, is of smaller diameter than the narrower portion of the bore, to define an annular clearance 19 through which fuel can flow from a space 20 defined by the wider portion of the bore lying beneath the sleeve 14. This space communicates with a fuel inlet passage 21 which in use, communicates with the outlet of a fuel injection pump.

The end of the narrower portion of the valve member remote from the step 17 is shaped to co-operate with the seating 13 but in addition, it has a projection 22 which extends with clearance through the outlet opening 12. The projection 22 is known in the art as a "pintle" and the pintle defines an annular clearance with the wall of the opening 12 and through which when the valve member is lifted from its seating as will be explained, fuel under pressure can flow. Although the example is of a "pintle" type nozzle, the invention is equally applicable to the form of nozzle in which no.

pintle is provided and in which the outlet is in the form of one or more fine drillings.

The end of the valve member remote from the seating is provided with an extension 23 which mounts a spring abutment 24 for one end of a coiled compression spring 25. The nozzle body 10 is mounted in use on a nozzle holder 31 and interposed between the end face of the nozzle holder and the adjacent end face of the nozzle body, is a distance piece 26. A cap nut can be utilised to secure the nozzle body to the nozzle holder and to apply sufficient clamping force between the end surfaces of the holder, distance piece and nozzle body as to ensure a fuel tight seal therebetween. It will be noted that the passage 21 is extended through the distance piece and the holder and terminates in a fuel inlet defined by the holder.

The distance piece 26 defines an annular rib 27 which projects into the enlarged portion of the bore and the rib 27 defines a stop surface 29 for the sleeve and also the valve member. It should be noted that the allowed movement of the sleeve represented in the drawing by the dimension 32, is less than the allowed movement of the valve member.

The sleeve 14 is provided with a plurality of apertures 28 which act to equalise the pressures in the working clearances between the valve member and the sleeve and the sleeve and the wall of the bore 11.

In operation, when fuel under pressure is supplied through the fuel inlet passage 21, the fuel pressure acts upon the end of the sleeve and also upon the differential area of the valve member and a force is generated which acts to move the valve member against the action of the spring 25. When the force is sufficiently high the valve member will lift from its seating to permit fuel flow through the annular clearance between the pintle and the wall of the outlet. The movement of the valve member- will continue until the end of the sleeve 14 engages the surface 29 defined by the rib. Thereafter no further movement of the sleeve can take place. However, further movement of the valve member is possible and is achieved when the fuel pressure applied to the fuel inlet of the nozzle increases and the further movement of the valve member will be limited by its abutment with the stop surface 29. The valve member has therefore two stages of lift to allow the pintle 22 to control the flow of fuel through the outlet.

It is of course necessary to carefully set the allowed movement of the sleeve so that the pintle can exercise proper control over the fuel flow through the outlet. The provision of the distance piece 26 greatly facilitates the setting of the nozzle since with the distance piece located against the end face of the nozzle body, it is possible very readily to measure the movement of the valve member between its open and closed positions and from this it is possible to determine the movement of the sleeve. If having checked the valve movement with one distance piece, it is possible if the movement of the sleeve is too small, to grind the rib 27. Alternatively, selective assembly can be carried out until the desired movement of the sleeve is attained.

It will be understood that the invention can be applied to conventional nozzles of the type in which the valve member is slidably mounted in the bore.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a nozzle body, a valve member which is movable axially by fuel under pressure supplied through a nozzle inlet, away from a seating to permit fuel flow from the inlet to an outlet, resilient means biasing the valve member into contact with the seating, a nozzle holder, a distance piece located between an end face of the holder and an end face of the nozzle body, said distance piece being provided with a central aperture through which extends means connecting the resilient means and the valve member, the distance piece defining a machined rib which defines a stop surface for the valve member, the arrangement being such that the adjustment of the valve member is effected by altering the dimensions of said rib.

2. A nozzle according to Claim 1 including a sleeve surrounding the valve member and being acted upon by the fuel pressure, the valve member being slidable in the sleeve and the sleeve in the nozzle body, the movement of the sleeve in the body being limited by its abutment with said rib, and the sleeve and valve member defining interengageable means whereby the initial force acting against the resilient means is due to the fuel under pressure acting upon the sleeve and the valve member, the movement of the valve member after the engagement of the sleeve with the rib being due to the fuel under pressure acting on the valve member.

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 drawing.