GB2200950A

GB2200950A - I.C. engine fuel infection nozzle

Info

Publication number: GB2200950A
Application number: GB08801573A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-02-06
Filing date: 1988-01-25
Publication date: 1988-08-17
Also published as: GB8801573D0

Abstract

The valve member 20 is slidable within an axially slidable sleeve 16 which is subject at one end to the fuel pressure. The force produced is transmitted to the valve member through an outwardly extending step 26 formed in the internal surface of the sleeve which engages with a ring 25 located in a groove 24 in the valve member but which projects from the groove. <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 sleeve which is axially slidable in a bore in a nozzle body, the sleeve at one end being subjected to the pressure of fuel supplied through a nozzle inlet, means for limiting the movement of the sleeve under the action of fuel pressure, a valve member axially slidable within the sleeve, one end of the valve member being shaped for co-operation with a seating, resilient means biasing the valve member into contact with the seating to prevent flow of fuel from the nozzle inlet to an outlet, inter engaging means on the sleeve and the valve member whereby during the limited range of movement of the sleeve the pressure of fuel acting on said one end of the sleeve will generate a force which acts on the valve member in opposition to the force exerted by the spring, the continued movement of the valve member away from the seating at the end of the allowed movement of the sleeve being due to the pressure of fuel acting upon a surface of the valve member.

Such a nozzle is known from British Patent Specification 2145468B and in the example shown in that specification the sleeve is provided with an inwardly extending lip or projection for engagement with a step on the valve member, the lip and step constituting the interengageable means whereby the force generated by the fuel under pressure acting on the sleeve is applied to the valve member. The provision of the lip on the sleeve poses problems when machining and fine finishing the bore in the sleeve.

It is known from British patent specification 1531580 to utilise a plain cylindrical sleeve and to form an outwardly extending step on the valve, the step being of sufficient radial width as to provide an adequate abutment surface for the end surface of the sleeve. The formation of the step and the machining of the surface of the valve member is facilitated by the provision of an undercut adjacent the step.

However, the requirement to provide the step means that the valve member must be machined from bar stock having a diameter at least equal to the diameter of the step. As a result a substantial amount of expensive metal has to be machined away during the course of production of the valve member.

The object of the invention is to provide a nozzle of the kind specified in a simple and convenient form.

According to the invention in a nozzle of the kind specified said interengaging means comprises a peripheral groove adjacent the end of the valve member remote from the seating, a ring located in said groove and projecting therefrom and an outwardly extending step formed in the internal surface of the sleeve, said step engaging with the projecting portion of said ring.

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

Referring to the drawing the nozzle comprises a nozzle body 10 of stepped cylindrical form and in which is formed a stepped bore 11, the bore 11 having intermediate its ends an enlargement 12 which is connected to a fuel supply passage 13 and at its narrower end, a seating 14 about an outlet 15.

The passage 13 is continued in a nozzle holder (not shown) to which the nozzle body may be secured by a cap nut, the passage in the nozzle holder being connected to a fuel inlet which in use receives fuel from a fuel injection pump.

Slidable within the wider portion of the bore is a sleeve 16 the inner end of which is exposed to the fuel pressure which exists in use, in the space 12. The other end of the sleeve is provided with an outwardly extending flange 17 which is located within a recess 19 formed in the open end of the bore 11. Slidable within the sleeve is a valve member 20 which has a reduced portion extending beyond the sleeve so as to define an annular clearance 21 with the wall of the bore. The valve member is shaped for co-operation with the seating 14 and it has an extension 22 which projects through the outlet 15, the extension is more commonly known as a wpintle", and is shaped so as to control the fuel flow through the outlet 15.

At its opposite end the valve member 20 is provided with an extension 23 upon which is mounted a spring abutment against which bears a coiled compression spring shown in dotted outline and which biases the valve member into engagement with the seating 14. The abutment and spring are located in a chamber in the aforementioned holder.

Formed in the periphery of the valve member adjacent its end remote from the seating, is a circumferential groove 24.in which is located a metal ring 25 conveniently of cylindrical section which projects from the groove. Moreover, the ring is engageable by an outwardly extending step 26 formed in the bore in the sleeve the projecting portion of the ring locating in the recess formed during the production of the step 26, the wall of the recess acting to prevent displacement of the ring during the transmission of the force.

In operation, when fuel under pressure is supplied through the passage 13 the pressure acts upon the inner end of the sleeve and also the differential area of the valve member. The force generated on the sleeve moves the sleeve upwardly and by way of the metal ring, the force is applied to the valve member which in conjunction with the force generated by the fluid pressure acting on the valve member, moves the valve member against the force exerted by the spring. The movement of the sleeve is limited by its abutment with, for example, the end face of the aforesaid holder or by an appropriate abutment surface formed on an insert located between the nozzle body 10 and the holder.

The initial movement of the valve member up to the point where the sleeve movement is halted, is sufficient to allow a limited flow of fuel through the outlet 15. Continued movement of the valve member takes place as the pressure of fuel supplied through the passage 13 increases and thereafter the valve member will move relative to the sleeve until the valve member itself is halted by an abutment surface.

During the continued movement of the valve member, the ring 25 is held in the groove 24 by the wall of the recess in the sleeve which is utilised to form the step 26.

In order to balance the fuel pressure in the working clearances between the sleeve 16 and the wall of the bore 11 and the surface of the valve member 20, apertures 27 are formed in the sleeve.

When the valve member is in the closed position, it is essential that it should engage the seating 14.

For this reason a small clearance is provided between the flange 17 and the step formed in the wall of the bore 11. The purpose of the flange is to prevent the sleeve falling downwardly when there is no fuel pressure within the space 12 such as will occur due to leakage when the engine has stopped.

Since there might be slight local deformation of the sleeve and the ring when force is being transmitted therebetween, it may be desirable to provide a slight enlargement of the bore in the sleeve adjacent the step 26.

It will be appreciated that with the construction described it is possible to reduce the diameter of the guiding portion of the valve member that is to say the portion which lies within the bore of the sleeve, below that of the aforementioned reduced portion of the valve member. This will of course mean that there will be a greater difference in the fuel inlet pressure required to effect continued movement of the valve member once the sleeve movement has been halted and it may mean depending upon the dimensions chosen, that the force acting on the sleeve alone serves to lift the valve member from its seating. Once the valve member is lifted from its seating there is an increase in the area of the end portion of the valve member which is acted upon by fuel pressure and it is the fuel pressure acting on this area which will cause continued movement of the valve member.

Although the specific example shows a so-called Zpintlew nozzle, the invention may be applied to the so-called single or multi hole type of inwardly opening nozzle, in this case the throttled fuel flow across the valve seat provides the low initial rate of fuel flow to the engine.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine comprising a sleeve which is axially slidable in a bore in a nozzle body, the sleeve at one end being subjected to the pressure of fuel supplied through a nozzle inlet, means for limiting the movement of the sleeve under the action of fuel pressure, a valve member axially slidable within the sleeve, one end of the valve member being shaped for co-operation with a seating, resilient means biasing the valve member into contact with the seating to prevent flow of fuel from the nozzle inlet to an outlet, interengaging means on the sleeve and the valve member whereby during the limited range of movement of the sleeve the pressure of fuel acting on said one end of the- sleeve will generate a force which acts on the valve member in opposition to the force exerted by the spring, the continued movement of the valve member away from the seating at the end of the allowed movement of the sleeve being due to the pressure of fuel acting upon a surface of the valve member, said interengageable means comprising a peripheral groove adjacent the end of the valve member remote from the seating, a ring located in said groove and projecting therefrom, and an outwardly extending step formed in the internal surface of said sleeve, said step engaging with the projecting portion of said ring.

2. A nozzle according to Claim 1 in which the bore in the sleeve is enlarged slightly adjacent said step.

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.