GB2200690A

GB2200690A - I.C. engine fuel injection nozzle

Info

Publication number: GB2200690A
Application number: GB08801572A
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: 1988-08-10
Also published as: GB8801572D0

Abstract

The valve member 23 is slidable in a sleeve 18 also subject to fuel under pressure and also movable against the action of the spring 20, the extent of movement of the sleeve away from the seating being limited. The movement of the sleeve towards the seating 13 is limited by its engagement with an abutment 26 on the valve member. <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 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, the valve member being slidable within a sleeve which is itself axially slidable in a bore in a nozzle body and is subject to the fuel pressure at said inlet, a spring abutment engageable by the valve member, a coiled compression spring engaging said abutment for biasing the valve member into contact with the seating, said sleeve also being engageable with the abutment whereby when fuel under pressure is supplied through said inlet the forces produced by the fuel pressure acting on the sleeve will assist the movement of the valve member against the action of the resilient means, stop means for limiting the movement of the sleeve under the action of fuel pressure and further stop means for limiting the movement of the valve member under the action of fuel pressure.

An example of such a nozzle is seen in Figure 4 of British patent specification 1531580. In this example the sleeve is of plain cylindrical form and it is possible for the sleeve to move away from the abutment when the associated engine is at rest, with the result that at least the initial quantity of fuel which is delivered to the fuel inlet will be at least partly absorbed by movement of the sleeve towards the abutment.

A nozzle of a similar kind is shown in British specification 2145468B and the movement of the sleeve as described is prevented by an enlargement on the outer surface of the sleeve. The provision of such an enlargement does render the production of the sleeve more difficult and it also adds substantially to the weight of the sleeve.

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

According to the invention in a nozzle of the kind specified an abutment means is mounted on the valve member for engagement by the sleeve to limit, when the valve member is in the closed position, the movement of the sleeve away from said spring abutment.

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

The nozzle unit comprises a stepped body 10 in which is formed a stepped bore the wider portion of which is indicated at 11 with the narrower portion thereof being indicated at 12. At the end of the portion 12 of the bore remote from the portion 11 thereof there is formed a seating 13 and below the seating there is defined a so-called "sac" 14 from which extends an outlet orifice or orifices 15.

Intermediate the portions 11 and 12 of the bore there is formed an enlargement 16 which communicates by way of a supply passage 17 with a fuel inlet formed in a holder to which the body 10 is secured in known manner, by means of a cap nut.

Slidably mounted within the portion 11 of the bore is a sleeve 18 which extends from the bore and locates within a spring abutment 19 against which bears a coiled compression spring 20, the spring and the abutment together with the extension of the sleeve, being located within a chamber formed in the aforesaid holder. The sleeve defines a peripheral step 21 for abutment in the particular example, with a stop plate 22 which is sandwiched between the body 10 and the holder. The stop plate may be constituted by the end face of the aforesaid holder.

Slidably mounted in the sleeve is a valve member 23 which is shaped for co-operation with the seating and which adjacent the seating has a tapered portion.

The valve member defines a clearance 24 with the portion 12 of the bore so that fuel can flow from the enlargement 16 through the outlet orifice 15 when the valve member is lifted from its seating. It will be noted that throughout most of its length the valve member is of plain cylindrical form, the diameter of the valve member being slightly reduced at its end portion remote from the seating. The valve member abuts the spring abutment 19.

In operation, when fuel under pressure is supplied to the inlet 17 the pressure will act upon the end area of the sleeve 18 and also upon the annular area of the valve member which lies outside the seating. The forces produced by the fuel under pressure acting upon the aforesaid areas oppose the action of the spring and when the forces become sufficient, the valve member and the sleeve will move against the action of the spring 20 thereby lifting the valve member from its seating to allow fuel to flow at a controlled rate through the outlet orifice 15. As soon as the valve member is lifted from its seating an increased area thereof is exposed to fuel under pressure with the result that the valve member and the sleeve will move upwardly until the step 21 on the sleeve engages the stop plate 22.

When this occurs no further movement of the sleeve is possible. However, as the pressure in the inlet passage 17 continues to increase, a pressure will be reached at which the force developed on the valve member alone is sufficient to move the valve member against the action of the spring 20. The maximum movement of the valve member 23 is determined by its abutment with a stop 25 which extends within the spring 20. As the valve member continues to move towards the stop 25, the restriction to flow of fuel between the seating and the valve member will decrease so that normal flow of fuel takes- place to the associated engine through the outlet orifice or orifices 15.

When the pressure of the fuel delivered to the injection nozzle falls, the valve member and the sleeve will return under the action of the spring 20 to the positions shown in the drawing.

When the engine has been halted for a considerable length of time, it can be expected that the fuel pressure in the enlargement 16 will fall to zero and in this situation it is possible for the sleeve 18 to fall under the action of gravity into the enlargement 16.

As a result at least the initial delivery of fuel when an attempt is made to start the associated engine will be impaired. Moreover, during the injection process cavities may be formed in the high pressure line connecting the inlet of the nozzle to the outlet of the injection pump. Such cavities may persist after the closure of the delivery valve in the outlet of the injection pump and after closure of the valve member 23. In collapsing the cavities will draw the sleeve downwardly. Furthermore, in the normal operation of the nozzle the sleeve will gain appreciable inertia due to the action of the spring during closure of the valve member and the inertia will tend to cause the sleeve to continue its movement after the valve member has contacted its seating. In order to minimise the extent of downward movement of the sleeve, it is proposed to provide abutment means on the valve member for engagement by the sleeve to limit the movement of the sleeve. In the example the abutment means is in the form of a "C" spring 26 which is located within a groove formed in the valve member. The abutment means may however be constituted by a flange formed on the valve member the flange being formed during the machining of the valve member from bar stock, or by a collet or a dowel or a circlip.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine, the nozzle comprising 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, the valve member being slidable within a sleeve which is itself axially slidable in a bore in a nozzle body and is subject to the fuel pressure at said inlet, a spring abutment engageable by the valve member, a coiled compression spring engaging said abutment for biasing the valve member into contact with the seating, said sleeve also being engageable with the abutment whereby when fuel under pressure is supplied through said inlet the forces produced by the fuel pressure acting the sleeve will assist the movement of the valve member against the action of the resilient means, stop means for limiting the movement of the sleeve under the action of fuel pressure, further stop means for limiting the movement of the valve member under the action of fuel pressure, and abutment means mounted on the valve member for engagement by the sleeve to limit, when the valve member is in the closed position, the movement of the sleeve away from said spring abutment.

2. A nozzle according to Claim 2 in which said abutment means is located within a groove formed in the valve member.

3. A nozzle according to Claim 2 in which said abutment means comprises a "C" spring.

4. A nozzle according to Claim 1 in which said abutment means comprises a dowel on the valve member.

5. 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.