GB2143274A

GB2143274A - Fuel injection nozzle

Info

Publication number: GB2143274A
Application number: GB08413572A
Authority: GB
Inventors: Godfrey Greeves; Keith Richard Browne; David Eric Draper
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-07-12
Filing date: 1984-05-29
Publication date: 1985-02-06
Also published as: GB8413572D0; GB2185070A; GB2143274B; GB8629672D0; GB2185070B

Abstract

A valve member 17 is provided 17 with an extension 18 which projects into the outlet opening 20 and has a working clearance with the wall of the opening to prevent combustion gases entering the chamber 21 downstream of the seating 12 in the closed position of the valve member. Bores (25, Fig. 3) or grooves in the chamber wall may provide fuel flow paths terminating immediately upstream of the opening 20. The chamber wall and extension may have various forms (Figs. 4 and 5). <IMAGE>

Description

SPECIFICATION Fuel injection nozzles This invention relates to fuel injection nozzles of the so-called inwardly opening type comprising a nozzle body, a blind bore formed in the body, a seating defined at the blind end of the bore, a valve member movable in the bore, said valve member being shaped to cooperate with the seating, resilient means for biasing the valve member into contact with the seating, a fuel inlet in the body through which fuel under pressure can flow to act on the.valve member to lift the valve member from the seating thereby to allow fuel flow from the inlet through an outlet.

Various forms of nozzle of the aforesaid type are known in the art. The so-called "hole" type nozzle has a chamber disposed downstream of the seating and the outlet is in the form of a fine drilling or drillings extending from the chamber to the exterior of the nozzle. The so-called "pintle" nozzle has an extension on the valve member which projects with clearance through an opening from said chamber to the exterior of the nozzle, the wall of the opening and/or the extension being shaped to control the fuel flow through the clearance as the valve member moves away from the seating.

At the end of delivery of fuel after the valve member has moved into contact with the seating, a small quantity of fuel will be left in the chamber downstream of the valve member and because of the fact that combustion gases can gain access to the chamber through the drilling or clearance, a gradual build-up of carbon will occur in the chamber. The carbon deposit affects the performance of the nozzle and therefore the associated engine.

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

According to the invention in a fuel injection nozzle of the kind specified there is disposed downstream of the seating a chamber, an opening from said chamber to the exterior of the nozzle, an extension on said valve member, said extension extending within said opening and in the closed position of the valve member preventing ingress of combustion gases into said chamber, said opening forming said outlet.

Examples of fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a portion of a nozzle, Figure 2 is a view to an enlarged scale of a portion of the nozzle seen in Figure 1, Figure 3 is a view similar to Figure 2 showing a modification, and Figures 4 and 5 are views similar to Figures 2 and 3 showing further modifications.

Referring to Figures 1 and 2 of the drawings the nozzle comprises a body 10 of stepped form the narrower end of the body in use, being exposed within a combustion space of an associated engine. The nozzle body in practice, is secured to a support member or holder by means of a cap nut. Formed within the body is a blind bore 11 and this extends from the wider end of the body to adjacent the narrower end thereof.At the blind end of the bore there is formed a seating 1 2 and intermediate the ends of the bore there is formed an enlargement 14 which communicates with a fuel inlet conveniently formed in the aforesaid holder, by means of an inlet passage or passage 1 5. The passage or passages in use, is/are connected to an outlet of a fuel injection pump 1 6. Located within the bore is a valve member 1 7 and at its end adjacent the seating, the valve member is shaped to co-operate therewith.The valve member carries an extension 1 8 of right cylindrical form and in the closed position of the valve member as shown in the drawings, the extension extends into and forms a working clearance with the wall of an opening 20 onto the exterior of the nozzle, the outer portion of the opening being of right cylindrical form.

Downstream of the seating there is formed a chamber 21 which communicates with the enlargement 14 when the the valve member is lifted from its seating, by way of an annular clearance 1 9 which is defined between the valve member and the wall of the bore, the clearance conveniently being formed by reducing the diameter of the valve member.

The valve member at its end remote from the seating is formed with an integral peg 22 which carries a spring abutment 23, the latter being engaged by a coiled compression spring 24 which conveniently is mounted within a vented chamber defined in the aforesaid holder or supporting body.

In operation, when fuel under pressure is supplied to the enlargement 14, the fuel pressure acts upon the differential area of the valve member to create a force acting to move the valve member against the action of the spring 24. When the force exerted by the spring is overcome the valve member is lifted from its seating to allow fuel flow into the chamber 21. When the valve member has been lifted sufficiently so that the extension 1 8 is removed from the opening 20, fuel can flow from the chamber 21 to the exterior of the nozzle. The effective flow area from the chamber 21 varies as the valve member is lifted away from its seating by the fact that the wall of the chamber 21 which leads to the right cylindrical portion is of tapering form, in the particular example the taper being formed by a series of inclined zones.The nozzle is therefore of the variable area type.

It is emphasised once again that the exten sion 1 8 has a working clearance with the wall of the opening 20 so that in the closed position of the valve member ingress of combustion gases into the chamber 21 is prevented. By preventing this flow of combustion gases the fuel which is trapped therein does not carbonize and therefore the formation of carbon deposit within the chamber and on the parts forming the walls of the chamber, is minimised. The working diametral clearance will need to be about 5 microns or less.The fact that the extension 18 has a working clearance with the wall of the opening 20 provides for centralisation of the valve member as it moves towards the closed position and this centralisation is facilitated by the fact that the portion 1 A of the wall of the bore which is disposed between the enlargement 14 and the wider end of the body tapers inwardly away from the extension. The valve member can therefore align itself as it moves towards the closed position.

A modification of the nozzle is seen in Figure 3. In this case the opening 20 is of extended length and flow channels in the form of drillings 25 extend from the wall of the opening into the chamber. Once again the clearance between the extension 18 and the wall of the opening is a working clearance so that in the closed position of the valve member combustion gases cannot flow into the chamber 21. As the valve member starts to move away from its seating the exits of the drillings will be exposed by the extension and fuel will flow through the drillings and pass through the opening forming jets of fuel spray; The fact that the valve member gradually exposes the exits of the drillings means that a variable area is presented for the flow of fuel.

It will of course be appreciated that the drillings 25 are blanked off from the opening by the extension 18 in the closed position of the valve member. In a modification the drillings 25 are replaced by grooves which are easier to construct than the drillings. The grooves are formed in the body but terminate short of the end of the body so that in the closed position of the valve member they are closed off from the combustion chamber. The construction shown in Figure 3 together with the modification has the advantage over the construction of Figure 2 in that the wall of the opening guides the movement of the valve member.

The nozzles shown in Figures 4 and 5 have so-called obturators 26 formed integrally with the extensions 1 8 of the valve members. The obturators comprise first and second tapering portions 27, 28 which in the closed position of the valve member extend beyond the end surface of the nozzle body 10.

In the example of Figure 4 the extension is of right cylindrical form and the opening 20 is also of right cylindrical form as in the example of Figure 2. As with the example of Figure 2 the working clearance between the extension and the wall of the opening is such that in the closed position of the valve member the chamber 21 is closed off. The steeply inclined portion 27 of the obturator makes the nozzles less sensitive to variations in the maximum lift of the valve member as the maximum lift stop of the nozzle wears in use. Any carbon which may form on the surface of the obturator has little effect upon the flow characteristics of the nozzle at high lift.

In the example of Figure 5 the opening is constituted by the edge defined by the end surface of the body part and the outer end of the tapered wall of the chamber 21. Moreover, the extension 29 is in this example tapered the angles of the tapers on the extension and the wall of the chamber being slightly different so that the chamber 21 is of tapering form. In the closed position of the valve member the clearance between the extension and the aforesaid edge is reduced to the extent that the chamber 21 is closed off.

Moreover, the slight difference in the tapers provides a progressive guiding effect as the valve member moves to the closed position.

With this example even if carbon deposit does accumulate within the chamber, the opening of the valve member will separate the tapers and will thus ensure an effective area for fuel flow at part and full lift conditions. The mechanical action on closure of the valve member will ensure that the deposits do not grow to the extent to hinder closure of the valve member.

Claims

1. A fuel injection nozzle of the inwardly opening type comprising a nozzle body, a blind bore formed in the body, a seating defined at the blind end of the bore, a valve member movable in the bore, said valve member being shaped to co-operate with the seating, a fuel inlet in the body through which fuel under pressure can flow to act on the valve member to lift the valve member from the seating thereby to allow fuel flow through an outlet from the inlet, a chamber formed in the body downstream of the seating and an opening from said chamber to the exterior of the nozzle, an extension on said valve member, said extension extending within said opening and in the closed position of the valve member preventing ingress of combustion gases into said chamber said opening forming said outlet.

2. A nozzle according to Claim 1 in which the outer portion of said opening is of right cylindrical form, said extension being of complementary shape.

3. A nozzle according to Claim 2 in which inwardly of said outer portion the opening is of tapering form, the extension with the tapering portion of the opening forming a variable flow area.

4. A nozzle according to Claim 1 including flow channels in said body, said flow channels extending from said chamber into said opening, the ends of the flow channels remote from said chamber terminating within the opening so that in the closed position of the valve member said flow channels will be closed off by said extension.

5. A nozzle according to Claim 4 in which said flow channels are defined by passages.

6. A nozzle according to Claim 4 in which said flow channels are defined by grooves.

7. A nozzle according to Claim 2 including an obturator mounted at the free end of the extension.

8. A nozzle according to Claim 1 in which said opening tapers inwardly from the chamber to its junction with the exterior surface of the body.

9. A nozzle according to Claim 8 in which said extension is of tapering form, the taper being less than the taper of the opening.

10. A nozzle according to Claim 9 including an obturator mounted at the free end of the extension.

11. A nozzle according to any one of Claims 1-10 in which the valve member and the bore are constructed so as to allow alignment of the extension within the opening as the valve member moves into contact with the seating.

1 2. A fuel injection nozzle of the inwardly opening type comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.