GB2185070A

GB2185070A - Fuel injection nozzle

Info

Publication number: GB2185070A
Application number: GB08629672A
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: 1987-07-08
Also published as: GB2185070B; GB2143274B; GB8413572D0; GB2143274A; GB8629672D0

Abstract

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

Description

SPECIFICATION Fuel injection nozzles This invention relates to fuel injection nozzles ofthe so-called inwardly opening type comprising a nozzle body, a blind bore formed in the body, a seating defined atthe blind end ofthe bore, avalvemember movable in the bore, said valve member being shaped to co-operate with the seating, resilient means for biasing the valve member into contact with the seating, a fuel inlet in the body th rough which fuel under pressure can flow to act on the valve member to lift the valve memberfrom the seat- ingtherebytoallowfuelflowfromthe inletthrough 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 theform of fine drilling ordrillings 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 clearancethrough an opening from said chamberto theexteriorofthe nozzle,thewalloftheopening and/or the extension being shaped to control the fuel flow th rough 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 offuel will be left in the chamber downstream ofthe valve member and because of the factthatcombustion gases can gain access to the chamberthrough the drilling or clearance, a gradual build-up of carbon will occur in the chamber. The carbon deposit affects the performance ofthe nozzle and therefore the associated engine.

The object ofthe present invention is to provide a fuel injection nozzle ofthe 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 ofthe 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 ofthe 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 refer ence to the accom panyi ng d rawings in which :- Figure lisa sectional side elevation of a portion of a nozzle, Figure 2 is a viewto an enlarged scale of a portion ofthe nozzle seen in Figure 1, Figure3 is a viewsimilarto Figure2 showing a modification, and Figures4and 5areviews similarto Figures 2 and3 showing further modifications.

Referring to Figures 1 and 2 of the drawings the nozzle comprises a body 10 of stepped form the narrower end ofthe 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 12 and intermediate the ends of the bore there is formed an enlargement 14which communicates with a fuel inlet conveniently formed in the aforesaid holder, by means of an inlet passage or passage 15. The passage or passages in use, is/are connected to an outlet of a fuel injection pump 16.

Located within the bore is avalve member 17 and at its end adjacent the seating, the valve member is shaped to co-operatetherewith. The valve member carries an extension 18 of right cylindrical form and in the closed position ofthe 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 ofthe opening being of right cylindrical form.

Downstream of the seating there is formed a chamber 21 which communicates with the enlargement 1 4when the the valve member is lifted from its seating, by way of an annular clearance 19 which is defined between the valve member and the wall of the bore, the clearance conveniently being formed by reducing the diameter ofthevalve member.

The valve member at its end remote from the seating isformedwith 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 holderorsupporting body.

In operation, when fuel under pressure is supplied to the enlargement 14, the fuel pressure acts upon the differential area ofthevalve 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 18 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 leadstothe right cylindrical portion is of tapering form, in the particular examplethe taper being formed by a series of inclined zones. The nozzle is therefore ofthe variable area type.

It is emphasised once again that the extension 18 has a working ciearance 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 car bonize and therefore the formation of carbon deposit within the chamber and on the parts forming the walls ofthe chamber, isminimised.Theworking dia- metral clearance will need to be about 5 microns or less.Thefactthat 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 11 A ofthewall of the bore which is disposed between the enlarge ment 14 and the wider end of the body tapers inwardly away from the extension. The valve member can therefore align itself as it moves towardsthe closed position.

A modification ofthe 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 ofthe opening into the chamber. Once again the clearance between the extension 18 and the wall ofthe 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 awayfrom its seating the exits ofthe driliings will be exposed by the extension and fuel will flow through the drillings and pass through the opening forming jets of fuel spray.

Thefactthatthevalve member gradually exposes the exits of the drillings means that a variable area is presented forthe flow of fuel. It will of course be appreciated thatthe 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 easierto con- structthan the drillings. The grooves are formed in the body but terminate short ofthe end ofthe body so that in the closed position ofthe valve member they are closed off from the combustion chamber.

The construction shown in Figure 3 togetherwith the modification has the advantage overtheconstruc- tion of Figure 2 in thatthewall ofthe opening guides the movement of the valve member.

The nozzles shown in Figures 4 and 5 have socalled obturators 26 formed integrally with the extensions 18 ofthe valve members. The obturators comprise first and second tapering portions 27,28 which in the closed position ofthevalve memberextend beyond the end surface of the nozzle body 10.

In the example of Figure 4the extension is of right cylindrical form and the opening 20 is also of right cylindrical form as in theexample of Figure 2.As with the example of Figure 2 the working clearance between the extension and the wall ofthe opening is such that in the closed position ofthe valve member the chamber21 is closed off. The steeply inclined portion 27ofthe obturator makes the nozzles less sensitive to variations in the maximum lift ofthe valve member as the maximum lift stop of the nozzle wears in use. Any carbon which may form onthesur- face ofthe obturator has little effect upon the flow characteristics ofthe nozzle at high lift.

In the example of Figure the opening is constituted by the edge defined by the end surface ofthe 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 ofthe tapers on the extension and the wall ofthe chamber being slightly different so thatthe 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. Mornover,theslightdiffernnceinthetapersprn- vides a progressive guiding effect as the valve member moves to the closed position.With thisexample even if carbon deposit does accumulate within the chamber, the opening ofthe valve member will separate the tapers and will thus ensure an effective area for fuel flow at part and full lift con- ditions. The mechanical action on closure ofthe valve memberwill ensurethatthe deposits do not growtotheextentto hinder closure of the valve member.

Claims

1. Afuel 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 ofthe 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 memberfrom the seating therebyto allowfuel flow through an outlet from the inlet, a chamberformed in the body downstream of the seating and an opening from said chamber to the ex teriorofthe nozzle, an extension on said valve member, said extension extending within said opening and intheclosed position ofthevalve 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. Afuel injection nozzle of the inwardly opening type comprising the combination and arrangement of parts substantially as herein before described with reference to the accompanying drawings.

3. A nozzle according to Claim 2 in which inwardly of said outer portion the opening is oftapering 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 ofthe flow channels remote from said chamberterminating within the opening so that in the closed position ofthe valve member said flow channels will be closed off by said extension.

5. Anozzleaccordingto ClaimLinwhichsaid 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 ofthe 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 isoftapering form, the taper being lessthan thetaperoftheopening.,

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

11. A nozzle according to anyone ofClaims 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.

12. Afuel injection nozzle ofthe inwardly open- ing type comprising the combination and arrangement of parts substantially as herein before described with reference to the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1-12 above have been deletedortextually amended.

(b) New ortextually amended claims have been filed as follows:- 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 ofthe 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 liftthevalve memberfrom the seating therebyto allowfuel flowthrough an outlet from the inlet, a chamberformed in the body downstream of the seating, an opening from said chamber to the exterior of the nozzle, an extension on said valve member, and pasageswithin the body said passages extending from said chamber and terminating within said opening, said extension extending within said opening and in the closed position ofthevalve member closing off said passages and preventing ingress of combustion gases into said chamberthe opening forming said outlet.

2 Anozzle according to Claim 1 inwhichthe outer portion of said opening is of right cylindrical form, said extension being of complementary shape.