GB2131875A

GB2131875A - I.c engine fuel injection valve

Info

Publication number: GB2131875A
Application number: GB08328715A
Authority: GB
Inventors: David M Bacon; Richard T Shaw
Original assignee: Perkins Engines Group Ltd
Current assignee: Perkins Engines Group Ltd
Priority date: 1982-11-12
Filing date: 1983-10-27
Publication date: 1984-06-27
Also published as: GB8328715D0; GB2131875B; EP0137788A1; IT8323685A0; JPS59502032A; IT1209489B; CA1199242A; WO1984001980A1

Abstract

A fuel injection valve for a diesel engine comprises a fuel delivery nozzle body (14) formed with a central bore (16), a fuel spray orifice (21) co-axial with said bore (16), a frusto-conical valve seat (20) co-axial with, and tapering inwards towards said orifice (20), and a fuel supply passage (25) that suplies fuel to said valve seat (20) an orifice (21); and a needle member (15) that is slidably received in said bore (16) and has a cylindrical end portion (17) of reduced diameter terminating in a conical tip (18) that co-operates with said valve set (20) to open and close said orifice (21); characterised in that said nozzle body (14) is formed with a chamber (16') that communicates with said fuel supply passage (25) and into which a shoulder portion (15') of the needle member (15) projects so that pressurisation of the fuel moves the needle member (15) axially to disengage its conical end from the valve seat (20), and in that the nozzle body (14) is formed with a plurality of fuel supply passages (27) that extend tangentially of, and open into, a cylindrical portion (19) of said central bore (16) adjacent to the wider end of the valve seat (20) and in which said cylindrical end portion (17) of the needle member (15) slides to open said passages (27) as the needle member (15) moves axially to disengage the valve seat (20).

Description

SPECIFICATION Fuel injection valve This invention relates to a fuel injection valve for a diesel engine.

Conventional diesel injectors incorporate a needle valve formed bythe conical tip of a needle member that cooperates with a frusto-conical valve seat to control the flow of fuel. Fuel is supplied to an annular chamber surrounding the needle member adjacent its tip so that a pressure impulse in the fuel supply serves to move the needle memberaxially separate the needle tip from the valve seat. Fuel then fiows directly from said annular chamber through the central orifice ofthe valve seat.In a single spray injector, the spray orifice is aligned axially with the needle member and valve seat, but in a multi-spray injector a plurality of spray orifices are formed in a nozzle with the outlet side of the valve seat. Multi-spray injectors are preferred where it is desired to disperse the injected fuel in the combustion system.

An objectofthe present invention isto provide an improved fuel injection valve, in particular a valve that will produce a spray in the form of a swirling cone of fuel.

According to the invention, a fuel injection valve for a diesel engine comprises a fuel delivery nozzle body formed with a central bore, a fuel spray orifice co-axial with said bore, a frusto-conical valve seat co-axial with and tapering inwards towards said orifice, and a fuel supply passage that supplies fuel to said valve seat and orifice, and a needle member that is slidably received in said bore and has a cylindrical end portion of reduced diameter terminating in a conical tip that co-operateswith saidvalveseattoopen and close said orifice; characterised in that said nozzle body is formed with a chamber that communicates with said fuel supply passage and into which a shoulder portion of the needle member projects so that pressurisation of the fuel moves the needle member axially to disengage its conical end from the valve seat, and in that the nozzle body is formed with a pluralityoffuel supply passages that extend tangentially of, and open into, a cylindrical portion of said central bore adjacent to the wider end of the valve seat and in which said cylindrical end portion of the needle member slides to open said passages as the needle members moves axially to disengage the valve seat.

The cylindrical end portion of the needle member together with the fuel supply passages opening into the cylindrical portion of the central bore, constitutes a spool valve which controls opening of these passages independently of, though in a manner related to, the opening ofthe valve seat as the needle member is moved axially. The opening ofthe spool valve occurs progressively thereby exercising control over the flow of fuel to the valve seat. The axial spacing of said openings ofthefuel supply passages in relation to the valve seat can be varied to produce a delay in the two opening actions.

The invention will now be described by way of example with reference to the accompanying drawings in which Figure 1 is an axial section through an injection valve according to a first embodiment of the invention Figure 2 is a section in the plane 2-2 of Figure 1, Figure3 is a section in the plane 3-3 of Figure 1, Figure4 is an enlarged view of the end of the injector nozzle in Figure 1 with the needle member lifted off the seat, FigureS is a part axial section through an injection valve according to a second embodiment of the invention, Figure 6 is an axial section through an injection valve according to a third embodiment of the invention, Figure 7 is a section in the plane 7-7 in Figure 6, and Figure 8 is a transverse vertical section through the cylinder of a diesel engine fitted with an injector incorporating an injection valve according to the invention.

Figure 8 shows a fuel injector 1 mounted in the head 2 of a diesel engine so as to inject a spray of fuel into a combustion chamber defined by the underside of the head, the cylinder3 in the block4 and the crown of the piston 5. A bracket 6 and stud 7 clamp the injector down in a bore 8 in the head, and a fuel pipe 9 supplies fuel to the top of the injector.

Injector comprises a body 10 to which the fuel pipe 9 is connected at its upper end, and which is adapted to supply fuel through an internal passage 11 (see Figure 1) to a nozzle assembly 12 connected to the lower end ofthe body by a cap nut 13.

The injector body 10 and the means for mounting it in the head may be of known design, but the nozzle assembly 12 is specially adapted according to the invention, as shown in Figures 1 to7,soasto produce an injected fuel spray in the form of a cone.

The nozzle assembly 12 comprises a nozzle body 14 and a needle member 15 that is smoothly slidably within a central cylindrical bore 16 ofthe body 14. The lower portion 17 ofthe needle member is of reduced diameter and terminates in a conical nose 18. This portion 17 extends through a corresponding bore 19 at the lower end of the body 14, and the nose 18 of the needle member co-operates with a frusto-conical seat 20 at the lower end of bore 19 surrounding a fuel injection hole 21. A compression spring 22 is mounted on a spigot 23 at the upper end of the needle member 15 and acts between the injector body 10 and the needle member 15 to urge the latter downwards and engage the nose 18 with the seat 20, thereby closing the fuel injection hole 21 and forming a liquid and air-tightseal.

The upper surface of the nozzle body 14 is formed with an annularfuel gallery 24 that communicates with the fuel passage 11 in the injector body, and four equi-anularly spaced fuel passages 25 extend down wards from the gallery 24to the lower end of the nozzle body. An opening 26 is formed between one of these passages 25 and the lower end 16' of the central bore 16so that pressurisation ofthe fuel will be effective within the lower end of bore 16 to act upon the shoulder portion 15' ofthe needle memberand lift the latter against the bias of spring 22.

The lower end of each passage 25 communicates with an inwardly extending passage 27 that opens into the bore 19 adjacent the top of the seat 20. These four passages 27 are directed tangentially ofthe bore 19 and seat 20so as to directfuel in a common sense of rotation aboutthe central longitudinal axis of the injector, as shown in Figure 3. The lower reduced diameter portion 17 of the needle member immediately adjacentthe nose 18 constitutes a land 28 which obstructsthetangential passages27toavarying degree during movementofthe needle member 15.

In operation, high pressure impulses of fuel are supplied to the injector from an injection pump. On receiving a high pressure impulse through passages 11 and 25, the lower end 16' of the central bore is pressurised and the needle member is lifted against the bias of spring 22to a degree depending on the intensity of an duration ofthe pressure impulse.

Lifting of the needle member 15 results in separation ofthe conical nose 18 and the seat 20 thereby opening the hole 21. Lifting of the needle member 15 also causes the land 28 to open the tangential passages 27 and fuel flows between the nose and seat in a rotary manner which produces a conical hollow spray shown as 29 in Figure 8. There is therefore a dual action of lifting the needle member to open the hole 21 and openingthetangential passages27toallowtheflow of fuel. The axial position of the opening of passages 27 relative to thefrusto-conical seat 20, will determine the delay between lifting ofthe needle member and the flow of fusel to produce the spray.

The choice of the size of the fuel passages, their number and disposition may be such as to control the pressure and volume of fuel flowing between the nose 18 and the seat 20 for a given separation between the nose and the seat, thereby enabling the choice of cone angleto be made independently of these parameters.

In an alternative embodiment of the invention, as shown in FigureS, the passages 27 may, instead of lying in a plane perpendicularto the needle axis, lie on a frusto-conical surface so that they are directed inwards and downwards at the angle O.

The nozzle body 14 shown in Figures 1 to 5, is formed as a one-piece body, with the fuel passages 25, 26 and 27 being bored therein, and with the outer portions ofthose boreholes for passages 26 and 27 being plugged at 30. However, in an alternative embodiment, shown in Figures 6 and 7, the nozzle body 14 may be formed as an assembly comprising an inner cylindrical portion 31 received as a close fit within an outer sleeve portion 32, grooves being formed in the outer surface ofthe inner portion 31 to be closed bythe inner surfaces ofthe sleeve portion 32 and thereby form the passages 25 and 27.

Claims

1. Afuel injection valve for a diesel engine comprising a fuel delivery nozzle body formed with a central bore, a fuel spray orifice co-axial with said bore, a frusto-conical valve seat co-axial with and tapering inwards towards said orifice, and a fuel supply passage that supplies fuel to said valve seat and orifice, and a needle memberthat is slidably received in said bore and has a cylindrical end portion of reduced diameter terminating in a conical tip that co-operates with said valve seat to open and close said orifice; characterised in that said nozzle body is formed with a chamber that communicates with said fuel supply passage and into which a shoulder portion ofthe needle member projects so that pressurisation of the fuel moves the needle member axially to disengage its conical end from the valve seat, and in that the nozzle body is formed with a plurality of fuel supply passagesthat extend tangentially of, and open into, a cylindrical portion ofsaid central bore adjacent to the wider end ofthe valve seat and in which said cylindrical end portion of the needle member slides to open said passages as the needle member moves axially to disengage the valve seat.

2. A valve as claimed in claim 1 in which the needle member comprises a main cylindrical body portion joined by said shoulder portion to said cylindrical end portion of reduced diameter, and said central bore comprises a main cylindrical portion in which said main body portion isslidably received and through which part of said cylindrical end portion of the needle member extends so as to define said chamber as an annulus extending axially between said shoulder portion of the needle member and the junction ofthe main cylindrical portion of the central bore with said cylindrical portion in which the cylindrical end portion ofthe needle member slides.

3. Avalve as claimed in claim 1 in which said tangential fuel supply passages lie in a common plane perpendicularto the axis of the needle member.

4. A valve as claimed in claim 1 in which said tangential fuel supply passages lie are directed radially inwards and axially towards said orifice.

5. Avalve as claimed in claim 1 in which the openings of said tangential fuel supply passages into said cylindrical portion of the central bore are equi-angularly spaced about said cylindrical portion.

6. A valve as claimed in claim inwhichthenozzle body is an assembly comprising an inner core and an outer sleeve with said tangential fuel supply passages formed as grooves on the outer surface of said inner core.