GB2136500A

GB2136500A - Electromagnetic fuel injector

Info

Publication number: GB2136500A
Application number: GB08404214A
Authority: GB
Inventors: Paul Stuart Renowden
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-03-16
Filing date: 1984-02-17
Publication date: 1984-09-19
Also published as: GB8404214D0

Abstract

A valve seat member 21 has an outlet orifice 22 and an annular seating rib surrounding the orifice against which a valve plate is spring biased. The valve plate is provided with a circular row of apertures 25 the axes of which are inclined to the perpendicular of the valve plate so that the fuel before it enters the outlet orifice has a swirling motion about the axis of the orifice. <IMAGE>

Description

SPECIFICATION Fuel injector This invention relates to a fuel injector of the kind comprising an injector body, a fuel inlet defined in the body, means defining a fuel outlet orifice, an annular seating defined about the orifice, a valve plate for co-operation with the seating, resilient means biasing the valve plate into contact with the seating, a solenoid device carried by the body, said valve plate being formed from magnetisable material and being movable upon energisation of said solenoid away from said seating to allow fuel flow through said orifice, and apertures in said valve plate, said apertures being positioned outwardly of said annular seating, said apertures forming part of the flow path for fuel flow through the nozzle between said inlet and said outlet orifice.

A nozzle of the kind specified will normally tend to produce a fuel spray pattern of pencillike form that is to say, the spray will be in the form of a jet. In some applications of the injector it is desirable that the fuel spray pattern should be of a bushy form that is to say, the spray pattern should be of generally conical form.

The object of the invention is to provide a fuel injector of the kind specified in a form in which this desideratum is achieved.

According to the invention in a fuel injector of the kind specified the axes of said apertures are inclined to the perpendicular of the valve plate whereby the fuel before it enters said orifice has a swirling motion about the axis of said orifice.

One example of a fuel injector in accordance with the invention will now be de scabed with reference to the accompanying drawings in which: Figure 1 is a longitudinal sectional view of a fuel injector for an internal combustion engine, Figure 2 is a view to an enlarged scale of part of the injector seen in Fig. 1, Figure 3 is a plan view of part of the valve plate of the injector, and Figure 4 is a section on the line A-A of Fig.

3.

Referring to the drawings, the injector comprises a hollow generally cylindrical outer body 11 formed from magnetisable material and defining a fuel inlet 1 2 at one end thereof. Within the body there extends a magnetisable and hollow core 1 3 through which extends a passage 1 4 which connects the inlet 1 2 with an outlet 1 5 of the body.

Surrounding the core 1 3 within the body is a former 1 6 formed from synthetic resin material upon which is wound a solenoid winding 17.

Adjacent the outlet 1 5 the body 11 defines an integral radially inwardly extending circumferential shoulder 1 8 against which a steel annulus 1 9 is trapped by a steel valve seat member 21. The valve seat member 21 is in the form of a disc the diameter of which is equal to the internal diameter of the body 11, the disc having a centrally disposed outlet orifice 22. The core 1 3 terminates short of the valve seat member 21 and an annular clearance exists between the core and the inner face of the shoulder 1 8. Moreover, the face of the seat member 21 which is presented to the end of the core 1 3 is shaped to provide an annular rib like seating 23 about the end of the orifice 22.Located within the annulus 19 between the member 21 and the end of the core 1 3 is a valve plate 24 formed from magnetisable material. The valve plate is in the form of a disc slidably received within the annulus 1 9 and having extending therethrough a plurality of apertures 25 which are arranged in a circular row about the central axis of the plate. The mean diameter of the circular row of apertures 25 is greater than the diameter of the seating 23 and a compression spring 26 housed within the passage 14, urges the valve plate 24 into engagement with the seating 23.This is the closed position of the injector since engagement of the valve plate 24 with the seating 23 prevents flow of fuel between the inlet 1 2 and the outlet 1 5. The spring 24 is located within a recess formed in the valve plate.

The internal diameter of the shoulder 1 8 is less than the diameter of the annulus 1 9 and the shoulder therefore overlies the outer peripheral region of the valve plate 24. When therefore the winding is energised the valve plate is attracted towards the flange and the end of the core 1 3. The thickness of the valve plate 24 is less than the thickness of the annulus 1 9 by a predetermined amount to permit the valve plate 24 to move by said predetermined amount.The movement of the valve plate is arrested by the shoulder and when in this position, fuel can flow through the passage in the port 13, across the upper face of the valve plate 24, through the apertures 25 therein, beneath the valve plate 24, over the top of the seating 23 and through the outlet orifice 22 into the outlet 1 5.

When the solenoid winding 1 7 is de-energised the spring 26 returns the valve plate 24 to its closed position in engagement with the seating 23.

In order to minimise the risk of the valve plate 24 tilting as it closes onto the seating 23 a further annular rib 28 is provided on the valve seat member 21. The rib 28 is disposed outwardly of the annular seating 23.

In order to ensure that the valve plate 24 returns quickly to its closed position when the solenoid is de-energised, a non-magnetic spacer 27 is placed between the shoulder 18 and the valve plate 24. The spacer 27 thus prevents metal contact btween the valve plate 24 and the shoulder 1 8 and thus improves the "drop off" characteristic of the valve.

The outlet orifice 22 shown in Fig. 1 includes an entrance portion of truncated conical form and an exit portion of right cylindrical form and the spray pattern produced by the orifice will be of pencil-like form that is to say it will be more in the form of a jet of fuel. In some instances it is desirable that the spray should be bushy in form to facilitate mixing of the droplets of fuel in the spray, with the airstream into which it is directed.

In order to achieve the desired effect the apertures 25 formed in the valve plate have their axes inclined as shown in Figs. 3 and 4.

The effect of inclining the apertures is to impart a circumferential velocity component to the fuel flowing through the apertures 25 into the space which when the winding is energised, lies between the valve plate 24 and the valve seat member 21. The swirling of the fuel in the aforesaid space results in the formation of a bushy spray of fuel in and beyond the outlet 1 5. As shown in the lower portion of Fig. 3 the axes of the apertures 23 are inclined to the vertical axis of the valve plate and at a tangent to the pitch circle of the apertures. The amount of swirl imparted to the fuel depends upon the inclination of the axes. It has been found that angles as low as 10 produce a variation in the spray pattern tending towards the desired bushy spray. An angle of 45 produces an even bushier spray in view of the greater swirling of the fuel.

The formation of the bushy spray can be further enhanced by in addition to the inclination above, inclining the axes towards the central axis of the valve plate. This inclination together with the inclination previously described being shown in the upper portion of Fig. 3. The inclination towards the central axis can be as much as 35 .

Claims

1. A fuel injector comprising an injector body, a fuel inlet defined in the body, means defining a field outlet orifice, an annular seating defined about the orifice, a valve plate for co-operation with the seating, resilient means biasing the valve plate into contact with the seating, a solenoid device carried by the body, said valve plate being formed from magnetisable material and being movable upon energisation of said solenoid away from said seating to allow fuel flow through said orifice, and apertures in said valve plate, said apertures being positioned outwardly of said annular seating, said apertures forming part of the flow path for fuel flow through the nozzle between said inlet and said outlet orifice, the axes of said apertures being inclined to the perpendicular of the valve plate whereby the fuel before it enters said orifice has a swirling motion about the axis of said orifice.

2. An injector according to Claim 1 in which the axes of said apertures are tangential to the pitch circle of said apertures.

3. An injector according to Claim 2 in which the inclination of said axes lies between 10 and 45 .

4. An injector according to Claim 3 in which the axes of said orifices are additionally inclined towards the central axis of the valve plate.

5. An injector according to Claim 4 in which the additional inclination lies between 0" and 35 .

6. A fuel injector comprising the combination and arrangement of parts substantially as hereinbefore described withg reference to Figs. 1 and 2 as modified by Figs. 3 and 4 of the accompanying drawings.