GB2147949A

GB2147949A - Fuel injector for an I.C. engine

Info

Publication number: GB2147949A
Application number: GB08423921A
Authority: GB
Inventors: John Herbert Kenning
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-10-14
Filing date: 1984-09-21
Publication date: 1985-05-22
Also published as: GB2147949B; GB8327527D0; GB8423921D0

Abstract

A fuel injector comprises a valve seat member 21 which defines on one face inner and outer annular seating elements 23, 23A from between which extend outlet orifices 22. A valve plate 24 is spring biased into engagement with the seating elements to prevent fuel flow through the orifices, the plate being movable against the action of the spring by magnetic forces. The valve plate has a central aperture 24A smaller in diameter than the inner seating element 23 and a plurality of further apertures 24B outside the outer seating element 23A. Fuel flows through the apertures to the orifices when the valve plate is lifted from the seat member. The orifices 22 are inclined towards the centre line of the valve seat member 21 (Fig. 3) to minimise the risk of fuel spray contacting the sides of the outlet (15, Fig. 1). <IMAGE>

Description

SPECIFICATION Fuel injector This invention relates to a fuel injector for supplying fuel to an internal combustion engine more particularly a petrol injector for supplying fuel to an air inlet manifold of a spark ignition engine, the injector comprising a valve seat member having at least a pair of orifices formed therein and through which fuel can flow from a fuel inlet, a valve plate biased into contact with the seat member to prevent flow of fuel through the orifices and means operable to lift the valve plate away from the seat member to allow fuel flow through the orifices.

An example of such an injector is described in British Patent Specification 858966. In the injector described therein the orifices are formed in inserts respectively which are located in the seat member and each insert defines an annular seating about the orifice, which lies above the surface of the seat member, for engagement by the valve plate. The jets of fuel produced by the orifices combine in an outlet to produce a fuel spray.

One disadvantage of such an injector is that the valve plate must seat on relatively small seatings which are widely spaced on the seat member. The valve plate must therefore be carefully guided particularly where only two orifices are provided to ensure correct seating.

Moreover, it is not easy to manufacture the inserts and the seat member to the degree of accuracy such that the inserts can be mounted in the seat member and assembled straight into the injector.

The object of the present invention is to provide an injector of the kind specified in an improved form.

According to the invention in an injector of the kind specified said valve seat member is provided with first and second annular seat elements disposed one within the other, for engagement by the valve plate, said orifices opening into the space defined between said seat elements.

An example of a fuel injector in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a longitudinal sectional view of the injector.

Figure 2 is a view to an enlarged scale of part of the injector seen in Fig. 1, and Figure 3 is a further enlarged view of part of the injector seen in Fig. 2.

Referring to Fig. 1 of the drawings, the injector comprises a hollow general 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 flanged 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 and upon which is wound a solenoid winding 1 7. The outlet which is in the form of a sleeve retained within the body, projects in use into the air inlet manifold of a spark ignition engine.

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 is in the form of a disc the diameter of which is equal to the internal diameter of the body 11, the disc having in the particular example, a pair of outlet orifices 22 formed therein. The orifices extend from the surface of the valve seat member remote from the outlet and from between a pair of annular seat elements 23, 23A, which project above the general level of the aforesaid surface.

Located within the steel annulus 1 9 is a valve plate 24 which is formed from magnetisable material. The valve plate is in the form of a disc slidably received within the annulus 1 9 and the disc has a central aperture 24A and a plurality of apertures 24B disposed in a circle about the axis of the plate. The aperture 24A has a diameter which is smaller than that of the seat element 23 and the aperatus 24B lie outside the seat element 23A. The valve plate is biased into contact with the seat elements 23, 23A by means of a coiled compression spring 26 housed within the passage 14.

The internal diameter of the shoulder 1 8 is iess than the diameter of the annulus 1 9 and the shoulder therefore overlies the outer peripheral portion of the valve plate 24. When therefore the winding is energised the valve plate is attracted towards the shoulder and the end of the core 1 3. The thickness of the valve plate is less than the thickness of the annulus 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 core 13, across the upper face of the valve plate 24, through the apertures 24A and 24B and then through the orifices 22 into the outlet 1 5. When the solenoid winding 1 7 is de-energised the spring 26 returns the valve plate to its closed position in engagement with the seatings 23, 23A.

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. The spacer thus prevents contact between the valve plate and the shoulder and thus improves the "drop off" characteristic of the valve.

The valve seat member as described above is particularly easy to manufacture and furthermore, the valve plate when moving towards the closed position, aligns very quickly with the seat elements since these are of a comparatively large diameter. The number of orifices 22 in the particular example is two but these can be increased in number to increase the rate of fuel flow through the injector. As will be seen from Fig. 3 the axes of the orifices 22 are inclined towards the centre line of the valve seat member by an angle of about 5 . Moreover, the opening from the annular depression defined between the seat elements is flared slightly. The inclination of the orifices minimises the risk of the spray formed at the exits of the orifices contacting the sides of the outlet 1 5. It will be noted that when the valve plate is lifted from the seat member fuel to one orifice passes through both the apertures 24A and 24B and the area through which the fuel can flow into the annular depression defined between the seat elements 23 and 23A and from which the orifices extend, is substantially larger for a given valve lift as compared with the arrangement shown in the aforementioned British patent specification. As a result, for a given lift of the valve plate, there is a smaller pressure drop between the valving surfaces and this means that there is a greater pressure drop across the orifices 22 leading in use to more accurate metering of the fuel.

Claims

1. A fuel injector for supplying fuel to an air inlet manifold of a spark ignition engine, the injector comprising a valve seat member having at least a pair of orifices formed therein and through which fuel can flow from a fuel inlet, a valve plate biased into contact with the seat member to prevent flow of fuel through the orifices and means operable to lift the valve plate away from the seat member to allow fuel flow through the orifices, said valve seat member being provided with first and second annular seat elements disposed one within the other, for engagement by the valve plate, said orifices opening into the space defined between said seat elements.

2. An injector according to Claim 1 in which said valve plate has a central aperture and a plurality of further apertures, the central aperture having a diameter smaller than the diameter of the inner seat element and the further apertures lying outside the outer seat element.

3. An injector according to Claim 1 in which the axes of said orifices are inclined towards the centre line of the valve seat member.

4. An injector according Claim 3 in which said orifices have flared openings from said space.

5. A fuel injector for supplying fuel to an internal combustion engine more particularly a petrol injector for supplying fuel to an air inlet manifold of a spark ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.