Fuel injector

Abstract

 A fuel injector of the type in which a pencil-shaped jet of fuel is directed onto a break-up disc or target (22) for atomization and mixing with the air stream inlet of an internal combustion engine, is arranged so that the air stream passes over opposing surfaces of the target (22). In this way any fuel which might have settled on the injector or the target (22) is carried away by the air stream, thereby reducing unwanted hydrocarbon emissions from the engine.

Description

[0001] The invention relates to a fuel injector of the type known as a pintle, plate or disc injector in which a pencil-shaped jet of fuel is urged on to a target or break-up disc and thereby atomised into droplets which are then fed into the air stream of an internal combustion engine. Such a fuel injector is exemplified by GB-A-2144178A.

[0002] The invention is based on the realisation that by the disposition of the target, the level of hydrocarbon emissions from the associated engine is reduced.

[0003] According to one aspect of the invention, there is provided a fuel injector for use with an internal combustion engine, the injector including means for producing a pencil-shaped jet of liquid fuel, a target being located in the path of the jet and arranged to break up the jet into a spray of droplets for feeding into a stream of air characterised in that the target is disposed relative to the air stream such the air stream will remove droplets of fuel which would otherwise settle on the target.

[0004] Preferably, the target is disposed such that the air stream passes over the opposite sides of the target. In a preferred feature, the jet is arranged to impinge on a mesh surface of the target.

[0005] Preferably the injector is mounted on a wall of an inlet manifold, and the target is disposed in the air stream inlet of the manifold. In such a case, the target is joined to the outlet end of the injector body such that the air stream may pass over both sides of the target. In one preferred construction a pipe extends from within the outlet end of the body and the target extends across the end wall of the pipe, the side wall of the pipe having through holes, the pipe extending in use into the air stream so that air may pass over the opposite faces of the target.

[0006] Most preferably, the injector comprises a body having an inlet for the fuel and a fuel outlet orifice, valve means being located in the orifice for controlling the flow of fuel and a solenoid for controlling the valve means.

[0007] In another aspect, the invention also provides a method of injecting an air fuel mixture into the inlet manifold of an internal combustion engine without causing the build up of deposits, the method comprising passing liquid fuel through an injector arranged to release a pencil jet of fuel on to a target arranged to break up the jet into a spray of droplets and feeding the droplets into an air stream characterised by disposing the target relative to the air stream such that the stream of air removes droplets of fuel which would otherwise settle on the target.

[0008] In order that the invention may be well understood, it will now be described with reference to the accompanying drawings in which

Figure 1 is a side view of an injector of the invention:

Figure 2 is an end view of the injector of Figure 1:

Figure 3 is an enlarged longitudinal sectional view along line A - A of Figure 1; and

Figure 4 is an enlarged view showing detail of part of Figure 3

[0009] The injector comprises a hollow generally cylindrical stepped multi-part body 1 formed from a magnetisable material, eg, iron and defining a fuel inlet 2 at one end, (the top as shown in Figures 1 and 3) and a fuel outlet 3 at the other end. A generally cylindrical flanged hollow core 4 formed from a magnetisable material extends coaxially within the body 1 and includes a passageway 5 which connects the inlet 2 with the outlet 3 of the body 1. A generally cylindrical former 6 made from a synthetic resin material coaxially surrounds the core 4 about the outlet end thereof. Solenoid windings 7 are wound about the former 6 and are connected to electrical connection pins 8. Upstream of the outlet end 3 the body 1 defines an integral radially inwardly extending shoulder 9 against which a steel annulus is trapped by a steel valve seat member 11. The valve seat member 11 is in the form of a disc, the diameter of which is equal to the internal diameter of the body 1. The valve seat member 11 has a centrally disposed outlet orifice 12 which includes an entrance portion of truncated conical form and an exit portion of cylindrical form.

[0010] An annular space is present between the outlet end of the core 4 and the radially adjacent face of the shoulder 9. The core 4 terminates short of the valve seat member 11 and the opposing face of the core 4 is at a higher level than the lower face of the shoulder 9.

[0011] A valve plate 14 is located within the steel annulus 10 between the valve seat member 11 and the opposing face of the core 4. The valve plate 14 is in the form of a disc made from a magnetizable material and having a plurality of apertures 15 which are arranged in a circular row about the central axis of the plate 14. The upper face of the valve seat member 11 is formed with an annular rib 16 to provide a valve seating. The diameter of the rib 16 is less than that of the circular row of apertures 15. A further rib 17 is disposed radially outwardly from the first rib 16. A compression spring 18 housed within the passageway 5 of the core 4 urges the valve plate 14 onto the valve seating rib 16. A spring adjustment plug 19 is arranged, e.g., by threading, to move up and down within the core 4 to vary the strength of the spring force. The bottom of the spring 18 is received within a recess 20 formed in the upper face of the valve plate 14.

[0012] The internal diameter of the shoulder 9 is less than that of the annulus 10 and the lower face of the shoulder 9 therefore overlaps the outer peripheral region of the valve plate 14. When, therefore, the solenoid winding 7 is energised by electrical signals applied to the pin 8 from, e.g., an engine control unit (not shown), the valve plate 14 is attracted towards the lower face of the shoulder 9. The thickness of the valve plate 14 is less than the thickness of the annulus 10 by a predetermined amount to permit the valve plate 14 to move by said predetermined amount. The movement of the valve plate 14 is arrested by the shoulder 9 which contacts the valve plate 14 about the periphery thereof. When the plate 14 is in this position fuel can flow from the inlet 2, through the passageway 5 in the core 4, across the upper face of the valve plate 14, through the apertures 15 therein, over the top of the annular seating rib 16 and through the outlet orifice 12 into the outlet 3 of the body 1. Because of the shape of the orifice 12, the spray pattern produced from the orifice 12 will be of pencil-like form, that is to say it will be in the form of a jet of fuel.

[0013] When the solenoid winding is de-energised the spring 18 returns the valve plate 14 to its closed condition in engagement with the valve seating rib 16. As best shown in Figure 4, a non-magnetic spacer 13 is present between the lower face of the shoulder 9 and the valve plate 14 and annulus 10 to prevent contact between the valve plate 14 and the shoulder 9 and to improve the "drop off" characteristic of the valve.

[0014] A cylindrical pipe 21 formed of, e.g., steel is retained at one end by welding or the like within the outlet end 3 of the body 1 and at the other end projects in use, e.g., into the inlet manifold of an engine.

[0015] A target 22 comprising a thin disc of metal gauze extends across the end face of the pipe 21 so that in use it is coaxial with the jet of fuel from the orifice 12. The target 22 is mounted in an annular recess 23 in the side wall of the pipe 21. Four circular holes 24 are formed through the side wall of the pipe 21 adjacent the target 22 and the holes are separated by four spaced apart arms 25.

[0016] In use, the injector is mounted on an engine so that the free end of the pipe is located within the air stream leading to the combustion chambers of an engine. During the injection of fuel a pencil-like jet of fuel leaves the orifice 12 and hits the target 22. The impingement of the jet of fuel onto the target 22 causes the jet of fuel to be atomized for mixing with the air stream flowing through the inlet manifold of the associated engine and across opposing faces of the target 22.

[0017] When a vehicle associated with the engine is accelerating a high rate of fuel flow will take place, but when the vehicle is deccelerating or idling and the flow rate of air and fuel is reduced, there is a risk that droplets of fuel will settle upon the target 22 or an adjacent part of the injector or manifold. These dro!plets of fuel may later pass into the engine and be incompletely burned thereby causing hydrocarbon emissions. This effect is reduced because of the holes 24 in the pipe 21 and the disposition of both faces of the target 22 in the air stream whereby any fuel droplets settling on the target or any adjacent part of the injector will be swept away by the air stream. As a result, the level of hydrocarbon emissions from the engine falls and pollution is reduced. Further more, the holes 24 ensure the air flow through the manifold is not significantly reduced by the presence of the pipe 21 so that power output of the engine is not significantly reduced.

Claims

1. A fuel injector for use with an internal combustion engine, the injector including means for producing a pencil shaped jet of liquid fuel, a target (22) being located in the path of the jet and arranged to break up the jet into a spray of droplets for feeding into a stream of air characterised in that the target (22) is disposed relative to the air stream such that the air stream will remove droplets of fuel which would otherwise settle on the target (22).

2. An injector according to Claim 1, characterised in that the target (23) is disposed such that the air stream passes over opposite sides of the target (22).

3. An injector according to Claim 1 or 2 characterised in that the target (22) is a disc of metal mesh.

4. An injector according to any preceding Claim, characterised in that the injector is mounted on a wall of an inlet manifold of an internal combustion engine and the target (22) is disposed in the air stream within the interior of the inlet manifold.

5. An injector according to Claim 4, characterised in that the injector comprises a body (1) having an inlet (2) for the fuel and a fuel outlet orifice (12) and a valve (14) controlled under the action of a solenoid (7) and arranged to produce a pencil shaped jet of fuel.

6. An injector according to Claim 5 characterised in that the target (22) is located at the free end of a pipe (21) retained within the outlet end (3) of the body (1) and the pipe (21) has through holes (24) formed through the side wall thereof whereby air can pass over opposing surfaces of the target (22).

7. A method of injecting an air fuel mixture into the inlet manifold of an internal combustion engine without causing the build up of deposits the method comprising passing liquid fuel through an injector arranged to release a pencil jet of fuel on to a target (22) arranged to break up the jet into a spray of droplets and feeding the droplets into an air stream characterised by disposing the target (22) relative to the air stream such that the stream of air removes droplets which would otherwise settle on the target (22).

8. A method according to Claim 7, characterised in that the target (22) comprises a plate located edge-on to the air stream so that the air prevents droplets from settling on opposite sides thereof.

9. A method according to Claim 7 or 8, characterised in that the target (22) comprises a disc of metal mesh.

10. A method according to any of Claims 7 to 9, characterised in that the flow of liquid fuel through the injector is regulated by solenoid controlled valve means (7, 14, 11).

Drawing