GB2213650A

GB2213650A - Fuel injection valve

Info

Publication number: GB2213650A
Application number: GB8828434A
Authority: GB
Inventors: Brian Colin Pagdin
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-12-08
Filing date: 1988-12-06
Publication date: 1989-08-16
Also published as: GB8728628D0; GB8828434D0

Abstract

The fuel injection valve includes an outer body 1 and a core member 3 extending within the body. The body and core member are formed from magnetisable material and define pole faces presented to a valve member 12 which is spring biased into contact with a seating 10. Interposed between the body and core member is a permanent magnet 100 which drives magnetic flux through the core member and body. The flux produced by the magnet is sufficient to hold the valve member in contact with the pole faces but not sufficient to lift the valve member from the seating. The flux produced by the magnet is enhanced when a coil 7A is energised to lift the valve member and when a coil 7B is energised the flux produced by the magnet is opposed to allow the spring 15 to return the valve member to the seating. <IMAGE>

Description

FUEL INJECTION VALVE The invention relates to a fuel injector of the type designed to be operated by a solenoid. In such an injector a coil is energised to open a magnetisable valve and allow the passage of fuel into the inlet manifold of an internal combustion engine.

With known devices an electrical current must pass through the coil during the entire time that the valve is held open.

GB 2,175,452 discloses a valve comprising a valve plate made of a relatively bulky permanent magnet which is mounted between a pair of solenoids which control the valve plate. The valve plate in view of its bulk, will have a high degree of inertia, so that fast response times are impossible for this configuration.

According to the invention a fuel injector for the injection of fuel to an internal combustion engine, comprises a body, a through passageway through which fuel can flow from an inlet to an outlet, a magnetisable valve member and a valve seating therefor, spring means urging the valve member onto its seating, a magnetic circuit including the valve member, a permanent magnet and control means, the magnetic circuit being arranged in one condition to provide a relatively weaker magnetic force allowing the spring means to hold the valve member on the seating and in another condition to provide a relatively stronger magnetic force by which the valve member is held away from its seating.

Preferably, the permanent magnet has sufficient strength to hold the valve member off its seating but insufficient strength to lift the valve member off its seating, and the magnetic circuit includes a coil which can be arranged to exert an auxillary magnetic force to draw the valve member off its seating. Also preferably, a further coil is present which can be arranged to provide a magnetic force to counter the effect of the force of the permanent magnet so that the valve member can be released to return to its seating.

It is a key feature of the invention that the coil is pulsed with current at the beginning and at the end of the inection cycle. This results in savings in electrical power but it also means that savings can be made in the drive units for the coils which do not have to carry current for such a long time. Once open the valve is held open by means of the permanent magnet.

The valve may be of any suitable type such as a single point injector, it may have a bottom fuel feed or it may be a ball valve.

In order that the invention may be better understood it will be descrbied with reference to the accompanying drawings in which: Figure 1 is a longitudinal sectional view of an injector according to the invention, with the valve in the open condition and showing the magnetic flux lines in one half of the section; Figure 2 is a portion of Figure 1 drawn to an enlarged scale, better to show the detail of the valve, with the valve in the closed condition; and Figure 3 is the same as Figure 2 with the valve shown in the open condition.

The injector comprises a hollow generally cylindrical body 1 formed from a magnetisable material e.g. iron and defining a fuel inlet 2 at one end thereof. Within the body 1 there extends a magnetisable and hollow second generally cylindrical core member 3 through which extends a passageway 4 which connects the inlet 2 with an outlet 5 of the body. A permanent magnet 100 in the form of an annular ring is present about a longitudinal middle portion of the core member 3. In the embodiment shown, the interior of the annular ring presents a north pole and the exterior of the ring present a south pole. A further annulus 110, formed from a magnetisable material surrounds the permanent magnet and contacts an inside wall of the body 1.Surrounding the core member 3 within the first body 1 and below the permanent magnet 100 is a former 6 made from a synthetic resin material upon which is wound solenoid windings or coils 7a and 7b. Coil 7a, or the direction of current flow therein is arranged in such a manner, that when energised, a magnetic flux is produced which is in the same direction as that from the permanent magnet 100.

Coil 7b or the direction of current flow therein is arranged so that when energised a magnetic flux is produced which is in the opposite direction to that from the permanent magnet 100.

The outlet 5 which is in the form of a pipe retained within the narrower end of the body 1 projects in use into the inlet manifold of an engine (not shown). As shown in Figures 2 and 3 adjacent the outlet 5, the body 1 defines an integral radially inwardly extending shoulder 8 against which a steel annulus 9 is trapped by a valve seat member 10 which in the particular example is formed from preferably non magnetisable steel. The valve seat member 10 is in the form of a disc, the diameter of which is equal to the internal diameter of the body 1, the disc having a centrally disposed outlet orifice 11.

An annular space is defined between the bottom of the core member 3 and the face of the shoulder 8. The core member 3 terminates short of the valve seat member 10 at the same level as the underside of the shoulder 8 the lower faces of the core member 3 and shoulder 8 defining pole faces. A plurality of holes 120 is formed in the member 3 to form communication between the passageway 4 and the interior of the body 1.

Located within the steel annulus 9 between the valve seat member 10 and the end of the core member 3 is a valve plate 12, formed of a magnetisable material. The valve plate 12 is in the form of a disc and is guided for movement by the annulus 9. Formed in the valve plate is a plurality of apertures 13 which are arranged in a circular row about the central axis of the disc.

As best seen in Figure 2 the face of the valve seat member 10 is shaped to provide an annular seating 14 about the orifice 11 but within the apertures 13. A further annular rib 140 is disposed outwardly of the annular seating 14. A compression spring 15 housed within the passageway 4 of the member 3. The lower end of the spring is received in a recess in the valve plate 12 and-the spring urges the valve plate onto the seating 14. A spring adjustment plug 150 is engaged by the upper end of the spring and is adjustable, within the member 3, to enable the force exerted by the spring to be varied.

The internal diameter of the shoulder 8 is less than the diameter of the annulus 9 and the shoulder 8 therefore overlaps the outer peripheral region of the valve plate 12.

The core member 3 and the body 1 form a magnetic circuit through which magnetic flux is driven by the permanent magnet 100. The strength of the magnet is such that if the valve plate is urged into engagement with the pole faces defined by the core member and body it will be retained by the action of the magnetic flux. The strength of the magnet is not sufficient to lift the valve plate from the seating 14 against the action of the spring and the fuel pressure.

At the beginning of the injection cycle a pulse of electrical current flows from an electronic control unit (not shown) to energise the coil 7a. This produces a magnetic flux in the same sense as that produced by the permanent magnet. The valve plate 12 is drawn up towards the bottom face of the core member 3 to complete the magnetic circuit 130. The coil 7a is then de-energised but the magnetic attraction of the permanent magnet 100 is sufficient to hold the plate 12 in contact with the core member 3. Fuel can now flow from the inlet 2 through the passageway 4 out through the holes 120 in the core member 3, down through the apertures 13 in the valve plate 12 and then under the plate and down through the outlet orifice 11, to emerge from the outlet 5.

At the end of the injection cycle, a pulse of current is'sent to the coil 7b. This coil produces a magnetic flux which is opposite to that produced by the permanent magnet with the result that the flux flowing in the valve member is cancelled and the force retaining the valve member disappears. The valve member is therefore urged by the spring into contact with the seating 14. The cycle is repeated at a frequency proportional to the rotational speed of the engine.

The invention is not limited to the embodiment shown, thus the permanent magnet could be at any point in the magnetic circuit, and may not be in annular ring form. The construction of the coils may differ, for example the coil may be of a centre-tapped variety or alternatively a single coil may be supplied with current in one direction for opening the valve and in the opposite direction to close the valve.

Claims

1. A fuel injector for the injection of fuel to an internal combustion engine comprising a body, a through passageway through which fuel can flow from an inlet to an outlet, a magnetisable valve member and a valve seating therefor, spring means urging the valve member onto its seating, a magnetic circuit including the valve member, a permanent magnet and control means, the magnetic circuit being arranged in one condition to provide a relatively weaker magnetic force allowing the spring means to hold the valve member on the seating and in another condition to provide a relatively stronger magnetic force by which the valve member is held away from its seating.

2. An injector according to Claim 1 in which said control means includes winding means which can be energised in one mode to increase the magnetic flux flowing in the magnetic circuit due to the permanent magnet in order to lift the valve member from the seating against the action of the spring, the winding means also being energised in a different mode to produce a magnetic flux which opposes the magnetic flux produced by the permanent magnet when it is required to allow the valve member to move into contact with the seating.

3. An injector according to Claim 2 in which said winding means comprises a single winding wound about the magnetic circuit, the winding being energised by current flowing in one direction in the one mode and in the other direction in the other mode.

4. An injector according to Claim 2 in which said winding means comprises a pair of coils wound about the magnetic circuit, one of said coils being energised in said one mode and the other coil in said other mode.

5. An injector according to Claim 4 in which said coils are formed by a centre tapped winding.

6. An injector according to any one of Claims 2-5 in which said body is hollow and there is located therein in spaced relationship a core member which defines said passageway, said winding means being located about said core member, the core member and the body defining pole faces which are presented to the valve member, said permanent magnet being of annular form and being located between the body and the core member at a position remote from said pole faces, said winding means being positioned between said magnet and the pole faces.

7. An injector according to Claim 6 in which said magnet is located about said core member, and an annular member formed from magnetisable material is located between the magnet and the body.

8. A fuel injector for the injection of fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.