GB2215776A - I.C. engine intake fuel injection system - Google Patents

Abstract

Manifold injectors 11 with fuel pressure opened valves (29, Fig 2) have their regulated fuel pressure supply controlled by respective pairs of solenoid valves 15 at their inlets or their supply pressure is reduced to below the valve opening pressure by a pair of solenoid valves (24, fig 4). The solenoid valves may be remotely located from the injectors. <IMAGE>

Description

FUEL SYSTEM FOR INTERNAL COMBUSTION ENGINE This invention relates to a fuel injection system for supplying fuel to a high performance internal combustion engine of the spark ignition type such as an engine for a rally or racing car.

A known system for supplying fuel to a spark ignition engine comprises a solenoid operated fuel injector which includes a valve member which is moved to the open position upon energisation of a solenoid and which returns to the closed position under the action of a spring when the solenoid is de-energised. Such a system is adequate for passenger carrying vehicles but for engines which require high flow rates of fuel at high engine speeds a problem arises in that in order to cope with the high flow rate of fuel the valve must be made larger and this means that the mass of the valve member will be increased. With an increase in the mass of the valve member the size of the solenoid must be increased and in general the larger the valve the lower the response time due to an increase in the mechanical inertia of the valve member and the electrical inductance of the solenoid.In order to preserve the fast response time and have an increased flow rate it would be possible to provide at the or each position where it is required to deliver fuel, two or more smaller injectors.

The injectors are normally mounted on the air inlet manifold of the engine and in most cases it would be difficult to locate an increased number of smaller injectors on the air inlet manifold.

Fuel injection nozzles for compression ignition engines commonly employ a valve member which is spring biased into contact with a seating and is lifted from the seating by fuel under pressure supplied to an inlet, to allow fuel flow from the inlet to an outlet. Such nozzles can provide high fuel flow rates.

The object of the invention is to provide a fuel injection system for a high performance engine of the spark ignition type.

According to the invention a fuel injection system for a high performance spark ignition engine comprises an injection nozzle including a fuel pressure actuated valve member, the nozzle in use being mounted so that fuel delivered from an outlet of the nozzle flows into an air inlet of the engine and a plurality of solenoid operated valves for controlling the supply of fuel under pressure.

Examples of fuel injection systems in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a diagrammatic layout of one form of the system.

Figure 2 is a cross sectional side elevation of one example.of an injection nozzle which can be used in the system of Figure 1.

Figure 3 is a cross sectional side elevation of a solenoid operable valve which can be used in the system of Figure 1, and Figure 4 is an alternative form of the fuel system.

Referring to Figure 1 of the drawings, part of an engine air inlet manifold is shown at 10 and mounted on the manifold 10 are a plurality of fuel injection nozzles 11 which are positioned to direct fuel into the air inlet ducts of the engine cylinders respectively. Each injection nozzle 11 has a fuel inlet which is connected by a respective pipe 12, to a collection chamber 13 associated with each nozzle.

Each collection chamber receives fuel from a fuel supply conduit 14 by way of a pair of solenoid operable valves 15, the solenoid windings of which are shown diagrammatically at 16. The windings are connected to a control system 17 by cables 18. Fuel is supplied to the conduit 14 by means of an electrically driven pump 17 and the fuel pressure within the conduit is controlled by a relief valve 18 which operates by spilling fuel from the conduit. The spilled fuel is returned to a fuel tank 19 along a return conduit 20 and any fuel lacking within the injection nozzles is returned to the tank along a drain conduit 21.

In operation, the pump 17 pressurizes the fuel in the conduit 14 to a pressure determined by the valve 18. In order to achieve delivery of fuel through an injection nozzle 11 the solenoid windings 16 of the associated valves 15 are energised and fuel flows into the associated collection chamber 13 and along the respective pipe 12 to the injection nozzle. As will be described, the injection nozzle incorporates a fuel pressure operable valve and this will be opened to allow fuel flow into the associated air inlet duct. When the windings 16 are de-energised the valves close and the flow of fuel to the injection nozzle ceases and the valve member therein closes under the action of a spring. It will be understood that the time during which the valves 15 are open determines the amount of fuel which is supplied through the associated injection nozzle to the engine.

The control system 17 includes a computer which determines the aforesaid time of opening in response to various engine operating parameters and desired operating parameters. Sensors about the engine can provide information regarding the battery voltage, the altitude, the air flow to the engine, the temperatures of the engine and that of the air flowing to the engine, the engine speed and the throttle position amongst others. The computer determines the opening time of the valves in order to provide the most advantageous engine operating condition.

The solenoid operated valves can be held open for as little as 1.0 ms and when open the rate of fuel supply to the engine can be up to 2.0 litres/min.

As described the system has one fuel injection nozzle per engine cylinder. The system can however be applied to an engine of the type in which the conventional carburettor is replaced by a single injection nozzle.

In the system as described with reference to Figure 1 the valves 15 are connected in series with the respective injection nozzles. It is possible to use a parallel arrangement which is shown in Figure 4. In Figure 4 the inlets of the injection nozzles 11 are connected directly to the supply conduit 14. The valve 24 are also connected to the supply conduit 14 and when open allow fuel flow into a collection chamber 13 which is connected by a return conduit 22 to the fuel tank in which is located a pressurising valve 25.The pump 17 in this case is a mechanical pump driven by the associated engine which has a maximum outlet pressure which is higher than the setting of the valve 23 and the valve 23 is set so that when the valves 24 are closed, the pressure in the supply conduit 14 is slightly higher than the pressure required to open the valves in the fuel injection nozzles 11. When the valves 24 are open the pressure in the supply conduit falls to a value set by the pressurising valve 25 and this is set at a pressure below the closing pressure of the injection nozzles 11. When the valves 24 are closed by energising the windings therein the pressure quickly builds up in the supply conduit 14 and the valves in the nozzles 11 open to allow fuel flow to the engine and when the valves 24 are opened, the fuel pressure in the supply conduit falls to allow closure of the valves in the nozzles.In the arrangement shown in Figure 4 fuel will be delivered through the nozzles 11 at the same time whereas in the arrangement shown in Figure 1 the flow through the nozzles 11 can if desired, be arranged to take place in a sequence.

Figure 2 shows an example of a fuel injection nozzle 11 and it comprises a nozzle body 24 which is secured to a holder 25 in which is formed a fuel inlet 26. Formed in the nozzle body is a bore 27 which at its end remote from the holder is provided with a seating surrounding an outlet 28. A valve member 29 is slidable in the bore and is biased by a spring 30 into contact with the seating. The spring is located in a chamber in the holder 25 and a drain passage 31 extends from the chamber and communicates with the drain conduit 21. The valve member defines a surface against which the fuel pressure at the inlet 26 can act and when the fuel pressure attains a sufficiently high valve the valve member is lifted from the seating to allow fuel flow through the outlet 28.

The nozzle shown in Figure 2 has an inwardly opening valve member. An alternative form of nozzles has an outwardly opening valve member in which the valve member is in the form of a poppet.

Figure 3 shows an example of a valve 15 and it comprises a central tubular core member 33 formed from magnetic material which is surrounded in spaced relationship by a tubular body 34. In one end of the body is mounted a tubular outlet 35 which locates in the collection chamber 13 and interposed between the inner end of the tubular outlet and an inwardly directed flange on the body, is a seating member 36 and an annular distance piece 37, the distance piece being intermediate the seating member and the flange. The flange projects inwardly beyond the distance piece and with the core member forms a pair of pole faces which assume opposite magnetic polarity when the winding 16 surrounding the core member is energised.A valve member in the form of a disc 38 is guided by the distance piece for movement towards the pole pieces under the action of the magnetic forces and away from the pole pieces by a spring 39.

The seating member is provided with a central orifice 40 and is surrounding by inner and outer seating elements which are engaged by the valve member when the winding is de-energised. The core member projects from the body to form a fuel inlet 41 which is connected to the supply conduit 14. The armature is provided with through openings which are located outermost from the inner seating element so that when the valve member is lifted from the seating element fuel can flow from the inlet 41 into the outlet 35 by way of the orifice 40.

By the arrangement described high flow rates of fuel can be achieved with good atomization of the fuel as it is delivered to the engine. In addition, fast response times are obtained by the use of a number of small electromagnetically operable valves which control the fuel flow to the injection nozzles. In the example two valves are illustrated to control the flow of fuel to each nozzle.

It will be understood that more valves can be provided and that not all the valves associated with each nozzle need be operated if only small flow rates of fuel are required.

The valves and collection chambers can be mounted on the engine at a position removed from the air inlet manifold or they can be mounted on for example, the engine bulkhead.

Claims (9)

1. A fuel injection system for a high performance spark ignition engine comprising an injection nozzle including a fuel pressure actuated valve member, the nozzle in use being mounted so that fuel delivered from an outlet of the nozzle flows into an air inlet of the engine and a plurality of solenoid operated valves for controlling the supply of fuel under pressure to the nozzle.

2. A system according to Claim 1 in which said valves are connected in series with the nozzle and a source of fuel under pressure.

3. A system according to Claim 2 in which said source of fuel comprises a fuel supply conduit, the system further including a pump for supplying fuel to said conduit and a relief valve for controlling the pressure of fuel in the conduit.

4. A system according to Claim 3 in which said valves are provided with outlets through which fuel flows into a collection chamber when the valves are open, said collection chamber being connected to an inlet of the nozzle.

5. A system according to Claim 4 including a plurality of injection nozzles, each nozzle having an associated collection chamber and a plurality of valves, and an electronic control system for controlling the supply of electric current to the solenoids of the valves.

6. A system according to Claim 1 comprising a fuel supply conduit, a pump for supplying fuel under pressure to the supply conduit, the nozzle having a fuel inlet connected to said conduit, and the valves having fuel inlets connected to said conduit, said valves when open effecting a reduction of the fuel pressure at the inlet of said nozzle so that the valve member of the nozzle remains in the closed position.

7. A system according to any one of the preceding claims in which the valve member of the nozzle is biased to the closed position by a spring.

8. A fuel injection system for a high performance spark ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 1, 2 and 3 of the accompanying drawings.

9. A fuel injection system for a high performance spark ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 2, 3 and 4 of the accompanying drawings.