BACKGROUND OF THE INVENTION (1 ) Field of the Invention

THIS INVENTION relates to a fuel supply system for engines .

The invention may be applied to internal com¬ bustion engines which operate on liquid hydrocarbon fuels (e.g. petrol, gasoline, benzine, kerosene and the like) or other liquid fuels but is particularly suitable for petrol engines. 2. Prior Art

An engine designer faces three, sometimes con¬ flicting, goals. The engine should have good power and/ or torque characteristics, low exhaust emissions and good fuel economy.

It is known that "lean burn" engines which operate at high air/fuel ratios (e.g. of the order of 18:1) have low emission levels and good fuel economy but they often have poor and unacceptable performance characteristics.

To enable leaner air/fuel mixtures to be used, it has been proposed to introduce the fuel into the engine in vapour form as the finer droplets in the fuel mist are more easily ignited than the fuel droplets, with a wide size distributor, supplied by conventional carburettor or fuel injection systems. Examples of systems which supply the fuel in vapour form include the Patent Specifications AU 11982/67 (506950) (Little et al); AU 28171/77 ( ) (Barber); O82/03660 (JEB Energy Research Inc.) and O85/03330 (Onics Inc.). To date no such vapour supply system has proved commercially acceptable.

SUMMARY OF THE PRESENT I:-'-SNTI0N It is an object of the present invention to provide an engine fuel supply system where the liquid

fuel is supplied to the engine in gaseous or vapourous form.

It is a preferred object of the present invention to provide such a system where the air/fuel 5 mixture is very lean.

It is a further preferred object of the present invention to provide such a system where the vapourization of the fuel and the supply of the vapour to the engine is effected in two stages. L0 ^" It is a further preferred object of the present invention to provide a system where, at full throttle, liquid fuel is supplied direct to the engine for maximum power.

Other preferred objects of the present will 15 become apparent from the following description.

In one aspect the present invention resides in an engine fuel supply system including: at least two pressure vessels; pump means to supply liquid fuel from a 20 supply to the pressure vessels; means to heat the pressure vessels to cause at least a portion of the liquid fuel in the pressure vessels to be vapourized; and means to supply the vapourized fuel to the 25 intake of an engine; wherein: the pressure vessels are arranged in parallel ; and valve means are provided to selectively connect the pressure vessels to the pump means and the 30 vapour supply means so that while one pressure vessel is connected to the vapour supply means to supply the vapourized fuel to the engine, the other pressure vessel is disconnected from the vapour supply means while the liquid fuel in the other pressure vessel is being 35 vapourized.

Preferably the intake of the engine is a car¬ burettor or fuel injection unit and the vapour supply means includes a vapour line having a one-way check valve. Preferably a petrol (or other liquid f el) line is provided in parallel with the vapour supply means and interconnects the pump means to the engine intake via a selectively operable control valve.

Preferably a respective first solenoid (or other control valve selectively connects each pressure vessel to a fuel line from the pump and a respective second solenoid (or other) control valve connects each pressure vessel to the vapour supply means. Preferably the first solenoid valve of the pressure vessels and the second solenoid valve of the pressure vessel are opened .simultaneously, the other solenoid valves being closed and vice versa.

Preferably the heating means for the pressure vessels include induction heaters with coils wound around the pressure vessels which cause metal plates or blocks within pressure vessels to be heated. Alter¬ native heating means include hot coolant or engine or transmission oil passed through heat exchange coils in the pressure vessels; electric heating coils within or around the vessels; or microwave heating of the vessels The pressure vessels may be formed as part of the exhaust manifold and be heated by the hot exhaust gases

Preferably the system is controlled by an electronic logic control unit which incorporates a microprocessor. Preferably the control unit is connected to sensors which monitor the accelerator (or throttle) portion and pressure sensors on the pressure vessels. Preferably the control unit controls the solenoid valves and their sequence of opening and closing. Preferably the control unit incorporates

timers which cause a pulse of petrol to be supplied to the engine when the engine is at idle or at regular intervals.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully under¬ stood, a number of preferred embodiments will now be described with reference to the accompanying drawings , in which :

FIG. 1 is a schematic layout of the system; FIG. 2 is a schematic sectional side view of a pressure vessel;

FIG. 3 is a plan view of a vapour control valve of a second embodiment ; and

FIG. 4 is a sectional side view of the valve of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

-Referring to FIGS. 1 and 2, the fuel supply system 10 incorporates three interconnected systems: the fuel system 11, the logic system 12 and the accel¬ erator system 13.

The fuel system 11 has a fuel tank 14 fitted with an electric fuel pump 15 (rated at e.g. 420 kPa (60 p.s.i.)) which pumps petrol under pressure into petrol line 16.

A branch line 17 is fitted with a solenoid val.ve 18 and one-way check valve 19 and is connected to the fuel input of an electronic fuel injection (E.F.I.) unit 20 fitted to a petrol engine 21. (If preferred, pressure regulator (not shown) may be provided upstream of the solenoid valve 18.)

The petrol line 16 is fitted with a pressure regulator 19 (set at e.g. 40 kPa (20 p.s.i.)) and is split into lines 20, 21 which supply respective pressure vessels 22, 23 via solenoid valves 24, 25 and one-way

check valves 26, 27.

Referring to FIG. 2, each pressure vessel 22,

23 has a closed body with the petrol inlet lines 20, 21 sealed by suitable blocks 28. An induction heater unit 29 is provided for each pressure vessel with a housing 30 enclosing an electric coil 31 connected to an AC supply (not shown) and controlled by an electric switch 32. Metal plates

33 in the pressure vessels are heated by induction and in turn heat the pressure vessels and the petrol 34 and vapour 35 therein.

Pressure sensors 36, 37 monitor the pressure of the vapour 35 in the pressure vessels 22, 23.

Vapour lines 38, 39 from the pressure vessels are provided with solenoid valves 40, 41 and one-way check valves 42, 43 and are connected to a main vapour line 44. A one-way check valve 45 is provided in the main vapour line, which is connected to the input of the

E.F.I, unit 20. The solenoid valves 18, 24, 25, 40 and 41, and the pressure sensors 36, 27 are connected to the logic system 12, as is the E.F.I, unit 20.

The logic system 12 has a microprocessor 46 , which is programmable to suit the particular intended application, and a pair of internal timing circuits 47,

48.

The microprocessor 46 is connected to a sensor

49 which monitors the position of the accelerator pedal

50, this sensor 49 also being connected to the E.F.I. unit 20 either by a conventional accelerator linkage or by an electronic circuit.

A sensor 51 indicates when the pedal 50 is released i.e. into idle, while a sensor 52 indicates when the pedal is at full throttle. The sensor 52 may be connected to the "kick-down" unit of an automatic

transmission connected to the engine 21.

The operation of the unit will now be described.

The engine will be at part-throttle for most of its operation. This is indicated by sensor 49 and is monitored by the microprocessor 46.

The pump 15 draws petrol from the tank 14 and pumps it under pressure through petrol line 16. The logic circuit closes solenoid valve 18 so that liquid petrol is not fed to the E.F.I, unit 20.

The regulator valve 19 reduces the petrol pressure in lines 20 and 21 to e.g. 140 kPa.

Solenoid valve 24 is open and solenoid valve 25 is closed so that the liquid petrol is fed to the pressure vessel 22. The solenoid valve 40 from that vessel is closed as the solenoid valve 41 is opened to supply the vapourized fuel to the E.F.I, unit 20 via the main vapour line 44. (The check valve 19 prevents the vapour entering the branch line 17.) The liquid petrol is pumped into the pressure vessel 22 while it is being heated by the induction heater 29 which is switched on, via switch 32, when the solenoid valve 24 is opened and solenoid valve 40 is closed for the vessel 22. The petrol is vapourized and the flow of liquid petrol into the vessel 22 via line 20 continues until the vapour pressure equals (or exceeds) the petrol pressure. This is detected by the pressure sensor 36 which sends a signal to the logic circuit 12 and the solenoid valve 24 may be closed. When the vapour pressure in the other vessel

23 is very low e.g. 10 kPa, the pressure sensor 37 sends a signal to the logic system 12.

The solenoid valve 41 is closed, isolating the vessel 23 from the main vapour line 44 as the solenoid valve 40 on vessel 22 is simultaneously opened. If not

already closed, solenoid valve 24 is closed and the heater unit 29 may be turned off as the pressure vessel 22 supplies the vapour to the E.F.I, unit.

Solenoid valve 25 is opened to admit liquid petrol to the vessel 23 to be vapourized.

As will be readily apparent to the skilled addressee, one pressure vessel supplies the vapourized fuel to the engine while the other is vapourizing in¬ coming liquid fuel to ensure a constant supply of vapour to the engine. This is not possible with existing systems referred to above in the "Prior Art".

In an experimental system fitted to a "Nissan RB20E" engine in a "Holden Commodore" vehicle, where the E.F.I, unit 20 was unmodified, the fuel consumption fell from approximately 11.3 L/100 km (25 m.p.g.) to 4.6 L/100 km (62 m.p.g. ) .

The driveability and apparent power of the engine appear unchanged. However, it was found that the engine became rough after approximately 5 km (3 miles). To overcome this problem, the timer 48, tripped by the sensor 49, caused the solenoid valve 18 to be opened momentarily, while the solenoid valves 40, 41 were sim¬ ultaneously closed, to direct a "pulse" of liquid petrol to the E.F.I, unit 20. It is believed that the pulse is necessary, using the unmodified E.F.I, unit on the

"Nissan" engine, because such a unit measures actual fuel flow at the injectors and at present cannot monitor the vapour flow accurately and so close the injector, starving the engine of fuel. The petrol pulse appears to open the injectors and the engine runs smoothly. By providing the pulse e.g. every 3 km, no roughness is noted.

At idle, the sensor 51 operates timer 47 which also causes a pulse of petrol to be fed to the E.F.I. unit 20 e.g. every one second for smoother operation.

At full throttle, or on kick-down, sensor 52 trigger the logic system 12 to isolate the vapour system and to open solenoid valve 18 so that the engine runs on liquid petrol supplied to the E.F.I, unit 20 for full power output. As full throttle is rarely used in a passenger vehicle, the effect on the improved fuel consumption due to the vapour system is minimal.

As hereinbefore described, the engine normally runs on the vapourized fuel from one of the two pressure vessels, where one is "charged" while the other supplies the vapour to the engine. In the experimental system, using a 3 litre engine, it has been found that the vapourization of approximately 300 mL of fuel in each 1L pressure vessel supplies a continuous supply of vapour to the engine as each pressure vessel reaches maximum vapour pressure before the other is depleted.

While two pressure vessels are shown in parallel, three or more may be employed if required. Alternatively, one pressure vessel may be used where such a vessel has a plurality of separate zones or cells which can be charged and depleted with vapour indepen¬ dently.

The embodiment described above is electronic and is particularly useful for engines fitted with an E.F.I, unit.

It has been found with the experimental system that the engine may run hotter when operating on the vaporized f el. A water injection system may be connected to the intake manifold of the engine and the logic system 12 may operate the water injection system to spray water vapour into the intake manifold when the engine coolant temperature exceeds a preset level.

According to a modified form of this invention shown in FIGS. 3 and 4, a mechanical pressure take-off valve 60 may be used in lieu of the solenoid valves 40,

41 for the control of the vapour or gas. The valve 60 has a bore 61 in which a piston 62 is slid past an out¬ let 62 within the bore, enabling the vapour or gas with¬ in the pressure vessel 22, 23 to escape through the out- let into the main vapour line 44. (If preferred, a pressure regulator may be incorporated in the line.) The crown 64 of this piston is provided with a ramp portion which coacts with a corresponding ramp portion 65 on a secondary piston 66 having its axis at right angles to the first piston 62 and spring-urged to an extended position using an adjustable pressure spring 67. The secondary piston is provided with a push rod 6 which co-operates with an electronic contact switch assembly 69. In operation, as the pressure vessel 22, 23 is pressurized by the heat applied, the pressure pushes against the piston 61 to enable the vapour or gas pro¬ duced within the pressure vessel 22 by the heat to escape through the outlet 63 to the main vapour line 44. However, the piston 61 will not move until the pressure is at its preselected level , at which the force exerted against the back of the piston 61 will cause retraction of the secondary piston 60 through the co-operating ramps 64, 65 of both pistons. When this is achieved, the push rod 68 onn the secondary piston 66 will close the two-way electronic contact switch 69, which closes the solenoid valve 24, 25 and switches off the heating 29, 30. At this stage, the first piston 61 will move past the outlet 63 so that the pressure vessel 22, 23 is placed in communication with the main vapour line 44. A return spring 70 is provided to return the first piston 61 to its retracted position, opening the two-way electroic contact switch 69, to open the solenoid valve 24, 25 and switch on the heater 29, 30. Of course, as the pressure vessels 22, 23 are connected in parallel,

one is being pressurized while the other is being used, so that at all times there will be a pressurized vapour ready for use when needed.

The embodiments described are by way of illustrative examples only, and various changes and modifications may be made thereto without departing from the scope of the invention defined in the appended claims.