AU2005100566A4 - A Fluid Pumping Means - Google Patents

Description

A FLUID PUMPING MEANS FIELD OF INVENTION This invention relates to fluid pumping means and in particular a fuel pumping means for use in small internal combustion engines. More particularly, this invention relates to improvements to an electromagnetically operated fuel pump with the aim of reducing the associated manufacturing costs thereof whilst improving the functional performance of a pump when used to effect the delivery or injection of fuel to an internal combustion engine.

In one form, the invention is realised in a fluid pump which includes a positivedisplacement piston acting as an electromagnetic armature means which is alternatively activated and de-activated by the energy obtained from a magnetic field developed from a permanent magnet housed in the rotating flywheel of an internal combustion engine.

BACKGROUND ART It is well known in the area of engine technology for an internal combustion engine with electronic fuel injection to include a fuel pump which is actuated electrically by a rotating DC motor.

It is also well established that in order to accurately meter fuel to an internal combustion engine that an injector or delivery valve may be actuated so as to allow pressurised fuel to be delivered over a specific time in order to meter a specific quantity of fuel. There are many well-known fuel systems of this general type in regular usage around the world and this pressure-time metering principle is reliable and well established.

-2- However, the cost of the fuel pump needed to deliver pressurised fuel for such a system may often be prohibitively high for many small engine applications. This in part arises due to the fact that many fuel pumps are manufactured to exacting standards and that the cost of manufacture of an entire fuel system may be so high that it is not economically feasible to apply such systems to many smaller engine applications, such as utility or other low cost engines. A typical fuel pump for a large engine typically incorporates a rotating electrical DC motor actuating a fluid turbine or gerotor pump, these components typically representing a significant cost in the overall fuel system.

Smaller utility engines are typically one-cylinder engines as used, for example, in chainsaws, cutters and other garden and cleaning appliances. The cylinder displacement for such engines, for example, may be 25 cubic centimetres or less, or as much as 125 cubic centimetres. Invariably, many such applications at present utilise a conventional flow carburettor rather than fuel injection.

Furthermore, many engines of this type are typically two-stroke engines and most small engines do not have excess electrical power available to drive an electric fuel pump. Typically, the manufacturers of such engines do not wish to apply a direct drive from the engine crankshaft for a number of technical and commercial reasons.

Accordingly, such engine applications very often require a simple low cost fuel system. Still further, and importantly, statutory standards for emission control are leading to the requirement for more precise control over the delivery of fuel and ignition on such engines.

The use of timed fuel injection to provide charge stratification and the benefits ensuring therefrom are well known in the field of engine technology. If it were not prohibitively expensive to apply timed fuel injection to small engines, it is reasonably likely that such systems would be used on small engines rather than simple flow carburettors.

-3- Accordingly, this invention seeks to provide a low cost fuel pump which may be conveniently applied to small engines so as to provide the basis of a timed fuel injection system using pressurised fuel.

SUMMARY OF INVENTION It is an object of the present invention to provide an improved fuel pump for lowcost engines, and particularly for small utility engines. More particularly, the invention aims to provide part of an effective and economical fuel delivery system for small internal combustion engines.

With this object in mind and in accordance with one aspect of the present invention, there is provided a fluid pumping means which includes a piston armature engaged for reciprocal movement in one end of a bore, a fluid inlet port formed at this one end of the bore for enabling fluid to enter the pumping means for subsequent delivery thereby, said fluid passing adjacent the piston armature in clearances provided between the piston armature and the bore and entering a pumping chamber formed within the bore between the piston armature and a first end of a pole piece arranged at the other end of the bore, the pole piece housing a check valve means arranged to allow the delivery of fluid from the pumping chamber and through the pole piece upon actuation of the piston armature, said actuation of the piston armature being effected by the attraction between the piston armature and an end face of said pole piece within said bore under the influence of energy developed from a magnetic field derived from the influence of a passing magnetic element.

Preferably, the fluid pumping means is a fuel delivery or injection means for use in an internal combustion engine. Conveniently, the magnetic field which is developed to energise the piston armature is derived from the influence of a passing magnetic element arranged on a flywheel rotor of the internal combustion engine. Preferably, the bore is a cylindrical bore.

Preferably, the ferromagnetic piston is normally urged away from the end face of the pole piece by a resilient means, typically a spring, said piston armature being forced onto an axial stop forming part of said fluid inlet port when the energy from the magnetic field is absent from the magnetic circuit, the absence of the magnetic field being due to the absence of the magnetic field derived from a permanent magnet in the flywheel rotor of the internal combustion engine.

More particularly, the piston armature defines one element of a temporary magnetic circuit developed by one of two alternative means, the first of such alternative means being derived from a coil winding disposed around the piston armature and its local magnetic circuit. The coil winding is conveniently supplied with electrical current derived from a charge coil forming part of a local magnetic circuit which includes said permanent magnet in the flywheel rotor of the internal combustion engine. The second alternative means is conveniently derived by the magnetic flux developed directly by the passing proximity of the permanent magnet in the rotating flywheel rotor of the engine.

The cylindrical bore is conveniently provided in the form of a non-magnetic tube, the non-magnetic tube forming the outer shell of a central magnetic core assembly, the magnetic core containing the main elements of the fluid pumping means. The main elements of this magnetic core assembly include the piston armature which is arranged within the bore of the non-magnetic tube, said nonmagnetic tube being closed at one end by the pole piece having the check valve means located therein so as to allow the egress of fluid from fluid pumping means. The pole piece also comprises a port of egress for fluid displaced by the motion of the piston armature under the action of the magnetic field and the biasing spring.

The inlet end of the fluid pumping means is provided with the fluid inlet port which is open to a main fluid or fuel supply. The fluid inlet port forms a circular disk-like stop for the piston armature in its normally quiescent state, said fluid inlet port being located at the alternative axial end of the non-magnetic tube relative to the pole piece.

The piston armature is primarily actuated by the influence of the pole piece disposed about the check valve means at the discharge end of the nonmagnetic tube. Conveniently, the piston armature is urged from the inlet stop against the opposing force of the spring, said piston armature being drawn to the attracting end face of the pole piece by a magnetic force, said magnetic force being induced between the pole piece and the piston armature due to the energy provided by the magnetic circuit powered by the passing permanent magnet in the flywheel rotor of the engine. Preferably, ferromagnetic limbs are defined to extend from the vicinity of stationary pole shoes facing the poles of the permanent magnet across air gaps at one end of the respective pair of limbs, said limbs conducting magnetic flux to one or the other of two alternative means of actuation for the piston armature.

Conveniently, the first alternative provides for the connection of said limbs to one another, said limbs thereby forming a common yolk about which is disposed a first coil winding connected to a second coil winding disposed around the piston armature and the enclosing non-magnetic tube.

Conveniently, the second alternative means provides for said limbs to be connected directly to respective separated ferromagnetic poles, one limb being connected to one pole which is attached directly to said pole piece of said fluid pumping means, the other limb being connected to a pole disposed radially about the non-magnetic tube which contains the piston armature. Both alternative magnetic circuits provide a path for magnetic flux so as to effect actuation of the piston armature as described during the time that the permanent magnet is generally within the respective magnetic circuit so defined in either the said first alternative means of actuation or the said second alternative means of actuation.

The invention provides that, when the permanent magnet in said flywheel rotor has passed the stationery shoes during normal rotation of the flywheel, the magnetic flux is to decay in said magnetic circuits, allowing the piston armature to return to its quiescent position on the inlet stop by the action of the aforementioned spring.

-6- During normal operation of the pump, and after the return stroke of the piston armature following a fluid or fuel pumping event, fluid at the inlet port is drawn past the piston armature via the clearance between the outer cylindrical surface of the piston armature and the internal bore of the non-magnetic tube and into the pumping chamber. The fluid subsequently passes through the attracting pole piece and past the check valve means during a fuel pumping event, the fluid being contained during said fluid pumping event within the non-magnetic tubular member enclosing the major parts of the magnetic core.

The pump is designed such, that the leakage of fluid past the piston armature during a so-called power stroke is minimised by the selection of a high rate of actuation during the power stroke of the piston armature during a fluid pumping event. The high rate of actuation is provided by a selected magnetic flux density developed in the working gap between the piston armature and the attracting pole piece. In contrast, a relatively lower rate of actuation is selected during the return stroke of the piston armature by providing a relatively lower actuation force from the spring adapted to return the piston armature to the quiescent state when the magnetic circuit around the piston armature is not energised.

Conveniently, the duration of the power stroke is selected to be less than the duration of the return stroke, said means of selection including a reduced arc of influence of the magnetic field within the flywheel developed by the permanent magnet, said reduced arc of influence being relative to the total circular arc defined by the path of the permanent magnet within the flywheel rotor of the engine during one rotational cycle of the engine.

It may be appreciated that a further check valve means may conveniently be provided in the body of the piston armature to allow fluid to pass more easily from the inlet port of the pump to the working or pumping chamber, therein said valve means being adapted to check the flow of fluid in the alternative direction.

Such a construction would however add further complexity and will not be described further herein.

-7- Alternative constructions may also be provided for the fluid inlet port, one such construction involving the provision of fixed inlet ports formed in the cylindrical wall of the non-magnetic tube, said inlet ports facing a reduced diameter of the piston armature at a location generally near the axial centre of the piston armature. In this case, the maximum diameter of the piston armature may be selected so that it passes across said inlet ports in the cylindrical wall during the course of axial and radial motion of the piston armature in the bore during actuation by the magnetic field developed around said piston armature. Again, such a construction is more complex and will not be described further.

In yet a further alternative arrangement of the invention, electrical connection may be provided between a first coil winding and a second coil winding, the said first winding being in the magnetic circuit closed by said permanent magnet in the flywheel rotor and a said second coil winding being in the magnetic circuit containing the piston armature. Conveniently, said connection between said coils may contain a series diode to allow the rapid transfer of electrical charge in a first direction of current flow, whilst limiting said current flow in the alternative direction, one of said coils being provided with a capacitive element connected across the coil winding so as to temporarily store electrical charge during one rotational cycle of the engine having the flywheel rotor as an integral part.

Furthermore, it may be appreciated that the piston armature may be of an external shape alternative to a cylindrical piston, including a construction using a generally spherical shape.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings, which illustrate several embodiments of a fluid pump formed in accordance with the present invention.

In the drawings:- -8- Figure 1 is a cross-sectional view of a fluid pump according to the present invention which uses a first means of actuation; Figure 2 is a cross-sectional enlarged view of the details of the pump shown in Figure 1, showing certain details at expanded scale; Figure 3 is a cross-sectional view of a fluid pump according to the present invention which uses a second means of actuation; Figure 4 is a cross-sectional enlarged view of the details of the pump shown in Figure 3, showing certain details at expanded scale; and Figure 5 is a further cross-sectional enlarged view of the details of the pump shown in Figure 3, showing details of an alternative embodiment.

BEST MODE(S) FOR CARRYING OUT THE INVENTION Referring now to Figures 1, 2, 3 and 4 there is shown a fluid pumping means formed in accordance with present invention. The fluid pumping means (3) includes a piston armature engaged for reciprocation in a lower end of a cylindrical bore and a fluid inlet port formed at the lower end of the cylinder bore The inlet port communicates with a source of fluid, typically fuel, to be delivered by the pumping means The fluid passes adjacent the piston armature via clearances provided between the surfaces of the piston armature and the bore and enters a pumping chamber formed between the piston armature and a pole piece (26) arranged within an upper end of the cylindrical bore The pole piece (26) houses a check valve means (10) which allows the egress of fluid from the pumping chamber and through the pole piece (26) upon actuation of the piston armature by energy developed from a magnetic field derived from the influence of a passing magnetic element (14) in a flywheel rotor (11) of an internal combustion engine. Actuation of the piston armature is effected by the attraction between the piston armature and an end face of the pole -9piece (26) under the influence of energy derived from the influence of said passing magnetic element (14) in said flywheel rotor (11).

Preferably, the ferromagnetic piston armature is normally urged away from the end face by a spring the piston armature being forced onto an axial stop (13) forming part of said fluid inlet port when the energy from the magnetic field is absent from the magnetic circuit containing the piston armature said absence of the magnetic field being due to the absence of the magnetic field derived from the permanent magnet (14) in the flywheel rotor (11) of the engine.

More particularly, the piston armature defines one element of a temporary magnetic circuit developed by one of two alternative means, the first of such alternative means being derived by a coil winding (20) disposed around the piston armature and energising its local magnetic circuit. The coil winding is supplied with electrical current derived from a charge coil (21) forming part of an alternative local magnetic circuit which includes said permanent magnet (14) in the flywheel rotor (11) of the engine. The second alternative means is derived from the magnetic flux developed directly by the passing proximity of the permanent magnet (14) contained in the rotating flywheel rotor (11) of the engine.

The cylindrical bore is provided in the form of a non-magnetic tube (22) and forms the outer shell of a central magnetic core assembly the magnetic core containing the main elements of the fluid pumping means which includes the piston armature which is arranged within the bore of the nonmagnetic tube said non-magnetic tube (22) being closed at one end by the pole piece (26) having the check valve means (10) located therein so as to allow the egress of fluid from pumping means The pole piece (26) also forms a port of egress (24) for fluid displaced by the motion of the piston armature (1) under the action of the magnetic field and the biasing spring (12).

The inlet end of the fluid pumping means is provided with the fluid inlet port (4) which is, as alluded to above, open to the fluid contents of a fluid supply tank (100). The fluid port forms a circular disk-like stop (13) for the piston armature in its normally quiescent state, said fluid inlet port being located at the alternative axial end of the non-magnetic tube (22) relative to the pole piece (26).

The piston armature is primarily actuated under the influence of the pole piece (26) disposed about the check valve means (10) at the discharge end of the non-magnetic tube The piston armature is urged from the inlet stop (13) against the opposing force of the spring said piston armature being drawn to the attracting end face of the pole piece (26) by a magnetic force, said magnetic force being induced between the pole piece (26) and the piston armature due to the energy provided by the magnetic circuit powered by the permanent magnet (14) in the flywheel rotor (11) of the engine. Ferromagnetic limbs (27) (28) are arranged to extend from the vicinity of stationary pole shoes (29) (30) facing the poles (31) (32) of the permanent magnet (14) across air gaps (33) (34) at one end of the respective pair of limbs, said limbs (27) (28) conducting magnetic flux to one or the other of two alternative means of actuation for the piston armature The first alternative as shown in Figure 1 provides for the connection of said limbs (27)(28) to one another, said limbs (27)(28) thereby forming a common yolk (35) about which is disposed a first coil winding (21) connected to the second coil winding (20) disposed around the piston armature and the enclosing non-magnetic tube (22).

The second alternative means as shown in Figure 3 provides for said limbs (27) (28) to be connected directly to respective separated ferromagnetic poles (39) one limb (28) being connected to one pole (38) which is attached directly to said attracting pole piece (26) of said fluid pumping means the other limb (27) being connected to a pole (39) disposed radially about the non-magnetic tube (22) which contains the piston armature The magnetic circuits provide a path for magnetic flux so as to effect actuation of the piston armature as described during the time that the permanent -11 magnet (14) is generally within the respective magnetic circuit so defined in either the said first alternative means of actuation or the said second alternative means of actuation.

The invention provides that, when the permanent magnet (14) in said flywheel rotor (11) has passed the stationery shoes (30) (31) during normal rotation of the flywheel, the magnetic flux is to decay in the magnetic circuits, allowing the piston armature to return to its quiescent position on the inlet stop (13) by the action of the aforementioned spring (12).

During normal operation of the pump, and during the return stroke of the piston armature following a fuel pumping event, fluid at the inlet port is drawn past the piston armature via the clearance between the outer cylindrical surface (40) of the piston armature and the internal bore of the nonmagnetic tube The fluid subsequently passes through the attracting pole piece (26) and past the check valve means (10) during a fuel pumping event, the fluid being contained during said fluid pumping event within the nonmagnetic tubular member (22) enclosing the major parts of the magnetic core.

The pump is designed such that the leakage of fluid past the piston armature (1) during a so-called power stroke is minimised by the selection of a high rate of actuation during the power stroke of the piston armature during a fluid pumping event. The high rate of actuation is provided by a selected magnetic flux density developed in the working gap (41) between the piston armature (1) and the attracting pole piece In contrast, a relatively lower rate of actuation is selected during the return stroke of the piston armature by providing a relatively lower actuation force from the spring (12) adapted to return the piston armature to the quiescent state when the magnetic circuit around the piston armature is not energised. The duration of the power stroke is selected to be less than the duration of the return stroke, said means of selection including a reduced arc of influence of the magnetic field within the flywheel developed by the permanent magnet said reduced arc of influence being relative to the total circular arc defined by the path of the permanent magnet (14) within the flywheel rotor (11) of the engine during one rotational cycle of the engine.

-12- It may be appreciated that a further check valve means may be provided in the body of the piston armature to allow fluid to pass more easily from the inlet port of the pumping means to the working or pumping chamber said valve means being adapted to check the flow of fluid in the alternative direction.

Alternative constructions may also be provided for the fluid inlet port one such construction as shown in Figure 5 involving the provision of fixed inlet ports formed in the cylindrical wall of the non-magnetic tube said inlet ports facing a reduced diameter (51) of the piston armature at a location generally near the axial centre of the piston armature In this case, the maximum diameter of the piston armature is selected so that it passes across the said inlet ports (50) in the cylindrical wall (22) during the course of axial and radial motion of the piston armature in the bore during actuation by the magnetic field developed around said piston armature In yet a further alternative embodiment of the invention, electrical connection may be provided between the first coil winding (21) and the second coil winding the first winding (21) being in the magnetic circuit closed by said permanent magnet (14) in the flywheel rotor (11) and the second coil winding being in the magnetic circuit containing the said piston armature The connection between the said coils may contain a series diode to allow the rapid transfer of electrical charge in a first direction of current flow, whilst limiting said current flow in the alternative direction, the second of the coils (20) being provided with a capacitive element connected across the coil winding so as to temporarily store electrical charge during one rotational cycle of the engine having the flywheel rotor (11) as an integral part.

It may also be appreciated that the piston armature may be of an external shape alternative to a cylindrical piston, including a construction using a generally spherical shape.

Modifications and variations as would be known to the skilled addressee are considered to be within the scope of this invention. For example, whilst application of the invention has in the main been described with reference to a two-stroke engine, the invention may of course be adapted for use with engines -13operating on the four-stroke cycle. Furthermore, the fluid pumping means and magnetic circuit arrangements of the present invention may be adapted for use with different types of fluid or fuel delivery systems, including single fluid fuel systems and dual fluid fuel systems (where a metered quantity of fuel is typically entrained and delivered by way of a quantity of compressed gas, typically air), whether used for the delivery of liquid or gaseous fuels.

Claims (4)

1. A fluid pumping means which includes a piston armature engaged for reciprocal movement in one end of a bore, a fluid inlet port formed at this one end of the bore for enabling fluid to enter the pumping means for subsequent delivery thereby, said fluid passing adjacent the piston armature in clearances provided between the piston armature and the bore and entering a pumping chamber formed within the bore between the piston armature and a first end of a pole piece arranged at the other end of the bore, the pole piece housing a check valve means arranged to allow the delivery of fluid from the pumping chamber and through the pole piece upon actuation of the piston armature, said actuation of the piston armature being effected by the attraction between the piston armature and an end face of said pole piece within said bore under the influence of energy developed from a magnetic field derived from the influence of a passing magnetic element.

2. A fluid pumping means as claimed in claim 1 wherein the fluid pumping means is a fuel delivery or injection means for use in an internal combustion engine and further wherein the magnetic field which is developed to energise the piston armature is derived from the influence of a passing magnetic element arranged on a flywheel rotor of the internal combustion engine.

3. A fluid pumping means as claimed in claim 1 or 2, wherein the piston ferromagnetic is of a ferromagnetic material, such piston being normally urged away from the end face of the pole piece by a resilient means, said piston armature being forced onto an axial stop forming part of said fluid inlet port when the energy from the magnetic field is absent from the magnetic circuit, the absence of the magnetic field being due to the absence of the magnetic field derived from a permanent magnet in the flywheel rotor of the internal combustion engine.

4. A fluid pumping means as claimed in any of the preceding claims wherein the piston armature defines one element of a temporary magnetic circuit developed by one of two alternative means, the first of such alternative means being derived from a coil winding disposed around the piston armature and its local magnetic circuit, the coil winding being supplied with electrical current derived from a charge coil forming part of a local magnetic circuit which includes said permanent magnet in the flywheel rotor of the internal combustion engine. A fluid pumping means as claimed in any of the preceding claims, wherein the bore is cylindrical and is provided in the form of a non-magnetic tube, the non-magnetic tube forming the outer shell of a central magnetic core assembly, the magnetic core containing the main elements of the fluid pumping means, the magnetic core assembly including the piston armature which is arranged within the bore of the non-magnetic tube, said non-magnetic tube being closed at one end by the pole piece having the check valve means located therein so as to allow the egress of fluid from fluid pumping means, the pole piece also comprises a port of egress for fluid displaced by the motion of the piston armature under the action of the magnetic field and the biasing spring. DATED this 13 th day of July 2005 ORBITAL AUSTRALIA PTY LTD 4 WHIPPLE STREET BALCATTA WA 6021 AUSTRALIA