The present invention relates to an engine and air filter for a gas fuelled vehicle.

Two and three wheel motor vehicles are an important mode of transport used for commuting in and around cities. Such vehicles have engines operating on the two and four stroke cycle, employing petrol or other liquid fuel. As environmental laws become more stringent, emissions from such vehicles are required to reduce. One way of achieving lower emissions is to use gas fuelled internal combustion engines. Such gaseous fuel may be selected from LPG (Liquefied Petroleum Gas) or CNG (Compressed Natural Gas). These gas fuels typically have lower carbon content than gasoline or diesel fuels and therefore produce less C02 upon combustion. They also typically combust more efficiently than most liquid fuels, therefore further reducing emissions, and provide economic benefit since they are currently of lower cost than liquid fuels such as petrol.

Where supply of gaseous fuel is assured, vehicles may operate with only a gas fuel supply. However, as there may be regions where supply of gaseous fuel is less certain, vehicles may be fitted with a back-up liquid fuel system. Such vehicles are called dual fuelled vehicles. Typically, the back-up fuel is petrol since this is the easiest fuel to obtain, being available even in many remote regions. However, other back up fuels - such as ethanol and ethanol/gasoline blends -may be conceived and are within the scope of the present disclosure.

The fuel supply for a gas fuelled vehicle comprises a pressurised fuel tank and, accordingly, as the pressure of the fuel tank is higher than can be handled by a gas fuelled internal combustion engine, a pressure regulator is required to control the gas fuel supply pressure to the engine through a gas fuel supply duct. Gaseous fuel at appropriate pressure is supplied to a mixer for mixing gas and air to form a combustible fuel mixture for delivery to the engine. To this end, the mixer is connected both to the gas fuel supply and an air intake system. The air intake system includes an air filter to remove particulates from air prior to entering the engine as well as an air intake duct which is connected to the air filter. The air intake duct or manifold is also connected to the mixer.

The amount of gaseous fuel to be supplied to the mixer is set, in accordance with air intake manifold pressure, by a carburettor or throttle body. All of these components are typically packaged in close proximity to each other on the engine. The mixer is typically located in the space, or duct, formed between the air filter housing or air box and the carburettor or throttle body. This space is limited and provides constraints of both size and shape making it sometimes difficult to accommodate the mixer and air intake duct. The issue has previously been addressed by a compromised design in which the mixer may not be optimised to achieve most efficient combustion of fuel in the engine.

An additional issue may also arise with operability of the mixer following maintenance, for example of the carburettor or throttle body. In such cases, the mixer may be displaced in position with consequential problems with the operation of the mixer.

It is an object of the present invention to provide an engine less subject to constraints on mixer design encountered in prior gas fuelled engines.

It is a further object of the present invention to provide an air filter for use in an engine, for example to avoid constraints on mixer design encountered in prior gas fuelled engines.

With this object in view, the present invention provides an engine for a gas fuelled vehicle comprising:

a) a gaseous fuel supply system comprising a gaseous fuel supply tank, a gaseous fuel pressure regulator and a mixer for mixing air and gaseous fuel to form a combustible mixture; and

b) an air intake system for supplying air to the engine for combustion of gaseous fuel and comprising an air filter and an air intake duct connected to the air filter and mixer wherein said mixer is at least partly accommodated within a housing of said air filter.

The mixer may be completely accommodated within said housing of said air filter, thus enabling removal of the design constraint requiring that a space be left between the air filter and fuel metering means, whether that be for a carburettor or throttle body or other means such as a valve. Even if the mixer is only partly accommodated within said air filter housing, the design constraint -requiring a space dictated in shape and size by the required mixer - may be relaxed and the packaging of gaseous fuel supply and air intake components made easier. Further, as the mixer is connected to the air intake duct and the position of the mixer along the intake duct may be of some importance, yet constrained in the prior art for the above discussed reasons, accommodation of the mixer at least partly within the air filter housing allows for greater flexibility in location of the mixer along the air intake duct.

The mixer housing, as opposed to its connection to the air filter and air intake duct, may be located either on the upstream or downstream side of, or straddling across, the air filter exit so there is flexibility as to accommodation of the mixer at least partly within the housing of the air filter. The mixer will still be fluidly connected to the air intake duct downstream of the air filter.

The air filter housing may be moulded plastic in which case it may be convenient for the mixer, typically a metallic component, to be included within the moulding for the air filter housing whether or not in combination with at least a portion of the air intake duct. An over-moulding process may be used for this purpose.

A mixer typically comprises respective inlets for air and gaseous fuel and an outlet for the combustible fuel air mixture to be supplied to the engine. It is convenient for the mixer to be provided with a nozzle through which the gas inlet is connected to the gaseous fuel pressure regulator. Accordingly, this nozzle which may be of metallic material - may be included within the moulding of the air filter housing.

In another aspect of the invention, there is provided an air filter for a gas fuelled vehicle, said air filter comprising a housing; and a mixer for a gaseous fuel supply system having connections to an air supply system and a gaseous fuel supply system, wherein the mixer is at least partly accommodated within said housing. The air filter including a mixer accommodated at least partly within its housing may be factory installed or available as an after-market option.

The mixer connection to the gaseous fuel supply system may pass through a seal formed in a wall of the housing of the air filter.

In a still further aspect of the invention, there is provided a method of fabricating an air filter for a gas fuelled vehicle comprising the step of moulding a housing for the air filter in a moulding wherein said moulding includes, within a moulded body of said air filter housing, a mixer for a gaseous fuel supply system,

The mixer may include a nozzle for connection to a gaseous fuel supply system. The moulding may then include the nozzle, which may be of different material (typically metal or other metallic material), than the plastic of the air filter housing. The air filter housing may be moulded over this nozzle in an over-moulding process as noted above. The nozzle may be located, during the manufacturing process in a selected position within the moulding using locating devices such as pin(s) or similar devices.

In a still further aspect, the present invention provides a moulding for an air filter housing wherein said moulding includes, within a moulded body of said air filter housing, a mixer for a gaseous fuel supply system.

The engine and air filter of the present invention are particularly suitable for inclusion within two wheel, three wheel and four wheel vehicles such as motorcycles, scooters, three wheelers and automobiles. These vehicles may be spark ignited or dual spark ignited, carburetted or fuel injected. The engine may be of small capacity. The engine may be configured and tuned for dual fuelled operation with liquid fuel, such as petrol, being used as a back-up fuel.

The engine and air filter of the present invention provide easier packaging of the mixer than prior designs. Further, the accommodation of the mixer within the air filter housing gives it protection from shocks that could result in mis-positioning and less efficient operation.

An engine according to a preferred embodiment of the present invention may be more fully understood from the following description made with reference to the accompanying drawings in which:

Figure 1 is a schematic of the air filter and gaseous fuel supply including mixer arrangement for a gas fuelled engine of the prior art;

Figure 2 is a schematic of the air filter and gaseous fuel supply including mixer arrangement for a gas fuelled engine according to one embodiment of the present invention;

Figure 3 is a schematic of the air filter and gaseous fuel supply including mixer arrangement for a gas fuelled engine according to another embodiment of the present invention.

Figure 4 is an illustration of details pertaining to mixer mounting arrangements.

Referring now to Figure 1, there is shown the relative positions, in a gas fuelled engine, of carburettor 3, gaseous fuel pressure regulator 7 and air filter 2 of a gas fuelled engine for a three wheel vehicle. The gaseous fuel is LPG and so LPG will be referred to as the gaseous fuel in the remainder of this specification. The engine may be bi-fuelled, having provision for operation with a second fuel such as petrol.

It may be noted that the carburettor 3, LPG pressure regulator 7 and air filter 2 are required to be packaged in this manner due to space constraints in the vehicle. Therefore, it is necessary for mixer 5, which mixes LPG with air to form a combustible fuel mixture for combustion in the engine, to be located in a duct or space 22 located between carburettor 3 and air filter 2 because the mixer 5 requires to be fixed within the air intake duct or manifold 1 and that manifold 1 extends also through space 22. There is little or no flexibility for the shape and other design features of the mixer 5 due to the design constraint imposed by the requirement to locate the mixer 5 in limited space 22. The limited nature of space 22 is highlighted by the abutment of the mixer 5 against the wall of the carburettor 3. Accordingly, the design of mixer 5 is subject to a design constraint that may prevent selection of a mixer 5 that is optimised to achieve most efficient combustion of LPG fuel within the engine.

Other design features of this engine may also be noted. Mixer 5 is connected to pressure regulator 7 through a hose 6 which includes a nozzle 8. It is necessary to provide clamping of mixer 5 to intake manifold 1 to prevent road induced vibration hindering the efficient operation of the mixer 5. It may be noted that, if servicing of any of the components of the air and LPG fuel supply systems is required, the alignment of the mixer 5 may be disturbed also leading to inefficient operation of mixer 5.

Referring now to Figure 2, the gas fuelled engine has a different design in which mixer 15 is completely accommodated within the housing of the air filter 12 which has sufficient volume to enable significant flexibility as to the location of the mixer 15. There is no design constraint or compromised design imposed by the need to locate mixer 15 within space 22 between the carburettor 13 and air filter 12. Accordingly, mixer 15 may be selected with a view to achieving the most efficient mixing of LPG fuel and air to form a combustible mixture for combustion in the engine.

The positioning of the LPG pressure regulator 17 remains the same as in the prior art engine with the hose 16 connecting the LPG pressure regulator 17 to mixer 15 being connected to nozzle 18. Nozzle 18 extends below the mixer 15 and through a side wall of mixer 15 proximate the wall of air intake duct or manifold 11.

It may be noted that, unlike the construction of Figure 1, the location of mixer 15 allows a straight portion of air intake duct 11 of observable length to be left between the mixer 15 and carburettor 13. Provision of this straight portion of air intake duct 11 may also enable benefits for engine operation.

While the mixer 15 still is clamped to the air intake duct 11 by a clamp 20 to minimise vibration, the location of mixer 15 within the housing of the air filter 12 enables more latitude as to the nature of the clamp 20 and the required clamping force because this location is less subject to adverse effects due to road induced vibration.

Referring now to Figure 3, there is shown an embodiment where mixer 15 is partly accommodated within the housing of air filter 12, other design aspects being the same as described with reference to Figure 2. While this location for mixer 15 may not be quite as advantageous as that shown in Figure 2 it nevertheless considerably eases the packaging of the mixer 15 within the engine. It is still possible in this embodiment to have a straight portion of air intake duct 11, this being advantageous as discussed above.

In each of the engine arrangements schematised in Figures 2 and 3, the air filter 12 is of moulded plastic and it is possible for the mixer 15 also to be included within the moulding even though mixer 15 is a metallic component. Particular attention may be drawn to the nozzle 18, of mixer 15, which though a metal part, may be included within the moulding with the housing of air filter 12 being moulded over the nozzle 18 in an over-moulding process. As the location of nozzle 18 is important from the point of view of engine packaging, it must be carefully positioned. If necessary, the nozzle 18 may be positioned and located using locating devices in the form of pin(s) or similar means to ensure that the moulding is correctly done.

Another aspect of the mounting arrangement is illustrated in Figure 4, where nozzle 23, though forming a connection to the gaseous fuel supply via LPG regulator 17, is an integral part of the air intake duct 11 with one end of nozzle opening in the mixer 15 and other end disposed within air filter housing 12. This connection to the gaseous fuel supply passes through a seal formed in a wall of the air filter housing 12 as described below. A rubber hose 24 is inserted through an opening 21 provided in air filter housing 12 and connected to the nozzle 23. The other end of the hose 24 is connected to LPG regulator 17 (though not shown in Figure 4). The said opening 21 is provided with suitable grommet arrangement 25 to prevent leakage of air from air filter housing 12.
In a situation where the nozzle 23 is not integrally moulded to the air intake duct 11, the nozzle 23 may be connected to mixer 15 through air intake duct 11 by providing suitable fixing and sealing arrangements.

The engine and air filter of the present invention provide easier packaging of the mixer, and potentially better operation of a gas fuelled engine, than prior compromised designs. Further, the accommodation of the mixer 15 within the air filter housing 12 gives it protection from shocks, such as those due to road induced vibrations that could result in mis-positioning and less efficient operation.

Modifications and variations to the engine and air filter of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present disclosure.

WE CLAIM:

1. An engine for a gas fuelled vehicle comprising:

a) a gaseous fuel supply system comprising a gaseous fuel supply tank, a gaseous fuel pressure regulator and a mixer for mixing air and gaseous fuel to form a combustible mixture; and

b) an air intake system for supplying air to the engine for combustion of gaseous fuel and comprising an air filter and an air intake duct connected to the air filter and mixer wherein said mixer is at least partly accommodated within a housing of said air filter.

2. An engine of claim 1 wherein said mixer is completely accommodated within said housing of said air filter.

3. An engine of claim 1 or 2 wherein a housing of said mixer is flu idly connected to said air intake duct downstream of said filter.

4. An engine of any one of the preceding claims wherein said air filter housing is moulded plastic and said mixer is a metallic component included within a moulding for the air filter housing.

5. An engine of claim 4 wherein said mixer is included within said moulding in combination with at least a portion of the air intake duct.

6. An engine of claim 4 or 5 wherein said mixer comprises inlets for air and gaseous fuel; an outlet for the combustible fuel air mixture to be supplied to the engine; and a nozzle to be connected to the gaseous fuel pressure regulator wherein said nozzle is of metallic material and is included within the moulding of the air filter housing.

7. An air filter for a gas fuelled vehicle, said air filter comprising a housing wherein a mixer for a gaseous fuel supply system, and having connections to an air supply system and a gaseous fuel supply system, is at least partly accommodated within said air filter housing.

8. An air filter of claim 7 wherein said connection to said gaseous fuel supply system passes through a seal formed in a wall of said housing of said air filter.

9. A method of fabricating an air filter for a gas fuelled vehicle comprising the step of moulding a housing for the air filter in a moulding wherein said moulding includes, within a moulded body of said air filter housing, a mixer for a gaseous fuel supply system.

10. A method of claim 9 wherein said mixer includes a nozzle for connection to a gaseous fuel supply system, said moulding including the nozzle.

11. A method of claim 10 wherein said nozzle and air filter housing are of different material.

12. A method of claim 11 wherein said nozzle is of metallic material and said air filter housing is of plastic.

13. A method of any one of claims 10 to 12 wherein said air filter housing is mouided over said nozzle in an over-moulding process.

14. A method of claim 13 wherein said nozzle is located, during said over-moulding process, in a selected position within the moulding using locating devices.

15. A method of claim 14 wherein said locating devices are pins.

16. A moulding for an air filter housing wherein said moulding includes, within a moulded body of said air filter housing, a mixer for a gaseous fuel supply system.