CLIAMS:We claim,
1. An assembly (10) for supplying fuel to an engine of a vehicle, said device comprising,
a fuel tank (12) storing the fuel;
a fuel chamber (14) in fluid communication with said fuel tank (12);
a valve (16) controlling the fuel flow from said fuel tank (12) to said fuel chamber (14) based on fuel level in said fuel chamber (14); and
a fuel metering unit (18) adapted to inject fuel to said engine, said fuel metering unit (18) in fluid communication with said fuel chamber (14).
2. An assembly (10) as claimed in claim (1) wherein said valve (16) controlling the flow of fuel from said fuel tank (12) to said fuel chamber (14) is a float valve.
3. An assembly (10) as claimed in claim (1) wherein said valve (16) is electronically controlled based on the fuel level in said fuel chamber (14).
4. An assembly (10) as claimed in claim (1) wherein said fuel metering unit (18) is fitted on the operative lower end of said fuel chamber (14) to allow fuel feed by gravity.
5. An assembly (10) as claimed in claim (1) wherein a fuel hose (20) supplies fuel from said fuel chamber (14) to said fuel metering unit (18).
6. An assembly (10) as claimed in claim (1) wherein said fuel metering unit (18) is a fuel injector controlled using a pulse width modulated signal to inject fuel in said engine.
,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention:
[001] The invention relates to an assembly for supplying fuel to an engine of a vehicle. Particularly the invention relates to a gravity feed assembly for supplying fuel to an engine of a two wheeler.

Background of the invention:
[002] Fuel supply systems for two wheelers based on gravity feed are known. The low pressure fuel pump for supplying the fuel to the fuel injectors is eliminated and the fuel injector receives the fuel from the fuel tank by gravity. In such fuel supply systems the metering of the fuel from the tank to the fuel injectors depends on the fuel level or the fuel head in the tank. The pressure of the fuel supplied to the injector is proportional to the fuel head in the fuel tank.
[003] However there are constant changes in the fuel level of the fuel tank due to consumption of fuel for combustion, changes due to uneven and uphill or downhill road conditions and also due to refueling of the fuel tanks. This causes changes in the pressure of fuel supplied to the fuel injector. Due to the constantly varying pressure it becomes difficult to meter the fuel accurately during each injection cycle. Thus the fuel pressure at the inlet of the injectors needs to be monitored and adjusted to a predefined value for each injection cycle to achieve accurate metering. This monitoring and adjusting of fuel pressure requires additional sensors and actuators.
[004] US8479708 discloses a fuel supply system for an internal combustion engine based on gravity feed of fuel to an injector immersed in the fuel.

Brief description of the invention:
[005] The fuel supply systems based on gravity feed need means for monitoring and maintaining the fuel head and thus the fuel pressure.
[006] The present invention proposes an assembly to supply fuel comprising a fuel tank storing the fuel, a fuel chamber in fluid communication with the fuel tank and a valve controlling the fuel flow from the fuel tank to the fuel chamber based on the fuel level in the fuel chamber. A fuel metering unit in fluid communication with the fuel chamber is adapted to inject fuel to said engine. The fuel metering unit may be a fuel injector.
[007] The valve between the fuel tank and the fuel chamber enables to maintain a constant fuel level in the fuel chamber. Thus, due to the constant head of fuel, the pressure of fuel supplied to the injector due to gravity is always maintained at a constant value.
[008] The device in accordance with this invention is particularly used for supplying fuel to two wheeler vehicles driven by gasoline. The fuel assembly in accordance with this invention reduces costs as there is no need for an additional fuel pump and accurate metering of the fuel can be achieved due to the constant fuel head and constant fuel pressure.

Brief description of the drawings:
[009] The embodiments of the present invention are described with reference to the following drawings:
[0010] Fig. 1 illustrates an assembly for supplying fuel to an engine of a vehicle in accordance with one embodiment of the invention; and
[0011] Fig. 2 illustrates an assembly for supplying fuel to an engine of a vehicle in accordance with another embodiment of the invention.

Detailed description of the invention:
[0012] Fig. 1 illustrates an assembly (10) for supplying fuel to an engine of a vehicle in accordance with one embodiment of the invention wherein a fuel metering unit (18) and the engine are operatively positioned below the fuel chamber (14). The fuel supply assembly (10) in accordance with this embodiment includes a fuel tank (12) for storing the fuel. A fuel chamber (14) is in fluid communication with said fuel tank (12). The fuel chamber (14) is positioned below the fuel tank (12) so that the fuel can flow from the fuel tank (12) to the fuel chamber (14) by gravity. The fuel chamber (14) in accordance with this embodiment is mounted on to the operative lower side of the fuel tank (12). A valve (16) controls the fuel flow from the fuel tank (12) to the fuel chamber (14) based on fuel level in the fuel chamber (14). A fuel metering unit (18) is in fluid communication and connected to the fuel chamber (14). The fuel metering unit (18) can be a fuel injector. In accordance with this embodiment of the invention, the valve (16) used to control the flow between the fuel tank (12) and the fuel chamber (14) is a float type valve.
[0013] Fig. 2 illustrates an assembly (10) for supplying fuel to an engine of a vehicle in accordance with another embodiment of the invention. The fuel metering unit (18) and the engine are not operatively positioned below the fuel chamber (14). The fuel supply assembly (10) in accordance with this embodiment includes a fuel tank (12) for storing the fuel. A fuel chamber (14) is in fluid communication with the fuel tank (12). The fuel chamber (14) is positioned below the fuel tank (12) so that the fuel can flow from the fuel tank (12) to the fuel chamber (14) by gravity. The fuel chamber (14) in accordance with this embodiment is mounted on to the operative lower side of the fuel tank (12). A valve (16) controls the fuel flow from the fuel tank (12) to the fuel chamber (14) based on fuel level in the fuel chamber (14). A fuel metering unit (18) is in fluid communication with the fuel chamber (14) and is adapted to receive fuel from the fuel chamber (14) by means of a fuel hose (20). The fuel metering unit (18) may be a fuel injector. In accordance with this embodiment of the invention, the valve (16) used to control the flow between the fuel tank (12) and the fuel chamber (14) is a float type valve.
[0014] In accordance with one embodiment of the invention an air vent tube (24) may be provided to allow the air from the fuel chamber (14) to escape into the fuel tank (12) and allow the fuel to flow in. The fuel metering unit (18) when in form of a fuel injector stops the flow of fuel and hence there is no need for a petcock.
[0015] In accordance with another embodiment of the invention, the valve (16) adapted to control the fuel flow from the fuel tank (12) to the fuel chamber (14) is electronically controlled based on the fuel level in said fuel chamber (14). For accurate control of the fuel head and in turn the fuel pressure, the fuel chamber (14) may be provided with level sensing means. The valve (16) is opened when the fuel level in the fuel chamber (14) reaches a predefined lower threshold.
[0016] In accordance with one embodiment of the invention the fuel metering unit (18) is in form of a fuel injector mounted on the engine. It is envisaged further that the fuel injector is electronically controlled using a pulse width modulated signal to inject the desired quantity of fuel in the engine. The fuel injector receives the fuel from the fuel chamber (14) at a constant pressure. Due to the pulse width modulated control of the fuel injector the fuel is atomized and injected into the combustion chamber.
[0017] Typically low cost two wheelers are provided with a carburettor based fuel supply system. The engines operating on these systems are not very fuel efficient. Electronic fuel injection systems typically need a fuel pump to pump the pressurized fuel from the tank to the fuel injector. The present invention proposes to eliminate the fuel pumps and operate the metering unit (18) based on the fuel fed to the injector from the fuel tank (12) by gravity. The fuel metering unit (18) could be an electronic fuel injector. To maintain a constant pressure of the fuel supplied to the fuel injector (18) it is necessary to maintain the fuel head in the tank constant. To achieve a constant fuel level and hence a constant pressure for the fuel supplied to the fuel injector, the fuel tank (12) is provided with a supplementary fuel chamber (14). The fuel chamber (14) is positioned below the fuel tank (12) in its operative configuration. The fuel chamber (14) may be integrated part of the tank or may be fitted to the tank using any known technology like welding. The fuel chamber (14) may also include the fuel petcock (22) which is used for manually controlling the flow of fuel from the fuel tank (12) to the fuel chamber (14). A valve (16) is positioned at the inlet of the fuel chamber (14). Based on the level of fuel in the fuel chamber (14) the valve (16) opens and closes to allow fuel from the fuel tank (12) to flow into the fuel chamber (14). The valve (16) may be operated by a float, the position of which is varied based on the fuel level. The float operates the valve (16) when the level of the fuel in chamber reduces below a lower threshold. The valve (16) ensures that the fuel level in the fuel chamber (14) is maintained constant. In one embodiment the valve (16) may be an electronically controlled valve. The fuel chamber (14) has level sensing means integrated with it. An electronic control unit in the vehicle receives the fuel level in the fuel chamber (14) and opens the valve (16) when the fuel level falls below the threshold. The fuel injector mounted on the engine is adapted to receive the fuel from the fuel chamber (14). In one embodiment the operative top end of the fuel metering unit (18) is fitted to the fuel chamber (14) and receives the fuel from the fuel chamber (14) directly. In another embodiment, if the fuel metering unit (18) and the engine are not positioned immediately below the fuel chamber (14) then the fuel metering unit (18) receives the fuel from the fuel chamber (14) via a fuel hose (20).
[0018] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. The valve (16) controlling the fuel flow from the fuel tank (12) to the fuel chamber (14) may be a float valve, an electronically controlled valve, or any other known valve suitable for the application will also be covered within the scope of the invention. The control unit operating the fuel metering unit (18) may also operate the valve (16) to control the level of fuel in the fuel chamber (14). The fuel metering unit (18) may be a fuel injector controlled by an electronic control unit. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.