CLIAMS:I Claim:
1. A fuel feed pump 100 for an internal combustion engine, said fuel feed pump 100 supplies fuel to a high pressure fuel injection pump and characterized in this that a mechanical means is provided between an inlet 103 and an outlet 105 of the fuel feed pump 100, said mechanical means configured to throttle fuel supply by the fuel feed pump 100 based on pressure at said outlet 105 of the fuel feed pump 100.

2. The fuel feed pump 100 as claimed in claim 1, wherein the mechanical means is a valve 101 with a spring arrangement 102.

3. The fuel feed pump 100 as claimed in claim 2, wherein at least one part of the valve interacts with the fuel flowing out of said outlet of said fuel feed pump and at least a second part of the valve interacts with the fuel flowing in the inlet of said fuel feed pump.

4. The fuel feed pump 100 as claimed in claim 1, wherein the mechanical means is a membrane 200.

5. The fuel feed pump 100 as claimed in claim 4, wherein said membrane is located at the interface between the inlet and the outlet of the fuel feed pump.
,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of Invention
[001] The present invention relates to a fuel feed pump for an internal combustion engine.

Description of Prior Art
[002] In a direct injection internal combustion engine, a high pressure pump creates the necessary fuel flow at a defined fuel pressure to feed injectors, that will release the fuel to the combustion chamber. In most of the cases these high pressure pumps are not self sucking and fuel will have to be delivered from the fuel tank to the high pressure pump. Conventional direct injection internal combustion engines mainly use a mechanical fuel feed pump which supplies fuel from the fuel tank to the high pressure pump. In case of electrical fuel feed pumps, the fuel feed pump will operate in most of the applications continuously at full delivery. An overflow valve in front of the high pressure pump inlet will assure a stable filling condition of the high pressure pump. The overflow valve will route unused fuel back to the electrical fuel feed pump. Hydraulically this principle works fine. However, there is high relative energy consumption by the fuel feed pump since, irrespective of the demand or requirement of fuel at the high pressure pump, the fuel feed pump always operates at full delivery. This unnecessary energy consumption in turn results in higher fuel consumption. Further the fuel backflow circuit (overflow valve and the means for routing fuel back to the fuel feed pump) increases system complexity and costs.

[003] Therefore in view of the above drawbacks in the prior art, it would be highly desirable to have an arrangement which controls fuel supply by the fuel feed pump based on requirement of fuel at the high pressure pump, thereby optimizing energy consumption and reducing system complexity and costs.

Brief Description of Drawings
[004] Fig.1, Fig. 2 and Fig. 3 illustrates one embodiment of the fuel feed pump according to the present invention, in which the mechanical means is a valve with a spring arrangement.

[005] Fig. 4, Fig. 5 and Fig.6 illustrates another embodiment of the fuel feed pump according to the present invention, in which the mechanical means is a membrane.

Detailed Description of Invention
[006] The present invention is hereinafter described with reference to the accompanying figures. The same reference numerals are used throughout the figures to reference like features and components.

[007] A fuel feed pump supplies fuel to a high pressure fuel injection pump. Fuel supplied to the high pressure fuel injection pump is pumped from a fuel tank by the fuel feed pump 100. In the present invention, the fuel feed pump 100 is characterized by a mechanical means provided between an inlet 103 and an outlet 105 of the fuel feed pump 100. The mechanical means throttles fuel supply by the fuel feed pump 100 based on pressure (P) at the outlet 105 of the fuel feed pump 100. P varies based on demand for fuel at the high pressure fuel injection pump. Greater the demand for fuel from the high pressure fuel injection pump, lesser is the pressure build up at the fuel feed pump outlet 105. Therefore when P is below a threshold pressure limit (PLimit), throttling of the fuel feed pump 100 is at its lowest and the fuel feed pump 100 operates at full delivery. As the demand for fuel at the high pressure fuel injection pump decreases, P increases and the delivery of the fuel feed pump 100 is reduced accordingly by the mechanical means. Beyond PLimit, the mechanical means throttles the fuel feed pump 100 to the extent that fuel supply to high pressure fuel injection pump is fully stopped. PLimit could be (but not restricted) in the range 3 to 4.5 bars. Hence the overall energy consumption by the fuel feed pump 100 is considerably reduced.
[008] In one embodiment, the mechanical means is a valve with a spring arrangement. The valve is located between the inlet and outlet of the fuel feed pump such that at least one part of the valve interacts with the fuel flowing out of said outlet of said fuel feed pump and at least a second part of the valve interacts with the fuel flowing in the inlet of said fuel feed pump. Referring to Fig. 1, Fig. 2 and Fig. 3, the mechanical valve allows the fuel feed pump to work in full delivery when P is significantly lesser than PLimit(see Fig. 1). With increasing P, the inlet diameter keeps on reducing due to action of the valve and the spring arrangement (see Fig. 2). Once P becomes greater than PLimit, the valve completely blocks the inlet of the fuel feed pump, hence preventing fuel supply (see Fig. 3).

[009] In another embodiment of the present invention, the mechanical means is a membrane 200 provided between the inlet 103 and the outlet 105 of the fuel feed pump 100. The membrane 200 is located at the interface between the inlet 103 and the outlet 105 of the fuel feed pump. Referring to Fig. 4, Fig. 5 and Fig. 6, when P is substantially lesser than PLimit, the membrane 200 does not interfere with fuel flow and there is therefore high mass flow through the inlet 103 and the outlet 105 of the fuel feed pump 100 (see Fig. 4). As P increases, the membrane 200 penetrates more towards the inlet 103 of the fuel feed pump 100 and throttles the inlet diameter 104 (see Fig. 5). Consequently, the delivery of the feed pump 100 is reduced accordingly. When P becomes greater than PLimit, the membrane 200 totally blocks the inlet 103 of the fuel feed pump 100, thereby stopping fuel supply (see Fig. 6).

[0010] Thus, mechanical means in the present invention reduces energy consumption by the fuel feed pump. Due to the present invention, the CO2 reduction potential in a diesel engine in an Indian Driving Cycle (MIDC) would be in the range of 0.5-1.5%. Furthermore the system will operate without a fuel backflow circuit (overflow valve and the means for routing fuel back to the fuel feed pump) thereby reducing costs and system complexity.
[0011] The above description is illustrative and there is no intention whatsoever to limit the scope of the invention. All modifications and variations of the present invention which would be obvious to a person skilled in the art are intended to be included within the scope of the following claims. The above mentioned modifications and variations include, but is not limited to, the type of mechanical means, the material and type of membrane, material and type of valve, material and type of spring arrangement, and pressure values/ranges. The scope of this description is only limited by the scope of the claims