Claims:We Claim:

1. A fuel injection system (10) in a vehicle, said fuel injection system (10) comprising:
- a fuel tank (12);
- an electric feed pump (14) placed in said fuel tank (12);
- a mechanical feed pump (22) connected to a high pressure pump (24);
- a fuel filter (16) connected between said fuel tank (12) and said mechanical feed pump (22);
characterized in that:
- a first valve (18) positioned in an inlet (17) of said fuel filter (16) and a second valve (20) positioned in proximity to an outlet (21) of said fuel filter (16);
said first and said second valves (18, 20) adapted to operate based on pressure and direction of flow of said fuel in said fuel filter (16).

2. The fuel injection system (10) as claimed in claim 1, wherein said first valve (18) positioned in said inlet (17) is adapted to close and said second valve (20) positioned in proximity of said outlet (21) is adapted to open, when said electric feed pump (14) adapted to pump said fuel to said mechanical feed pump (22) via said fuel filter (12).
3. The fuel injection system (10) as claimed in claim 1, wherein said first valve (18) positioned in said inlet (17) and said second valve (20) positioned in proximity to said outlet (21) are adapted to open ,when said mechanical feed pump (22) sucks said fuel from said fuel tank (12) via said fuel filter (14).
4. The fuel injection system (10) as claimed in claim 1, further comprises a control unit (28) adapted to operate said electric feed pump (14), upon detection of cranking of an engine in said vehicle.
5. The fuel injection system (10) as claimed in claim 1, wherein said electric feed pump (14) is started before or at engine cranking and is operated for a predefined time after cracking of said engine.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001]This invention relates to the field of fuel injection system in a vehicle.

Background of the invention
[0002] A fuel injection system for supplying fuel to an engine by injection includes a high-pressure pump, which pressurizes the fuel to a high pressure and supplies the fuel to the engine through injection valves (injectors), and a low-pressure pump, which draws the fuel from a fuel tank and supplies the fuel to the high-pressure pump. The high-pressure pump has a rotary shaft rotated by the engine. If the rotary shaft rotates, the high-pressure pump suctions and pressurizes the fuel, which is supplied by the low-pressure pump, to the high pressure, and pressure-feeds the fuel to the injectors. The low-pressure pump is attached to an end of the rotary shaft of the high-pressure pump. If the rotary shaft rotates, the low-pressure pump draws the fuel from the fuel tank and supplies the fuel to the high-pressure pump. Thus, the high-pressure pump and the low-pressure pump are driven by the engine and supply the fuel to the engine according to an engine rotation speed, or a fuel quantity required by the engine. [0003]Prior art patent application US7207319 discloses a fuel injection system having electric low-pressure pump. A controlling means of a fuel injection system regulates an energization amount of an electric motor in accordance with a sensing signal outputted from common rail pressure sensing means. Thus, the controlling means controls a fuel supply quantity of a low-pressure pump. Thus, power consumption of the electric motor driving the low-pressure pump can be regulated in accordance with a pressure-feeding quantity of a high-pressure pump. As a result, the power consumption of the electric motor can be reduced and wasteful fuel supply of the low-pressure pump can be reduced.
Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates a fuel injection system in a vehicle according to one embodiment of the invention;
[0006] FIG. 2 illustrates the fuel injection system in the vehicle.

Detailed description of the embodiments
[0007] FIG. 1 illustrates a fuel injection system 10 in a vehicle according to one embodiment of the invention. The fuel injection system 10 comprises a fuel tank 12 and a mechanical feed pump 22 connected to a high-pressure pump 24. The fuel injection system 10 comprises a fuel filter 16 connected between the fuel tank 12 and the mechanical feed pump 22. The fuel injection system 10 comprises an electric feed pump 14 placed in the fuel tank 12 and a first valve 18 positioned in an inlet 17 of the fuel filter 16 and a second valve 20 positioned in proximity to an outlet 21 of the fuel filter 16. The first and the second valves (18, 20) adapted to operate based on pressure and direction of flow of the fuel in said fuel filter 16.

[0008] Further the construction of the fuel injection system 10 and the components of the fuel injection system 10 are explained as follows. The fuel filter 16 is connected between the electric feed pump 14 of the fuel tank 12 and the mechanical feed pump 22. According to one embodiment of the invention, the first and the second valves (18,20) present in the fuel filter 16 are plate valves. The opening and closing of the first and the second valves (18,20) are based on the direction of the flow of the fuel and the pressure of the fuel. The first and the second valves (18,20) are bi-directional valves. The position of the first and the second valves (18,20) are not restricted as disclosed above, but can be any where in the path of the fuel in the fuel filter 16, as known to a person in the skilled in the art. The fuel injection system comprises a control unit 28 adapted to operate the electric feed pump 14. According to one embodiment of the invention, the control unit 28 is an engine electronic control unit. The control unit 28 switches on the electric feed pump 14 and operates the electric feed pump 14 for a predefined time, after an engine of the vehicle is cranked.

[0009] Figure 1 illustrates the fuel injection system during a start of the vehicle.
The control unit 28 switches on the electric feed pump 14 present in the fuel tank 12 upon detecting the crank of the engine. The electric feed pump 14 pumps the fuel from the fuel tank 12 through the passage that connects the fuel tank 12 and the fuel filter 16. The first valve 18 present in the inlet17 of the fuel filter 16 is closed due to the direction of the flow of the fuel and due to the pressure of the fuel. The closing of the first valve 18 helps in avoiding the fuel returning to the fuel tank 12 through a passage as shown in the figure 1. From the first valve 18 of the fuel filter 16, the fuel flows to the second valve 20 and the second valve 20 is opened due to the direction and the pressure of the fuel. The opening of the second valve 20 facilitates to the flow of the fuel to enter the outlet 21, after being filtered in a fuel filter element of the fuel filter 16. From the outlet 21, the fuel flows to the mechanical feed pump 22 and then to the high-pressure pump 24, followed to a common rail injection unit 26. The lines and the arrows in the figure 1 shows the direction of the fuel from the fuel tank 12 to the mechanical feed pump 22 and the high pressure pump 26 via the first and second valves (18,20) present in the fuel filter 16.

[0010] Figure 2 illustrates the fuel injection system during a normal operation of the vehicle. The control unit 28 operates the electric feed pump 14 for the predefined amount of time after the crank of the engine. After the predefined time, the control unit 28 switches off the electric feed pump 14 and the mechanical feed pump 22 directly supplies the fuel to the high-pressure pump 24. The mechanical feed pump 22 creates a suction kind of environment to pump the fuel from the fuel tank 12 via the fuel filter 16. Due to the suction created by the mechanical feed pump 22, the fuel from the fuel tank 12 flows through the first valve 18 (the direction and the pressure of the flow opens, the closed first valve 18) and then to the second valve 20. From the second valve 20, the fuel flows towards the mechanical feed pump 22 via the outlet 21 of the fuel filter 16. The lines and the arrows in the figure 1 shows the direction of the fuel from the fuel tank 12 to the mechanical feed pump 22 and the high pressure pump 24 via the first and second valves (18,20) present in the fuel filter 16.

[0011] With the above disclosed arrangement in the fuel injection system 10,usuage of additional values in low pressure lines to prevent fuel flowing back into the fuel tank 12 during the cranking of the engine is avoided, simplifying the low pressure circuit. The valves present in the fuel filter 16 provides two flow paths for fuel, one path used during the normal operating conditions and one used during the start of the engine.

[0012] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of the type of injector used. 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.