CLIAMS:We Claim:
1 A fuel pump (100) comprising:
a plunger (115) adapted to reciprocate within a pumping chamber (120), wherein an operative top portion of said plunger (115) is proximal to a fuel side of said fuel pump (100) and an operative bottom portion is proximal to an oil side of said fuel pump (100);
Characterized in that
a groove (135) provided along circumference of said plunger (115), said groove (135) adapted to store fuel, wherein said stored fuel in said groove (135) creates a pressure difference between said oil side and said fuel side of said fuel pump (100) such that said pressure difference prevents oil from mixing with fuel.
2 The fuel pump (100) as claimed in claim 1, wherein said groove (135) is proximal to said operative top portion of said plunger (115).
3 The fuel pump (100) as claimed in claim 1, wherein location of said groove (135) from head of said plunger (115) is such that when said plunger (115) reaches said TDC, said groove (135) is aligned with at least one of an inlet port (125) and a fuel return port (130).
4 The fuel pump (100) as claimed in claim 1, wherein height and width of said groove (135) is such that pressure of fuel in said groove (135) is greater than pressure that is existing in said oil side. ,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This invention relates to fuel pump.

Background of the invention
[002] A fuel pump is a component of the fuel injection system for pumping high pressure fuel from a fuel tank into a combustion chamber. A plunger adapted to reciprocate within a pumping chamber of the fuel pump enables pressurizing of the fuel. The reciprocal movement of the plunger is enabled by cam assembly comprising a cam shaft and cam lobes. Rotation of the cam lobes enable lifting of the plunger through a roller tappet.

[003] The cam assembly needs to be lubricated with oil for smooth rotation of the cam shaft, cam lobes and the roller tappet. However care should be taken that the oil does not mix with the fuel because when the fuel mixed with oil is pumped into the combustion chamber results in lower efficiency and higher emissions.

[004] Since the oil used for lubrication is of higher density when compared to the fuel, the plunger drags the oil towards fuel. Because of such dragging phenomenon, the fuel and oil tend to mix with each other. Hence, there is a need to prevent dragging of the fuel towards the oil.

[005] In accordance with DE19847044, the piston comprises tee grooves. These grooves are adapted to store fuel that has leaked through the clearance between the piston and the pumping chamber. The fuel stored in the grooves ensures smooth reciprocation of the piston within the pumping chamber.

Brief description of the accompanying drawings
[006] Figure 1 illustrates a fuel pump in accordance with an embodiment of the present disclosure.

Detailed description
[007] Figure 1 illustrates a fuel pump 100 in accordance with an embodiment of the present disclosure.

[008] In accordance with this disclosure, a fuel pump comprises a plunger 115 adapted to reciprocate within a pumping chamber 120 wherein an operative top portion of the plunger 115 is proximal to a fuel side of the fuel pump 100 and an operative bottom portion is proximal to an oil side of the fuel pump 100. The fuel pump is characterized by a groove 135 provided along circumference of the plunger 115. The groove 135 creates a pressure difference between the oil side and the fuel side of the fuel pumps 100 such that the pressure difference prevents oil from mixing with fuel.

[009] The fuel enters into the fuel pump 100 through an inlet port 125 of the fuel pump. Fuel entered through the inlet port 125 is pressurized by the movement of the plunger 115 from BDC to TDC of the pumping chamber 120. Reciprocal movement of the plunger 115 from BDC to TDC within the pumping chamber 120 is achieved by lift provided by cam lobes 105. The cam lobes 105 are connected to the plunger 115 through the roller tappet 110 for lifting the plunger 115 so that the plunger 115 moves from the BDC to the TDC and then back to BDC. A cam assembly that includes a cam shaft, the cam lobes 105 and the roller tappet 110 should be lubricated using a lubricant like oil. The part of the fuel pump 100 where the oil is present is called the oil side and the part of the fuel pump 100 where the fuel is pumped is called the fuel side. The density of the oil is generally greater than the density of the fuel.

[0010] In accordance with the present disclosure, the plunger 115 is characterized by a groove 135 that is provided along the circumference of the plunger 115. During pumping of the fuel, when the plunger 115 moves from the BDC to TDC, the plunger 115 tends to drag the oil present at the BDC towards the fuel side. Due to such dragging effect, some quantity of fuel mixes with the oil before it is pumped into the pumping chamber 120.

[0011] In order to avoid such mixing of the fuel with the oil, a groove 135 adapted for storing fuel is provided along the circumference of the plunger 115. The groove 135 is obtained using machining process. When the fuel is stored in the groove 135, a temporary high pressure area is created around the groove 135 while the plunger 115 is moving from the BDC to the TDC. Due to the temporary high pressure area created around the groove 135, a pressure difference is obtained between the fuel side and the oil side. Due to such pressure difference, the oil tends to remain at the bottom of the pumping chamber 120. In one embodiment, the location of the groove 135 is proximal to the operative top portion of the plunger 115. The height and width of the groove 135 is designed such that when the fuel accumulates in the groove 135, the pressure of the fuel in the groove 135 is greater than the pressure that is existing in the oil side.

[0012] As the plunger 115 moves towards TDC, the fuel is highly pressurized. Location of the groove 135 from head of the plunger 115 is such that when the plunger 115 approaches TDC, the groove 135 aligns with the inlet port 125 and a fuel return port 130 of the fuel pump. The alignment of the groove 135 with the inlet port 125 and the fuel return port 130 relieves the pressure of the fuel stored in the groove 135. The pressure of the fuel stored in the groove 135 is relieved to prevent leakage of the fuel through clearance between the plunger 115 and the pumping chamber 120 since there is a pressure difference between the highly pressurized fuel and the pressure of the fuel stored in the groove 135.

[0013] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to process used for making the groove are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.