CLIAMS:We Claim:
1. A fuel injection system (10) at least a part of said fuel injection system (10) located in an engine block (13), said fuel injection system (10) comprising at least a high pressure pump;
said high pressure pump comprising a housing (12) located in a bore in said engine block (13) and a roller tappet (22) engaged to a cam located in said engine block (13);
Characterized in that;
a first valve (18) located in an inlet passage (14) provided in said engine block (13), said first valve (18) in fluid communication with at least a part of said high pressure pump in a manner such that said first valve (18) allows flow of air into said bore in said engine block (13) where said high pressure pump is located;
a second valve (20) located in said roller tappet (22), said second valve (20) adapted to extract air and lubricating oil from said high pressure pump.

2. The fuel injection system (10) in accordance with Claim 1, wherein said first valve (18) and said second valve (20) is at least one selected from a group of valves such as a ball valve, a solenoid valve and the like. ,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 a high pressure pump and specifically to an apparatus for reducing mixing of lubricating oil with fuel in the high pressure pump.

Background of the invention:
[002] Fuel is channelled to a high pressure pump where it is pressurized and supplied to a high pressure common rail. Fuel channelled to the high pressure pump is supplied to a cylindrical bore where it is pressurized by a reciprocating piston. Due to a clearance that exists between a housing of the high pressure pump and the reciprocating piston, fuel flows through the clearance. The fuel then flows into an oil sump that is positioned below the high pressure pump, thereby diluting the lubricating oil in the oil sump. In addition, lubricating oil from the oil sump may flow upwardly into the cylindrical bore through the clearance between the housing of the high pressure pump and the reciprocating piston where it mixes with the fuel in the cylindrical bore. In order to prevent fuel from mixing with the lubricating oil or vice versa in the high pressure pump, an arrangement to reduce mixing of the lubricating oil with the fuel is required.

[003] U.S. Patent Number 8,556,602 describes a high pressure pump. The high pressure pump comprises at least one pumping chamber. A piston is slidingly mounted inside the pumping chamber to vary the volume thereof. An intake duct is connected to the pumping chamber and regulated by an inlet valve. A delivery duct is connected to the pumping chamber and regulated by a one way valve that allows only outgoing fuel to flow from the pumping chamber. A seat is arranged below the pumping chamber around a lower portion of the piston. An annular seal is housed in the seat and prevents fuel leakage along a side wall of the piston. An annular element delimits the seat housing and the seal such that an axial dimension of the seat is not greater than an axial dimension of the seal to prevent the seal from axially shaking inside the seat as a consequence of axial movement of the piston.

Brief description of the accompanying drawings
[004] An exemplifying embodiment of the invention is explained in principle below with reference to the drawings. The drawings are:
[005] Figure 1 shows a schematic view of a high pressure pump; and
[006] Figure 2 shows a schematic view of a valve used in combination with the high pressure pump.

Detailed description of the invention:
[007] As shown in Figure 1, a fuel injection system 10 is described. At least a part of the fuel injection system 10 is located in an engine block 13. The fuel injection system 10 comprising at least a high pressure pump. The high pressure pump comprises a housing 12 located in a bore in the engine block 13 and a roller tappet 22 engaged to a cam located in the engine block 13. A first valve 18 is located in an inlet passage 14 provided in the engine block 13. The first valve 18 is in fluid communication with at least a part of the high pressure pump in a manner such that the first valve 18 allows flow of air into the bore in the engine block 13 where the high pressure pump is located. A second valve 20 is located in the roller tappet 22, the second valve 20 adapted to extract air and lubricating oil from the high pressure pump.

[008] A plunger 16 is positioned within the housing 12 of the fuel injection system 10, wherein the plunger 16 reciprocates within the housing 12. The housing 12 includes a compression chamber for sucking fuel from a suction port (not shown). The plunger 16 is positioned within the compression chamber to reciprocate and pressurize fuel for delivery through a fuel outlet supply path. A roller tappet 22 is coupled to a base portion of plunger 16 and facilitates reciprocating the plunger 16 within the compression chamber. The housing 12 of the fuel injection system 10 is inserted within a bore defined within an engine block 13.

[009] The engine block 13 includes an inlet passage 14. The inlet passage 14 is provided in the engine block 13 such that the inlet passage 14 extends from an air intake system of the engine to an inner surface of the engine block 13. A valve 18 is positioned within the inlet passage 14. The valve 18 is a uni-directional valve that facilitates channeling air from the air intake system of the engine to the bore defined within the engine block 13.

[0010] The outlet passage 15 is provided in the roller tappet 22 such that the outlet passage 15 extends from an inner surface of the roller tappet 22 to an outer surface of the roller tappet 22. A second valve 20 is positioned within the outlet passage 15. The second valve 20 is a uni-directional valve that facilitates channeling air and lubricating oil from the bore defined within the engine block 13 to an engine camshaft chamber that is positioned below the roller tappet 22.

[0011] For better understanding of the valves 18 and 20 in accordance with this disclosure, one embodiment of the the valve is shown in Figure 2. Figure 2 illustrates a schematic view of the first valve 18 and the second valve 20. The working principle of the valves is explained with respect to the first valve. The second valve works on the same principle. The first valve 18 includes an inlet 30 that is adapted to channel air into the engine block 13. The first valve 18 includes an outlet 32 that channels air out of the valve 18. A ball 34 is positioned against a spring member 36 within the valve 18. When a suction force is applied at the outlet 32 of the first valve 18, the ball 34 moves against a biasing force offered by the spring member 36. The movement of the ball 34 against the spring member 36 causes the outlet 32 of the first valve 18 to open. This facilitates channeling air from the inlet 30 of the first valve 18 to the outlet 32 of the first valve 18 and into the bore defined within the engine block 13.

[0012] An operation of the fuel injection system 10 is now described as an example. Lubrication oil is channeled into the bore defined within the engine block 13 from the clearance provided between the engine block 13 and the roller tappet 22. Therein, air in the bore mixes with the lubrication oil and is channeled from the bore within the engine block 13 via the valve 20 that is positioned within the outlet passage 15. This occurs due to a compressive pressure that is created in the bore due to the reduction in volume of the bore owing to the upward movement of the roller tappet 22 and plunger 16 during the compression stroke of the fuel injection system 10. During the return stroke of the plunger 16 and roller tappet 22, the suction force that is created in the bore due to the increase in volume of the bore owing to the downward movement of the roller tappet 22 and plunger 16 causes fresh air to be channeled to the bore via the inlet 30 of valve 18 that is positioned within the inlet passage 14.

[0013] The above described fuel injection system 10 is cost effective and highly reliable. The use of the first valve 18 facilitates channeling air within the bore of the engine block 13. The use of the second valve 20 facilitates channeling lubrication oil and air from the bore of the engine block 13 to the engine camshaft room. Therefore, mixing of the oil with fuel from an oil sump that is positioned below the fuel injection system 10 is mitigated. Moreover, the oil that is present in the engine block 13 is prevented from flowing upwardly into the fuel side of the fuel injection system 10.

[0014] The fuel injection system 10 comprises the first valve 18 and the second valve 20. The first valve 18 and the second valve 20 is at least one selected from a group of valves such as a ball valve, a solenoid valve and the like.

[0015] The first valve 18 and the second valve 20 may be different types of valves. In accordance with an embodiment of the present invention, the first valve 18 and the second valve 20 could be different types of valves. Any combination of the different types of valves comprising the first valve 18 and the second valve 20 may be used for the present application.

[0016] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.