CLIAMS:We Claim:
1. A high pressure radial piston pump (100), comprising
at least a housing (102) having a central hole (104) , said central hole (104) accommodating a shaft (106) and a polygonal ring (108) and a metering unit (110) located in the housing of said high pressure radial piston pump (100); characterized in that
a bore (112), said bore (112) adapted to establish flow communication between said central hole (104) and said metering unit (110) and lubricate said polygonal ring (108).

2. The high pressure radial piston pump (100) of claim 1, wherein said bore (112) has uniform cross-section.

3. The high pressure radial piston pump (100) of claim 1, wherein said bore (112) has varying cross-section.

4. The high pressure radial piston pump (100) of claim 1, wherein a first outlet (116) of said metering unit (110) is in flow communication with said central hole through said bore.

5. The high pressure radial piston pump (100) of claim 1, wherein a second outlet (118) of said metering unit (110) is in flow communication with an inlet of a pump chamber.

6. The high pressure radial piston pump (100) of claim 1, wherein said bore (112) has varying cross-section.

7. The high pressure radial piston pump (100) of claim 2 and 3, wherein cross-section of said bore (112) is chosen from a combination comprising a circular section, a semi-circular section, square section, rectangular section, quadrilateral section, trapezoidal section. ,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 the field of high pressure pump.

Background of the invention
[002] The primary aim of a high pressure pump is to delivery pressurized fuel to the rail for delivery into the injector. The components of high pressure pump require lubrication, hence a part of the fuel is utilized to lubricate the same and this is achieved by means of an overflow valve. Also, any excess fuel that is available in the high pressure pump has to be leaked back to the tank. Leakage of excess fuel is required, when the demand for fuel to be supplied to the rail is less, when compared to the actual demand of fuel that is required. Leakage of excess fuel from the high pressure pump to the fuel tank is achieved through a zero delivery throttle (ZDT). The location of the overflow valve and ZDT in the high pressure pump is such that it necessitates drilling of long bores within the body of the high pressure pump. Hence there is a need to reduce the length of the bores in order to reduce the manufacturing cost, and the length of travel of fuel within the high pressure pump.

[003] Prior art patent application DE-102011082729 discloses a high-pressure fuel pump that has pump element which is provided with lift able pump piston mounted on a cam. A push rod assembly is supported with respect to drive shaft arranged on shaft bearings. The shaft bearings are formed in housing bores. The drive shaft is provided with axially extending holes so that the lubricant from the shaft bearings is supplied via the holes by the feed pump.

Brief description of the accompanying drawing
[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[005] FIG. 1 illustrates a high pressure radial piston pump; and

Detailed description of the embodiments
[006] FIG. 1 illustrates a high pressure radial piston pump 100 comprising at least a housing 102 having a central hole (104) accommodating a shaft and a polygonal ring (108), and a metering unit (110) located in the housing (102) of the high pressure radial piston pump 100. The high pressure radial piston pump (100) is characterized in having a bore (112), the bore (112) is adapted to establish flow communication between the central hole (104) and the metering unit (110) and lubricate the polygonal ring (108). In an embodiment the bore (112) may have uniform cross-section. In another embodiment the bore may have varying cross-section. The cross-section of the bore is chosen from a combination comprising a circular section, a semi-circular section, square section, rectangular section, quadrilateral section, trapezoidal section.

[007] The high pressure radial piston pump (100) receives fuel at low pressure from a metering unit for pressurization of fuel. The function of the metering unit is to allow fuel to flow into the inlet of high pressure radial piston pump. A first outlet of said metering unit is in flow communication with the central hole 104 through the bore (112). A second outlet (118) of the metering unit is in flow communication with an inlet of a pump chamber. Thus the metering unit discussed above has at least two outlets (116 and 118), that is one outlet (116) for the fuel to flow to into central hole 104 during leakage and the other outlet (118) for fuel to flow into the pump chamber. With this, the zero delivery throttle that is generally used for leaking out excess fuel from the high pressure radial piston pumps can be eliminated.

[008] During normal working, the fuel from the fuel tank reaches the metering unit of the high pressure radial piston pump 100. Under normal working conditions, fuel flows through the second outlet (118) of the metering unit (110) and into the pump chamber for pressurization. Whenever the demand for fuel is more that what is required in the rail, the metering unit has to leak out the excess fuel. Hence, the fuel flows through the first outlet (116) into the bore and reaches the central hole 104. The central hole (104) houses the polygonal ring (108) that is mounted on shaft. The rotational movement of the shaft (106), and the polygonal ring (108) causes the fuel to be splashed towards different components of the pump for lubrication. An overflow valve may be used in the metering unit 110 to deliver a part of fuel back to the fuel tank.

[009] 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 shape and cross section of the bore. 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.