Claims:We Claim:
1. A high pressure fuel pump 10, said high pressure fuel pump 10 comprising:
a pump housing 12;
a drive shaft 14, at least a part of said drive shaft 14 located in said pump housing 12;
a shaft sealing ring 16 positioned between said pump housing 12 and said drive shaft 14;
a pressure control valve 18 located in said pump housing 12;
a fuel supply path 20 defined between said pressure control valve 18 and said shaft sealing ring 16, said fuel supply path 20 adapted to supply fuel from said pressure control valve 18 to said shaft sealing ring 16; characterized in that
a throttle 22 defined in said fuel supply path 20, said throttle 22 adapted to decrease a pressure of fuel flowing via said fuel supply path 20 to said shaft sealing ring 16.

2. The high pressure fuel pump 10 in accordance with Claim 1 wherein said throttle 22 may be sized so as to facilitate preventing a backflow of fuel in the fuel supply path 20 to said pressure control valve 18.

3. The high pressure fuel pump 10 in accordance with Claim 1 wherein said throttle 22 may be one selected from a group consisting of a constriction, a restriction, an obstruction, a capillary device, a venturi device, and the like. , Description:Field of the invention
[0001] This invention relates to a shaft sealing ring of a high pressure fuel pump.

Background of the invention
[0002] US Patent Number 5615894A describes a shaft seal ring as well as a method and a device for manufacturing the same. The shaft seal ring made of a PTFE compound comprises a sealing lip and a protective lip integrally formed therewith, wherein the sealing lip as well as the protective lip are provided with wavy recesses embossed during a manufacturing step of the shaft seal ring.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a high pressure fuel pump and more specifically to a shaft sealing ring of the high pressure fuel pump.

Detailed description of the invention
[0004] A high pressure fuel pump 10 is described. The high pressure fuel pump 10 comprises a pump housing 12, a drive shaft 14, at least a part of the drive shaft 14 located in the pump housing 12. A shaft sealing ring 16 is positioned between the pump housing 12 and the drive shaft 14. A pressure control valve 18 is located in the pump housing 12. A fuel supply path 20 is defined between the pressure control valve 18 and the shaft sealing ring 16, the fuel supply path 20 adapted to supply fuel from the pressure control valve 18 to the shaft sealing ring 16. A throttle 22 is defined in the fuel supply path 20, the throttle 22 adapted to decrease a pressure of fuel flowing via the fuel supply path 20 to the shaft sealing ring 16.
[0005] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a pump housing 12. A drive shaft 14 is located within the pump housing 12. The drive shaft 14 is located within the pump housing 12 such that the drive shaft 14 rotates within the pump housing 12. A shaft sealing ring 16 is positioned between the pump housing 12 and the drive shaft 14. The shaft sealing ring 16 prevents fuel from flowing past the shaft sealing ring 16 and out of the high pressure fuel pump 10. In an exemplary embodiment, the shaft sealing ring 16 may be press fitted to the high pressure fuel pump 10 to facilitate sealing the high pressure fuel pump 10. In an alternate exemplary embodiment, the shaft sealing ring 16 may be coupled in a sealing arrangement between the drive shaft 14 and the pump housing 12 via any fastening means known in the art. A fuel supply path 20 is defined between the pressure control valve 18 and the shaft sealing ring 16.
[0006] The fuel supply path 20 facilitates supplying fuel from the pressure control valve 18 to the drive shaft 14 via the shaft sealing ring 16 when the pressure control valve 18 is opened to facilitate lubricating the drive shaft 14. When the pressure control valve 18 is opened, fuel flows through the fuel supply path 20 to the shaft sealing ring 16, thereby exerting pressure on the shaft sealing ring 16. Due to the high pressure of the fuel acting on the shaft sealing ring 16, the shaft sealing ring 16 ruptures. Therefore, it is required to decrease a pressure of fuel acting on the shaft sealing ring 16 to avoid rupture of the shaft sealing ring 16.
[0007] A throttle 22 is provided in the fuel supply path 20 and decreases a pressure of fuel flowing through the fuel supply path 20 from the pressure control valve 18. More specifically, the throttle 22 that is provided in the fuel supply path 20 obstructs a flow of fuel flowing through the fuel supply path 20. Therefore, due to the obstruction in the flow of fuel through the fuel supply path 20, the pressure of the fuel exiting the fuel supply path 20 decreases. The decrease in the pressure of fuel flowing out of the fuel supply path 20 reduces the impact of the fuel on the shaft sealing ring 16. Therefore, the rupture on the shaft sealing ring 16 may be decreased substantially or eliminated.
[0008] A working of the high pressure fuel pump 10 is described as an example. When the pressure control valve 18 is opened to facilitate lubricating the drive shaft 14, fuel is channeled to the shaft sealing ring 16 via the fuel supply path 20. When pressurized fuel flows through the fuel supply path 20, it encounters the throttle 22 which decreases the pressure of the fuel that flows through the fuel supply path 20. Due to a decrease in pressure of fuel exiting the throttle 22 of the fuel supply path 20, the pressure of the fuel impinging on the shaft sealing ring 16 decreases use a different word. As a consequence, the working life of the shaft sealing ring 16 may be extended.
[0009] 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 leverage and dimensions of various levers are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.