Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12);
a driving shaft (14) inserted within said housing (12), said driving shaft (14) adapted to rotate within said housing (12); characterized in that
a bushing (16) secured to an outer surface of said driving shaft (14), said bushing (16) adapted to circumscribe said driving shaft (14) and secure said driving shaft (14) within said housing (12) of said high pressure fuel pump (10).

2. The high pressure fuel pump (10) in accordance with Claim 1 wherein said bushing (16) is shrink fitted onto an outer surface of said driving shaft (14) of said high pressure fuel pump (10).

3. The high pressure fuel pump (10) in accordance with Claim 2 wherein said bushing (16) is shrink fitted onto the outer surface of said driving shaft (14) of said high pressure fuel pump (10) by heating said driving shaft (14) to facilitate decreasing the diameter and increasing a length of said driving shaft (14), and inserting said bushing (16) onto the outer surface of said driving shaft such that said bushing (16) is retained on the outer surface of said driving shaft (14) in an interference fit when said driving shaft (14) is restored to its original diameter on cooling said driving shaft (14).

4. The high pressure fuel pump (10) in accordance with Claim 2 wherein said bushing (16) is manufactured from a mild steel material.

5. The high pressure fuel pump (10) in accordance with Claim 1 wherein said bushing (16) is adapted to increase a diameter of said driving shaft (14) and bushing assembly (16) to facilitate retaining said driving shaft (14) within said housing (12) of said high pressure fuel pump (10) when the diameter of said driving shaft (14) is lesser than a diameter of a receiving bore that is within said housing (12) of said high pressure fuel pump (10).
, 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 a high pressure fuel pump, and more specifically to a driving shaft of the high pressure fuel pump.

Background of the invention
[0002] US 6769889 B describes a gerotor pump for pressurizing gasoline fuel is capable of developing pressures up to 2 MPa with good mechanical and volumetric efficiency and satisfying the durability requirements for an automotive fuel pump. The pump has been designed with optimized clearances and by including features that promote the formation of lubricating films of pressurized fuel. Features of the improved pump include the use of a shadow port in the side plate opposite the outlet port to promote balancing of high fuel pressures on the opposite sides of the rotors. Inner and outer rotors have predetermined side clearances with the clearances of the outer rotor being greater than those of the inner rotor in order to promote fuel pressure balance on the sides of the outer rotor. Support of the inner rotor and a drive shaft on a single bushing with bearing sleeves maintains concentricity. Additional features are disclosed.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a high pressure fuel pump depicting a driving shaft that is secured within a bushing of the high pressure fuel pump in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a high pressure fuel pump 10 in one embodiment of the invention. The high pressure fuel pump 10 comprises a housing 12 and a driving shaft 14 inserted within the housing 12, the driving shaft 14 adapted to rotate within the housing 12. A bushing 16 is secured to an outer surface of the driving shaft 14, the bushing 16 adapted to circumscribe the driving shaft 14 and secure the driving shaft 14 within the housing 12 of the high pressure fuel pump 10.

[0005] In an exemplary embodiment, the high pressure fuel pump 10 comprises a housing 12. A driving shaft 14 is inserted within the housing 12 and secured within the housing 12. More specifically, the driving shaft 14 is adapted to rotate within the housing 12 to facilitate delivering fuel from a pumping chamber of the high pressure fuel pump 10 to a fuel injector that is in flow communication with the high pressure fuel pump 10. A bushing 16 is secured to an outer surface of the driving shaft 14. In the exemplary embodiment, the bushing 16 is adapted to circumscribe the driving shaft 14 and secure the driving shaft 14 within the housing 12 of the high pressure fuel pump 10.

[0006] More specifically, in the exemplary embodiment, the bushing 16 is shrink fitted onto the outer surface of the driving shaft 14 of the high pressure fuel pump 10. The bushing 16 is shrink fitted onto the outer surface of the driving shaft 14 of the high pressure fuel pump 10 by heating the driving shaft 14 to facilitate decreasing the diameter of the driving shaft 14. As the length of the driving shaft 14 increases thereby leading to a decrease in the diameter of the driving shaft 14 when the driving shaft 14 is heated, the bushing 16 is inserted through the length of the driving shaft 14 until the bushing 16 circumscribes around a desired length and location of the driving shaft 14 of the high pressure fuel pump 10. After the bushing 16 is inserted through the length of the driving shaft 14, the bushing 16 is retained on the outer surface of the driving shaft 14 in an interference fit when the driving shaft 14 is restored to its original diameter. More specifically, when the driving shaft 14 is cooled, it is restored to its original dimension, wherein the outer diameter of the driving shaft 14 forms an interference fit with the bushing 16 and presses tightly against the bushing 16 when the length of the driving shaft 14 and the diameter of the driving shaft 14 are each restored to their original dimensions.

[0007] 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 dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.