Field of the invention
[0001] This invention relates to a high pressure fuel pump, and more specifically to a stepped portion defined on a plunger of the high pressure fuel pump.
Background of the invention
[0002] GB825151A describes a swash plate pump or motor that includes a supplementary pump for supplying control or make-up liquid. A rotating block is provided with an eccentric cam surface which co-operates with a rotor housing and a sliding vane to form the pump. The outer end of the vane may be formed as a plunger movable in a cylinder to constitute a high-pressure pump.
Brief description of the accompanying drawing
[0003] Figure 1 illustrates a plunger of a 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. The high pressure fuel pump 10 comprises a barrel 12, and a plunger 14 positioned within the barrel 12 and adapted to reciprocate within the barrel 12. The plunger 14 comprises a cylindrical portion 16, and a vane 18 formed on the cylindrical portion 16. The vane 18 is adapted to arrest a translatory movement of the plunger 14, when the plunger 14 translates from a bottom dead center of the high pressure fuel pump 10 to a top dead center of the high pressure fuel pump 10. A stepped portion 20 is defined between the vane 18 and the cylindrical portion 16. The stepped portion 20 is adapted to enter the barrel 12, thereby allowing a greater length of the cylindrical portion 16 to enter the barrel 12 when the plunger 14 translates from the bottom dead center of the high pressure fuel pump 10 to the top dead center of the high pressure fuel pump 10.

[0005] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a barrel 12. In an exemplary embodiment, a plunger 14 is positioned within the barrel 12 and is adapted to reciprocate within the barrel 12. The reciprocatory motion of the plunger 14 within the barrel 12 facilitates delivering pressurized fuel from the high pressure fuel pump 10. The plunger 14 comprises a cylindrical portion 16, and a vane 18 that is formed on the cylindrical portion 16 and extends axially from the cylindrical portion. The vane 18 that is formed on the cylindrical portion 16 of the plunger 14 is adapted to arrest a translatory movement of the plunger 14 when the plunger 14 translates from a bottom dead center of the high pressure fuel pump 10 to a top dead center of the high pressure fuel pump 10. At the top dead center position of the plunger 14, at full lift there will be sufficient clearance defined between the vane and the barrel. The clearance that is defined between the vane and the barrel is sufficient to prevent the top dead center of the plunger from coming in contact with the valve seat. In the exemplary embodiment, the high pressure fuel pump 10 may be one of an A-pump and a PF pump. Moreover, the high pressure fuel pump 10, including the vane, the plunger, and the housing may be manufactured from 100 CR6 based resilient material.
[0006] In an exemplary embodiment, a stepped portion 20 is defined between the vane 18 and the cylindrical portion 16. More specifically, the stepped portion 20 extends axially upwardly from the vane 18 and therein extends radially inwardly to be integrated within the plunger 14 of the high pressure fuel pump 10. In an exemplary embodiment, the length of the stepped portion 20 may be defined by a user based on a specific application. In addition, a length of the stepped portion 20 may be increased by machining a greater length of the vane 18 from an outer diameter of the vane 18 to a predetermined depth towards the plunger 14. When the plunger 14 of the high pressure fuel pump 10 translates from the bottom dead center to the top dead center, the stepped portion 20 that is defined between the vane 18 and the cylindrical portion

16 is adapted to enter the barrel 12 as the plunger approaches the top dead center. Since the stepped portion 20 that is defined between the vane 18 and the cylindrical portion 16 is adapted to enter the barrel 12, a greater length of the plunger 14 is thereby adapted to enter the barrel 12 when the plunger 14 translates from a bottom dead center of the high pressure fuel pump 10 to a top dead center of the high pressure fuel pump 10. More specifically, the greater length of the plunger 14 is thereby adapted to enter the barrel when the plunger 14 translates from the bottom dead center to the top dead center than were previously possible if the stepped portion 20 that is defined between the vane 18 and the cylindrical portion 16 were non-existent. In addition, due to the creation of the stepped portion 20 that is defined between the vane 18 and the cylindrical portion 16, the bottom dead center of the plunger 14 can be raised by means of a screw that is positioned between the plunger 14 and the roller tappet. Therefore, while the plunger 14 is maintained at the same bottom dead center position, the plunger 14 may be raised by a displacement that is equal to the step length of the stepped portion 20. Therefore, the plunger 14 may be raised by a displacement that is equal to the step length of the stepped portion 20 without damaging the plunger at the top dead center position. In an exemplary embodiment, the stepped portion 20 may be created by machining around the stepped portion 20 and removing a layer of material from the vane 18 of the plunger 14. Therefore, by shaving off a layer of material of the vane 18 around the stepped portion 20, the thickness of the vane 18 may be reduced. By reducing the thickness of the vane 18, the plunger 14 can be raised of the bottom dead center of the plunger 14 without damaging the plunger at the top dead center position. The initial lifting of the plunger 14 at the bottom dead center position allows a user to decrease a pre-stroke of the high pressure fuel pump 10 as is known in the art.
[0007] A working of the high pressure fuel pump 10 is described as an example. In the exemplary embodiment, the vane 18 of the high pressure fuel pump 10 is machined to remove a layer of material from the vane 18 of the high pressure fuel pump 10, thereby

creating a stepped portion 20 between the vane 18 and the cylindrical portion 16 of the plunger 14. The creation of the stepped portion 20 between the vane 18 and the cylindrical portion 16 of the plunger 14 allows a greater length of the plunger 14 to enter within the barrel 12 of the high pressure fuel pump 10 when the plunger 14 translates from the bottom dead center to the top dead center of the high pressure fuel pump 10. Therefore the plunger 14 can be lifted at the bottom dead center position without damaging the plunger 14 at the top dead center position, the pre-stroke length of the plunger 14 may be effectively reduced.
[0008] 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.

We Claim
1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a barrel (12);
a plunger (14) positioned within said barrel (12) and adapted to reciprocate
within said barrel (12), said plunger (14) comprising: a cylindrical portion (16);
a vane (18) formed on the cylindrical portion (16), said vane (18) adapted to arrest a translatory movement of said plunger (14) when said plunger (14) translates from a bottom dead center of said high pressure fuel pump (10) to a top dead center of said high pressure fuel pump (10); characterized in that
a stepped portion (20) defined between said vane (18) and said cylindrical portion (16), said stepped portion (20) adapted to enter said barrel (12) thereby allowing a greater length of the cylindrical portion (16) to enter said barrel (12) when said plunger (14) translates from a bottom dead center of said high pressure fuel pump (10) to a top dead center of said high pressure fuel pump (10).
2. The high pressure fuel pump (10) in accordance with Claim 1 wherein allowing
a greater length of the cylindrical portion (16) to enter said barrel (12) when said plunger (14) translates from the bottom dead center of said high pressure fuel pump (10) to the top dead center of said high pressure fuel pump (10) permits decreasing a pre-stroke length of said plunger (14) of said high pressure fuel pump (10).

3. The high pressure fuel pump (10) in accordance with Claim 1 wherein said stepped portion (20) extends upwardly from a top surface of said vane (18), said stepped portion (20) having an outer diameter that is smaller than an outer diameter of said vane (18).
4. The high pressure fuel pump (10) in accordance with Claim 1 wherein said stepped portion (20) is created by machining an outer diameter of said vane (18) to a predetermined depth.
5. The high pressure fuel pump (10) in accordance with Claim 1 wherein a length of said stepped portion (20) may be defined by a user based on a specific application.
6. The high pressure fuel pump (10) in accordance with Claim 1 wherein a length of said stepped portion (20) may be increased by machining a greater length of said vane (18) from an outer diameter of said vane (18) to a predetermined depth.