Claims:We Claim:
1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12);
a cam chamber (14) adapted to house a cam (16), and a roller tappet (18) that is positioned against said cam (16); characterized in that
at least one fuel inlet path (20) in flow communication between an outer portion (22) of said housing (12) and said cam chamber (14), said at least one fuel inlet path (20) adapted to supply fuel to said cam chamber (14); and
at least one fuel outlet path (24) in flow communication between the outer portion (22) of said housing (12) and said cam chamber (14), said at least one fuel outlet path (24) adapted to deliver pressurized fuel from the cam chamber (14) to an inlet of the high pressure fuel pump (10).

2. The high pressure fuel pump (10) in accordance with Claim 1 wherein a rotation of said cam (16) causes pressurization of the fuel that is present in said cam chamber (14), and wherein pressurized fuel is delivered from said cam chamber (14) of said high pressure fuel pump (10) via said at least one fuel outlet path (24).
, Description:Field of the invention
[0001] This invention relates to a high pressure fuel pump and more particularly to a cam box for the high pressure fuel pump.
Background of the invention
[0002] GB 682913 A describes a fuel-injection pump for internal combustion engines having an actuator for the piston and means between the actuator and the piston adapted during the pressure stroke to be suddenly reduced in length and thereby cause a temporary interruption of the injection of the fuel. In the construction shown, the piston is urged by a spring towards a tappet attached to a piston with in a sleeve having a cross wall carrying a roller that engages the cam. The sleeve has a port that at the end of the suction stroke is in communication with fluid under pressure in a passage so that the piston is pressed against an abutment. During the delivery stroke, a port in the sleeve communicates with the exhaust port and no drive is transmitted to the piston until an abutment engages the piston. The disposition of the tappet and roller to the piston and sleeve respectively may be reversed. The sleeve or a further sleeve surrounding it may be provided with a helical slot to vary the time of release of the fluid pressure. A pad may be provided for lubricating the cam.
Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic diagram of a cam box for a high pressure fuel pump.
Detailed description of the invention
[0004] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a housing 12 and a cam chamber 14 adapted to house a cam 16. A roller tappet 18 is positioned against the cam 16. At least one fuel inlet path 20 is in flow communication between an outer portion 22 of the housing 12 and the cam chamber 14, the at least one fuel inlet path 20 adapted to supply fuel to the cam chamber 14. At least one fuel outlet path 24 is in flow communication between the outer portion 22 of the housing 12 and the cam chamber 14, the at least one fuel outlet path 24 adapted to deliver pressurized fuel from the cam chamber 14 to an inlet of the high pressure fuel pump 10.
[0005] The housing 12 comprises an outer portion 22 and an inner portion 23. A cam chamber 14 is defined within the housing 12 and is circularly shaped. A cam 16 is located within the cam chamber 14 and is adapted to rotate within the cam chamber 14. A roller tappet 18 is positioned within the cam chamber 14 and located above the cam 16 such that the rotation of the cam 16 causes the roller tappet 18 to lift upwardly, thereby delivering fuel from the high pressure fuel pump 10.
[0006] The housing 12 of the high pressure fuel pump 10 comprises a fuel inlet path 20 located between the outer portion 22 of the housing 12 and the inner portion 23 of the housing 12. The fuel inlet path 20 is adapted to supply fuel from the fuel tank to the cam chamber 14 for pressurization and delivery. The housing 12 of the high pressure fuel pump 10 comprises a fuel outlet path 24 located between the outer portion 22 of the housing 12 and the inner portion 23 of the housing 12. The fuel outlet path 24 is adapted to supply pressurized fuel from the cam chamber 14 out of the high pressure fuel pump 10.
[0007] The cam 16 comprises four flat shaped edges and circularly shaped outer edges at the end of the flat shaped edges. A space is defined between the four flat shaped edges of the cam 16 and the inner portion 23 of the housing 12. The space defined between the four flat shaped edges of the cam 16 and the inner portion 23 of the housing 12 is used to store fuel that is channeled through the fuel inlet path 20. When the cam 16 rotates, the fuel that is stored between the four flat shaped edges of the cam 16 and the inner portion 23 of the housing 12 is transported by the cam 16. Due to the rotation of the cam 16, the fuel that is stored between the four flat shaped edges of the cam 16 and the inner portion 23 of the housing 12 is pressurized. Pressurized fuel is therein delivered from the fuel outlet path 24 out of the high pressure fuel pump 10. As the cam 16 rotates, the pressurized fuel that is stored between the four flat shaped edges of the cam 16 and the inner portion 23 of the housing 12 is used to lubricate the inner portion 23 of the housing 12, the contact portions between the cam 16 and the inner portion 23 of the housing 12, and the roller tappet 18. Therefore, the rotation of the cam 16 serves to deliver pressurized fuel from the cam chamber 14 as well as to lubricate the inner portion 23 of the housing 12, the contact portions between the cam 16 and the inner portion 23 of the housing 12, and the roller tappet 18.
[0008] A working of the cam box for the high pressure fuel pump 10 is described as an example. Fuel is channeled into the cam chamber 14 via the fuel inlet path 20 that is located between the outer portion 22 of the housing 12 and the inner portion 23 of the housing 12. The fuel is channeled into the space defined between the housing 12 and the cam 16. Due to the rotation of the cam 16, the fuel that is channeled into the space defined between the housing 12 and the cam 16 is pressurized. The pressurized fuel is circulated throughout the cam chamber 14, wherein the pressurized fuel lubricates the inner portion 23 of the housing 12, the contact portions between the cam 16 and the inner portion 23 of the housing 12, and the roller tappet 18. The pressurized fuel is therein delivered out of the high pressure fuel pump 10 via the fuel outlet path 24. The pressurized fuel that is delivered from the fuel outlet path 24 of the high pressure fuel pump 10 is channeled into the fuel inlet path of the high pressure fuel pump 10 for delivery to a fuel injector. As the high pressure fuel pump 10 itself performs the function of pressurizing fuel before delivering it to the inlet of the high pressure fuel pump 10, a requirement of a pre-supply pump as an attachment to the high pressure fuel pump 10 that pressurizes fuel may be eliminated.
[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 components are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.