Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a cam (12), said cam (12) comprising at least one cam lobe (14);
a roller (16) of a roller tappet positioned against said at least one cam lobe (14), wherein a rotation of said at least one cam lobe (14) causes a rotation of said roller (16) of said roller tappet;
a roller pin (18) secured to said roller (16) and positioned within a tappet (20) of said roller tappet; characterized in that
a first groove (22) defined on a first portion of said roller pin (18), and a second groove (24) defined on a second portion of said roller pin (18);
a third groove (26) defined on a first portion of said tappet (20) of said roller tappet, and a fourth groove (28) defined on a second portion of said tappet (20) of said roller tappet;
a first spring member (30) positioned between the first groove (22) that is defined on the first portion of said roller pin (18) and the third groove (26) that is defined on the first portion of said tappet (20) of said roller tappet; and
a second spring member (32) positioned between the second groove (24) that is defined on the second portion of said roller pin (18) and the fourth groove (28) that is defined on the second portion of said tappet (20) of said roller tappet, wherein said first spring member (30) and said second spring member (32) are each adapted to be compressed when said roller (16) is displaced against a resistive force of said first spring member (30) and said second spring member (32) due to the rotation of said cam (12).

, 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 plurality of compression springs that are secured to a roller tappet of a high pressure fuel pump.

Background of the invention
[0002] GB 9617374 A describes a high-pressure fuel pump for an internal combustion engine. The high pressure fuel pump comprises a pump piston which can be actuated by the cam of a camshaft via a roller tappet and which, during the inwards stroke, acts counter to the force of a prestressed spring element, of which one end is supported on the tappet side on a spring plate, and the other end is supported on an adjustable support body. The prestressing force of the spring element, with increasing the rotational speed of the engine, is increased by loading the support body with pressure in dependence on rotational speed. The spring element may be a coil compression spring. It can also consist of a shape memory alloy having a spring constant which increases with increase in speed.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a roller of a high pressure fuel pump that is secured to a tappet of the high pressure fuel pump.

Detailed description of the embodiments
[0004] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a cam 12, the cam 12 comprising at least one cam lobe 14. A roller 16 of a roller tappet is positioned against the at least one cam lobe 14, wherein a rotation of the at least one cam lobe 14 causes a rotation of the roller 16 of the roller tappet. A roller pin 18 is secured to the roller 16 and positioned within a tappet 20 of the roller tappet. A first groove 22 is defined on a first portion of the roller pin 18, and a second groove 24 is defined on a second portion of the roller pin 18. A third groove 26 is defined on a first portion of the tappet 20 of the roller tappet, and a fourth groove 28 is defined on a second portion of the tappet 20 of the roller tappet. A first spring member 30 is positioned between the first groove 22 that is defined on the first portion of the roller pin 18 and the third groove 26 that is defined on the first portion of the tappet 20 of the roller tappet. A second spring member 32 is positioned between the second groove 24 that is defined on the second portion of the roller pin 18 and the fourth groove 28 that is defined on the second portion of the tappet 20 of the roller tappet, wherein the first spring member 30 and the second spring member 32 are each adapted to be compressed when the roller 16 is displaced against a resistive force of the first spring member 30 and the second spring member 32 due to the rotation of the cam 12.

[0005] The high pressure fuel pump 10 comprises a cam 12 that is secured to a drive shaft of an engine and is rotated by the rotation of the drive shaft of the engine. The cam 12 comprises at least one cam lobe 14 that is defined on the cam 12. A roller 16 of a roller tappet is positioned against the at least one cam 12. When the cam 12 rotates due to the rotation of the drive shaft of the engine, the cam lobe 14 that is integrally cast with the cam 12 also rotates. The rotation of the cam 12 causes a rotation of the roller 16 of the roller tappet. When the cam lobe 14 is in position below the roller 16 of the roller tappet and rotates further, the cam lobe 14 causes the roller tappet to lift upwardly, thereby causing pressurized fuel that is present within a cylinder of the high pressure fuel pump 10 to be delivered to the engine.

[0006] A roller pin 18 is secured to the roller 16 and positioned within a tappet 20 of the roller tappet. More specifically, the roller pin 18 is positioned within the tappet 20 of the roller tappet such that the tappet 20 circumscribes the roller pin 18, and wherein the roller pin 18 rotates within the tappet 20 of the roller tappet. A first groove 22 is defined on a first portion 50 of the roller pin 18, and a second groove 24 is defined on a second portion 52 of the roller pin 18. In the exemplary embodiment, the first groove 22 and the second groove 24 are each milled on the first portion 50 of the roller pin 18 and the second portion 52 of the roller pin 18 respectively. A third groove 26 is defined on a first portion 54 of the tappet 20 of the roller tappet, and a fourth groove 28 is defined on a second portion of the tappet 20 of the roller tappet. In the exemplary embodiment, the third groove 26 and the fourth groove 28 are each milled on the first portion 54 of the tappet 20 and the second portion 56 of the tappet 20 of the roller tappet respectively.

[0007] A first spring member 30 is positioned between the first groove 22 that is defined on the first portion of the roller pin 18 and the third groove 26 that is defined on the first portion of the tappet 20 of the roller tappet. The first spring member 30 is adapted to be compressed when the roller 16 of the roller tappet translates upwardly. When the roller 16 of the roller tappet stops translating due to the return movement of the cam 12 by means of a rotation of the cam lobe 14, the resistive force of the first spring member 30 causes the roller pin 18, and hence the roller 16 to be restored to its equilibrium position. A second spring member 32 is positioned between the second groove 24 that is defined on the second portion of the roller pin 18 and the fourth groove 28 that is defined on the second portion of the tappet 20 of the roller tappet. The second spring member 32 is adapted to be compressed when the roller 16 of the roller tappet translates upwardly. When the roller 16 of the roller tappet stops translating due to the return movement of the cam 12 by means of a rotation of the cam lobe 14, the resistive force of the second spring member 32 causes the roller pin 18, and hence the roller 16 to be restored to its equilibrium position. Therefore, the first spring member 30 and the second spring member 32 are each adapted to be compressed when the roller 16 is displaced against a resistive force of the first spring member 30 and the second spring member 32 due to the rotation of the cam 12.
[0008] A working of the high pressure fuel pump 10 with the first compression spring 30 and the second compression spring 32 that are secured to the roller tappet is described as an example. When the cam 12 rotates due to the rotation of the drive shaft, the cam lobe 14 that is secured to the cam 12 also rotates. When the cam lobe 14 come below the roller 16 of the roller tappet, the roller 16 is rotated and lifted upwardly due to the contact of the cam lobe 14 of the cam 12 with the roller 16. This upward movement of the roller 16 is translated into the tappet 20 of the roller tappet that causes the roller tappet to be lifted upwardly, thereby causing fuel to be delivered from the high pressure fuel pump. Over a period of time, due to the misalignment that occurs between the cam 12 and the roller 16, or due to dust particles that settle between the surface of the cam 12 and the roller 16, the roller 16 is lifted upwardly by the cam 12 to a marginally greater extent than previously under normal working conditions by the cam 12. The marginal increase in the height of the roller 16 that is lifted by the cam 12, causes the roller pin 18 to be translated in the upward direction. The translation of the roller pin 18 in the upward direction causes the first compression spring 30 and the second compression spring 32 to get compressed, thereby providing a small clearance for the upward translation of the roller 16 of the roller tappet. The upward translation of the roller 16 causes the forces acting on the roller 16 to be distributed more uniformly around the tappet 20. When the cam lobe 14 has rotated to its peak and is restored to its original equilibrium position, the restoring force of the first spring member 30 and the second spring member 32 causes the roller 16 to be restored to its original equilibrium position against the surface of the cam 12.

[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 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.