1. A roller tappet (10) of a high pressure fuel pump, said roller tappet (10) comprising:
a roller tappet body (12);
at least one leg (14) secured to said roller tappet body (12), said at least one leg (14) comprising:
a first circular shaped portion (16) having a first thickness;
a second circular shaped portion (18) having a second thickness, said second circular shaped portion (18) integrally formed on said first circular shaped portion (16), said second thickness greater than said first thickness, and wherein a bearing that is secured to said at least one leg (14) is adapted to rotate against a surface of said second circular shaped portion (18); and
a lubrication oil opening (20) defined on said second circular shaped portion (18), said lubrication oil opening (20) adapted to release lubrication oil on said second circular shaped portion (18) thereby forming a film of lubrication oil on said second circular shaped portion (18) and enables mitigation of wear on said second circular shaped portion (18) when said bearing rotates against a surface of said second circular shaped portion (18).
, 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 roller tappet and more specifically to a leg of the roller tappet of a high pressure fuel pump.

Background of the invention
[0002] US 6216583 B describes a piston pump of the roller tappet type for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in common rail injection systems. A drive shaft that is supported in the pump housing and has a number of cam-like projections in the circumferential direction. At least one tappet that is disposed in a cylinder chamber radially with regard to the drive shaft and in its radially inner end region has a rotatable roller which is supported so that it can roll in the circumferential direction against the drive shaft in the region of its projections in order to reduce the wear in the region of the roller bearing. The pump is embodied so that a lubricant supply opening that leads from the circumference of the tappet and feeds into the radially inner tappet end region supporting the roller and at least during a part of the stroke, communicates with a lubricant supply line of the housing, which line feeds into the cylinder chamber.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic representation of a roller tappet of a high pressure fuel pump.

Detailed description of the embodiments

[0004] Figure 1 illustrates a roller tappet 10 of a high pressure fuel pump. The roller tappet 10 comprises a roller tappet body 12 and at least one leg 14 that is secured to the roller tappet body 12. The at least one leg 14 comprises a first circular shaped portion 16 having a first thickness and a second circular shaped portion 18 having a second thickness, the second circular shaped portion 18 integrally formed on the first circular shaped portion 16, the second thickness greater than the first thickness, and wherein a bearing that is secured to the at least one leg 14 is adapted to rotate against a surface of the second circular shaped portion 18. A lubrication oil opening 20 is defined on the second circular shaped portion 18, the lubrication oil opening 20 adapted to release lubrication oil on the second circular shaped portion 18 thereby forming a film of lubrication oil on the second circular shaped portion 18 and enables mitigation of wear on the second circular shaped portion 18 when the bearing rotates against the surface of the second circular shaped portion 18.

[0005] The roller tappet 10 for the high pressure fuel pump comprises a roller tappet body 12 that is secured to a piston of the high pressure fuel pump. The roller tappet body 12 further comprises two legs that are axially spaced from one another, each of which are secured to the roller tappet body 12. A bearing that is positioned between the two legs of the roller tappet body 12 is secured thereto. In an exemplary embodiment, the bearing rotates between the two legs of the roller tappet body 12. When the bearing rotates between the two legs of the roller tappet body 12, the bearing rubs against a circumferential portion of each of the two legs of the roller tappet body 12 as will be explained in further detail below.

[0006] Each of the two legs of the roller tappet body 12 comprises a circular shaped portion and a lubrication oil opening 20 that is defined on the circular shaped portion. The circular shaped portion of the roller tappet body 12 comprises a first circular shaped portion 16 having a first thickness and a second circular shaped portion 18 having a second thickness. In an exemplary embodiment, the second circular shaped portion 18 is integrally formed on the first circular shaped portion 16. Moreover, the second thickness of the second circular shaped portion 18 is greater than the first thickness of the first circular shaped portion 16 to facilitate the bearing rubbing against the second circular shaped portion 18 as will be explained in further detail. The lubrication oil opening 20 is defined on the second circular shaped portion 18 such that the lubrication oil opening 20 is defined on the top portion of the second circular shaped portion 18. The lubrication oil opening 20 that is defined on the top portion of the second circular shaped portion 18 is adapted to release lubrication oil on the second circular shaped portion 18 of the at least one leg 14 of the roller tappet 10. The lubrication oil that is released on the second circular shaped portion 18 of the at least one leg 14 of the roller tappet 10 forms a film of lubrication oil on the second circular shaped portion 18. The bearing is secured between the two legs of the roller tappet 10 and is adapted to rotate against a surface of the second circular shaped portion 18 because the second circular shaped portion 18 has a greater thickness than the first circular shaped portion 16 and also maintains contact with the bearing. Therefore, as the bearing rotates, the bearing forces against the surface of the second circular shaped portion 18 and rubs against the surface of the second circular shaped portion 18, and does not maintain any contact with the first circular shaped portion 16. The lubrication oil that is released from the lubrication oil opening 20 is drawn by the rotation of the bearing, thereby forming a film of lubrication oil on the circumference of the second circular shaped portion 18. The lubrication oil that is formed on the circumference of the second circular shaped portion 18 enables mitigation of wear on the second circular shaped portion 18 when the bearing rotates and rubs against the surface of the second circular shaped portion 18 of the roller tappet 10.

[0007] A working of the roller tappet 10 of the high pressure fuel pump is described as an example. The bearing that is secured between the two legs of the roller tappet 10 is adapted to rotate against the second circular shaped portions 18 of the two legs of the roller tappet 10. The bearing however does not come in contact with the first circular shaped portion 16 of the two legs of the roller tappet 10. The lubrication oil is supplied to the second circular shaped portion 18 of the two legs of the roller tappet 10. The lubrication oil on coming in contact with the bearing flows along the direction of rotation of the bearing, thereby spreading and forming a film of lubrication oil on the second circular shaped portion 18 of each of the two legs of the roller tappet 10. The lubrication oil flows around the circumference of the second circular shaped portion 18 of the two legs of the roller tappet 10 and then flows downwardly towards a camshaft that is positioned below the roller tappet 10. When the bearing that is secured between the two legs of the roller tappet 10 rotates against the second circular shaped portion 18 of the two legs of the roller tappet 10, the lubrication oil that forms a film on the surface of the second circular shaped portion 18 of the two legs of the roller tappet 10 lubricates and hence prevents the second circular shaped portion 18 of the two legs of the roller tappet 10 from being eroded. As a consequence, the working life of the second circular shaped portion 18 of the two legs of the roller tappet 10 is substantially extended.

[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 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 scope of the claims.