CLIAMS: We Claim:
1. A roller tappet (10) of a high pressure pump, said roller tappet (10) comprises
a main tappet body (12);
a roller (14) and
a pin (16) supporting said roller (14);
characterized in that:
said pin (16) supporting said roller (14) is press fitted into a slot (19) which is integral with said main tappet body (12).
2. The roller tappet (10) claimed in claim (1), wherein said slot (19) has a first sealing surface (22) at one side and a second sealing surface (24) at other side
3. The roller tappet (10) claimed in claim (2), wherein said first sealing area (22) is larger than said second sealing area (24).
4. The roller tappet (10) claimed in claim (1), wherein said pin (16) comes into contact with said first sealing surface (22) of said slot (19) to withstand a high force exerted during a forward stroke of a camshaft (20).
5. The roller tappet (10) claimed in claim (1), wherein said second sealing surface (24) of said slot (19) withstands a low force during a return stroke of said camshaft (20). ,TagSPECI:Field of the invention
[001] This invention relates to a roller tappet of a high pressure pump.

Background of the invention
[002] High-pressure pumps of internal combustion engines have a tappet assembly with a roller in which a roller is inserted into the tappet body in the direction of the longitudinal axis with the help of a pin. The tappet body is guided in a movable manner in a bore of a housing part of the high-pressure pump. The tappet assembly is driven in a reciprocating movement by a drive shaft. The high-pressure pump has a pump piston and the tappet assembly is arranged between the pump piston and a drive shaft. The drive shaft has at least one cam or eccentric on which the roller runs. The tappet assembly serves to convert the rotational movement of the drive shaft into a stroke movement of the pump piston. The tappet assembly must reliably absorb lateral forces acting perpendicular to the axis of rotation of the roller and of the drive shaft.

[003] A German patent application 19857376 discloses a roller tappet comprising a body which has a surrounding groove with a locking ring similar to a piston ring and a hub in a roller. The roller axle rotates in the main body and the length of the roller axle, and the retaining prevents the roller axle from working loose from the hub. The locking ring retains the axle supporting the roller tappet and prevents unwanted loosening.

Brief description of the accompanying drawings
[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[005] Figure 1 illustrates a roller tappet of a high pressure pump according to one embodiment of the invention;
[006] Figure 2 illustrates a cross-sectional area of a roller tappet according to one embodiment of the invention.

Detailed description of the invention
[007] Figure 1 illustrates a roller tappet 10 in a high pressure pump (not shown) according to one embodiment of the invention. The roller tappet 10 comprises a main tappet body 12, a roller 14 and a pin 16 supporting the roller 14. The pin 16 supporting the roller 14 is press fitted into a slot 19 which is integral with the main tappet body 12.

[008] Figure 2 illustrates a cross-sectional area of a roller tappet 10 according to one embodiment of the invention. The slot 19 has a first sealing surface 22 at one side of the slot and a second sealing surface 24 at the other side. The first sealing surface 22 is larger than the second sealing area 24.

[009] The roller tappet 10 also comprises a bush 18 placed between the roller 14 and the pin 16. The function of the roller tappet assembly 10 is to convert a rotational motion of the camshaft 20 into a translational motion of the roller tappet assembly 10 by sliding in a specified housing or path of a pump (not shown). The roller pin assembly (14, 16) is press fitted into the slot 19 of the main tappet body 12 by applying a preload on the main tappet body 12. The preload is a force applied on the main tappet body 12 (as represented by arrows in the figure 2). The pin 16 is pressed fitted into the slot 19 in a predefined angle and under a high temperature. Due to the high temperatures, the main tappet body 12 will expand in size and the pin 16 is fitted into the slot 19. The preload of the roller tappet 10 can be removed after the assembly.

[0010] During a forward stroke of the camshaft 20 (i.e. say from 0 degrees to 180 degrees, rotating in a clock wise direction for a single lobe cam), due to the rotation of the camshaft 20, the roller 14 also experiences a linear movement in the vertical axis. The movement of the roller 14 in the main tappet body 12 moves a plunger upwards to pressurize a fuel. The pin 16 which supports the roller 14 also moves upwards and gets into contact with the first sealing surface 22 of the slot 19. The pin 16 at the first sealing surface 22 of the slot 19 withstands a high force developed due to high hydraulic pressure acting on the plunger and also due to a force exerted by the plunger return spring (not shown). The first sealing surface 22 of the slot 19 ensures that the contact stress developed on the sealing surface 22, does not cross a safety stress limit of the material by which the sealing surface 22 is made of.

[0011] During a return stroke of the camshaft 20 (i.e., say from 180 degrees to 360 degrees), after pressurization of the fuel, the plunger returns to an initial position due to which the roller 14 moves downwards. The pin 16 along with the roller 14 moves downwards and gets into contact with the second sealing surface 24 of the slot 19. Since, the combined force acting on the second sealing surface 24 is less due to the less force developed due to low hydraulic pressure acting on the plunger and also due to a force exerted by plunger return spring, the second sealing surface 24 of the slot 19 will be smaller in width than the first sealing area 22.

[0012] With the roller tappet 10 design disclosed above, the assembling of the components of the roller tappet 10 will be assembled easily. The translational movement as well as the rotational movement of the pin 14 during the working of the roller tappet 10 can be avoided. The usage of the clip to limit the translational movement of the pin 14 can be eliminated with this design of the slot 19 in the main tappet body 12.

[0013] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims.