Claims:We Claim:
1. A high pressure fuel injection pump (200); comprising at least:
a plunger (202) located within a pump body (204);

said pump body (204) mounted on a pump housing (206);

said pump housing (206) accommodating at least:

a roller tappet (208), axis of rotation of said roller tappet (208) being perpendicular to axis of said plunger (202); characterized in that:

said plunger (202) having uniform diameter along a length of the plunger (202).

2. The high pressure fuel injection pump (200) of claim 1, wherein said plunger (202) is unsupported along a barrel of said pump body. , Description:Field of the invention
[0001] This invention relates to the field of a high pressure fuel injection pump.

Background of the invention
[0002] A fuel injection pump is used to provide pressurized fuel to an injector. The pressurization of fuel within the pump happens by the means of a reciprocating plunger. The plunger moves between bottom dead centre (BDC) and top dead centre (TDC) in order to compress the fuel. The movement of the plunger happens due to combined movement of roller and roller tappet, the roller being driven by a cam mounted on a cam shaft. It is observed the lift that the plunger makes every time the fuel needs to be pressurized is the same irrespective of the amount of fuel being present in the fuel injection pump. This leads to consumption in energy for driving the plunger, even though the plunger need not lift to the maximum extent possible during every compression stroke of the plunger. Hence there is a need to restrict the movement of plunger only to extent as required.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0004] FIG. 1 illustrates a high pressure fuel injection pump used in state of art; and
[0005] FIG. 2 illustrates a high pressure fuel injection pump; and

Detailed description of the embodiments
[0006] FIG. 1 illustrates a high pressure fuel injection pump 100 used in state of art. The fuel injection pump 100 comprises a plunger 102 located within a pump body 104. The pump body 104 is mounted on a pump housing 106. The pump housing 106 accommodates the drive elements comprising at least a cam shaft with a cam, a roller tappet and roller. The base of the plunger comprises a step 105, the step 105 is in contact with the roller tappet. A spring plate 109 guides the plunger on the roller tappet and ensures the contact between the step 105 of the plunger with the roller tappet.
[0007] During working of the fuel injection pump 100, the fuel from the feed pump enters the inlet of the fuel injection pump 100. The plunger 102 present in the pump body 104, moves downward because of the pressure at which fuel enters the inlet of the fuel injection pump 100. Now, the fuel needs to be compressed before being sent to the injector. This happens through the upward movement of the plunger 102. The plunger 102 derives this upward movement from the roller tappet 108. The roller tappet 108 in turn is driven by the rotation of roller and cam. The cam is mounted on the cam shaft. Hence, the for receiving and compressing the fuel into the fuel injection pump, the plunger has to travel the entire length of the pump body downwards and then lift again to compress the fuel. This happens irrespective of the volume of fuel entering the fuel injection pump leading to loss in energy as, every time the plunger needs to traverse the same distance irrespective of the amount of fuel being filled. In order to avoid this, the plunger is now modified in a manner such that the plunger lift is only to the extent required, the same will be explained in the detailed description of FIG. 2.
[0008] FIG. 2 illustrates a high pressure fuel injection pump 200. The fuel injection pump 200 comprises at least a plunger 202 located within a pump body 204, the pump body 204 is mounted on a pump housing 206. The pump housing 206 accommodates at least a roller tappet 208. The axis of rotation of the roller tappet 208 being perpendicular to axis of the plunger 202. The plunger 202 has uniform diameter along the length of the plunger 202. The plunger 202 is also unsupported along the pump body 204. The term unsupported refers to the fact the plunger is free to traverse along the barrel of the pump body 204.
[0009] The working of the proposed fuel injection pump 200 will now be explained as against the fuel injection pump 100 described in state of art (FIG. 1). Fuel from the feed pump enters the inlet of the fuel injection pump 200. The plunger 202 present in the pump body, moves downward because of the pressure at which fuel enters the inlet of the fuel injection pump 200. The movement of the plunger 202, is only to the extent of filling of fuel in the fuel injection pump 200. Since the plunger 202 is unsupported along the pump body 204, the plunger 202 can move freely downwards while the fuel enters the fuel injection pump 200. Now, the fuel needs to be compressed before being sent to the injector. This happens through the upward movement of the plunger 202. The plunger 202 derives its movement from the roller tappet 208. The roller tappet in turn is driven by the rotation of roller and cam. The cam is mounted on the cam shaft. Hence, the for receiving and compressing the fuel into the fuel injection pump, the plunger 202 has to travel along the length of the pump body downwards and then lift again, only to the extent to which fuel is filled, so as to compress the fuel.
[00010] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of the type of plunger and material and geometry of the plunger. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.