Claims:We Claim:
1. A fuel injection pump (200), said fuel injection pump (200) mounted on an engine (202) and comprising at least:
a cam (204) driven by a crank shaft (206) of said engine (102);
a roller (108) driven by said cam (204);
a roller tappet body (210) adapted to receive motion form said cam (204), said roller tappet body (210) drives a plunger (209) located within a spring chamber (207) of said fuel injection pump (200); characterized in that
said roller tappet body (210) comprising a cavity (212), said cavity (212) adapted to receive lubricant oil,
said roller tappet body (210) isolates said spring chamber (207) of said fuel injection pump (200) from said lubricant oil in said cavity (212).
2. The fuel injection pump (200) of claim 1, wherein a part of said roller (108) is located in said cavity (212).

3. The fuel injection pump (200) of claim 1, wherein said fuel injection pump 100 comprises at least one outlet 214 for venting out of said lubricant oil. , Description:Field of the invention
[0001] This invention relates to the field of a fuel injection pump.

Background of the invention
[0002] In a reciprocating fuel injection pump, a cam and roller assembly is used to convert rotary motion of cam into reciprocating motion of plunger. The roller tappet body holds the roller assembly. The roller assembly consists of roller, bush and bearing bolt. To reduce the friction between the moving components lube oil is provided through cross holes in the roller tappet body. In the present design of roller tappet, cross holes have been provided in the roller tappet body to lubricate all the contact interfaces between the roller-cam, roller-bush and bush-bearing bolt in order to reduce the friction between the moving components. Additionally a passage is been provided in the roller tappet body to remove the air from the spring chamber in order to reduce the pressure peaks.
[0003] FIG. 1 illustrates a fuel injection pump 100 used in state of art. The fuel injection pump 100 is driven by a cam 101. The cam 101 derives its motion from the crankshaft of the engine. The rotational motion of the cam 101 is transferred to the roller tappet 102. The roller tappet 102 then converts this rotary motion of cam into reciprocating movement of the plunger 104. The plunger 104 is located in a spring chamber 106 of the fuel injection pump 100. The components in the roller tappet 102, and cam 101 and roller interface require lubrication. In order to meet the lubrication requirement, passages 108 are provided in the roller tappet body. These passages 108 help in flow of lubricant. The lubricant can be engine oil or the fuel itself. In addition to passage for flow of lubricant, an air flow passage 110 is also provided in the roller tappet body. This air flow passage 110 helps in venting out air from the spring chamber 106. This is required in order to maintain a stable pressure in the fuel injection pump 100. In order to meet, certain requirements, the orientation of pump 100 needs to be changed, (for example, the pump may be mounted in inverted condition with respect to FIG.1), in such case it is observed that lubricant oil coming in the roller tappet body through lube oil passage 108 will flow into the spring chamber 106 via the air flow passage 110. In the spring chamber 106 the plunger 104 comes in direct contact of the lubricant oil. So now when the plunger 104 reciprocates it carries the lubricant oil which gets mixed with the fuel resulting in diesel blackening and nozzle choking issues. Additionally, due to the change in the mounting of the pump, the lubricant oil will not flow in the intended path resulting in the scarcity of lubricant oil in the critical interfaces (like roller-bush, bush-bearing, bolt).

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0005] FIG. 1 illustrates a fuel injection pump used in the current state of art; and
[0006] FIG. 2 illustrates a fuel injection pump.

Detailed description of the embodiments
[0007] FIG. 2 illustrates a fuel injection pump 200. The fuel injection pump 200 is mounted on an engine 202 and comprises at least, a cam 204 driven by a crank shaft 206 of the engine 202 and a roller 208 driven by the cam 204. A roller tappet body 210 is adapted to receive motion from the cam 204, the roller tappet body 210 drives a plunger 209 located within a spring chamber 207 of the fuel injection pump 200. The roller tappet body 210 comprises a cavity 212, the cavity 212 is adapted to receive lubricant oil. The roller tappet body 210 isolates the spring chamber 207 of the fuel injection pump 200 from the lubricant oil in the cavity 212. A part of the roller 208 is located in the cavity 212. The fuel injection pump 200 is provided with at least one outlet 214 for venting out of the lubricant oil.

[0008] The constructional feature of the proposed fuel injection pump 200 is disclosed in further detail for the purpose of better understanding with reference to FIG. 2. The fuel injection pump 200 is driven by the crank shaft 206 of the engine 202. The cam 204 gets the drive from the engine crankshaft 206. The rotational motion of the cam gets converted to reciprocating motion of the plunger 209 via roller tappet body 210. The roller tappet body 210 is now modified and comprises a cavity 212. The function of the cavity 212 is to receive and store the lubricant oil. The lubricant oil may be received from a jet that is located is located in the engine to supply lubricant oil to lubricate cam 204 and roller 208 interface. The fuel injection pump 200 is also provided with at least one outlet 214 for venting out of the lubricant oil. The oil from the cavity 212 lubricates at least the following components namely cam 204 and roller 208 interface, roller 208 and bush, and bush and bearing bolt.

[0009] The working of the proposed fuel injection pump 200 will now be explained in further detail. During working of the fuel injection pump 200, the fuel enters into the fuel injection pump 200, is pressurized and then delivered to a common rail or the injector. This is achieved with the help of a reciprocating plunger 209 that receives motion from a roller tappet body 210 driven by a cam 204. The cam 204 is driven by the crank shaft 206 of the engine 202. In order to provide lubrication to cam 204, roller tappet body 210 and other components a jet is used. The jet is located in way, such that, the flow of lubricant oil from the jet, impinges on the cam 204 and then flows into the cavity 212 provided on the roller tappet body 210 of the fuel injection pump 200. Since a part of the roller is located in the cavity 212, the lubricant oil lubricates the roller tappet body 210 components for example roller, bush and bearing bolt. A path is provided in the fuel injection pump 200, for the lubricant oil to flow from the cavity 212 to the outlet 214 for venting out of the lubricant oil. Hence the lubricant oil that is received in the cavity 210 lubricates cam, roller, roller tappet body 210 and then flows to the outlet 214 without entering into the spring chamber 207.

[0010] The proposed concept of having a cavity 212 in roller tappet body 210 can be used in the cases where the orientation of the fuel injection pump 200 is such that, there is chance for oil to enter the spring chamber 207 and there will be scarcity of lubricant oil at the critical interfaces. In the provided cavity 212 the lubricant oil will get accumulated and as the roller assembly rotates it will carry the lubricant oil with it and will lubricate all the critical interfaces.

[0011] 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 type of fuel injection pump used and orientation and/ or mounting of the fuel injection pump with respect to the engine. 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.