Claims:We Claim:
1. A fuel injection pump 100, said pump comprising at least:
a housing 102 comprising at least one fuel flow path 104, and accommodating a plunger 106, said plunger 106 deriving motion from a shaft 111;
said shaft 111 comprising a first end 108 and a second end 110, said first end 108 of said shaft 111 located within said housing 102 and said second end 110 mechanically engaged to an engine drive shaft; characterized in that
said shaft 111 comprising a central bore 112 and at least a first flow path 114 located proximal to said first end 108 and along a diameter of said shaft 111, said first flow path 114 in flow communication with said fuel flow path 104; and

at least one second flow path 116, said second flow path 116 located proximal to said second end 110 and along diameter of said shaft 111, said second flow path 116 in flow communication with said central bore 112.

2. The fuel injection pump 100 of claim 1, wherein said at least one fuel flow path 104 receives fuel from an overflow valve 105.

, 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 the field of fuel injection pump.

Background of the invention
[0002] A fuel injection pump is used pressurize fuel received from a fuel tank before the fuel is delivered to an injector. A reciprocating plunger derives motion from a shaft for pressurizing the fuel. A part of the fuel also lubricates the components of the fuel injection pump through a lubrication circuit. The lubrication circuit plays an important role in ensuring the integrity of the shaft-bushing interfaces by ensuring availability of adequate lubrication quantity, the bushing here being used to support the shaft within the housing of the fuel injection pump. The shaft of the fuel injection pump is mounted on two locations, namely the housing side and the flange side, the flange side receives drive from the engine, while the housing side supports the shaft within the fuel injection pump. The flow path of fuel for lubrication in the existing fuel injection pump is as follows. From the overflow valve the fuel flows towards the shaft-bushing interface and then towards the polygon ring chamber and finally towards the flange side shaft-bushing interface. The flange side of the shaft is prone to wear and subsequent bush melting. In the existing design, a large quantity of the fuel lubricates the housing side and the polygon ring chamber thus making it a lubrication rich region. Small amount of fuel lubricates the flange side shaft-bushing interface, making it a lubrication-starved region. There is no direct lubrication on the flange side interface. This may lead to wear and subsequent melting of bushing on the flange side.

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 fuel injection pump.

Detailed description of the embodiments
[0005] FIG. 1 illustrates a fuel injection pump 100. The fuel injection pump 100 comprises at least a housing 102 comprising at least one fuel flow path 104, the housing 102 accommodates a plunger 106, and the plunger 106 derives motion from a shaft 111. The shaft 111 comprises a first end 108 and a second end 110, the first end 108 of the shaft 111 located within the housing and the second end is mechanically engaged to an engine drive shaft (not shown). The shaft 111 comprises a central bore 112 and at least a first flow path 114 located proximal to the first end 108 and along a diameter of the shaft 111, the first flow path 114 in flow communication with the fuel flow path 104. The central bore 112 may be formed on the shaft 111 by drilling operation. The shaft 111 comprises a second flow path 116 that is located proximal to the second end 110 and along diameter of the shaft 111, the second flow path 116 is in flow communication with the central bore 112. In an embodiment the fuel flow path 104 receives fuel from an overflow valve 105.

[0006]The construction of the fuel injection pump 100 will be explained in further detail. The fuel injection pump 100 disclosed herein is used to pressurize fuel received from the fuel tank (not shown). The pressurization happens with the help of a reciprocating plunger 106 that is located within the housing 102 of the fuel injection pump 100. The plunger 106 is driven by the shaft 111. The shaft 111 comprises a first end 108 and a second end 110, the first end 108 of the shaft 111 is located within the housing 102 and the second end 110 is mechanically engaged to an engine drive shaft (not shown). The shaft 111 comprises a central bore 112 and at least a first flow path 114 located proximal to the first end 108 and along a diameter of the shaft 111, the first flow path 114 is in flow communication with the fuel flow path 104. The second flow path 116 is located proximal to the second end and along diameter of the shaft 111, the second flow path 116 is in flow communication with the central bore 112. The holes for second flow path 116 may be drilled along the diameter of shaft 111. The orientation of the holes in either the first flow path 114 and/ or the second flow path 116 may be such that fuel that is received from the fuel path reaches the first flow path 114 and the second flow path 116.

[0007]The working of the fuel injection pump 100 will be explained in further detail with reference to FIG. 1. Fuel is received into the fuel injection pump 100 through the fuel tank (not shown). Fuel, upon entering the fuel injection pump 100, reaches the pressurizing chamber that is located within the housing 102. The reciprocating movement of the plunger 106 pressurizes the fuel that is present in the pressurizing chamber. The plunger 106 derives motion from a shaft 111. The shaft 111 may be supported within the housing 102 with the help of bushings. The interface between the shaft 111 and housing 102 require lubrication. This is now achieved by circulating a part of fuel received in the fuel injection pump 100. The fuel injection pump 100 comprises an overflow valve 105, the function of the overflow valve 105 is to enable flow of fuel within the fuel injection pump 100 for the purpose of lubrication. Fuel flows the via the overflow valve 105 and through the fuel flow path 104. Fuel from the fuel flow path 104 reaches the first flow path 114 that is located proximal to the first end 108 of the shaft 111. The fuel then enters the central bore 112. From the central bore 112 the fuel flows into the second flow path 116. The second flow path 116 supplies fuel that lubricates the interfaces between the shaft 111 and housing 102, thereby ensuring that the interfaces with respect to the shaft 111 are lubricated. After lubricating the interface between the shaft 111 and the housing 102, the fuel flows through a return flow path (not shown) that is located in the housing, the return flow path enables fuel to reach fuel tank (not shown). Hence, by providing a shaft 111 with a central bore 112 and multiple second flow paths 116, lubrication of all the regions around shaft 111 and housing 102 interfaces is improved. Hence, by providing a central bore in the shaft 111, the interfaces of the shaft with respect to the housing may be lubricated completely, this ensures that any interface of shaft and housing is not devoid of lubrication.

[0008]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 fuel injection pump used. 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.