CLIAMS:We Claim:

1. A fuel injection pump 100, comprising;
a piston 102;
a housing 104 accommodating said piston 102 and said housing having an inlet 106, characterized in that.
a circumferential groove 108 is provided at the inner diameter of said housing 104 at the region where the inlet 106 interfaces with said housing 104.
2. The fuel injection pump of claim 1, wherein profile of said circumferential groove 108 is symmetrical with respect to said inner diameter of said housing 104.
3. The fuel injection pump of claim 1, wherein said fuel injection pump 100 is a port controlled pump.
,TagSPECI:FIELD OF THE INVENTION
[001] This invention relates to the field of fuel injection pump.

BACKGROUND OF THE INVENTION
[002] A fuel injection pump, pumps a required quantity of fuel at higher pressure to combustion chamber of the internal engine through injector; this is achieved by means of a reciprocating piston that is enclosed within the pump housing. The fuel from the feed pump in the low pressure circuit reaches the fuel injection pump high pressure chamber through the inlet port. The inlet port opening and closing is controlled by the reciprocating action of the piston. The filling in of the fuel starts when the inlet port opens during the downward stroke of the piston and it stops when inlet port closes during the forward or the upward stroke of the piston. After port closure during the forward stroke the fuel present inside the pump high pressure chamber gets compressed by the piston and is sent to the rail through the delivery valve.

[003] During the working motion of the piston it is observed that the high pressure fuel tends to leak through the working clearance between the barrel and piston. This leakage of fuel from the pump chamber to the inlet port creates the uneven pressure difference in the annular clearance between piston and inner wall of the pump housing, pushes the piston on one side, causing the piston to rub against the wall of the housing. This leads to creation of high frictional forces between the piston and the inner wall of the pump housing leading to wear and tear of piston. The wear and tear of piston could lead to seizure of piston inside the barrel. Hence the design life time of the piston and barrel assembly is reduced.

[004] Patent application number EP-1363016 discloses a fuel pump for fuel injection system, that includes return passage provided with venturi and low pressure drain, such that leakage fuel flow in collection groove is allowed to flow to the drain through venturi. The pumping plunger and plunger bore are provided with a collection groove that is in communication with a return passage during pumping cycle. The return passage is provided with a venturi and a low pressure drain, such that leakage fuel flow in the groove is allowed to flow to the drain through the venturi.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[005] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[006] FIG. 1 illustrates a fuel injection pump in accordance with one of the embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS
[007] FIG. 1 illustrates a fuel injection pump in accordance with one of the embodiments. The fuel injection pump 100 comprises a piston 102 and housing 104. The housing 104 has an inlet 106 and accommodates the piston 102. The fuel injection pump 100 is characterized in that a circumferential groove 108 is provided at the inner diameter of the housing 104 at the region where the inlet 106 interfaces with the housing 104. The circumferential groove 108 is symmetrical with respect to the inner diameter of the housing 104. The fuel injection pump 100 is a port controlled pump.

[008] The circumferential groove 108 ensures uniform pressure distribution of leakage fuel between the piston 102 and the inner diameter of the housing 104. The leakage of fuel does not get concentrated towards the inlet 106 instead the fuel is distributed over the complete circumference of piston 102 and the inner diameter thereby minimizing wear on the piston 102. Since the circumferential groove 108 is interfacing with inlet 106, the fresh fuel is in contact with the piston 102 circumference, hence it is observed that there is better cooling of piston. Moreover, when there is a uniform pressure distribution, the possibility of piston tilt within the housing is minimized, thereby increasing the life of piston. Piston tilt is a phenomenon that is experienced, when the piston is under the influence of unequal fuel pressure. Under normal circumstances the piston reciprocates in an axis that is in line with the axis of the housing. However, when the fuel pressure acting on the piston is unequal, the piston gets tilted towards one of the side within the housing. Also, with the use of circumferential groove 108 the possibility of fuel in oil mix is avoided, as the fuel is sent to the inlet port without coming into contact with the lubricating oil that is displaced from the cam.

[009] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.