Claims:We Claim:
1. A fuel injector 100, said fuel injector 100 comprising at least:
a nozzle body 102;
a needle 104 located within said nozzle body 102, the needle 104 comprises a tip 106, the tip 106 adapted to translate into and out of a sac hole 108, said sac hole 108 in flow communication with a spray hole 110 in said nozzle body 102; characterized in that:
profile of said sac hole 108 and profile of said tip 106 are complementary to each other.

2. The fuel injector 100 of claim 1, wherein said needle tip 106 comprises a circular profile with a convex periphery and a concave center

3. The fuel injector 100 of claim 2, wherein said sac hole 108 has a circular profile with a concave periphery and a convex center.
, Description:Field of the invention
[0001] This invention relates to fuel injectors.

Background of the invention
[0002] A fuel injector is used to deliver pressurized fuel into the combustion chamber. The fuel injector comprises a casing, one end of the casing receives fuel from the rail. The fuel that is received in the fuel injector flows via a flow path to reach the nozzle. The nozzle comprises a needle. The fuel occupies a space in between the needle and the nozzle body. This space is also called as a sac hole. It is observed that there is small quantity of fuel that remains in the sac hole after injection. This volume of fuel remaining is also called as dead volume or detrimental volume. This fuel remaining in this sac hole (dead volume) evaporates after combustion. The evaporated fuel produces a large part of the engine's hydrocarbon emissions. Hence, there is a need to alleviate this condition.

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 injector.

Detailed description of the embodiments
[0005] FIG. 1 illustrates a fuel injector 100. The fuel injector 100 comprises at least a nozzle body 102, and a needle 104 located within said nozzle body 102. The needle 104 comprises a tip 106, the tip 106 adapted to translate into and out of a sac hole 108. The sac hole 108 is in flow communication with a spray hole 110 in the nozzle body 102. The profile of the sac hole 108 and profile of the tip 106 are complementary to each other.
[0006] The needle tip 106 may have a circular profile with a convex periphery and a concave center, and the sac hole 108 may have a circular profile with a concave periphery and a convex center.
[0007] The convex periphery of the needle tip 106 matches with the concave periphery of the sac hole 108, and the concave center of the needle tip 106 matches with the convex center of the sac hole 108. This complementary geometric profile between the needle tip 106 and the sac hole 108 reduces the dead volume of fuel in the sac hole. In other words, all the fuel remaining in the sac hole 108 is flushed out through the spray hole 110 for injection into the engine cylinder.
[0008] The above mentioned profile is for the purpose of illustration only. The needle tip and the sac hole may have alternate profile like a concave periphery for the needle tip 106 with a convex center and convex periphery for the sac hole 108 with a concave center. In general any geometric profile which brings in complementary arrangement between the nozzle tip and the sac hole may be used interchangeably.
[0009] The construction of the fuel injector 100 will be explained in further detail. The fuel injector 100 is located upstream with respect to a combustion engine. The fuel injector 100 comprises a nozzle body 102, the needle 104 is located within the nozzle body 102. The function of the nozzle body 102 is to support the needle 104 and also to enable movement of the needle 104 within the nozzle body 102. The needle 104 rests on a nozzle seat 105 of the nozzle body 102. The nozzle body 102 comprises a sac hole 108. The sac hole 108 is located proximal to the spray hole 110 of the nozzle body 102. The profile of the sac hole 108 is such that the tip 106 of the nozzle and the sac hole 108 are complementary to each other. This reduces the volume between the sac hole 108 and the tip 106 of the needle 104.
[0010] The working of the fuel injector 100 will be explained in further detail. The fuel is received in the fuel injector 100 from a common rail or a fuel distributor block. The fuel than flows through fuel passage and then flows into the nozzle body 102. The nozzle body 102 has a needle 104. The needle tip 106 may have circular profile with a convex periphery and a concave center. This profile is complementary to the sac hole which has a circular profile with a concave periphery and a convex center. During injection the needle 104 lifts in a direction away from the sac hole 108, this causes the fuel to flow from the nozzle body 102 into the sac hole 108. The needle 104 then impinges on the fuel present in the sac hole 108, causing the fuel to flow into the spray hole 110 for injection into the engine cylinder/ combustion chamber. The profile of the needle tip 106 and the sac hole 108 is such that maximum amount of fuel in the sac hole is flushed into the spray hole. The volume of fuel that remains in the sac hole 108 after injection is negligible. Since the fuel that is reaching the sac hole 108 is getting injected into the engine cylinder, HC emissions are reduced.
[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. 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.
[0012] ‘Adapted’ or ‘arranged’, in the context of the instant disclosure, refers to the technical capability or the technical capacity of a component, in relation to which the term ‘adapted’ or ‘arranged’ is used, to carry out or execute a specified action or actions, upon the requirement of the specified action or actions to be carried out or executed. Moreover, the usage of the term ‘adapted’ or ‘arranged’ here, is in reference with the normal technical capability or technical capacity of the component, imparted by the design or the structure or the composition of the component, and not in reference with any special or extraneous capability or capacity, beyond the scope of the normal technical capability or technical capacity.