Claims:We Claim:
1. A fuel injector (100), said fuel injector comprising at least a body (102), a valve piston (104) adapted to reciprocate within said body (102), and a first flow path (106) located in said body (102), characterized in that:

a second flow path (108) connecting a fuel inlet line to said control chamber (107); and

a circumferential groove (110) formed on said valve piston (104), said circumferential groove (110) adapted to receive fuel from said second flow path (108) during reciprocation of said valve piston (104).

2. The fuel injector (100) of claim 1, wherein a first end of said valve piston 104 comprises an axial bore (112), said axial bore (112) enables flow communication between said second flow path (108) and said control chamber (107).
, Description:Field of the invention
[0001] This invention relates to the field of a fuel injector.

Background of the invention
[0002] A fuel injector is used to inject pressurized fuel into the engine cylinder. The fuel may be delivered to the fuel injector for fuel injection, from a common rail or a fuel distributor block. A valve piston is located within the fuel injector. The reciprocation of the valve piston happens due to energization and de-energization of solenoid. It is observed that when the solenoid is energized, the rate of piston lift vis-à-vis nozzle opening for injection into the engine cylinder is asynchronous. This is because of the difference in pressure of fuel close to the nozzle outlet and the fuel located proximal to the solenoid in the control chamber.
[0003] Prior art patent application US5566660 discloses a multipiece fuel pump plunger assembly for controlling the fuel injection rate and delivery during the initial injection portion of a fuel injection cycle for an internal combustion engine. The injector includes a two piece plunger assembly including a plunger and a plunger sleeve. The plunger having a small predetermined diameter and being slidable, is positioned within a plunger sleeve having a diameter greater than the diameter of the plunger. The multi-diameter plunger with two inlet ports is advantageous because it allows for shaping of the fuel injected into the combustion process which is reducing the fuel Injection rate in the early portion of the injection phase. Reduction in injection rate initially results in lower oxides of nitrogen and particulate exhaust emission levels and low engine noise.

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 injector; and
[0006] FIG. 2 illustrates a fuel injector during injection of fuel.

Detailed description of the embodiments
[0007] FIG. 1 illustrates a fuel injector 100. The fuel injector 100 comprises at least a body 102, a valve piston 104 adapted to reciprocate within the body 102, and a first flow path 106 located in the body 102. The fuel injector 100 comprises a second flow path 108 connecting a fuel inlet line 105 to the control chamber 107, and a circumferential groove 110 formed on the piston, the circumferential groove 110 is adapted to receive fuel from the second flow path 108 during reciprocation of valve piston 104. The piston 104 comprises an axial bore 112.
[0008] The construction of the fuel injector 100 will be explained in further detail. The fuel injector 100 is a part of the fuel injection system, the location of fuel injector 100 is downstream to a common rail or a fuel distributor block. The fuel injector 100 is mounted on the engine cylinder. A fuel supply line connects the common rail (not shown) or the fuel distributor block (not shown) to the inlet of fuel injector 100. The inlet of the fuel injector 100 opens into a first flow path 106 and a second flow path 108. The first flow path 106 and the second flow path 108 opens into a control chamber 107. The control chamber 107 is a volume defined with respect to the position of valve piston 104 proximal to a solenoid of the fuel injector 100 and the inner wall of the injector body 102. A nozzle is located away from the control chamber 107. The nozzle may be attached to the valve piston 104. The nozzle defines a volume with respect to the body 102 of the fuel injector 100. A part of the high pressure fuel is stored in this volume. An outlet 111 located proximal to the nozzle opens into the engine cylinder.
[0009] The working of the fuel injector 100 will be explained in further detail. The high pressure fuel from the common rail or the fuel distributor block flows through the inlet into the first flow path 106 and the second flow path 108. The fuel from the second flow path 108 reaches the control chamber 107 through the axial bore 112 located at the first end of the valve piston 104. A portion of the fuel also reaches the volume defined by the nozzle.
[0010] High pressure fuel is stored in body 102 at the control chamber and the nozzle chamber 109. The diameter of the piston 104 being larger than diameter of the nozzle needle 103, the force experienced by the piston would be higher when compared to the nozzle needle 103. This higher force on piston keeps the outlet 111 of the fuel injector 100 closed. This blocks injection of fuel into the engine cylinder. During injection, the outlet 111 needs to be opened, and the same will be explained in FIG. 2.
[0011] FIG. 2 illustrates a fuel injector 100 during injection of fuel. For the fuel to be injected from the fuel injector 100, the valve piston 104 needs to lift as shown by arrow in FIG. 2. The fuel injector 100 comprises an actuator, which when energized attracts a valve plate 113. As the valve plate 113 moves towards the solenoid the pressure in the control chamber 107 is relieved. As the pressure gets relieved, the valve piston 104 moves in the direction as shown in FIG. 2, during the movement of the valve piston 104 it is observed that the second flow path 108 is blocked by the valve piston 104, this leads to a throttling effect of the fuel in the second flow path 108.
[0012] The throttling effects leads to change in rate of movement of the valve piston 104. This rate of movement of the valve piston 104 will be proportional to the rate of fuel being delivered through the outlet 111 of the fuel injector 100. Thereby, rate of injection would be lower during initial injection phase. This results in controlled rate of movement of the valve piston 104.
[0013] 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.