Claims:We Claim:

1. A fuel injector (100) comprising a housing (102); a bore in said housing (102); a nozzle 104 reciprocally moving in said bore, an inlet 106 in said housing to receive fuel; a solenoid 110 located in said housing 102; solenoid 110 comprising magnetic elements; said solenoid 110 adapted to move nozzle 104 in a first direction to inject fuel in an engine; a return path 108 in said housing for returning excess fuel; said return path 108 characterized in that the fuel flowing through said return path 108 does not come in contact with the magnetic elements of said solenoid (110).
2. A fuel injector (100) according to claim 1 wherein said return path (108) is at an angle with respect to longitudinal axis of said injector (100).
3. A fuel injector (100) according to claim 1 wherein said injector (100) comprises an additional return path (109).
4. A fuel injector (100) according to claim 1 wherein said return path (108) and said additional return path (109) split the fuel returning to fuel reservoir.
5. A fuel injector (100) according to claim 1 wherein said return path (108) and said additional return path (109) balance the pressure of the fuel in the injector (100) by splitting the fuel returning to the fuel reservoir.
, 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
[001] This invention relates to the field of fuel injection systems in general. The invention relates to fuel injector in specific.

Background of the invention

[002] Common rail fuel injection systems use electronically controlled fuel injectors. The electronically controlled injectors use typically a solenoid to control the opening and closing of the injectors for fuel injection. The injectors receive the fuel which is under high pressure and when the injector opens, the fuel under high pressure is injected into the engine. The excess fuel keeps returning to the fuel reservoir through a return path. In prior-arts typically the fuel which is returning, comes in contact with the magnetic elements of the solenoid. The returning fuel is at high temperature. This leads to heating up of the magnetic elements thereby affecting the performance of the solenoid.

[003] Prior art

Brief description of the accompanying drawing

[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[005] FIG. 1 illustrates a schematic of a fuel injector according to one embodiment of the invention
[006] FIG. 2 illustrates a schematic of a fuel injector according to second embodiment of the invention

Detailed description of the embodiments

[007] Shown in fig. 1 is a fuel injector 100 according to one embodiment of the invention. The injector 100 comprises a housing 102, a bore in the housing in which a valve piston & nozzle arrangement 104 moves reciprocally, an inlet 106 to receive fuel for injection into an engine which is not shown, a return path 108 through which excess fuel returns to a fuel reservoir which is not shown. A solenoid 110 controls the movement of the valve piston & nozzle arrangement 104. The solenoid typically comprises a magnetic element, an armature etc. The solenoid 110 is controlled by an ECU which is not shown. When the solenoid 110 is energized by the ECU, the solenoid 110 opens the Valve ball giving a pressure differential for movement of the valve piston & nozzle arrangement 104 thereby opening the spray holes. The fuel is injected into the engine cylinder through the spray holes. When the solenoid is de-energized, the spring 112 closes the Valve ball & brings the valve piston & nozzle arrangement 104 back to its original position where the spray holes at the tip of the nozzle, are closed.

[008] Only the required parts of the injector which are relevant for explaining the invention are described in this document. All the other parts which are commonly known are not described in this document.

[009] The injector 100 receives fuel at high pressure through its inlet 106. The high pressured fuel enters into the space around the nozzle 104 creating high pressure around the nozzle 104. When the solenoid is in de-energized state, the nozzle 104 is in its original position closing the spray holes. When the spray holes are closed, the fuel keeps returning to the fuel reservoir through the return path 108. Based on the timing of the injection, the ECU energizes the solenoid 110. When the solenoid 110 is energized, the solenoid 110 attracts the armature. As nozzle 104 is coupled to the armature through a valve, the nozzle 104 moves towards the solenoid. The movement of the nozzle 104 opens the spray holes and the fuel which is under high pressure, is injected into the engine cylinder. The combustion happens in the cylinder generating power. Once the injection cycle is completed, the ECU de-energizes the solenoid 110. The spring 112 pulls the armature back to its original position. When the armature returns to its original position, the nozzle 104 also returns to its original position where the spray holes are closed and the injection stops.

[010] In prior arts the fuel returning to the reservoir comes in contact with the magnetic elements which form the part of the solenoid 104. As the fuel returning through the return path is at higher temperature. In the prior arts, this fuel comes in contact with the magnetic elements of the solenoid, the magnetic elements get heated up. This affects the functionality of the solenoid and may influence its life.

[011] Different embodiments of the invention overcome this problem and also provide additional benefits.

[012] In one embodiment, the invention proposes a return path 108 where the fuel which is returning to fuel reservoir, does not come in contact with magnetic elements of the solenoid 110 thereby avoiding heating up of the magnetic elements of the solenoid 110. This ensures the functioning of the solenoid 104 correctly without any deviations. Here the return path 108 is taken out from the side of the injector 100. The return path 108 is at an angle to the longitudinal axis of the injector. The return path 108 is constructed in such a way that the fuel returning through it, is diverted away from the magnetic elements of the solenoid 110.

[013] In another embodiment of the invention, there is an additional return line 109 like it existed in prior-arts. The fuel flowing through return line 109 comes in contact with the magnetic elements of the solenoid 110. But the amount of fuel flowing through the return line 109 is considerably less because the return lime 108 and additional return line 109 split the fuel returning to the fuel reservoir. This results in better balance of the fuel pressure within the injector 100. This will also result in reduction of contaminated particles getting accumulated around the valve seat in the injector and armature area of the solenoid 110. A non-return valve is provided in the return path 108 outside of the injector 100.

[014] In the first embodiment shown in fig 1, there is only one return path 108 and the fuel coming in contact with the magnetic element is completely avoided. This eliminates the possibility of magnetic elements getting heated up thereby affecting the functioning of the solenoid.

[015] In the second embodiment there is additional return path 109 to split the fuel returning to the fuel reservoir, providing better balancing of fuel pressure.

[016] The invention reduces the temperature profile of the magnetic elements of the solenoid 110 thereby ensuring their correct operations. The invention provides better fuel quantity balancing with an effective path for return of fuel and at the same time lowering the temperature. The valve piston in the injector and nozzle can be controlled optimally through controlled backpressure. The invention reduces the particle content flow around the valve seat and armature area near the solenoid. The return path 108 and additional return path 109 balance the pressure of the fuel in the injector 100 by splitting the fuel returning to the fuel reservoir.