Claims:CLAIMS
We Claim:
1. A fuel injection system 100 comprising at least:
a fuel tank 102;
a high pressure pump 104 in flow communication with said fuel tank 102; and
an injector 106 in flow communication with said high pressure pump 104 and a flow path 108 from said injector 106 in flow communication with said fuel tank 102; characterized in that:
a pilot operated pressure relief valve 110 located downstream to said injector 106 and upstream to said fuel tank 102 and along said flow path 108, said pilot operated pressure relief valve 110 adapted to open in dependence on the backflow pressure of fuel from said injector 106.


2. The fuel injection system 100 of claim 1, wherein said pilot operated pressure relief valve 110 is electronically controlled.
, 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 system.

Background of the invention
[0002]An injector is used in a fuel injection system to inject fuel that is received from the rail/ high pressure pump into the engine for combustion. A certain amount of pressure needs to be maintained in the injector return flow line to ensure consistent injection functionality & reliability over the designed lifetime. This pressure is maintained to the desired value in the injector return flow line with use of a check valves or combination of jet pump (an integral part of pre-supply pump located in the tank) with check valve. A check valve is located in the flow path relieves any excess return flow pressure in the injector by allowing fuel to flow to the fuel tank. The return flow back pressure is specific for every application and depends on number of the number of injectors and injector pressure range. Hence, the same check valve cannot be used for all applications. Depending on the specific return flow pressure of the injector, multiple check valves need to be used. Hence there is need to use valves that can maintain the return flow back pressure irrespective of the type of injector and the injector pressure range.

[0003]Prior art patent application US7549410 a fuel injection system for an internal combustion system includes an Engine Management System (EMS), a fuel feed pump, a return line, a high-pressure pump, supplying fuel under pressure to a common rail, a hydraulically operated valve forming an outlet chamber connected to the injector and fuel tank, the valve being designed such that it has pilot valve and poppet valve built in which are normally closed. This pilot valve prevents the flow out until the specific return flow pressure is built. This pilot line is capable of handling small volume of return flows which is applicable for smaller engines (1 or 2 injectors). When the return flow from the injectors (2 or above injectors are used) is high poppet valve which is normally closed will open to maintain the specific return flow pressure by leaking the excess flow in to the fuel tank. when the A nozzle with a resilient member that biases the nozzle towards closing is connected to the outlet of the hydraulically operated valve in such a way that pressure at the outlet of the hydraulically operated valve tends to overcome the force of the resilient member and open the nozzle. Auto operated inbuilt valve is connected between the outlet of the hydraulically operated valve and the return line.

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 injection system.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a fuel injection system 100. The fuel injection system 100 comprises at least a fuel tank 102, a high pressure pump 104 in flow communication with the fuel tank 102, an injector 106 in flow communication with the high pressure pump 104 and a flow path 108 from the injector 106 in flow communication with the fuel tank 102. A pilot operated pressure relief valve 110 located downstream to the injector 106 and upstream to the fuel tank 102 and along the flow path 108. The pilot operated pressure relief valve 110 is adapted to open in dependence on the backflow pressure of fuel from the injector 106. In an embodiment the pilot operated pressure relief valve 110 may be electronically controlled.

[0007]The working of the fuel injection system 100 will be explained in further detail. Fuel from the fuel tank 102 flows through a pipe to the high pressure pump 104. The fuel is pressurized in the high pressure pump 104 and the pressurized fuel is delivered to the injector 106. The injector 106 injects fuel into the engine cylinder. The injector 106 is designed in a manner so as to deliver fuel at a particular pressure into the injector 106. In order to maintain stability of the injector 106 and to prevent excess pressure build up, a part of the fuel present in the injector 106 needs to be relieved. This is done with of the pilot operated pressure relief valve 110. The pilot operated pressure relief valve 110 is located downstream to the injector 106 and upstream to the fuel tank 102 and along the flow path 108 connecting the injector 106 and the fuel tank 102. The pilot operated pressure relief valve 110 is designed in a way such that it allows fuel to flow through either a first flow passage or a second flow passage depending upon the pressure of fuel to be relieved. Based on the operating pressure of the injector 106, the pilot operated pressure relief valve 110 will open at a minimum valve 110 of the fuel pressure or maximum value of the fuel pressure. The fuel from the pilot operated pressure relief valve 110 will flow through the flow path 108 to reach the fuel tank 102. Hence, by using the pilot operated pressure relief valve 110 it is possible to avoid multiple check valve for multiple injectors 106 and different operating pressures.

[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 injector 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.