Claims:We Claim:

1. A fuel feed pump (100) in a fuel injection system, said fuel feed pump located downstream from a fuel tank (102) and upstream from a high pressure pump (104); characterized in that:
at least one outlet (106) of said fuel feed pump (100) in flow communication with a dosing injector (108), said dosing injector (108) located along an exhaust path external to said fuel injection system.

2. The feed pump of claim 1, wherein said fuel feed pump is one chosen from a group comprising an electric feed pump, a mechanical feed pump.

3. A fuel injection system, said fuel injection system comprising at least:
a fuel tank (200), a fuel feed pump (202), a metering unit (204), a high pressure pump (206) and a rail (208); characterized in that:
at least one outlet (106) of said fuel feed pump (202) in flow communication with a dosing injector (108), said dosing injector (108) located along an exhaust path external to said fuel injection system; and
said dosing injector (108) comprising at least a first flow path, said first flow path in flow communication with inlet of said high pressure pump (206).

4. The fuel injection system of claim 3, wherein said dosing injector (108) is in flow communication with said inlet of said high pressure pump (206) via a suction valve.

5. A method for controlling flow rate of fuel through a fuel feed pump in a fuel injection system, said fuel feed pump located downstream from a fuel tank and upstream from a high pressure pump, said method comprising:

Receiving (300) ( by a control unit, a request for dosing from said dosing injector;
Controlling (301) the output flow rate of fuel through said fuel feed pump; and
Delivering (302) fuel through said at least one outlet of said fuel feed pump to said dosing injector.

6. The method of claim 5, further comprising detecting a shut-off request from said dosing injector (108).

7. The method of claim 5 and 6, further comprising, upon detection of said shut-off request, delivering fuel from said dosing injector to inlet of said high pressure pump (206). , Description:Field of the invention
[0001] This invention relates to the field of fuel feed pump in a fuel injection system.

Background of the invention
[0002] A fuel feed pump is used to suck fuel from a fuel tank and deliver the same to a high pressure fuel injection pump. In a fuel injection system, a fuel feed pump is a part of low pressure circuit. In case of single cylinder diesel engines employing the above mentioned feed pump, there is a need for implementing Bharat Stage 6 (BS6) regulation. Single cylinder diesel engines are generally used in low cost markets and hence are devoid of costlier solutions like selective catalytic reduction (SCR) to combat emission. Hence there is a need to enable BS6 emission legislation for single cylinder diesel engines without SCR system, but with NSC (NOx Storage Catalyst) and hydro carbon (HC) injection.

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 feed pump in a fuel injection system;
[0005] FIG. 2 illustrates a fuel injection system with the feed pump and a dosing injector; and
[0006] FIG. 3 illustrates a method for controlling flow rate of fuel through a fuel feed pump.

Detailed description of the embodiments
[0007] FIG. 1 illustrates a fuel feed pump 100 in a fuel injection system. The fuel feed pump 100 is located downstream from a fuel tank 102 and upstream from a high pressure pump 104. At least one outlet 106 of the fuel feed pump is in flow communication with a dosing injector 108, the dosing injector 108 is located along an exhaust path external to the fuel injection system. The fuel feed pump is one chosen from a group comprising an electric feed pump, a mechanical feed pump.
[0008] The proposed fuel feed pump 100 performs two functions. Firstly receive fuel from the fuel tank 102, and secondly direct the fuel to the inlet of the high pressure pump 104, and in case a dosing is required in the exhaust path, a part of the fuel from the fuel feed pump 100 flows through the outlet 106 that is in flow communication with the dosing injector 108. Hence, the disclosed feed pump has two outlet. The first outlet 105 delivers fuel from the feed pump to the inlet of the high pressure pump, while another outlet 106 (second outlet) delivers fuel from the fuel feed pump 100 to the dosing injector 108. Fuel in the dosing injector 108 is then injected into the exhaust path for hydro-carbon injection (HCI) dosing. A control unit, controls the rate of flow of fuel through the feed pump.
[0009] FIG. 2 illustrates a fuel injection system with the fuel feed pump 202 and a dosing injector 108. The fuel injection system comprises at least a fuel tank 200, a fuel feed pump 202, a metering unit 204, a high pressure pump 206 and a rail 208. At least one outlet 106 of the fuel feed pump 202 is in flow communication with a dosing injector 108, the dosing injector 108 is located along an exhaust path external to the fuel injection system. The dosing injector 108 comprises at least a first flow path 210, the first flow path 210 is in flow communication with inlet of the high pressure pump 206. The dosing injector 108 is in flow communication with the inlet of the high pressure pump via a suction valve.
[0010] The working of the fuel injection system for circulating fuel from the fuel tank 200 to the rail 208, and in addition also circulating fuel to a dosing injector 108 will be explained. The fuel required in fuel injection system is obtained from a fuel tank 200. A fuel feed pump 202 is used to suck the fuel from the fuel tank 200. In others words the fuel feed pump 202 is used to build a small amount of sucking pressure for the fuel to start flowing in the lines of the fuel injection system. The fuel feed pump 202 is controlled by a control unit 212. Based upon the demand of fuel in the rail 208, the control unit 212 controls the amount of fuel that needs to be delivered to the high pressure pump 206 from the fuel feed pump 202. Apart from this, in case there is request for dosing function in the exhaust line, the control unit 212 will proportionately increase the amount of fuel reaching the fuel feed pump 202. This is required so that, the fuel feed pump 202 has enough quantity of fuel to perform this additional task of directing fuel to flow through the outlet 106 (second outlet) and into the dosing injector 108. The dosing injector 108 injects fuel into the exhaust line. The dosing injector 108 has a flow path connecting to the inlet of the high pressure pump 206. In case dosing is not required, fuel from the dosing injector 108 flows to the inlet of the high pressure pump 206 through the above mentioned flow path. The fuel that reaches inlet of the high pressure pump 206 may reach the fuel tank 200 through the overflow valve or enter into the pressurizing chamber of the high pressure pump 206. The fuel that is pressurized in the high pressure pump 206 is then sent to the rail 208 for injection into engine cylinder. Also, it should be noted that when there is no requirement for dosing of fuel in the exhaust path, the control unit 212 will regulate the flow of fuel in the fuel feed pump 202 only to the extent of demand from the high pressure pump 206. Hence, the flow of fuel through the fuel feed pump 202 is dynamically controlled with the help of the control unit 212.
[0011] FIG. 3 illustrates a method for controlling flow rate of fuel through a fuel feed pump. The fuel feed pump is located downstream from a fuel tank and upstream from a high pressure pump. The method comprises receiving 301 by a control unit, a request for dosing from the dosing injector, controlling 302 the output flow rate of fuel through the fuel feed pump and delivering 303 fuel through at least one outlet of the fuel feed pump 202 to the dosing injector 108. The method further comprises detecting a shut-off request from the dosing injector 108, and upon detection of the shut-off request, delivering fuel from the dosing injector 108 to inlet of the high pressure pump 206. In case a hydro-carbon (HCI) dosing is required, the fuel feed pump 202 gets the signal from the control unit to increase the delivered quantity into the system, so that besides the high pressure quantity into the suction valve of the high pressure pump, the HCI dosing quantity in pipe which is then injected into the exhaust by the HCI dosing module is delivered by the fuel feed pump. If the HCI dosing module does not inject, all the quantity goes to the suction valve for compression of the high pressure pump 206 and through the zero delivery throttle into the backflow of the system.
[0012] The proposed system layout has advantages in fuel consumption due to avoidance of exhaust temperature generation by engine injection parameters and / or rich mode operation especially in the case of single cylinder engines due to its air system have problems in stable combustion and therefore drive-ability. The fuel quantity for the HC injection can be simple and cost effective provided by the feed pump control system.
[0013] 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 pump 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.