Field of the invention
[0001] This invention relates to a fuel injection system.
Background of the invention
[0002] Emission requirements in emerging economies are undergoing rapid
changes. In India Bharat Stage VI norms are proposed to be implemented across all categories of vehicles. Emerging economies in other regions too, like, China, south¬east Asia have also committed to cut emissions. Low cost commercial vehicles are in popular demand owing to their ease and practicability in carry heavy loads. Using a common rail in the low cost vehicles will add to the cost. The existing system currently makes use of a mechanical injector receiving fuel from a high pressure pump. Hence, there is a need to use the existing system arrangement in order to cut down on emissions.
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 injection system; and
[0005] FIG. 2 illustrates method for operating a mechanical injector in a fuel
injection system
Detailed description of the embodiments
[0006] FIG. 1 illustrates a fuel injection system 100. The fuel injection system
100 comprises a low pressure circuit 102, a high pressure circuit 104 comprising an electronically controlled high pressure pump 106 adapted to receive fuel from a fuel tank of the low pressure circuit. The electronically controlled high pressure pump 106 comprises a suction valve. The system is characterized in that a mechanical injector 108 is adapted to receive fuel from the electronically controlled high pressure pump 106. The fuel injection system 100 combines an electronically controlled high pressure pump 106 and a mechanical injector 108. The

electronically controlled high pressure pump 106 comprises a suction valve. The suction valve may be an electrical suction valve.
[0007] FIG. 2 illustrates a method of controlling flow of fuel in a fuel injection
system 100. The fuel injection system 100 comprises a low pressure circuit 102, a high pressure circuit 104 comprising an electronically controlled high pressure pump 106 adapted to receive fuel from a fuel tank of the low pressure circuit 102. The electronically controlled high pressure pump 106 comprises a suction valve. A mechanical injector 108 is adapted to receive fuel from the electronically controlled high pressure pump 106. The method comprises the step of receiving (200) by a control unit at least one operating condition of an engine Calculating (202) by control unit the quantity of fuel that needs to be supplied to the mechanical injector 108 based on said at least one operating condition, and actuating (204) the electronically controlled suction valve of the high pressure pump 106 to open and/ or close the suction valve in order to get the required quantity of fuel into the pump for pressurization so as to match the calculated injection quantity of fuel.
[0008] The suction valve is controlled 205 in order to deliver the required
quantity of fuel into the pump for pressurization so as to match said calculated injection quantity of fuel Furthermore, electronically controlled suction valve of high pressure pump 106 is actuated (206) to change the timing of opening and/ or closing of the suction valve with respect to a reference to a engine position, to achieve injection timing variation, so as to achieve target injection timing as calculated by the control unit. The engine position herein may refer to piston being at top dead center (TDC), bottom dead center (BDC), or between TDC and BDC. The operating condition is at least one of engine speed, engine load and engine temperature.
[0009] The operation of fuel injection system 100 is explained herewith. The
fuel is drawn into the high pressure pump 106 from the low pressure circuit via the suction valve. The low pressure circuit may comprise at least a fuel tank and an

electric feed pump. The suction valve is electronically controlled. Based upon the signals received from the electronic control unit (ECU) the suction valve can be opened and/ or closed to control the amount of fuel that is drawn during the suction stroke of the high pressure pump 106. The pressurized fuel is then delivered to a mechanical injector 108. Hence, by electronically controlling the suction valve of the high pressure pump 106, it is possible control injection quantity. Additionally, by varying the timing of closing/opening of the suction valve during suction stroke with respect to a reference like the engine TDC, injection timing can be varied. This provides injection timing flexibility. The suction valve can be either normally open or normally closed type. Hence by using the suction valve both timing and quantity control of fuel entering the injector can be controlled.
[00010] Hence, by combining a common rail pump with electronic suction valve
with a mechanical injector 108 the resulting system is an electronic fuel injection equipment with mechanical injector 108, with wider flexibility for injection quantity and/or timing as compared to a purely mechanical system. Additionally a cost effective fuel injection system 100 with a mechanical injector 108 for low cost vehicles can be provided.
[00011] It should be understood that embodiments explained in the description
above are only illustrative and do not limit the scope of this invention type high pressure pump and the injector. 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.

CLAIMS
We Claim:
1. A fuel injection system (100), comprising at least:
a low pressure circuit (102);
a high pressure circuit (104) comprising an electronically controlled high pressure pump (106) adapted to receive fuel from a fuel tank of said low pressure circuit (102); characterized in that:
a mechanical injector (108) adapted to receive fuel from said electronically controlled high pressure pump 106.
2. The fuel injection system (100) of claim 1, wherein said electronically
controlled high pressure pump 106 comprises a suction valve.
3. A method of controlling flow of fuel in a fuel injection system 100, said fuel
injection system 100 comprising at least:
a low pressure circuit (102);
a high pressure circuit (104) comprising an electronically controlled
high pressure pump (106) adapted to receive fuel from a fuel tank of
said low pressure circuit (102);and
a mechanical injector (108) adapted to receive fuel from said
electronically controlled high pressure pump 106; said method
comprising:
receiving (200) by a control unit at least one operating condition of an engine;

calculating (202) by said control unit the quantity of fuel that needs to be supplied to said mechanical injector 108 based on said at least one operating condition; and
actuating (204) an electronically controlled suction valve of high pressure pump 106 to deliver the calculated quantity of fuel to the mechanical injector 108.
4. The method of claim 3, wherein said operating condition is at least one of
engine speed, engine load and engine temperature.
5. The method of claim 3, further comprising controlling 205 said suction
valve in order to deliver the required quantity of fuel into the pump for
pressurization so as to match said calculated injection quantity of fuel.
6. The method of claim 5, further comprising actuating (206) said
electronically controlled suction valve of high pressure with respect a
reference an engine position.