Claims:We Claim:

1. A common-rail fuel injection system (100) for an engine, comprising:
a fuel pump (102) adapted to pressurize drawn fuel and discharge the fuel from common rail (104) through a plurality of the injectors (106);
a fuel filter (108) disposed in a fuel return line (105) and adapted to remove foreign matters contained in the fuel discharged from the fuel pump (102);
a fuel tank (110) connected to the fuel pump (102), by way of the filter (108) and adapted to accumulate the fuel; and
characterized that a connecting block (112) disposed at the fuel return line (105) and connected to the fuel filter (108) and the fuel tank (110), adapted for recirculating the fuel discharged by the fuel pump (102) into the fuel filter (108), wherein the connecting block (112) comprises;
a first non-return valve (114) and a second non-return valve (116), adapted to divert the flow of the return fuel, at predefined set of pressures values (P1 or P2), based on requirements of the common-rail fuel injection system.

2. The common-rail fuel injection system (100) as claimed in claim 1, wherein the first non-return valve (114) and second non-return valve (116), adapted to divert the flow of the return fuel in one direction either in the fuel tank (110) or fuel filter (108) based on the fuel requirement of the system (100).

3. The common-rail fuel injection system (100) as claimed in claim 1, wherein the first non-return valve (114) diverts the flow of a required quantity of return fuel at pressure (P1) from the fuel pump (102) into the fuel filter (108).

4. The common-rail fuel injection system (100) as claimed in claim 1, wherein the second non-return valve (116) diverts the flow of a required quantity of return fuel at pressure (P2) from the fuel pump (102) into the fuel tank (110).
, 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] Present invention relates to a fuel supply apparatus with modified pressure circuit design for effective utilization of return fuel in a common rail system.

Background of the invention
[0002] In the existing common rail fuel injection system, the fuel is supplied to high pressure pump by filtering inlet fuel with fuel filter. Further, fuel will be pressurized by high pressure pump and delivered to common rail. The common rail system will maintain the high pressure based on the driver demand and fuel will be injected in combustion chamber by means of an actuating injector. Fuel tank acts as a reservoir of fuel from where the fuel is sucked into the pump. This system has a filter outside the tank to filter the fuel before it flows to the pump so that the filtered fuel flows into the system in order to increase the efficiency.

[0003] In the conventional common rail fuel injection system, return fuel is available at each hydraulic component of the system. The return fuel is the fuel that is not consumed in the engine and is recirculated to the fuel tank. Above mentioned return fuel from the system will be send back to fuel tank. However, the drawback of such a system is the lack of fuel balancing at the fuel filter inlet during high fuel requirement during running of the vehicle/engine. Moreover, there will be issues related to starvation of the fuel during starting of the vehicle due to the empty portion of the fuel filter.

[0004] The prior art, EP1319821A2 discloses a common rail type fuel injection system has a pressure reducing valve (6). The pressure reducing valve (6) is opened in order to increase quantity of return fuel recirculated from a common rail (1) to an inlet of a fuel filter (9) when the fuel is in low temperature in which wax easily precipitates out of the fuel, and when an engine is starting or idling, or when high fuel pressure is not required. Thus, the temperature of the fuel flowing into the fuel filter (9) and the temperature of the filter (9) are increased quickly. As a result, precipitation of wax out of the fuel flowing into the fuel filter (9) is inhibited and the clogging of the fuel filter (9) by the precipitation of the wax is prevented.

Brief description of the accompanying drawing
[0005] Different modes of the invention is disclosed in detail in the description and illustrated in the accompanying drawings:

[0006] Figure 1 illustrates a common-rail fuel injection system for an engine with modified pressure circuit design, in accordance with embodiments of the invention.

Detailed description of the embodiments
[0007] Fig. 1 illustrates a common-rail fuel injection system 100 for an engine with a modified design. The common-rail fuel injection system 100 comprises a fuel pump 102, a common rail 104 along with a plurality of injectors 106, a fuel filter 108, a fuel tank 110 and a connecting block 112. Each component is described in further detail below.

[0008] The fuel pump 102 is adapted to pressurize drawn fuel and discharge the fuel from common rail 104 through a plurality of the injectors 106. In operation, the fuel flows from the fuel tank 110 to the fuel pump 102 after being filtered from the fuel filter 108. In the pump 102, the fuel is pressurized and this pressurized fuel flows to common rail 104 and from common rail 104 to the plurality of injectors 106. In one embodiment, the fuel pump 102 feeds the compressed fuel into a high-pressure line and the common rail 104 (high-pressure reservoir) connected to it. A further high-pressure line leads from the common rail 104 to the plurality of injectors 106. A metering unit which is a part of the fuel injection system 100, regulates the amount of fuel that is delivered to the common rail 104. The plurality of injectors 106 injects the pressurized fuel into the engine based on the requirement. The fuel tank 110 connected to the fuel pump 102, by way of the filter 108 and adapted to accumulate the fuel. The fuel pump 102 draws fuel from the fuel tank 110, supplies the fuel at a given pressure but at excess volume to the common rail 104 and returns unused fuel to tank 110 through a fuel return line 105. The backflow of fuel from the fuel pump 102 flows through the fuel return line 105 to the inlet 105a of the filter 108.

[0009] The fuel filter 108 is disposed in fuel return line and adapted to remove foreign matters contained in the fuel discharged from the fuel pump 102. The fuel filter 108 removes foreign matters such as dust, and water included in the fuel supplied to the engine in order to prevent mechanical friction and rusting in sliding portions of the pump 102 and the like.

[0010] With specific reference to this disclosure the focus can be laid on the low pressure circuit of the fuel injection system. The low pressure circuit with reference to this disclosure is defined as the flow paths of the fuel injection system that carry low pressure fuel. Typically, the low pressure fuel flows in a downstream path from the fuel tank 110 to the fuel filter 108 and then to the fuel pump 102. The low pressure fuel flow in the return line 105a, wherein the fuel flows from the fuel pump 102 back to the tank 110.

[0011] The connecting block 112 is disposed at the fuel return line 105 and connected to the filter 108 and the fuel tank 110. The connecting block 112 comprises a first non-return valve 114 and a second non-return valve 116, adapted to divert the flow of the return fuel in only one direction, at predefined set of pressures values (P1 or P2), based on requirements of common-rail fuel injection system. The first non-return valve 114 and second non-return valve 116 adapted to open and closed at predefined set of pressures values (P1 or P2). In one example, the opening pressure of the second non-return valve 116 is greater than opening pressure of the first non-return valve 114. In one embodiment, the connecting block 112 may be a T connector or T joint block comprising two non-return valves (114 and 116) which will open at different set of pressures (P1 or P2) based on the requirement.

[0012] The first non-return valve 114 and second non-return valve 116, adapted to divert the flow of the return fuel in one direction either in the fuel tank 110 or fuel filter 108 based on the fuel requirement of the system 100. The return fuel from the fuel return line 105 flows to the fuel filter 108 through the connecting block 112. The supply of the return fuel flows from the common rail system 100 to the fuel filter 108. Once the fuel filter 108 is filled, a backpressure is created on non-return valve 114. This backpressure from the filled fuel filter 108 will cause the non-return valve 114 to be closed at pressure value P1. In this case, there will be no flow of the return fuel to the fuel filter 108. This will increase the pressure at the connecting block 112 which in-turn makes non-return valve 116 to open at pressure value P2 and excess return fuel will be send to the fuel tank.

[0013] In another embodiment, as the pressure and flow of the return fuel will vary, it may in certain cases be necessary to switch the return fuel from the normal situation of being supplied to the fuel filter 108 to the alternative of being supplied to the fuel tank 110.

[0014] In one embodiment, by using this type of fuel injection system 100, the complete usage of filter 108 is ensured. The common issue of starving of fuel while starting the vehicle due to the empty portion of the fuel filter 108 is avoided by using this kind of the system 100. This in turn increases the system efficiency. This type of fuel injection system 100 ensures that the fuel is always present in the fuel filter. The time consumption is reduces as during the start of the fuel injection system, no time is wasted for the first filing.

[0015] 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.