CLIAMS:We Claim:
1. A fuel delivery assembly (200) for a common rail fuel injection system, said fuel delivery assembly (200) located in low pressure circuit of said common rail fuel injection system , said fuel delivery assembly 200 comprising at least:
a filter (202) in fluid communication with a fuel tank;
an electrical gear pump (204); and
a pump control unit (206) for said electrical gear pump (204);
said electrical gear pump (204) adapted to be controlled by said pump control unit (206) for metering flow of fuel through said electrical gear pump (204) in dependence of the amount of fuel to be delivered to the inlet of a high pressure pump (104) of said common rail fuel injection system.

2. The fuel delivery assembly 200 of claim 1, wherein said pump control unit 206 communicates with an electronic control unit (ECU) of said common rail system.

3. The fuel delivery assembly 200 of claim 1, wherein said electrical gear pump, said filter 202 and said pump control unit 206 are integrated to form the fuel delivery assembly 200.

4. The fuel delivery assembly 200 of claim 1, wherein said electrical gear pump and pump control unit 206 are integrated and mounted onto said filter 202 to form the fuel delivery assembly 200.

5. A filter (202) for a common rail fuel injection system,
said filter (202) located downstream of a fuel tank, said filter 202 characterized in having
an interface adapted to receive an electrical gear pump and a pump control unit 206 in a manner such that said electrical gear pump and said pump control unit 206 are mounted on said filter 202.
6. The filter (202) as claimed in claim 5, wherein said electrical gear pump and said pump control unit 206 are integrated and mounted on said filter 202.

7. A method for controlling flow of fuel through a fuel delivery assembly 200 of a common rail fuel injection system, said fuel delivery assembly 200 comprising
a filter 202, an electrical gear pump (204) and a pump control unit (206), said method comprising the following step:
receiving (400) in an electronic control unit rail pressure information from a rail pressure sensor;
communicating (401) said rail pressure information to a pump control unit 206;
actuating (402) by a pump control unit 206 said electrical gear pump to meter flow of fuel through said electrical gear pump in dependence of said rail pressure information; and
controlling (403) the flow of fuel to said inlet of a high pressure pump 104 from said electrical gear pump.
,TagSPECI:Field of the invention
[0001] This invention relates to the field of fuel delivery in a common rail fuel injection system.
Background of the invention
[0002] In a common rail fuel injection system, fuel is delivered to a high pressure pump with the help of a mechanical or electrical device in the low pressure circuit of a fuel injection system. The high pressure pump is generally controlled with a metering unit (MeUn). Rail pressure control via an electric feed pump (EFP), fitted in the fuel tank, is the latest development. This rail pressure control technology is called Feed Pump Control (FPC). Since feed pump control happens due to EFP, a metering unit is not required. A distinction is made between feed pump control for a common rail system with the help of an electric feed pump and an electrical gear pump. The subject of the present invention is the latter type of system, that is, feed pump control with the help of an electrical gear pump. In the current state of art, an electrical gear pump relies on a control unit to pump fuel to the inlet of high pressure pump. The volume of fuel being pumped into the inlet of the high pressure pump is still controlled by a metering unit that is located close to the inlet side of the high pressure pump. In order to simplify the low pressure circuit in the common rail fuel injection system, there is a need to transfer the functionality of inlet metering to an electrical gear pump.
[0003] Prior art patent application DE-102012223911 discloses an electrically operated gear pump arrangement for use as pre-feed pump for pre-compression of fuel for high-pressure pump of reservoir-common-rail-system of diesel engine, has gear pump, which has suction side for intake of fuel. The electrically operated gear pump arrangement has a gear pump, which has a suction side for intake of the fuel and a pressure side for delivery of fuel. The pressure side of the gear pump is arranged to supply a second fuel flow with a second pressure to an additional load by a second 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 common rail fuel injection system of the type employing a fuel delivery assembly;
[0006] FIG. 2 illustrates a fuel delivery assembly;
[0007] FIG. 3 illustrates a filter used in the common rail fuel injection system; and
[0008] FIG. 4 illustrates a method for controlling flow of fuel through a fuel delivery assembly of a common rail fuel injection system.

Detailed description of the embodiments
[0009] FIG. 1 illustrates a common rail fuel injection system of the type employing a fuel delivery assembly 200. The common rail fuel injection system comprises a fuel tank 100. Fuel from the fuel tank 100 passes through the proposed fuel delivery assembly 200 and reaches the inlet of the high pressure pump 104 where the fuel is pressurized. The fuel delivery assembly 200 performs the following main functions. a) Efficient transport of fuel from the fuel tank to the high pressure pump 104, b) Filtration of fuel, and c) The fuel delivery assembly 200 in communication with the electronic control unit ensures that only the quantity of fuel as required to be pressurized reaches the high pressure pump 104, that is, the fuel delivery assembly 200 helps in achieving inlet metering control for the high pressure pump 104. Pressurized fuel from the high pressure pump 104 is sent to the common rail 106 for injection through the injector. The components of the fuel injection system are controlled through an Electronic control unit (ECU). A series of supply lines connect each of the components of the fuel injection system for efficient transport of fuel. The fuel injection system comprises a low pressure circuit and the high pressure circuit. The part of the circuit downstream from the high pressure pump 104 is the high pressure circuit, and the part of the circuit upstream of the high pressure pump 104 is the low pressure circuit. The low pressure circuit comprising the proposed fuel delivery assembly 200 is now described in further detail.
[00010] FIG. 2 illustrates a fuel delivery assembly 200. The fuel delivery assembly 200 is located in the low pressure circuit of the common rail fuel injection system and comprises at least a filter 202 in fluid communication with a fuel tank 100, an electrical gear pump 204, and a pump control unit 206 for the electrical gear pump 204. The electrical gear pump 204 is adapted to be controlled by the pump control unit 206 for metering flow of fuel through the electrical gear pump 204 in dependence of the amount of fuel to be delivered to the inlet of a high pressure pump 104 of the common rail fuel injection system. The pump control unit 206 communicates with an electronic control unit (ECU) of the common rail system. As explained previously, since the metering control to the inlet of the high pressure pump 104 is now achieved with the help of the fuel delivery assembly 200, the requirement for a separate metering unit is no longer required. In an embodiment the electrical gear pump 204, the filter 202 and the pump control unit 206 are integrated to form the fuel delivery assembly 200. In another embodiment the electrical gear pump 204 and pump control unit 206 are integrated and mounted onto the filter 202 to form the fuel delivery assembly 200. The electrical gear pump 204 may also be directly controlled by the electronic control unit (ECU). The control to the electrical gear pump 204 via the pump control unit 206 will happen when the ignition is under “ON” condition.
[00011] FIG. 3 illustrates a filter 202 used in the common rail fuel injection system. The filter 202 is located downstream of a fuel tank 100. The filter 202 is characterized in having an interface adapted to receive an electrical gear pump 204 and a pump control unit 206 in a manner such that the electrical gear pump 204 and the said pump control unit 206 are mounted on the filter 202. The interface is such that the electrical gear pump 204 and the pump control unit 206 can be easily attached with respect to one another. The electrical gear pump 204 and the pump control unit 206 are integrated and mounted on the filter 202. The electrical gear pump 204 and the pump control unit 206 may be mounted on the inlet side the filter 202. Alternately the electrical gear pump 204 and the pump control unit 206 may be mounted on the outlet side of the filter 202.
[00012] FIG. 4 illustrates a method for controlling flow of fuel through a fuel delivery assembly 200 of a common rail fuel injection system. The fuel delivery assembly 200 comprises a filter 202, an electrical gear pump 204 and a pump control unit 206. The rail pressure information from a rail pressure sensor is received 400 in an electronic control unit (ECU). The rail pressure information is communicated 401 to a pump control unit 206. The electrical gear pump 204 is actuated 402 by a pump control unit 206 to meter flow of fuel through the electric gear pump 204 in dependence of the rail pressure information. The flow of fuel to the inlet of the high pressure pump 104 from the electrical gear pump 204 is controlled 403 based upon the actuation of the electrical gear pump 204 by the pump control unit 206.
[00013] For the sake of better understanding, the working of the proposed common rail fuel injection system having a fuel delivery assembly 200 is now explained in further detail with respect to the above mentioned method. Initially, when the ignition is switched “ON”, the electrical gear pump 204 receives power and sucks fuel from the fuel tank 100, as a result the fuel reaches the fuel delivery assembly 200. In the fuel delivery assembly 200 the fuel is filtered and then the metered quantity of fuel flows to the inlet of the high pressure pump 104, where the fuel is pressurized and sent to the common rail for injection into the engine cylinder. The metering of fuel to the inlet of the high pressure pump 104 happens through the pump control unit 206. Once the speed and load on the engine increases, the fuel being injected from the common rail has to match the engine demand. The rail pressure sensor present on the common rail, stores the rail pressure information and the same is received by the ECU. The information from the ECU is then communicated to a pump control unit 206. Based upon the information received, the electrical gear pump 204 is actuated to meter the flow of fuel through the electrical gear pump 204 in dependence of the rail pressure information. The electrical gear pump 204 will be operational based upon the metering requirement of the high pressure pump 104. The facility to actuate and/ or de-actuate the electrical gear pump 204 will be available with the pump control unit 206. The above mentioned process of metering of fuel, monitoring the parameters of fuel in the common rail and actuating the electrical gear pump 204 happens throughout the working of the engine.
[00014] As can be seen from the above mentioned example, with the use of the proposed fuel delivery assembly we are able to achieve the following advantages a) The function of pumping of fuel, filtration of fuel, and metering of fuel to the inlet of the high pressure pump 104 is now achieved by using only the fuel delivery assembly. This leads to savings in space and cost in the low pressure circuit, since a metering unit is no longer required. The inlet metering with the help of fuel delivery assembly, helps in better fuel management at the common rail, thereby reducing emissions. The leakage of fuel in the low pressure circuit in the common rail system can also be avoided with the help of the proposed fuel delivery assembly.
[00015] 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 and capacity of the electrical gear pump used, different configurations of the high pressure pump and type of common rail system 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.