Claims:We Claim

1. A low pressure circuit (10) for a fuel injection system, said low pressure circuit (10) comprising:
a first low pressure fuel pump (12);
a fuel filter (14) positioned downstream from the first low pressure fuel pump (12); characterized in that
a hydrocarbon fuel injector (16) positioned downstream from said fuel filter (14), said hydrocarbon fuel injector (16) adapted to inject pressurized fuel to an exhaust gas flow path (18);
a first overflow valve (20) positioned downstream from said fuel filter (14), said first overflow valve (20) in flow communication with a second low pressure feed pump (22) and adapted to supply pressurized fuel to said second low pressure feed pump (22); and
a second overflow valve (24) positioned downstream from said first overflow valve (20), said second overflow valve (24) in flow communication with a fuel tank (26) and adapted to supply excess pressurized fuel that is delivered to said second overflow valve 24 via said first overflow valve (20) to said fuel tank (26).

2. A fuel filter assembly for a fuel injection system, said fuel filter assembly comprising:
a fuel filter (14); characterized in that
a hydrocarbon fuel injector (16) positioned downstream from said fuel filter (14), said hydrocarbon fuel injector (16) adapted to inject pressurized fuel to an exhaust gas flow path (18);
a first overflow valve (20) positioned downstream from said fuel filter (14), said first overflow valve (20) in flow communication with a low pressure feed pump (22) and adapted to supply pressurized fuel to said low pressure feed pump (22); and
a second overflow valve (24) positioned downstream from said first overflow valve (20), said second overflow valve (24) in flow communication with a fuel tank (26) and adapted to supply excess pressurized fuel that is delivered to said second overflow valve 24 via said first overflow valve (20) to said fuel tank (26).

3. An overflow valve assembly for a fuel injection system, said overflow valve assembly comprising:
a first overflow valve (20) positioned downstream from a fuel filter (14), said first overflow valve (20) in flow communication with a low pressure feed pump (22) and adapted to supply pressurized fuel to said low pressure feed pump (22); and
4. a second overflow valve (24) positioned downstream from said first overflow valve (20), said second overflow valve (24) in flow communication with a fuel tank (26) and adapted to supply excess pressurized fuel that is delivered to said second overflow valve 24 via said first overflow valve (20) to said fuel tank (26).
, Description:Field of the invention
[0001] This invention relates to a plurality of overflow valves in a low pressure circuit of a fuel injection system.

Background of the invention
[0002] DE 102011084675 A1 describes a system that has a feed pump for supplying fuel from a fuel tank over a set of fuel lines of a high pressure pump. A set of fuel filters is arranged between the feed pump and the high pressure pump. An overflow valve is arranged in a downstream of the feed pump and upstream of the fuel filter to control pressure in the system. A balancing volume is formed between the feed pump and the fuel filter and limited by a set of spring loaded input pistons. The pistons are switched parallel to the change of the balancing volume. The feed pump is designed as a gear pump.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic representation of a fuel injection system for an internal combustion engine.

Detailed description of the embodiments

[0004] Figure 1 illustrates a schematic representation of a fuel injection system for an internal combustion engine. In the fuel injection system, a low pressure circuit 10 for the fuel injection system is described. The low pressure circuit 10 comprises a first low pressure fuel pump 12 and a fuel filter 14 positioned downstream from the first low pressure fuel pump 12. A hydrocarbon fuel injector 16 is positioned downstream from the fuel filter 14, the hydrocarbon fuel injector 16 adapted to inject pressurized fuel to an exhaust gas flow path 18. A first overflow valve 20 is positioned downstream from the fuel filter 14, the first overflow valve 20 in flow communication with a second low pressure feed pump 22 and adapted to supply pressurized fuel to the second low pressure feed pump 22. A second overflow valve 24 is positioned downstream from the first overflow valve 20, the second overflow valve 24 in flow communication with a fuel tank 26 and adapted to supply excess pressurized fuel that is delivered to the second overflow valve 24 via the first overflow valve 20 to the fuel tank 26.

[0005] In addition, a fuel filter assembly for a fuel injection system is described. The fuel filter assembly comprises a fuel filter 14. A hydrocarbon fuel injector 16 is positioned downstream from the fuel filter 14, the hydrocarbon fuel injector 16 adapted to inject pressurized fuel to an exhaust gas flow path 18. A first overflow valve 20 is positioned downstream from the fuel filter 14, the first overflow valve 20 in flow communication with a low pressure feed pump 22 and adapted to supply pressurized fuel to the low pressure feed pump 22. A second overflow valve 24 is positioned downstream from the first overflow valve 20, the second overflow valve 24 in flow communication with a fuel tank 26 and adapted to supply excess pressurized fuel that is delivered to the second overflow valve 24 via the first overflow valve 20 to the fuel tank 26.

[0006] Moreover, an overflow valve assembly for a fuel injection system is described. The overflow valve assembly comprises a first overflow valve 20 positioned downstream from a fuel filter 14, the first overflow valve 20 in flow communication with a low pressure feed pump 22 and adapted to supply pressurized fuel to the low pressure feed pump 22. A second overflow valve 24 is positioned downstream from the first overflow valve 20, the second overflow valve 24 in flow communication with a fuel tank 26 and adapted to supply excess pressurized fuel that is delivered to the second overflow valve 24 via the first overflow valve 20 to the fuel tank 26.

[0007] Figure 1 illustrates a schematic representation of a fuel injection system for an internal combustion engine. The fuel injection system comprises a first feed pump 12 that draws fuel from a fuel tank 26 and delivers pressurized fuel to a fuel filter 14. The pressurized fuel from the fuel filter 14 is delivered to a hydrocarbon fuel injector 16 from where it is delivered to an exhaust gas flow path 18. A first overflow valve 20 is positioned downstream from the fuel filter 14. The first overflow valve 20 is typically a spring loaded ball valve that opens against the pressure of the fuel that acts on the spring loaded ball valve. The remaining pressurized fuel from the fuel filter 14 that bypasses the hydrocarbon fuel injector 16 is channeled to the first overflow valve 20. When the pressure of the fuel exceeds the spring constant of the first overflow valve 20, the pressurized fuel is channeled through the spring loaded ball valve of the first overflow valve 20 and delivered to a first fuel supply path 25.

[0008] A second fuel supply path 27 is in flow communication with the first fuel supply path 25. A second feed pump 22 is in flow communication with the second fuel supply path 27 and receives fuel that is supplied from the spring loaded ball valve of the first overflow valve 20. From the second feed pump 22, the fuel is pressurized further and delivered to a high pressure fuel pump. A second overflow valve 24 is in flow communication with the first fuel supply path 25 and receives pressurized fuel that is delivered from the first overflow valve 20. A downstream end of the second overflow valve 24 is in flow communication with a fuel tank 26 of the vehicle. When the pressure of the fuel exceeds the spring constant of the second overflow valve 24, the pressurized fuel is channeled through the spring loaded ball valve of the second overflow valve 24 and delivered to the fuel tank 26 of the vehicle.

[0009] A working of the fuel injection system for the internal combustion engine is described as an example. Pressurized fuel is supplied from the low pressure fuel pump 12 to the fuel filter 14 at a first value of pressure. This pressurized fuel at the first value of pressure is delivered to the hydrocarbon fuel injector 16 from where it is injected into the exhaust gas flow path 18. The pressurized fuel at the first value of pressure is supplied to the first overflow valve 20. As the pressure of the fuel that is supplied to the first overflow valve 20 exceeds the spring constant of the first overflow valve 20, the pressurized fuel is channeled through the spring loaded ball valve of the first overflow valve 20 and delivered to the first fuel supply path 25. When the pressure of the fuel that is supplied to the second overflow valve 24 exceeds the spring constant of the second overflow valve 24, the pressurized fuel is channeled through the spring loaded ball valve of the second overflow valve 24 and delivered to the fuel tank 26. Therefore, from the first fuel supply path 25, the excess pressurized fuel is supplied back to the fuel tank 26 via the second overflow valve 24. The pressurized fuel that is contained within the first fuel supply path 25 is now channeled to the second feed pump 22 which further pressurizes and delivers the fuel to the high pressure fuel pump. Therefore, the second overflow valve 24 relieves the pressure of fuel in the first fuel supply path 25 and delivers only the required quantity of fuel that is required to be supplied to the engine for further pressurization to the second feed pump 22.

[0010] The first overflow valve 20 and the second overflow valve 24 allow fuel to be supplied to the hydrocarbon fuel injector 16 as well as the second feed pump 22, while channeling the excess pressurized fuel from the first fuel supply path 25 back to the fuel tank via the second overflow valve 24. Therefore, a requirement for an independent high pressure fuel pump to deliver pressurized fuel to the hydrocarbon fuel injector is avoided. The application is typically for a fuel injection system for internal combustion engines.

[0011] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to leverage and dimensions of various levers are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.