Claims:We claim:
1. A fuel filter (10) comprising a filter body (12), filter element (14) located in said filter body (12), a cap (16) located in said filter body (12) such as to hold said filter element (14) in position and a cover plate (18) adapted to be placed over said cap (16), at least a part of said cover plate (18) in contact with said cap (16),
Characterized in that
- an air passage (20) in said cap (16) in a manner such that air passed from a clean side (24) of said fuel filter (10) to a dirt side (22) of said fuel filter (10);
- a felt material component (26) located in said air passage (20) adapted to ensure no flow occurs from said dirt side (22) to said clean side (24); and
- a washer (28) located on said cap (16) in a manner such that said washer (28) provides sealing between said cap (16) and said cover plate (18).

2. A low pressure circuit for a fuel injection system, said low pressure circuit comprising at least a fuel tank, a fuel filter (10) and a fuel flow path between said fuel tank and said fuel filter (10), characterized in that said fuel filter (10) comprising an accumulated air evacuation components adapted to facilitate removal of air from a clean side of said fuel filter to a dirt side of said filter in a manner such that pressure difference between the air in said clean side and said dirt side is reduced.

3. A low pressure circuit as claimed in claim 3, wherein said accumulated air evacuation components comprising:
- an air passage (20) in a cap (16) of said fuel filter (10) in a manner such that air passed from said clean side (24) of said fuel filter (10) to said dirt side (22) of said fuel filter (10);
- a felt material component (26) located in said air passage (20) adapted to ensure no flow occurs from said dirt side (22) to said clean side (24); and
- a washer (28) located on said cap (16) in a manner such that said washer (28) provides sealing between said cap (16) and said cover plate (18).
, Description:Field of the invention
[0001] This disclosure relates to a fuel filter.
Background of the invention:
[0002] Fuel injection systems are sensitive to contaminants that are present in fuel. Fuel filter are the primary source of removing contaminants that are present in fuel. Fuel filters offer amongst others two specific functions i.e. reduce particulate impurities to avoid particulate erosion and separation of water from the fuel to avoid corrosion damage. Reducing particulate impurities is one of the functions of the fuel filter. In this way, it protects the wear-prone components of the fuel-injection system. Besides wear protection, fuel filters must also have a sufficient particulate storage capacity; otherwise they could become blocked before the end of the change interval. If they do become blocked, they would reduce fuel delivery quantity as well as engine performance. It is therefore essential to fit a fuel filter depending on the requirements of the fuel-injection system.
[0003] A European patent EP655269 B1 discloses a liquid filter for fuel, especially diesel fuel, with a housing which, in addition to an inlet for the fuel, has an outlet situated at the top in the housing, and with a filter insert which is arranged in the housing and extends downwards from the outlet and is arranged in such a way that it is inserted between the inlet and the outlet into the fuel flow to be cleaned, and with a leak tight dividing wall which extends underneath the outlet and is arranged downstream of the filter insert, on the clean side of the latter, and serves to form a gas-collecting space which is connected to the outlet via at least one restrictor opening arranged in the dividing wall and serving the purpose of controlled gas discharge and in which the dividing wall has, at the bottom, at least one opening, past which the fuel flow is guided to the outlet, characterized in that the dividing wall arranged below the outlet is designed as a gas-collecting bell, the closed end of which lies at the top and is thus adjacent to the outlet, while its open end, that forming the opening, lies at the bottom and thus remote from the outlet, in that the restrictor opening or openings, which is connected to the gas-collecting space, is/are arranged in the region of the upper end of the gas-collecting bell, in that the fuel flow in the region of the bottom opening of the gas-collecting bell undergoes a deflection which assists the elimination of the gas and then is guided around the outside of the gas-collecting bell to the outlet.
Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings;
[0005] Figure 1 illustrates a fuel filter in accordance with this disclosure; and
[0006] Figure 2 illustrates a detailed view of a part of the fuel filter in accordance with this disclosure.
Detailed description of the embodiments:
[0007] Figure 1 illustrates a fuel filter 10 comprising a filter body 12, filter element 14 located in the filter body 12, a cap 16 located in the filter body 12 such as to hold the filter element 14 in position and a cover plate 18 adapted to be placed over the cap 16, at least a part of the cover plate 18 in contact with said cap 16. The fuel filter 10 is characterized such that it comprises an air passage 20 in the cap 16 in a manner such that air passed from a dirt side 22 of the fuel filter 10 to a clean side 24 of the fuel filter 10. A felt material component 26 is located in the air passage 20 adapted to ensure that particle do not no flow from the clean side 24 to dirt side 22; and a washer 28 located on the cap 16 in a manner such that the washer 28 provides sealing between the cap 16 and the cover plate 18.

[0008] For better understanding of the fuel filter in accordance with this disclosure, the fuel filter functions and some components can be disclosed in the following manner. Reducing particulate impurities is one of the functions of the fuel filter. In this way, it protects the wear-prone components of the fuel-injection system. Requirements regarding filter fineness have increased in the last few years and depend on the generation common-rail systems and the vehicle type. Depending on the application such as operating conditions, fuel contamination, engine life, new systems require filtration efficiencies ranging from 65% to 98.6%. Longer servicing intervals in more recent vehicles require greater particulate storage capacities as well as intensive fine particulate filtration.

[0009] The fuel filter has a plurality of components which are located in the filter housing or filter body. The filter element which is located in the filter body may be composed of several synthetic layers and cellulose. The filter media employ a preliminary fine filtering effect and guarantee maximum particulate retention capacity by separating particles within each filtering layer. Thus when the fuel containing the particulate matter comes in contact with the filter element, the filter element retains the particulate matter and allows the fuel to flow through the filter element. Another function that is also performed by the fuel filter is water separation. Water is also separated by the filter element as the droplets of water are formed on the filter element due to different surface tension of water and fuel. The separated water collects at the bottom of the filter body. Water level sensor are used in the fuel filter to determine the amount of water and water is either drained manually or using an automatic water disposal system.

[00010] In the context of the fuel injection system which contains amongst other components the fuel tank and the fuel filter, the fuel filter is located in the low pressure circuit downstream of the fuel tank. However, when the fuel tank is filled with fuel and when hand priming is performed in the filter head to fill the low pressure circuit the fuel is available till the fuel pump inlet. When the vehicle is cranked the engine starts with ease, but when the engine is stopped due to degasification effect of the fuel air/gases are released. This air/ gases get accumulated at the top volume of the fuel filter. In some cases the accumulation of air may be as much as 1/4th the fuel filter volume. When the engine is now cranked with the accumulated air at the top of the fuel filter only air is available at the pump inlet and not fuel. Due to presence of air accumulated at the top of the fuel filter, the fuel pump is starved of the presence of fuel and leads to non startability of the vehicle. The fuel filter 10 in accordance with this disclosure focuses on the task of removing the air that is accumulated at the top of the fuel filter.

[00011] In accordance with one aspect of this disclosure there is also provided a low pressure circuit for a fuel injection system. The low pressure circuit comprises at least a fuel tank, a fuel filter 10 and a fuel flow path between the fuel tank and the fuel filter 10. The low pressure circuit is characterized such that the fuel filter 10 comprises accumulated air evacuation components adapted to facilitate removal of air from the dirt side 22 of the fuel filter to the clean side 24 of fuel filter 10 in a manner such that pressure difference between the air in the dirt side 22 and the clean side 24 is reduced.

[00012] As mentioned earlier the low pressure circuit of the fuel injection system has accumulated air evacuation components. The accumulated air evacuation components comprises an air passage 20 in the cap 16 of the fuel filter 10 in a manner such that air passed from the dirt side 22 of the fuel filter 10 to the clean side 24 of the fuel filter 10, a felt material component 26 is located in the air passage 20 adapted to ensure that particles do not no flow from the clean side 24 to the dirt side 22 and a washer 28 is located on the cap 16 in a manner such that the washer 28 provides sealing between the cap 16 and said cover plate 18.

[00013] The construction of the fuel filter 10 in accordance with this disclosure can be explained in the following manner. The filter element 14 is filter element 14 located in the filter body 12 and a cap is fitter onto the filter body 12 to hold the filter element 14 in position. Further a cover plate 18 adapted to be placed over the cap 16. At least a part of the cover plate 18 in contact with the cap 16. When the cover plate 18 is in contact with the cap 16 an air passage exists. The air passage 20 allows movement of air or fluid from the dirt side 22 of the fuel filter 10 to the clean side 24 of the fuel filter 10. The dirt side 22 of the fuel filter 10 is defined as a side which is downstream of the filter element 14, where the fuel flowing is the fuel after filtration and after removal of the impurities. The clean side 24 of the fuel filter 10 is defined as the side which is upstream of the filter element 14. Further a felt material component 26 is located in the air passage 20 adapted to ensure that particle do not flow from the clean side 24 to dirt side 22 and a washer 28 located on the cap 16 in a manner such that the washer 28 provides sealing between the cap 16 and the cover plate 18.

[00014] The working of the fuel filter 10 can be explained in the following manner. The working principle of the fuel filter 10 in accordance with this invention is reduction in the pressure difference between the clean side and dirt side. During the function of the fuel filter 10 in the fuel injection system, if there is any accumulation of air in the dirt side, the air passage 20 and the felt material allows the air to flow from the dirt side 22 to the clean side 24. As the air flows from the dirt side 22 to the clean side 24 the difference in pressure of air at the clean side 24 with respect to the pressure of air in the clean side is reduced. The reduction in pressure difference allows ease flow of air. Once the air that is accumulated is reduced the fuel volume raises and the fuel will be available at the dirt side and thereby at the pump side. The presence of fuel at the pump side also ensures that the pump is not starved of fuel and there will be no engine startability issue.

[00015] 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.