CLIAMS:We Claim:
1. A fuel metering unit (10), said fuel metering unit (10) comprising:
a housing (12) having a cavity (13) and a passage (15) extending from said cavity (13), said passage (15) in fluid communication with an inlet (14) of said fuel metering unit (10) and said cavity (13) in fluid communication with an overflow passage (24) of said fuel metering unit (10);
characterized in that
an element (22) located at least at the interface of said passage (15) and said cavity (13);
a spring (20) positioned in contact with said element (22); and
a plug (18) fitted at one end of said cavity (13) such that at least a portion of the plug (18) is in contact with said spring (20) and at least a portion of the plug (18) seals said fuel metering unit (10).
2. The fuel metering unit (10) in accordance with Claim 1, wherein said element (22) is located at the interface of said passage (15), said cavity (13) and said overflow passage (24).
3. The fuel metering unit (10) in accordance with Claim 1, wherein a metallic insert (17) is located in contact with said spring (20) and at least a portion of the plug (18) engages with said metallic insert (17).
4. The fuel metering unit (10) in accordance with Claim 1, wherein said element (22) is a ball.
5. The fuel metering unit (10) in accordance with Claim 1, wherein said element (22) is a cap.
6. The fuel metering unit (10) in accordance with Claim 1 and 4, wherein said ball is located at the interface of said passage (15), said cavity (13), and said overflow passage (24).
7. The fuel metering unit (10) in accordance with Claim 1 and 5, wherein said cap is located at the interface of said passage (15) and said cavity (13).
8. The fuel metering unit 10 in accordance with Claim 1 and 5, wherein said cap includes at least one hole extending from an outer surface of said cap to an inner surface of said cap, said at least one hole facilitates channeling fuel from said outer surface to said inner surface. ,TagSPECI:The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention:
[001] This invention relates to a fuel metering unit.

Background of the invention
[002] An overflow valve is used in a conventional fuel metering unit. The overflow valve used in the conventional fuel metering unit is inserted within the fuel metering unit and screwed on to a clamping device that is integrated within the fuel metering unit. Due to longer lead times associated with manufacturing and assembling the overflow valve within the fuel metering unit, it is desired to provide a simpler design to accommodate the overflow valve within a housing of the fuel metering unit.

[003] Indian Patent Application Number 2013/CHE/3901 describes an overflow valve used in a fuel metering unit. The overflow valve has screw threads defined on its outer periphery. The fuel metering unit has screw threads defined on its inner periphery that synchronizes with the screw threads of the overflow valve. The overflow valve is inserted within the fuel metering unit and screwed on to the fuel metering unit to facilitate fastening the overflow valve to the fuel metering unit.

Brief description of the accompanying drawings
[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawings:
[005] Figure 1 illustrates an overflow valve in a fuel metering unit in one embodiment of the invention; and
[006] Figure 2 illustrates an overflow valve in a fuel metering unit in another embodiment of the invention.

Detailed description of the embodiments
[007] Figure 1 illustrates a fuel metering unit 10. The fuel metering unit 10 comprises a housing 12 having a cavity 13 and a passage 15 extending from the cavity 13. The passage 15 is in fluid communication with an inlet 14 of the fuel metering unit 10. The cavity 13 is in fluid communication with an overflow passage 24 of the fuel metering unit 10. An element 22 is located at least at the interface of the passage 15 and the cavity 13. A spring 20 is positioned in contact with the element 22. A plug 18 is fitted at one end of the cavity 13 such that at least a portion of the plug 18 is in contact with the spring 20 and at least a portion of the plug 18 seals the fuel metering unit 10.

[008] The fuel metering unit 10 includes the housing 12 of the fuel metering unit 10. The housing 12 includes an inlet 14 that is in flow communication with a feed pump. The inlet 14 is adapted to receive fuel from the feed pump. The housing 12 of the fuel metering unit 10 includes an outlet 16 that is in flow communication with a high pressure pump. A metallic insert 17 is positioned within the housing 12 of the fuel metering unit 10. The metallic insert 17 includes a flanged portion that contains a plurality of grooves defined on the flanged portion.

[009] The fuel metering unit 10 includes a plug 18 that is disposed within an opening defined at the centre of the metallic insert 17. The plug 18 is inserted within the metallic insert 17 such that the plug 18 forms an interference fit against an inner surface of the metallic insert 17. In an alternate embodiment, the plug 18 is screwed on to the inner surface of the metallic insert 17. Alternatively, the plug 18 is fastened within the inner surface of the metallic insert 17 using any fastening means known in the art. The plug 18 facilitates sealing the fuel metering unit 10 thereby preventing escape of fuel while the fuel metering unit 10 is operational. A spring 20 is disposed within the fuel metering unit 10 and is in contact with the plug 18 of the fuel metering unit 10. An element 22 is disposed within the fuel metering unit 10 and is in contact with the spring 20 of the fuel metering unit 10. The element 22 facilitates closing an overflow passage 24 while the flow metering unit 10 is non-operational. The spring 20 is located within the housing 12 of the fuel metering unit 10 in a manner such that one end of the spring 20 abuts the plug 18 while the opposite end of the spring 20 is inserted within the element 22 and is in contact with the element 22. In an embodiment, the element 22 may be cap. In an alternate embodiment, the element 22 may be a calotte.

[0010] The element 22 includes a first portion that is proximate to a passage 15. The element 22 has a first portion and a second portion. The first portion is of a smaller diameter than a second portion that is formed below the first portion. The first portion includes at least one through hole drilled from an outer surface of the first portion to an inner surface of the first portion. The through hole facilitates channeling fuel from the outer surface of the first portion to the inner surface of the first portion. The fuel that is channeled to the inner surface of the first portion flows downwardly into the cavity that houses the spring 20. Therein, the fuel is channeled out of the fuel metering unit 10 through the overflow passage 24.

[0011] As shown in Figure 2, another embodiment of the fuel metering unit 10 is described. In accordance with this embodiment, the fuel metering unit 10 includes a plug 18 that is integrally formed within the housing 12 of the fuel metering unit 10. More specifically, the plug 18 may be partially melted on its outer periphery and inserted into the cavity within which the spring 20 is housed. When the plug 18 solidifies completely, the outer periphery of the plug 18 grips firmly against an inner surface of the cavity within which the spring 20 is housed. The plug 18 therefore maintains a tight sealing contact with the housing 12 of the fuel metering unit 10.

[0012] The principle of working of the fuel metering unit 10 is now explained as an example. Fuel from the feed pump is channelled to the fuel metering unit 10 via the inlet 14. During this stage, the spring 20 will be in a completely expanded state with the overflow passage 24 being in a closed state due to the through hole of the element 22 in sealing contact against the housing 12. When the pressure of fuel entering the fuel metering unit 10 through the inlet 14 exceeds the operating pressure, the spring 20 gets compressed. The compression of the spring 20 causes the element 22 to move downwardly, thereby causing the outer portion of the through hole of the element 22 to be exposed. Fuel channelled into the fuel metering unit 10 from the inlet 14 flows from the outer portion to the inner portion of the through hole and is channelled through the overflow passage 24 of the fuel metering unit 10. In this manner, excess fuel that is channelled to the fuel metering unit 10 is channelled out of the fuel metering unit 10 through the overflow passage 24.

[0013] In accordance other embodiments of the disclosure the metallic insert 17 and plug 18 may be integrated within the housing 12. Such integration facilitates simplifying the design for coupling the metallic insert 17 and the plug 18 to the housing 12 of the fuel metering unit 10.

[0014] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.