Claims:We Claim

1. A fuel control unit (10) for a fuel injection system, said fuel control unit (10) comprising:
a piston (12), wherein the piston comprises an outer diameter and an inner diameter that is radially inward from the outer diameter; characterized in that
a sleeve (14) positioned within said piston (12), the wall of the inner diameter of the piston (12) adapted to translate along an outer surface of the sleeve (14).

2. The fuel control unit (10) for the fuel injection system in accordance with Claim 1 further comprising a spindle (16) positioned axially within said sleeve (14) and said piston (12), said spindle (16) adapted to reciprocate within said sleeve (14), and wherein said spindle (16) is adapted to close an outlet of said sleeve (14) to facilitate preventing fuel from flowing out of said sleeve (14) of said fuel control unit (10).

3. The fuel control unit (10) for the fuel injection system in accordance with Claim 2 wherein said spindle (16) comprises a tapered portion (18) that is secured against a tapered portion of said sleeve (14) to facilitate preventing fuel from flowing out of said sleeve (14) of said fuel control unit (10).

4. The fuel control unit (10) for the fuel injection system in accordance with Claim 2 further comprising an orifice (20) defined proximate a clearance between said piston (12) and said sleeve (14), said orifice (20) adapted to withdraw fuel that is channeled through the clearance defined between said piston (12) and said sleeve (14) and out of said fuel control unit (10).

5. The fuel control unit (10) for the fuel injection system in accordance with Claim 2 further comprising an armature (22) secured to said spindle (16), said armature (22) adapted to translate said spindle (16) within said sleeve (14).
, Description:Field of the invention
[0001] This invention relates to a fuel control unit.

Background of the invention
[0002] US 3208218 A describes a fuel control unit for a gas turbine engine and comprises a governor operable at different manually settable speed settings so as to control the steady state operation of the engine and incorporating means responsive to one or more parameters for example compressor discharge pressure, which operates during acceleration to limit the fuel flow in accordance with a pre-selected maximum fuel schedule that will avoid overheating of the turbine. The unit is shown in Fig. 1 and comprises a fuel control valve having a spool valve member comprising a pair lands and a valve stem having stop members at the upper end thereof. Fuel is supplied from a reservoir by the pump to the passage, the fuel then passing under control of the land to the passage leading to the burners in the engine combustion equipment. The pressure drop across the valve is maintained constant by means of a spring loaded valve member which controls a passage leading from the passage back to the suction side of the pump. A by-pass passage controlled by an adjustable valve is provided so as to maintain a minimum flow of fuel when the throttle lever is in the shutdown position.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a fuel control unit for a fuel injection system.

Detailed description of the embodiments

[0004] Figure 1 illustrates a fuel control unit 10 for a fuel injection system. The fuel control unit 10 comprises a piston 12, wherein the piston comprises an outer diameter and an inner diameter that is radially inward from the outer diameter. A sleeve 14 is positioned within the piston 12, the wall of the inner diameter of the piston 12 adapted to translate along an outer surface of the sleeve 14.

[0005] The fuel control unit 10 comprises a piston 12. The piston 12 comprises an outer diameter and an inner diameter. A sleeve 14 is positioned in the bore defined within the inner diameter of the piston 12 such that an outer surface of the sleeve 14 is flush against the inner diameter of the piston 12. In the exemplary embodiment, the inner diameter of the piston 12 is adapted to translate against the outer surface of the sleeve 14. A spindle 16 is positioned axially within the sleeve 14 and the piston 12 such that the spindle 16 is adapted to reciprocate within the sleeve 14. The spindle 16 comprises a tapered portion 18. The tapered portion 18 of the spindle 16 is secured against a tapered portion 19 of the sleeve 14. More specifically, when the tapered portion 18 of the spindle 16 is secured against the tapered portion 19 of the sleeve 14, fuel is prevented from flowing out of the sleeve 14 of the fuel control unit 10. An armature 22 is secured to the spindle 16 via mechanical means such as but not limited to a fastener. The armature 22 that is electronically coupled to an engine control unit is adapted to translate, thereby translating the spindle 16 and opening the inlet of the sleeve 14 of the fuel control unit 10. A spring 21 is positioned within the bore of the piston 12. A first end of the spring 21 is positioned against the piston 12, and the opposite second end of the spring 21 is positioned against the sleeve 14. The spindle 16 is secured to the spring 21 such that the spring 21 applies a restoring force on the spindle 16 after fuel flows out of the fuel control unit 10.

[0006] The fuel control unit 10 comprises a clearance that is defined between the piston 12 and the sleeve 14. An orifice 20 is defined proximate the clearance between the piston 12 and the sleeve 14. The orifice 20 is adapted to withdraw fuel that is channeled through the clearance defined between the piston 12 and the sleeve 14 and out of the fuel control unit 10 when the spindle 16 is stationary and not translated by the armature 22. More specifically, when the spindle 16 is stationary, the pressurized fuel entering the fuel control unit 10 flows through the clearance defined between the piston 12 and the sleeve 14 to the orifice 20. From the orifice 20, the pressurized fuel is channeled back to the fuel tank.

[0007] A working of the fuel control unit 10 is described as an example. When fuel is not required to be supplied from the fuel control unit 10, the spindle 16 is stationary. Therein, pressurized fuel that flows into the fuel control unit 10 is channeled through the clearance defined between the piston 12 and the sleeve 14 and out of the fuel control unit 10 via the orifice 20, thereby bypassing the high pressure fuel pump that is positioned downstream from the fuel control unit 10. When it is required to supply fuel from the fuel control unit 10 to the high pressure fuel pump, the piston 12 is translated against the force of the spring member 21 such that the fuel entering the fuel control unit 10 is directed to the bore defined within the piston 12. Simultaneously, the spindle 16 is translated towards the left against the force of the spring member 21 by means of the armature 22 that is actuated by the engine control unit. When the spindle 16 is translated towards the left against the force of the spring member 21, the fuel that is present in the bore of the fuel control unit 10 is channeled out of the fuel control unit 10 and delivered to the high pressure fuel pump. After the fuel is completely delivered from the fuel control unit 10 to the high pressure fuel pump, the solenoid 22 is returned to its original position. Thereby, the restoring force of the spring member 21 causes the spindle 16 to be displaced to the right, thereby closing the outlet opening of the sleeve 14 and preventing further fuel from flowing out of the fuel control unit 10 to the high pressure fuel pump.

[0008] 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 components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.