초록 ▼

A fuel system includes a first fuel line carrying fuel at a first line pressure (P22), a second fuel line carrying fuel at a second line pressure (PFNC) greater than the first line pressure (P22), at least one pressure regulating section 102 having an input 101 connected to the second fuel line and

A fuel system includes a first fuel line carrying fuel at a first line pressure (P22), a second fuel line carrying fuel at a second line pressure (PFNC) greater than the first line pressure (P22), at least one pressure regulating section 102 having an input 101 connected to the second fuel line and at least one output (103), a first pressure regulator (120) connected to the input and a second pressure regulator (130) connected between the first pressure regulator (120) and the at least one output (103), and a controller (160) controlling the position of the first and second pressure regulators (120, 130) to produce at the output (103) one of a predetermined number of output pressures relative to the first line pressure (P22).

대표청구항 ▼

We claim: 1. A fuel system, comprising: a first fuel line carrying fuel at a first line pressure; a second fuel line carrying fuel at a second line pressure greater than said first line pressure; at least one pressure regulating section comprising an input connected to said second fuel line and at

We claim: 1. A fuel system, comprising: a first fuel line carrying fuel at a first line pressure; a second fuel line carrying fuel at a second line pressure greater than said first line pressure; at least one pressure regulating section comprising an input connected to said second fuel line and at least one output, a first pressure regulator connected to said input and a second pressure regulator connected between said first pressure regulator and said at least one output, said first pressure regulator and said second pressure regulator each comprising a valve having a control surface and a metering orifice; and a spool of an electro-hydraulic servo valve regulating a fluid control pressure applied against the control surface of each of said first and second valves so as to control the position of said first and second pressure regulators to produce at said output one of a predetermined number of output pressures relative to said first line pressure. 2. The fuel system of claim 1 including a linear variable differential transducer connected to said spool. 3. The fuel system of claim 1 wherein said first and second pressure regulators each include a control side, and said controller controls a pressure applied against said control side. 4. The fuel system of claim 1 wherein said first pressure regulator regulates at a first valve pressure and said second pressure regulator regulates at a second valve pressure different than said first valve pressure. 5. The fuel system of claim 1 wherein said pressure regulating section further comprises a third pressure regulator connected between said second pressure regulator and said at least one output and a fourth pressure regulator connected between said third pressure regulator and said at least one output, said first pressure regulator regulating at a first valve pressure, said second pressure regulator regulating at a second valve pressure greater than said first valve pressure, said third pressure regulator regulating at a third valve pressure greater than said second valve pressure, and said fourth pressure regulator regulating at a fourth valve pressure greater than said third valve pressure. 6. The fuel system of claim 1 wherein said predetermined number of output pressures comprises four. 7. The fuel system of claim 5 including a first flow path from said second fuel line to said first pressure regulator control side, a second flow path from said second fuel line to said second pressure regulator control side, a third flow path from said second fuel line to said third pressure regulator control side and a fourth flow path from said second fuel line to said fourth pressure regulator control side. 8. The fuel system of claim 7 wherein said movable member is positionable to block zero or more of said first, second, third and fourth flow paths. 9. The fuel system of claim 7 wherein said movable member is shiftable among first, second, third, fourth and fifth positions, said movable member in said first position blocking none of said first, second, third and fourth flow paths; said movable member in said second position blocking said first flow path; said movable member in said third position blocking said first and second flow paths; said movable member in said fourth position blocking said first, second and third flow paths; and said movable member in said fifth position blocking said first, second, third and fourth flow paths. 10. The fuel system of claim 9 wherein said output pressure is related to the number of flow paths blocked by said movable member. 11. The fuel system of claim 5 wherein said at least one output comprises first and second outputs and including a first flow path from said first pressure regulator to said first output, a second flow path from said second pressure regulator to said second output; a third flow path from said third pressure regulator to said first output and a fourth flow path from said fourth pressure regulator to said second output. 12. The fuel system of claim 11 wherein said movable member is shiftable among first, second, third, fourth and fifth positions, said movable member in said first position blocking said first, second, third and fourth flow paths; said movable member in said second position blocking said second, third and fourth flow paths; said movable member in said third position blocking said third and fourth flow paths; said movable member in said fourth position blocking said fourth flow path; and said movable member in said fifth position blocking none of said first, second, third and fourth flow paths. 13. The fuel system of claim 11 wherein said output pressure at said first and second outputs is related to the flow paths blocked by said movable member. 14. The fuel system of claim 12 including a fifth flow path from said second fuel line to said first output and a sixth flow path from second fuel line said second output. 15. The fuel system of claim 14 wherein said movable member blocks said fifth and sixth flow paths in said first, second, third, fourth and fifth positions, unblocks said fifth flow pats in a sixth position and unblocks said sixth flow path in a seventh position. 16. In a fuel system comprising a first fuel line carrying fuel at a first pressure and a second fuel line carrying fuel at a second pressure greater than said first pressure, a method of establishing at least one location a signal pressure at one of a plurality of discrete levels relative to said first pressure comprising the steps of: providing a flow path between the second fuel line and the at least one location; providing a first pressure regulator regulating at a first pressure and a second pressure regulator regulating at a second pressure in the flow path, each of said pressure regulators comprising a valve having a control side and a metering orifice; and providing an electro-hydraulic servovalve having a spool and adjusting the position of the spool to control a pressure applied against the control side of each pressure regulator to control the positions thereof and to establish first and second signal pressures at the at least one location. 17. In a fuel system comprising a first fuel line carrying fuel at a first pressure and a second fuel line carrying fuel at a second pressure greater than said first pressure, a method of establishing first and second locations of a signal pressure at one of a plurality of discrete levels relative to said first pressure comprising the steps of: providing a flow path between the second fuel line and the at least one location; providing a first pressure regulator regulating at a first pressure and a second pressure regulator regulating at a second pressure in the flow path; and controlling the positions of the first and second pressure regulators to establish a first or second signal pressure at each of the first and second locations. 18. In a fuel system comprising a first fuel line carrying fuel at a first line pressure and a second fuel line carrying fuel at a second line pressure greater than said first line pressure, a method of establishing at a first location a first signal pressure at one of a plurality of discrete levels relative to said first line pressure and at a second location a second signal pressure at one of the plurality of discrete levels relative to the first line pressure comprising the steps of: providing a first flow path connecting the second fuel line and the first and second locations; providing a first pressure regulator regulating at a first pressure and a second pressure regulator regulating at a second pressure in the flow path; providing a third pressure regulator regulating at the first pressure and a fourth pressure regulator regulating at the second pressure in the flow path; and controlling the positions of the first, second, third and fourth pressure regulators to establish first and second signal pressures at the first and second locations. 19. In a fuel system comprising a first fuel line carrying fuel at a first line pressure and a second fuel line carrying fuel at a second line pressure greater than said first line pressure, a method of establishing at first and second outputs of a pressure regulating section first and second signal pressures each at one of a plurality of discrete levels relative to said first line pressure comprising the steps of: providing a first set of n pressure regulating valves in the pressure regulating section in communication with the second fuel line, each pressure regulating valve of the first set regulating at a different pressure than the other pressure regulating valves in the first set; controlling the positions of the n pressure regulating valves to produce one of at least n discrete pressure levels at said first output; providing a second set of m pressure regulating valves in the pressure regulating section in communication with the second fuel line, each pressure regulating valve of the second set regulating at a different pressure than the other pressure regulating valves in the second set; and controlling the positions of the m pressure regulating valves to produce one of at least m discrete pressure levels at said second output. 20. The method of claim 19 including the addition step of controlling an auxiliary valve to produce at least two different pressures at said first output when said n pressure regulating valves are in a given position. 21. The method of claim 19 wherein said steps of controlling the positions of the n pressure regulating valves and controlling the positions of the m pressure regulating valves comprises the steps of providing an electrohydraulic servo valve having a spool and controlling the position of the spool to control a pressure applied against each of the n pressure regulating valves and m pressure regulating valves. 22. A fuel system comprising: a first fuel line carrying fuel at a first line pressure; a second fuel line carrying fuel at a second line pressure greater than said first line pressure; at least one pressure regulating section comprising an input connected to said second fuel line and first and second outputs; a plurality of first pathways from said second fuel line to said first output; a plurality of second pathways from said second fuel line to said second output; a pressure regulating valve in each of said first pathways and second pathways; a spool valve positionable to selectively control fluid flow through each of said first and second pathways; and a controller for controlling the position of said spool to selectively produce a first pressure at said first output and a second pressure at said second output. 23. The fuel system of claim 22 wherein said first pressure is equal to said second pressure. 24. The fuel system of claim 22 wherein said second pressure is dependent upon said first pressure. 25. The fuel system of claim 22 wherein said first and second pressures are settable at a first level, a second level greater than said first level or a third level greater than said second level, said controller holding said second pressure at said first or second level when said first pressure is at said second level and holding said second pressure at said second or third level when said first pressure is at said third level. 26. The fuel system of claim 22 wherein said first and second pathways at least partially overlap.