Importance

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Abstract

A fuel system including a fuel pump for supplying fuel from a source through a variable orifice flow metering valve and then through a variable orifice pressurizing valve to an engine utilizes a determination of the pressurizing valve orifice area to ascertain the fuel flow through the pressurizing valve. The pressurizing valve includes a movable piston with a piston section movable linearly to open and close selectively an orifice. The pressurizing valve may take the form of a cylindrical cavity with the piston reciprocable therein. The cavity is provided with an Inlet port and at least one sidewall outlet port and the piston section slidable along the sidewall outlet port to increase and decrease selectively the effective size of the orifice. A transducer is coupled to the piston to provide an indication of piston position. A second piston section for opening and closing selectively a second orifice may be provided. The piston has one extreme position where both orifices are open, another extreme position where both orifices are closed, a first range of positions where the size of one orifice varies while the other orifice remains closed, and a second range of positions where the sizes of both orifices vary. A linear relationship between orifice area and piston position occurs wherever the outlet ports have a substantially constant circumferential dimension.

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First Claim