| 摘要 |
A fuel system including a fuel pump (15) for supplying fuel from a source through a variable orifice flow metering valve (17) and then through a variable orifice pressurizing valve (19) to an engine utilizes a determination of the pressurizing valve orifice area (29, 65) to ascertain the fuel flow through the pressurizing valve. The pressurizing valve includes a movable piston (45) with a piston section movable linearly to open and close selectively an orifice (41, 73). The pressurizing valve may take the form of a cylindrical cavity (59) with the piston reciprocable therein. The cavity is provided with an Inlet port (31) and at least one sidewall outlet port (61, 73; 63, 75) and the piston section slidable along the sidewall outlet port to increase and decrease selectively the effective size of the orifice. A transducer (29) is coupled to the piston to provide an indication of piston position. A second piston section (47) for opening and closing selectively a second orifice (63, 75) 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. |
