Patent ID: 6065451
Filing Date: 2000-05-23
Classification: F02C,F05D,H01F

Abstract:
A fuel system having a fuel pump for supplying fuel from a source through a variable orifice flow metering valve of a fuel control to an engine, including an improved control arrangement for controlling fuel pressure differential across the orifice of the metering valve comprising:a head sensor including a movable diaphragm, a bypass valve for diverting fuel away from the metering valve, and a coupling between the diaphragm and the bypass valve whereby the bypass valve opens and closes in response to diaphragm motion;means for replicating metering valve orifice fuel pressure differential across the diaphragm whereby the bypass valve may open and close to normally maintain the pressure differential across the metering valve substantially constant; andmeans for applying an electrically variable bias force to the diaphragm to increase or decrease selectively the normally maintained pressure differential across the metering valve and correspondingly increase or decrease the fuel flow to the engine, the means for applying comprising a linear actuator having an axis of actuation, a helical actuating coil, a rod extending along the axis and through the helical coil, a first permanent magnet fixed to the rod and spaced axially from the coil, the magnet and rod being supported for limited axial movement relative to the coil, means for supplying selectively an energizing current to the coil to apply a first force to the magnet which is generally inversely proportional to the distance between the coil and the magnet, and a second permanent magnet fixed to the rod on a side of the coil opposite the first permanent magnet, the means for supplying also effecting a second force to the rod which is generally inversely proportional to the distance between the coil and the second magnet, the resultant of the two forces being substantially independent of the spacing between the coil and the permanent magnets, the first force increasing as the second force decreases and the first force decreasing as the second force increases, whereby the limited axial movement of the rod is linearly proportional to the current to the coil while being independent of the axial position of the rod, thereby providing a linear adjustment of the position of the bypass valve and changing fluid flow accordingly.