LIMITING PUMP FLOW DURING OVERSPEED SELF-ACTUATION CONDITION

摘要

In an engine (10) equipped with a common rail fuel injection system (12), the engine (10) can sometimes experience an overspeed condition, and the pump (140 may respond to this overspeed condition with self-actuation even in the absence of any control signal. In order to prevent an over pressurization condition, a liquid supply into a pumping chamber of the pump (14) is limited during a retraction stroke of a pump plunger (31, 32) by energizing an electrical actuator (42) coupled to a spill valve (34, 35), to move the spill valve (34, 35) toward a closed position. The electrical actuator (42) is de-energized during a pumping stroke of the pump plunger (31, 32) to allow the spill valve (34, 35) to more toward an open position. Liquid from the pumping chamber is discharged through the spill valve (34, 35) during the pumping stroke, but over pressurization is avoided by limiting the amount of liquid that can enter the pumping chamber during the retraction stroke.