Patent ID: 6276610
Filing Date: 2001-08-21
Classification: F02M,F04B

Abstract:
A pump for a fuel injection system, the pump comprising:a pump body having a pumping chamber, a fuel inlet for supplying fuel to the pumping chamber, an outlet port, and a control valve chamber between the pumping chamber and the outlet port;a plunger disposed in the pumping chamber;an actuable control valve disposed in the control valve chamber for controlling fuel, the control valve being moveable over a stroke range between an open position in which full pressure relief is provided to the pumping chamber and a closed position in which pressure relief to the pumping chamber is blocked, the stroke range including a rate shape position between the open position and the closed position in which partial pressure relief is provided to the pumping chamber;a valve stop adjacent to the control valve chamber;a control valve spring arrangement biasing the control valve toward the open position;an armature at the control valve; anda stator near the armature and including a variable current actuator operable to urge the control valve toward the closed position against the bias of the control valve spring arrangement,wherein the control valve spring arrangement is configured to provide a first spring force when the control valve is between the closed position and the rate shape position, and to provide a second spring force that is less than the first spring force when the control valve is between the rate shape position and the open position, and wherein a stroke portion from the closed position to the rate shape position is sufficiently small such that the partial pressure relief provided in the rate shape position is substantially less than the full pressure relief of the open position to cause an injection event that begins while the control valve is in the closed position to continue when the valve is held in the rate shape position with varied actuator current, providing controlled injection rate shaping when the control valve is at the rate shape position.