Patent ID: 7398765

Claim:
A fuel injection device for an internal combustion engine, the fuel injection device comprising: a pressure accumulator that accumulates fuel under pressure; a pressure intensifier that operates a pressure intensifying piston with oil pressure in a control chamber to intensify the pressure of the fuel supplied from the pressure accumulator to a high-pressure chamber; an injection nozzle that injects the fuel supplied directly from the pressure accumulator or the fuel, the pressure of which is intensified by the pressure intensifier, the injection nozzle structured so that oil pressure in a back pressure chamber of the injection nozzle controls opening and closing of the injection nozzle; a control valve that controls the pressure intensifying operation of the pressure intensifier and the injection operation of the injection nozzle, wherein the control valve is a single two-way control valve driven by a two-position actuator and directly controls the oil pressure in the back pressure chamber to control the injection operation of the injection nozzle; and a flow passage switching valve that has a two-position three-way valve structure operated by control pressure controlled by the control valve, wherein the control chamber is selectively connected with a supply passage extending from a pressure supply source or with a pressure release passage leading to a low-pressure system through the flow passage switching valve to indirectly control the oil pressure of the control chamber so that the pressure intensifying operation of the pressure intensifier is controlled, the flow passage switching valve is structured so that a start of the operation thereof is delayed until the control pressure decreases to a predetermined operation pressure when the pressure is released from the control chamber to perform the pressure intensifying operation, so the pressure intensifying operation starts in retard of the injection operation, and the control chamber is supplied with pressure through the pressure release passage during a delay of the operation of the flow passage switching valve with respect to the operation of the control valve when the pressure is supplied to the control chamber to stop the pressure intensifying operation, so the pressure intensifying operation is stopped and a returning operation of the pressure intensifying piston is performed abreast of stoppage of the injection operation.