Fuel injector for an internal combustion engine

摘要

An electronically controllable, ultra-high pressure fuel injector comprises a differential pressure type injection nozzle which is opened and closed by an actuating element operated by a hydraulic power cylinder including a piston received in a working chamber. Working fuel to the working chamber of the power cylinder is ON/OFF controlled by an electronically controllable solenoid valve which when energized releases the pressure in the working chamber to open the injection nozzle. In order to ensure that the power cylinder is controlled by a compact, high response solenoid valve, the construction of the power cylinder and the injection nozzle is such that the force applied to the power cylinder piston by the working fuel pressure in the working chamber is substantially greater than the force applied to the actuating element by the fuel pressure in the pressure chamber in the injection nozzle or the fuel pressure in the passage for supplying the working fuel. Preferably, the fuel injector is provided with an injection rate control arrangement such as a flow control arrangement for limiting the flow rate of working fuel as it enters the working chamber and for increasing the flow rate of the working fuel as it is released therefrom, so that the rate of injection increases gradually at the outset of fuel injection but rapidly drops at the completion of the injection.