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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

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.

대표청구항 ▼

A fuel injector for an internal combustion engine, which comprises: a body having an axial bore; a normally closed injection nozzle mounted to said body in alignment with said bore, said injection nozzle being of the differential pressure type including a pressure chamber and a needle valve; injecti

A fuel injector for an internal combustion engine, which comprises: a body having an axial bore; a normally closed injection nozzle mounted to said body in alignment with said bore, said injection nozzle being of the differential pressure type including a pressure chamber and a needle valve; injection fuel supply means in said body for supplying a high pressure fuel to said pressure chamber of said injection nozzle; a power cylinder including a piston slidably received in said axial bore to define a working chamber therein, said piston being operative to be moved toward and away from said injection nozzle as said power cylinder is activated and deactivated; working fuel supply means in said body for supplying a pressurized fuel to said working chamber of said power cylinder; an electronically controlled solenoid valve placed in said working fuel supply means and selectively operable to close said wording fuel supply means, thereby precluding application of the fuel pressure in said working fuel supply means to said working chamber to deactivate said power cylinder upon energization of said solenoid valve and operable to open said working fuel supply means, thereby allowing transmission of said fuel pressure in said working fuel supply means to said working chamber to activate said power cylinder upon de-energization of said solenoid valve; and actuating means operatively connected with said piston of the power cylinder for selectively rendering said injection nozzle opened to allow the high pressure fuel in said pressure chamber to be injected through said nozzle as said solenoid valve is energized to deactivate said power cylinder allowing the piston to move away from said injection nozzle, and rendering said injection nozzle closed to terminate fuel injection as said solenoid valve is de-energized to activate said power cylinder causing the piston to be urged toward the injection nozzle; the size and construction of said piston of the power cylinder being such that the force applied to said piston by the fuel pressure in said working chamber is substantially greater than the force applied to said actuating means by the fuel pressure in said injection fuel supply means or in said pressure chamber; wherein said injection fuel supply means includes an injection fuel inlet (202) in said body for receiving an injection fuel pressurized at an ultra-high pressure and an injection fuel passage (227) in said body for communicating said inlet (202) with said pressure chamber, said working fuel supply means including a working fuel inlet (204) in said body for receiving a working fuel pressurized at a high pressure lower than said ultra-high pressure and a working fuel passage (236) in said body for transmitting the high pressure working fuel at said working fuel inlet (204) to said working chamber of said power cylinder, wherein said actuating means includes a valve seat (270) formed in said injection fuel passage (227) in alignment with and transversely of the axis of said piston and a needle valve (274) operated by said piston to become seated on said valve seat (270) to close the working fuel passage (236), and wherein said piston has a pressure receiving area larger than that of said needle valve (274) of said actuating means, the ratio of the pressure receiving area of said piston with respect to the pressure receiving area of said needle valve (274) of the actuating means being larger than the ration of the fuel pressure at said injection fuel inlet (202) with respect to the fuel pressure at said working fuel inlet (204).