Electrostrictive actuator device and fuel injection device using same

Claim 1

A fuel injection control system for an injection pump for a diesel engine having a pump chamber in which fuel pressure is repetitively increased and decreased by a plunger reciprocally movable within said pump chamber in timed relation with rotation of said diesel engine, said system comprising: electrostrictive actuator means, located in a chamber communicated with said pump chamber to receive the fuel pressure which is changed by said reciprocally movable plunger as a physical force, said electrostrictive actuator means for expanding and constricting in accordance with an electrical charging and electrical discharging thereof during a fuel pressure increase phase; fuel injection nozzle means coupled to said electrostrictive actuator means, for opening a nozzle valve to inject fuel to said diesel engine whenever a fuel pressure in said pump chamber becomes greater than a predetermined valve opening pressure; electrical charging means for electrically charging said electristrictive actuator means with an electric high voltage at a first timing before said pump chamber attains said valve opening pressure during said pressure increase phase, to expand said electrostrictive actutor means and to increase the fuel pressure to an amount greater than said valve opening pressure in said pump chamber to begin a pilot fuel injection; and electrical discharging means for electrically discharging said electrostrictive actuator means at a second timing after said first timing and during the increase of the fuel pressure in said pump chamber by said plunger so that said electrostrictive actuator means is constricted to rapidly decrease the fuel pressure in said pump chamber to complete said pilot fuel injection, and wherein a main fuel injection is subsequently performed when said valve opening pressure is again reached by said plunger continuing to increase fuel pressure in said pump chamber.