Method of electrolytically finishing spray-hole of fuel injection nozzle

摘要

A method of finishing spray-holes bored by machining in the body of a fuel injection nozzle for an IC engine by removing burrs that remain after machining around the inside mouth of each spray-hole. Employed is electrolytic polishing process wherein the nozzle body is made the anode. A tubular electrode having an insulator cover is inserted into the nozzle body, and electrolyte liquid is supplied through the tubular electrode to flow out through the spray-holes. An end portion of the insulator cover completely covers the tip portion of the electrode and comes into close contact with the inner surface of the nozzle body over an area in which the spray-holes are open. In the insulator cover, liquid passages are formed so as to inject the electrolyte liquid only at the location of the mouth of each spray-hole to thereby prevent dissolution of the nozzle body inner surface in unwanted areas. Accordingly the removal of the burrs is achieved without increasing the volume of dead space in the nozzle body.