To damp pressure applied on an O-ring generated when a plunger is moved toward an advance position by arranging an accumulating capacity between the end part of the pressure surface of the plunger and the O-ring, or a pressure release passage opened to a plunger bore on the lower side of the O-ring.
An injector main body 211 is provided with a plunger bore 12 and a fuel pressurizing chamber 17. One end opened to the plunger bore 12 and the other end opened to a low pressure fuel return passage are formed on a pressure release passage 219. The plunger 120 is provided with an O-ring seal 24 and an annular accumulating capacity 125. The pressure release passage 219 is arranged on the lower side of the O-ring 24, the accumulating capacity 125 are arranged between the pressure release passage 219 and the O-ring 24. When the plunger 120 is moved downward, pressure applied on the O-ring 24 is damped by a part of pressure leaked from the pressure release passage 219 and remaining pressure which is increased in the accumulating capacity 125.
TOMASESKI JAY E
WIEMKEN NORVAL J
