Patent ID: 7891579

Claim:
A fuel injector for injecting gaseous fuel and liquid fuel into a combustion chamber of an internal combustion engine, the fuel injector comprising: a nozzle member having injection holes formed at its longitudinal end portion; a needle having a valve surface for opening or closing the injection holes, the needle being slidably coupled to the nozzle member; a chamber for containing high-pressure gaseous fuel therein, the chamber being formed between the nozzle member and the needle so that the high-pressure gaseous fuel applies a force to the needle in a direction to open the injection holes; a gaseous fuel passage for introducing the high-pressure gaseous fuel into the high-pressure gaseous fuel chamber; a control chamber containing liquid fuel that applies a force to the needle in a direction to close the injection holes; a liquid fuel supply passage for introducing the liquid fuel into the control chamber; a liquid fuel leading passage for leading out the liquid fuel contained in the control chamber; a switching valve for controlling liquid fuel pressure in the control chamber; and an actuator for driving the switching valve, wherein: a connecting passage for connecting the liquid fuel leading passage to the injection holes through a small sliding space between the needle and the nozzle member, the needle slidably coupled to the nozzle member being lubricated by the liquid fuel flowing through the small sliding space; the liquid fuel leading passage includes a first one-way valve for preventing the liquid fuel from flowing from the connecting passage to the liquid fuel leading passage and for allowing the liquid fuel to flow from the liquid fuel leading passage to the connecting passage when a pressure difference between the liquid fuel leading passage and the connecting passage exceeds a predetermined first level; the fuel injector further includes a releasing passage connected to a liquid fuel tank; and the liquid fuel leading passage includes a second one-way valve for preventing the liquid fuel from flowing from the releasing passage to the liquid fuel leading passage and for allowing the liquid fuel to flow from the liquid fuel leading passage to the releasing passage when a pressure difference between the liquid fuel leading passage and the releasing passage exceeds a predetermined second level.