Gaseous fuel injector

A fuel injector for controlling delivery of gaseous fuel into an intake passage of an internal combustion engine, said fuel injector comprising:

• a fuel injector body defining a fuel flow passage extending in a direction of fuel flow from an inlet to an outlet;
• an actuator;
• an annular valve seat in a valve chamber, said valve seat having a valve seat surface inclined relative to the direction of fuel flow;
• an outflow passage having a first diameter D1 immediately downstream of the valve seat surface, and a second diameter D2 downstream of the first diameter D1, said second diameter D2 being smaller than the first diameter D1;
• a valve member having a valve member surface complementary to the valve seat surface, said valve member including an extension projecting into the outflow passage, said extension having an outside surface comprising a plurality of helical ribs defining a plurality of helical channels,
• wherein said valve member reciprocates between a closed position where said valve member surface is mated to said valve seat surface and an open position where said valve surface is separated from said valve seat surface allowing gaseous fuel to flow past the valve seat surface and into said outflow passage, said valve member moved from said closed position to said open position by said actuator, pressure of gaseous fuel in the valve chamber acting to bias said valve member toward the valve seat when said valve member is in the closed position and the inclination of said valve seat surface causing gaseous fuel to flow against the direction of fuel flow and act on the valve member in an opening direction when said valve member is in the open position, said helical ribs bearing on an inside surface of the outflow passage to guide movement of the valve member and said helical channels imparting a centripetal acceleration to said gaseous fuel as it flows through the outflow passage.