Fuel injector for internal combustion engine having throttle portion

Claim 1

A fuel injector for internal combustion engines comprising: a piezoelectric actuator which extends and contracts by conduction, a piston member which retracts and moves forward along with said piezoelectric actuator, a variable pressure chamber which is filled with a working fluid and made to rise in pressure when said piston member moves forward, a back pressure chamber which communicates with said variable pressure chamber, said working fluid flowing in sealed relation between said variable pressure chamber and said back pressure chamber, a needle valve which opens and closes a fuel injector hole in accordance with a pressure within said back pressure chamber, a throttle valve for throttling flow of said working fluid between said variable pressure chamber and said back pressure chamber, said throttle valve including a throttle hole and a bypass passage, said throttle valve being movable from a first end position when said piston member moves forward, wherein said throttle hole throttles flow of said working fluid from said variable pressure chamber to said back pressure chamber with said bypass passage being closed, causing said needle valve to close said fuel injector hole, to a second end position when said piston member retracts, wherein said bypass passage is open and enables said working fluid to flow from said back pressure chamber through said bypass passage and said throttle hole, so that said needle valve opens said fuel injector hole.