Fuel injector with piezoelectric actuator

Fuel injector (1; 101; 201) provided with a piezoelectric actuator (9; 109; 209), a valve (6, 106; 206) activated by the piezoelectric actuator (9; 109; 209) and regulating a fuel supply that flows in a working direction (3; 103; 203), and a mechanical transmission (20; 120; 220) placed between the piezoelectric actuator (9; 109; 209) and the valve (6, 106; 206); an expansion of the piezoelectric actuator (9; 109; 209) displaces the valve (6, 106; 206) in the working direction (3; 103; 203) from a closed position to an open position in an opposite direction (V1) to that (V2) of the fuel outlet.