Fuel injector

The device (1) has a piezoelectric, electrostrictive or magnetostrictive actuator (4) and a valve needle (3) that interacts with the valve needle with a valve closure body that interacts with a valve seat surface. The actuator is mounted with one end movable and the other acting on the valve needle. The second end (13) of the actuator is directly or indirectly axially guided by an elastic and flexible membrane (8).