Method for operating a piezo servo injector

A method for assembling and operating an injector of an internal combustion engine with a nozzle needle operated by a piezo actuator through a servo valve, the method comprising:

• eliminating idle travel of the piezo actuator by maintaining a permanent direct force connection between the piezo actuator and the servo valve, so that a change in force on the servo valve due to a change in pressure in the valve chamber when the servo valve is opened and closed and when the nozzle needle of the injector is closed is always transmitted to the piezo actuator as a change in force,
• setting the spring force for the servo valve to produce the permanent direct force connection,
• setting the valve stiffness relative to the stiffness of the piezo actuator to produce the permanent direct force connection, in a range of twice to four times the value of the stiffness of the piezo actuator,
• detecting a change in voltage and/or capacitance of the piezo actuator resulting from the change in force transmitted to the piezo actuator during operation, and
• regulating an injection quantity output by the injector based on the detected change.