Injection system with bipolar operated piezo actuator

The system (1) has a valve closing body (19) actuated by a piezoelectric actuator (10) i.e. piezoelectric multi-layer actuator, in an indirect manner and co-acting with a valve seat surface (20) at a sealing seat. A control (17) is connected with the actuator and utilized for controlling the actuator. The control is designed to control the actuator corresponding to polarization of the actuator and against polarization of the actuator to enable closing of the seat that is formed between the closing body and the seat surface. The piezoelectric actuator is supported at a valve housing (3).