Valve for controlling fluids

A valve (21) for controlling fluids, comprising a valve member (22) that is acted on in a closing direction by a compression spring (24) so that the valve member rests against a valve seat (20), a piston (25) which actuates the valve member, said piston, has a first end surface as a moving wall, which closes off a first side of a coupling chamber (30) filled with hydraulic fluid, said coupling chamber is defined on a second side by an actuator piston (31) of a piezoelectric actuator (32), said piezoelectric actuator has a work stroke which generates a pressure increase in the coupling chamber (30) which adjusts the valve member (22) in a valve opening direction counter to a force of the compression spring (24), the piston (25) is guided in a guide bore (28) and a leakage connection (40) is constituted between the guide bore and a jacket face of the piston (25), the leakage connection connects the coupling chamber (30) to a low pressure chamber (18, 56, 62), the low pressure chamber supplies and receives hydraulic fluid, and via a connection between the coupling chamber (30) and the low pressure chamber (18), a filling valve (33, 43, 54, 60, 70, 73) having a valve seat (38) is provided, and the valve seat is formed by a shoulder (35) of the piston (25).