The flow control servo valves D661 High Response Series are throttle valves for 2-, 3- and 4-way applications. These valves are suitable for electrohydraulic position, velocity, pressure or force control systems including those with high dynamic response requirements.

The spool of the main stage is driven by a jet pipe pilot stage in an electrically closed loop.

The integrated electronics of the valve is a new development featuring SMD technology and requires 24 VDC power supply.

The ServoJet High Response pilot stage consists mainly of torque motor, jet pipe and receiver. A current through the coil displaces the jet pipe from neutral. This displacement combined with the special shape of the nozzle directs a focused fluid jet more into one receiver opening than the other. The jet now produces a pressure difference in the control ports. This pressure difference results in a pilot flow which in turn causes a spool displacement. The pilot stage drain is through the annular area around the nozzle to tank.

An electric command signal (flow rate set point) is applied to the integrated control amplifier which drives the pilot stage. Thus the deflected ServoJet high response system produces a pressure difference across the drive areas of the spool and effects its movement. The position transducer which is supplied via an oscillator measures the position of the spool (actual value, position voltage). This actual value is being rectified by a demodulator and fed back to the control amplifier where it is compared with the command value. The control amplifier drives the torque motor until command voltage and feedback voltage are equal. Thus, the position of the spool is proportional to the electric command signal.