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Servo Valves (Electro-hydraulic Amplifiers)

Servo valves are the heart of many hydraulic control systems. In the design of control circuits for position control, the current actuator position is usually fed back using electrical signals. Sensors detect the position of the actuator and convert this position into an electrical signal. The signal conversion and processing in the controller are the limiting factors for position accuracy and the dynamic behavior of the control system.

With Voith servo valves (electro-hydraulic amplifiers), the current actuator position is fed back using a direct mechanical linkage and consequently in real time. This feedback uses either a gear rack, a spindle or a toothed belt directly to the valve piston.

As a result, short-stroke actuator movements can be realized freely programmable, highly dynamic and with maximum process reliability. This is the basis for high productivity of your machine or system. At the same time, tools have a long service life and the parts produced are of high quality.


Voith GmbH & Co. KGaA
Schuckertstr. 15
71277 Rutesheim, Germany

Tel. +49 7152 992-3
Fax +49 7152 992-400

Technical data

Volume flow Up to 1,500 l/min
Operating pressure 280 bar maximum
Settling time 5 – 10 ms typically
100% control time 10 – 15 ms typically
Control Using HS4 electronic control (RS-232, CAN, Profibus, Ethernet, USB)
Methods of mechanical position feedback
  • Gear rack
  • Spindle
  • Toothed belt

Typical applications

  • Machines with highly dynamic, short stroke actuator movements
  • Punching machines
  • Presses
  • Shearing machines
  • Cutting machines
  • Stamping machines

Advantages and benefits

Features Advantages Benefits
  • Mechanical feedback of the current actuator position using a gear rack, a spindle or a toothed belt.

  • Position control is simple, direct and highly dynamic.

  • The actuator position is controlled virtually in real time.

  • The control system has a high degree of stiffness.

  • You achieve high productivity with your machine or system because the actuator always reaches the target position in the shortest time.

  • Your tools and the machine itself experience minimum wear.

  • Process safety is exceptionally high.

  • A position measuring system is not needed.

  • There are no costs for the purchasing, integration, and maintenance and repair of a position measuring system.

  • Individual and easily adjustable overlaps of the piston control edges.

  • The servo valve is robust and insensitive to dirt.

  • The cost and effort in filtering and cleaning the pressure fluid are low.

  • The valve has a long lifetime.


Type SVIZ servo valve with a gear rack to mechanically feed the current actuator position back


The stepper or servo motor specifies the position setpoint and actuates a nut-shaft drive that moves the individual valve pistons. The valve pistons open the valve and the actuator moves. The gear rack is linked to the actuator and feeds the actual position back to the valve piston actuation system directly using the pinion (mechanical feedback). As soon as the actuator has reached the programmed position, the pinion returns the valve piston to its initial position. The valve closes again.

  1. Stepper or servo motor
  2. Actuator
  3. Nut-shaft drive
  4. Gear rack
  5. Pinion
  6. Valve piston
  7. Valve piston actuation system