Original Sauer Danfoss Valves MCV116 Series

The MCV116 Pressure Control Pilot (PCP) Valve is an inexpensive control valve for use in electrohydraulic systems which control machines used in construction, farming, material handling, marine, mining and industrial applications. The device is designed to control pilot-operated flow control valves (proportional main spool valves in the 5—50 gpm range), pilotoperated variable displacement pumps and motors and any other device which is pilot differential pressure actuated. The PCP is a torque-motor actuated, double-nozzle flapper valve that produces a differential output pressure proportional to the applied electrical input signal. It is a single-stage, standalone, closed loop pressure control valve which uses internal hydraulic pressure

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Theory of Operation

7 Jan 2019

The PCP accepts a dc current and produces a proportional hydraulic differential pressure output. See the Internal Workings Schematic. Input current controls the torque motor stage, a bridge network consisting of an armature mounted on a torsion pivot and suspended in the air gap of a magnetic field. Two permanent magnets polarized in parallel and a connecting plate form a frame for the magnetic bridge.

At null the armature is centered in the air gap between the magnets’ opposing poles by the equivalence of their magnetic forces and the null-adjust centering springs. As input current rises, the end of the armature becomes biased either north or south, depending on the direction of the current. The resulting armature movement is determined by the amperage of control current, the spring constant and the differential pressure feedback forces (which seek a torque balance, as explained below). Linearity of the input/output relationship is less than 10% through 80% of rated current.

7 Jan 2019

The magnetic bridge output, the flapper torque, in turn controls the hydraulic bridge ratio. At null, the flapper is centered between two nozzles. Upstream from each nozzle is an orifice which provides a nominal pressure drop when the system is at null. Between the nozzle and the orifice on each side is a control port. As the torque shifts the flapper away from one nozzle towards the other, a differential control pressure results, the high side being the one nearer the flapper.

The PCP is a closed-loop pressure control valve using internal hydraulic pressure reactions to effect an intrinsic feedback. With a step input from the current source, the flapper initially moves towards full stroke to close the (commanded) high-side nozzle. Fluid pressure rises on this side and moves the flapper back towards null. When the torque output from the motor equals the torque output from the pressure feedback, the system is in equilibrium. Deferential pressure is then proportional to command current.