Moog D680 Series - Description of Operation

5Rev. C, April 2017
INTRODUCTION Moog D680 Series Proportional Control Valves
DESCRIPTION OF OPERATION
5
INTRODUCTION
Rev. C, April 2017
Moog D680 Series Proportional Control Valves
DESCRIPTION OF OPERATION
Proportional Control Valves
Electric Feedback Valves
The Moog D680 Series Proportional Control Valves are
closed-loop hydraulic products that are used in industrial
machinery. These valves are electrical feedback valves,
which means that the position control loop for the main
stage spool, the position transducer and the pilot valve is
closed by the integrated valve electronics.
An electric command signal (spool position set point) is
applied to the valve electronics. A position transducer
(LVDT) measures the actual position of the spool. The
electronics compare the spool position and the command
signal and control the Pulse Width Modulated (PWM)
current to the linear force motor of the Direct Drive Pilot
Valve D633. The pilot valve moves the main stage spool to
the desired position. Thus, the position of the main stage
spool is proportional to the electric command signal.
Main Stage Version
For D683 and D684 (size 08 valves), Moog offers two
different versions of the main stage: Standard spool or
stub shaft spool.
With standard spools, the main stage spool is directly
driven by the pilot oil, which means the whole spool
diameter is exposed to the pilot pressure. This leads to
high control forces due to the large pressurized area, but
it also means that a large amount of pilot flow is needed to
move the main stage spool.
With stub shaft spools, the main stage spool is driven by
additional pistons which have a smaller diameter than the
main stage spool. This lowers the control forces, but also
reduces the amount of pilot flow needed to move the main
stage spool.
For the Moog D683 and D684 series valves, the pilot
valves for both the standard and the stub shaft spool
versions have the same rated flows. This means that
the stub shaft version reaches significantly lower step
response times for large signal changes.
D681 Proportional Control Valve with D633 Pilot Valve
D683/D684 Proportional Control Valve with standard spool
D683/D684 Proportional Control Valve with stub shaft spool
1 Direct Drive Pilot Valve D633
2 Valve connector
3 Position transducer (LVDT)
4 Ports
5 Spool
X YT A P B
T
V
B
V
P
V
A
V
1 5
2
3
4
X YT A P B
T
V
B
V
P
V
A
V
2
3
4
51
T
V
B
V
P
V
A
V
XX YT A P T
1
B
1
2
3
5
4