Under some circumstances, such as contamination, the control spool could stick and cause the pump to
stay at some displacement.
For the MDC with CCO option the brake port (X7) provides charge pressure when the coil is energized to
activate static function such as a brake release. The X7 port must not be used for any continuous oil
consumption.
The MDC is sealed by means of a static O-ring between the actuation system and the control block. Its
shaft is sealed by means of a special O-ring which is applied for low friction. The special O-ring is
protected from dust, water and aggressive liquids or gases by means of a special lip seal.
Manual Displacement Control
Pump displacement vs. control lever rotation
"0"
Lever rotation
"A"
Displa
ceme
nt
100 %
a
-a
100 %
"B"
-b
-d
b c
d
-c
P301 752
Deadband on B side: a = 3° ±1°
Maximum pump stroke: b = 30° +2/-1°
Required customer end stop: c = 36° ±3°
Internal end stop: d = 40°
MDC Operation
The MDC provides a mechanical dead-band required to overcome the tolerances in the mechanical
actuation. The MDC contains an internal end stop to prevent turning the handle into any inappropriate
position.
The MDC provides a permanent restoring moment appropriate for turning the MDC input shaft back to
neutral position only. This is required to take the backlash out of the mechanical connections between
the Bowden cable and the control.
C
Caution
High case pressure may cause excessive wear and the NSS to indicate that the control is not in neutral
position. In addition, if the case pressure exceeds 5 bar there is a risk of an insufficient restoring moment.
The MDC is designed for a maximum case pressure of 5 bar and a rated case pressure of 3 bar.
•
Customers must install some support to limit the setting range of their Bowden cable to avoid an
overload of the MDC.
•
Customers can apply their own handle design but they must care about a robust clamping
connection between their handle and the control shaft and avoid overload of the shaft.
•
Customers can connect two MDC’s on a tandem unit in such a way that the actuation force will be
transferred from the pilot control to the second control. The kinematic of the linkages must ensure
that either control shaft is protected from torque overload.
C
Caution
Using the internal spring force on the input shaft is not an appropriate way to return the customer
connection linkage to neutral, or to force a Bowden cable or a joystick back to neutral position. It is not
applicable for any limitation of the Bowden cable stroke, except the applied torque to the shaft will never
exceed 20 N•m.
Service Manual
H1P 069—H1P 250 Axial Piston Single Pumps
Operation
©
Danfoss | September 2020
AX152886482551en-000504 | 17