Warning
Unintended MOR operation will cause the pump to go into stroke.
Hydraulic Displacement Control (HDC), Option HF
Warning
Avoid designing a system which puts swashplate into full stroke when control operation is blocked by
contamination.
Operation
The hydraulic displacement control uses a hydraulic input signal to operate a 4-way servo valve, which
ports hydraulic pressure to either side of a double acting servo piston. The servo piston tilts the cradle
swashplate, thus varying the pump's displacement from full displacement in one direction to full
displacement in the opposite direction.
The control has a mechanical feedback mechanism which moves the servo valve in relation to the input
signal and the angular rotation of the swashplate. The hydraulic displacement control is designed so the
angular position of the swashplate (pump displacement) is proportional to the hydraulic input signal
pressure. Due to normal operating force changes, the swashplate tends to drift from the position preset
by the machine operator. Drift, sensed by feedback linkage system connecting the swashplate to the
control valve, activates the valve to supply pressure to the servo piston, maintaining the swashplate in its
preset position.
Features and Benefits
•
The hydraulic displacement control is a high gain control: With only small change of the input signal,
the servo valve moves to a full open position porting maximum flow to the servo cylinder.
Technical Information
Series 90 Axial Piston Pumps
Control Options
32 520L0603 • Rev 0804 • March 2016
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