Control Options; Pc Control - Danfoss 45 J Series Service Manual

Service Manual
Features (continued)

Control Options

12
Series 45 J Frame Open Circuit Axial Piston Pumps
The Series 45 Frames J have three possible general control options, a Load Sensing (LS) control with
Pressure Compensator (PC), a PC only control, or an electric control.
Operation
The bias spring (1) pushes against the servo
piston (2) which pulls the swashplate (3) to max
angle causing the pump to stroke. Internal
pressure on the servo piston acts against the bias
spring to reduce the swashplate angle causing
the pump to destroke. Swashplate angle
determines pump outlet flow. The pump control,
depending on conditions in the system circuit,
sets swashplate angle by metering system
pressure to the servo piston.

PC control

The PC control design maintains a constant
pressure in the hydraulic circuit as flow varies.
The PC control modulates pump flow accordingly
to maintain system pressure at the PC setting as
the PC adjusting plug (4) and spring (5) defines.
When system pressure, acting on the non-spring
end of the PC spool (6), overcomes the force of
the PC spring, the spool shifts porting system
pressure to the servo piston and the swashplate
angle decreases. When system pressure drops
below the PC setting, the PC spring shifts the
spool in the opposite direction connecting the
servo piston to pump case and the swashplate
angle increases. The swashplate is maintained at
whatever angle is required to keep system
pressure at the PC setting.
520L0607 • Rev AI • Sep 2013
Cross-section pump
2 1 3
Bias spring and servo piston set swashplate position
Cross-section PC control
6 5
PC spool shifts to port system pressure to servo
piston
P104 360
4
P104 049