table is available for each frame indicating available swashplate response times. Testing should be
conducted to verify the proper orifice selection for the desired response.
Typical response times at the following conditions:
∆p
250 bar [3626 psi]
Viscosity and temperature
30 mm
2
/s [141 SUS] and 50°C [122 °F]
Charge pressure
24 bar [348 psi]
Speed
1800 min
-1
(rpm)
Response Time
Stroking
direction
0.8 mm [0.03] orifice
1.0 mm [0.04] orifice
1.3 mm [0.05] orifice
28/32
38/45
28/45
38/45
28/45
38/45
Neutral to full
flow
1.5 s
2.2 s
0.9 s
1.4 s
0.6 s
0.8 s
Full flow to
neutral
0.9 s
1.1 s
0.6 s
0.7 s
0.4 s
0.5 s
Non-Feedback, Proportional Hydraulic (NFPH) Control
The Non-Feedback Proportional Hydraulic (NFPH) control is a hydraulic proportional control in which an
input pressure signal directly controls the pump servo piston to achieve pump displacement.
pumps with NFPH control have a special servo cylinder capable of providing proportional control with a
hydraulic input.
Swashplate position is proportional to the differential signal pressure at ports X1 and X2, but
displacement is also dependent on pump speed and system pressure. This characteristic of non-feedback
controls provides a natural power limiting function by reducing the pump swashplate angle as system
pressure increases. The accompanying graph shows typical operating characteristics.
The system may require tuning through the pump orifice combinations, control pressure supply line
sizing, actuation device output pressure and flow adjustments to achieve proper vehicle performance
characteristics.
Non-feedback proportional hydraulic control schematic
M4
M5
L2
X2
X1
Pump Flow Direction with NFPH control
Input Shaft Rotation
CW
CCW
High pressure at port:
X2
X1
X2
X1
Service Manual
MP1
Operation
©
Danfoss | April 2019
AX00000244en-000201 | 29
