Response Time; Non-Feedback, Proportional Hydraulic (Nfph) Control - Danfoss MP1 Service Manual

Service Manual
MP1
Operation

Non-Feedback, Proportional Hydraulic (NFPH) Control

© Danfoss | April 2019
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
Viscosity and temperature
Charge pressure
Speed

Response Time

Stroking 0.8 mm [0.03] orifice
direction
28/32
Neutral to full 1.5 s
flow
Full flow to 0.9 s
neutral
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
Pump Flow Direction with NFPH control
Input Shaft Rotation
High pressure at port:
250 bar [3626 psi]
2
30 mm /s [141 SUS] and 50°C [122 °F]
24 bar [348 psi]
-1
1800 min (rpm)
1.0 mm [0.04] orifice
38/45 28/45
2.2 s 0.9 s
1.1 s 0.6 s
X1 X2
L2
M5
M4
CW
X2
1.3 mm [0.05] orifice
38/45 28/45
1.4 s 0.6 s
0.7 s 0.4 s
CCW
X1 X2
AX00000244en-000201 | 29
38/45
0.8 s
0.5 s
X1