Hp Controls; Operation; Functional Description; Hp Control - Danfoss 51 Series Service Manual

Service Manual

HP Controls

Operation

Series 51 Hydraulic Proportional Controls Service Manual

Functional Description

The HP and HC two-line hydraulic proportional controls vary the motor displacement between maximum
and minimum by feeding hydraulic signal pressure to both ends of a piston. A pin connects the piston to
the 4-way valve. A threshold spring and ramp spring(s) act on the opposite end of the 4-way valve.
As deferential pressure moves the piston, it shifts the 4-way valve that ports servo supply pressure to the
ends of the servo piston. A threshold spring and ramp spring(s) act on the opposite end of the 4-way
valve. The threshold adjustment screw varies the threshold spring force and the signal pressure required
to move the 4-way valve and start the change in displacement. The ramp spring(s)—two used in 160 cc
and 250 cc motors, one in 80 cc and 110 cc motors—increases the force on the 4-way valve as the servo
piston moves toward minimum displacement. This provides a motor displacement proportional to the
input signal delta pressure. Optional orifices at locations T1, T2, T3, T7, and T8 regulate shift speed.
HP Schematic Diagram
A
XB XA
B
P101 871

HP Control

The HP control consists of a ported housing that mounts onto the multifunction block. The ported
housing contains a shuttle valve, a piston, a connecting pin, and a bias spring.

Shuttle Valve

The shuttle valve ports higher signal pressure to the top of the piston. It ports lower signal pressure to the
bottom of the piston.

Connecting Pin

The connecting pin links the piston to the 4-way valve. The bias spring holds the piston and pin against
the 4-way valve.
11009446 • Rev BA • July 2014
M4
M3
M1
L1
Max.
displ.
L2
M5
M2
X2 X1
25