General Description Of The Series 51 Variable Displacement Motors - Sauer Danfoss 51 Series Service Manual

Bent Axis Variable Displacement Motors

General Description of the Series 51 Variable Displacement Motors

The Series 51 variable displacement hydraulic mo-
tors use spherical pistons and piston rings. The angle
between the cylinder block and the output shaft can
be set between 32° and 6°, providing a 5 to 1
maximum to minimum displacement ratio.
At maximum displacement, the motor will provide a
certain maximum output shaft torque and minimum
speed corresponding to the pressure and flow sup-
plied to the motor. Under the same input conditions
but at minimum displacement, the shaft speed will be
approximately five (5) times faster while the available
output torque will decrease to approximately one-fifth
(1/5) the full displacement value. The displacement
is changed by a servo piston which is connected to
the valve segment.
Hydraulic
Proportional
Control
Control
Pressure
Port
Fig. 10-1 - Sectional view of Series 51 variable displacement motor (SAE Flange
Configuration) with Hydraulic Proportional Control
10 - 1
Minimum
Displacement Limiter
Pressure Compensator
Override
Servo Piston
Cylinder
Charge Pressure
Relief Valve
Various hydraulic and electrohydraulic controls may
be mounted on the motor end cap to control the servo
piston and the motor displacement. Servo pressure
oil may either be supplied internally from the motor, or
externally.
For all controls except the N2 and PC, servo pressure
oil is supplied to a four (4) way spool valve in the motor
end cap. When a combination of pilot pressure (or
force) from an external control assembly and internal
spring force shifts this valve, servo pressure is routed
to move the servo piston and change the motor's
displacement.
A synchronizing shaft, with spherical rollers, synchro-
nizes the rotation of the output shaft and the cylinder
block. The ball end of each piston runs in a socket
bushing, pressed into the output shaft. There are no
other parts used to connect the pistons to the shaft.
Two tapered roller bearings support the output shaft.
Valve Segment
Bearing Plate
Tapered Roller Bearings
Piston
Series 51
Synchronizing
Shaft
P001 196
5