Sauer Danfoss 51 Series User manual

Series 51
Bent Axis
Variable Motors
Service Manual

Bent Axis Variable Displacement Motors Series 51
2
●The Series 51 - Advanced Technology Today
●The Most Technically Advanced Hydraulic Units in the Industry
●SAE Flange and Cartridge Motors
●Cartridge Motors designed for Direct Installation in Compact
Planetary Drives
●Large Displacement Ratio (5:1)
●Complete Family of Control Systems
●Proven Reliability and Performance
●Optimum Product Configurations
●Compact, Lightweight
Motorsequippedwithcontrolsnormallystartatmaxi-
mumdisplacement. Thisprovidesmaximumstarting
torque (high acceleration).
The controls may utilize externally or internally sup-
plied servo pressure. They may be overridden by a
pressure compensator which functions when the
motor is operating in motor and pump modes. A
defeat option is available to disable the pressure
compensator override when the motor is running in
pump mode.
The pressure compensator option features a low
pressure rise (short ramp) to provide optimal power
utilization throughout the entire displacement range
of the motor. The pressure compensator is also
available as a stand-alone regulator.
Series 51 Variable Displacement Motors are bent
axis design units, incorporating spherical pistons.
Thesemotorsaredesignedprimarilytobecombined
withotherproductsinclosedcircuitsystemstotrans-
fer and control hydraulic power.
Series 51 Motors have a large maximum / minimum
displacement ratio (5 to 1) and high output speed
capabilities.SAEflangeandcartridgemotorconfigu-
rations are available.
A complete family of controls and regulators is avai-
lable to fulfill the requirements of a wide range of
applications.
Front page: Option - hydraulic two-position control
Copyright 1992-1997, Sauer-Sundstrand Company.
All rights reserved. Contents subject to change. Printed in U.S.A. 0992H
General Description

Bent Axis Variable Displacement Motors Series 51
3
Contents
Introduction ......................................................................................................................................................4
Basic Hydraulic Circuits ...................................................................................................................................4
General Description of the Series 51 Variable Displacement Motors ..............................................................5
Functional Description......................................................................................................................................6
Technical Specifications and Data - Variable Displacement Motors ..............................................................20
Safety Precautions .........................................................................................................................................21
Gauge Installation ..........................................................................................................................................23
Start-Up Procedure and Maintenance............................................................................................................25
Component Inspection and Adjustment .........................................................................................................27
Troubleshooting .............................................................................................................................................37
Exploded View of the Series 51 Variable Motor .............................................................................................41
Minor Repair and Replacement - Variable Motor...........................................................................................51
General .....................................................................................................................................................51
Shaft Seal (SAE Flange Configuration) ....................................................................................................52
Shaft Seal (Cartridge Configuration).........................................................................................................53
Loop Flushing Shuttle Valve (Option)........................................................................................................54
Charge Pressure Relief Valve...................................................................................................................55
MinimumAngle Servo Cover ....................................................................................................................55
Hydraulic 2-Position Control (Type N2).....................................................................................................56
Electrohydraulic 2-Position Controls (Types E1•E2 and F1•F2) ...............................................................57
Electric 2-Position Controls (Type S1) ......................................................................................................58
Hydraulic Proportional Control (Type HZ) .................................................................................................59
Hydraulic Proportional Control (Type HS).................................................................................................60
Hydraulic Proportional Control with MaximumAngle Over-ride (Types H1•H2 or K1•K2) ........................61
Two Connection Hydraulic Proportional Control (Type HP) ......................................................................62
Two Connection Hydraulic Proportional Control for “Dual Path” Vehicles (Type HC) ...............................64
Electrohydraulic Proportional Control (Types EP and EQ)........................................................................68
Pressure Control Pilot (PCP) Valve for Electrohydraulic Proportional Control (Types EP and EQ)..........70
Multi-function Block...................................................................................................................................71
Pressure Compensator Regulator (Type PC) ...........................................................................................76
Control Orifices .........................................................................................................................................77
Plug / Fitting Torques ................................................................................................................................77
0 - 1

Bent Axis Variable Displacement Motors Series 51
4
Introduction
Dirt or contamination is the greatest enemy of any
type of hydraulic equipment. The greatest possible
cleanliness is necessary when starting up the sys-
tem,changingfilters,or performinganyotherservice
procedure.
For Technical Information on Series 51 motors, refer
to publication BLN-10042 or 368753.
For Fluid Quality Requirements, refer to publication
BLN-9987 or 697581.
Sauer-Sundstrand provides a complete repair serv-
ice for its products. Contact any Sauer-Sundstrand
Authorized Service Center for details. Sauer-Sund-
strandAuthorizedServiceCenterlocationsarelisted
in publication BLN-2-40527 or 698266.
The purpose of this manual is to provide information
necessary for the normal servicing of the Series 51
family of variable displacement hydrostatic motors.
This manual includes unit and component descrip-
tion, troubleshooting, adjustments, and minor repair
procedures. By following the procedures in this
manual, inspections and minor repairs may be per-
formed without affecting the unit warranty.
A Series 51 motor does occasionally require servic-
ing,andtheseunitsaredesignedtomeetthisrequire-
ment.
Many repairs or adjustments can be completed with-
out removing the unit from the vehicle or machine,
providedtheunitisaccessibleandcanbethoroughly
cleaned before beginning any procedures.
INPUT PV MV
CASE
DRAIN
LINE
OUTPUT
FLOW (BI-DIRECTIONAL)
RESERVOIR
51000001
Fig. 0-1 - Basic Closed Circuit
Closed Circuit
Themainportsofthepumpareconnectedbyhydrau-
lic lines to the main ports of the motor. Fluid flows in
eitherdirectionfromthe pumptothemotorthen back
tothepumpinthisclosedcircuit.Eitherofthehydrau-
lic lines can be under high pressure. The direction
and speed of fluid flow (and the motor output shaft
rotation)dependsonthepositionofthepumpswash-
plate. The system pressure is determined by the
machine load.
Open Circuit
Theoutletportofthepumpisconnectedbyahydrau-
liclinetoadirectionalcontrolvalve.Theworkingports
of this valve are connected to the main ports of the
motor. When the valve is actuated, fluid flows first
fromthepumptothevalve.Thevalvethendirectsthe
fluid to the motor in either direction. The direction of
fluid flow (and motor output shaft rotation) depends
onthedirectionthecontrolvalveisshifted.Thespeed
of fluid flow (and motor output shaft speed) depends
on pump output volume and the distance the control
valve is shifted. The system pressure is determined
by the machine load.
Fluid returning from the motor is routed through the
controlvalve tothereservoir. Additionalcomponents
maybe necessarytoprovide dynamicbrakingandto
deal with over-running loads.
Basic Hydraulic Circuits
51000002
Fig. 0-2 - Basic Open Circuit
INPUT PUMP MV
CASE
DRAIN
LINE
OUTPUT
FLOW
(BI-DIRECTIONAL)
RESERVOIR
FLOW
(UNI-DIRECTIONAL)
CONTROL VALVE
0 - 2

Bent Axis Variable Displacement Motors Series 51
5
General Description of the Series 51 Variable Displacement Motors
The Series 51 variable displacement hydraulic mo-
torsusesphericalpistonsandpistonrings. Theangle
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
butatminimumdisplacement,theshaftspeed willbe
approximatelyfive(5)timesfasterwhiletheavailable
outputtorquewilldecreasetoapproximatelyone-fifth
(1/5) the full displacement value. The displacement
is changed by a servo piston which is connected to
the valve segment.
Various hydraulic and electrohydraulic controls may
bemountedonthemotorendcaptocontroltheservo
piston and the motor displacement. Servo pressure
oilmayeitherbesuppliedinternallyfromthemotor,or
externally.
ForallcontrolsexcepttheN2andPC,servopressure
oilissuppliedtoafour(4)wayspoolvalveinthemotor
end cap. When a combination of pilot pressure (or
force)fromanexternal controlassemblyandinternal
springforceshiftsthisvalve,servopressureisrouted
to move the servo piston and change the motor’s
displacement.
Asynchronizingshaft,withsphericalrollers,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.
Twotaperedroller bearings support the output shaft.
Fig. 10-1 - Sectional view of Series 51 variable displacement motor (SAE Flange
Configuration) with Hydraulic Proportional Control
P001 196
Pressure Compensator
Override
Servo Piston
Cylinder
Charge Pressure
Relief Valve
Piston Synchronizing
Shaft
Tapered Roller Bearings
Bearing Plate
Valve Segment
Hydraulic
Proportional
Control
Minimum
Displacement Limiter
Control
Pressure
Port
10 - 1

Bent Axis Variable Displacement Motors Series 51
6
Functional Description
Fig. 10-2 - Loop
Flushing
Components
Loop Flushing
Series 51 motors used in closed circuit applications
incorporate an integral loop flushing valve as stan-
dard equipment. Installations that require additional
fluid to be removed from the main hydraulic circuit
because of fluid cooling requirements, or circuits
requiring the removal of excessive contamination
from the high pressure circuit, can benefit from loop
flushing. Series 51 motors used in open circuit appli-
cations may have the optional loop flushing defeat
components installed.
Series 51 motors equipped with an integral loop
flushing valve also include a charge pressure relief
valve. The setting of the motor charge relief valve
affects the function of the flushing circuit. Higher
motor charge relief settings reduce the loop flushing
flow and increase the flow over the pump charge
pressure relief valve when the circuit is operating.
Lower motor charge relief settings increase the loop
flushing flow and may increase the motor case pres-
sure when the circuit is operating.
Anappropriatecombinationofpumpandmotorcharge
pressure settings should be maintained to insure the
proper function of the loop flushing circuit. Correct
chargepressuremustbe maintainedunderallcondi-
tions of operation to maintain pump control perfor-
mance in closed loop systems.
NOTE: An optional orifice may be installed between
themotorcharge relief and the motor caseto
limit the maximum flushing oil flow.
51000003 Fig. 10-3 - Loop
Flushing Defeat
Components
51000004
10 - 2

Bent Axis Variable Displacement Motors Series 51
7
Functional Description (Continued)
Fig. 10-4 - Minimum Displacement Limiter
with Tamper Resistant Cap (Cartridge
Motor Configuration Shown)
Fig. 10-6 - Internal Servo Pressure Supply
Screen with Multi-function Block and/or
Control Removed (Plug for External
Supply)
5100007
Fig. 10-7 - External Servo Pressure Supply
Fitting (Plug for Internal Supply)
51000008
Fig. 10-5 - Maximum Displacement Limiter
Screw
51000006
51000005
Displacement Limiters
All Series 51 motors incorporate mechanical dis-
placement limiters. The minimum displacement of
themotorcanbe limitedwithinthestandardrange by
a set screw in the motor housing. The maximum
displacementcanbelimitedwithspacersinstalledon
the servo piston.
Controls - General
A wide range of control options is available for the
Series 51 motors. These include pilot operated
Electrohydraulic 2-Position Controls, Hydraulic Pro-
portional Controls (single or two [2] connection), and
ElectrohydraulicProportionalControls.Adirectlyop-
erated Hydraulic 2-Position Control and a Pressure
Compensator regulator are also available.
The Series 51 variable motor servo piston (except
when equipped with N2 control or the PC regulator)
maybeoperatedeitherbyservopressureoilsupplied
internallyfromthemainportsofthemotor,orbyservo
pressure oil supplied from an external source. (The
N2control usesservopressure suppliedbyanexter-
nal control valve. The PC regulator obtains servo
pressure from the main ports of the motor.)
Orifice plugs are installed in the control spool sleeve
intheendcaptoregulatetheflowofoilfromtheservo
piston to the motor housing. Orifice plugs may be
installed in the end cap to regulate the flow of servo
pressure supply oil to the control valve, and to regu-
late the flow of oil from the control valve to the servo
piston.
10 - 3

Bent Axis Variable Displacement Motors Series 51
8
Fig. 10-8 - Series 51 Motor with N2 Control
Hydraulic 2-Position Control (Type N2)
This is a two (2) position (maximum - minimum
displacement) control, consisting of a cover plate
mounted on the end cap. An external control valve
supplies servo pressure from an external source
directly to the servo piston. PCOR is not available
with the N2 control.
When servo pressure is supplied to port “Y1,” the
settingpistonmovestothemaximummotordisplace-
ment position. When servo pressure is supplied to
port “Y2,” the setting piston moves to the minimum
motor displacement position.
Orificesmaybeinstalled in the external control valve
or its connections to regulate the speed of servo
piston movement.
Functional Description (Continued)
51000011
Fig. 10-10 - N2 Control Schematic
U4 (opt.)
max.
disp.
M2
M1
(M4) Y1 Y2 (M3)
M6
L2
B
A
L1

Fig. 10-9 - N2 Control Components 51000010
51000009
10 - 4

Bent Axis Variable Displacement Motors Series 51
9
Functional Description (Continued)
51000013
Fig. 10-11 - Series 51 Motor with E1•E2 or
F1•F2 Control
51000012
Fig. 10-12 - E1•E2 and F1•F2 Control
Components
X3 (M5)
Servo press,
external
M9
U5
(plug for
ext. servo
press.) T1
T7,
T8
T2
T3
max.
disp.
B1
A1
M2
M1
M4 M3M6
L2
B
A
Servo
Pressure
internal L1
E1•E2
M7
M8
U4 (opt.)
F1•F2
51000014
Fig. 10-13 - E1•E2 and F1•F2 Control
Schematic
Electrohydraulic 2-Position Control (Types
E1•E2 and F1•F2)
A12or24VDCsolenoidvalve,mountedonthemulti-
function block, connects the end of the control valve
spool in the end cap with pilot pressure (provided by
the shuttle spool in the multi-function block) or with
the motor case. The control valve in the end cap is
biased by a threshold spring, and controls oil flow to
theendsofthe servo piston. Servo pressure may be
supplied from an external source or internally by the
shuttle spool in the multi-function block. PCOR is
available with these controls.
With the E1 and E2 controls, energizing the solenoid
will cause the motor to shift to minimum displace-
ment. Whenthe solenoid isnotenergized,the motor
is held at maximum displacement.
With the F1 and F2 controls, energizing the solenoid
causes the motor to shift to maximum displacement.
Whenthesolenoidisnotenergized,themotorisheld
at minimum displacement.
10 - 5

Bent Axis Variable Displacement Motors Series 51
10
Functional Description (Continued)
Electric 2-Position Control (Type S1)
A 12 VDC solenoid valve, mounted on the multi-
function block, directly operates the control valve
spoolintheend cap.Thecontrolvalvein theendcap
is biased by a threshold spring, and controls oil flow
to the ends of the servo piston. Servo pressure may
be supplied from an external source or internally by
theshuttlespoolinthemulti-functionblock. PCORis
available with this control.
With the S1 control, energizing the solenoid causes
the motor to shift to maximum displacement. When
the solenoid is not energized, the motor is held at
minimum displacement.
51000163
Fig. 10-14 - Series 51 Motor with S1 Control
51000162
Fig. 10-15 - S1 Control Components
X3 (M5)
Servo press,
external
M9
U5
(plug for
ext. servo
press.) T1
T7,
T8
T2
T3
max.
disp.
B1
A1
M2
M1
M4 M3M6
L2
B
A
Servo
Pressure
internal L1
S1
U4 (opt.)
51000085
Fig. 10-16 - S1 Control Schematic
10 - 6