Danfoss LDU 20 User manual

Service Manual
LDU 20
Closed Circuit Axial Piston Transmission
powersolutions.danfoss.com

Revision history Table of revisions
Date Changed Rev
July 2017 Updated to Engineering Tomorrow 0202
March 2014 Danfoss layout BA
January 2011 First edition AA
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
2 | ©Danfoss | July 2017 11071687 | AX00000049en-US0202

Introduction Overview..............................................................................................................................................................................................5
Warranty.............................................................................................................................................................................................. 5
General Instructions........................................................................................................................................................................ 5
Remove the unit..........................................................................................................................................................................5
Keep it clean..................................................................................................................................................................................5
Lubricate moving parts.............................................................................................................................................................5
Replace all O-rings and gaskets............................................................................................................................................. 5
Secure the unit.............................................................................................................................................................................6
Safety Precautions............................................................................................................................................................................6
Unintended machine movement..........................................................................................................................................6
Flammable cleaning solvents.................................................................................................................................................6
Fluid under pressure..................................................................................................................................................................6
Personal safety.............................................................................................................................................................................6
Hazardous material.................................................................................................................................................................... 6
Symbols Used in Danfoss Literature..........................................................................................................................................6
General Description Basic Design........................................................................................................................................................................................8
Key Features....................................................................................................................................................................................... 8
Typical Applications........................................................................................................................................................................ 8
System Diagram................................................................................................................................................................................9
Schematic Diagram..........................................................................................................................................................................9
Operation HPRV (High Pressure Relief Valve) ...........................................................................................................................................10
Charge Check Relief Valve with Orifice.............................................................................................................................10
Bypass Function..............................................................................................................................................................................10
CPRV (Charge Pressure Relief Valve)....................................................................................................................................... 11
Control............................................................................................................................................................................................... 12
Direct Displacement Control................................................................................................................................................12
Control Handle Requirements............................................................................................................................................. 12
Operating Parameters Overview........................................................................................................................................................................................... 13
Input Speed......................................................................................................................................................................................13
System Pressure..............................................................................................................................................................................13
Input Power......................................................................................................................................................................................13
Charge Pressure..............................................................................................................................................................................13
Case Pressure...................................................................................................................................................................................14
Viscosity.............................................................................................................................................................................................14
Temperature....................................................................................................................................................................................14
Technical Specifications General Specifications..................................................................................................................................................................15
Physical Properties.........................................................................................................................................................................15
Operating Parameters..................................................................................................................................................................15
Fluid Specifications....................................................................................................................................................................... 15
Fluid and Filter MaintenanceFluid and Filter Recommendations......................................................................................................................................... 17
Pressure Measurements Port Locations and Gauge Installation...................................................................................................................................18
Initial Startup Procedure Startup Procedure..........................................................................................................................................................................19
Troubleshooting Overview........................................................................................................................................................................................... 20
System Operating Hot..................................................................................................................................................................20
Transmission Operates Normally in One Direction Only.................................................................................................20
System will not Operate in Either Direction.........................................................................................................................20
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Contents
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System Noise or Vibration...........................................................................................................................................................21
Sluggish System Response.........................................................................................................................................................21
Required Tools and Standard Procedures
Required Tools................................................................................................................................................................................ 22
Standard Procedures.................................................................................................................................................................... 22
Charge Check/HPRV Adjustments...........................................................................................................................................22
Checking for proper charge check/HPRV operation....................................................................................................22
Minor Repair Shaft Seals.........................................................................................................................................................................................23
Removal........................................................................................................................................................................................23
Inspection....................................................................................................................................................................................23
Assembly......................................................................................................................................................................................23
Charge Check/HPRV......................................................................................................................................................................24
Removal........................................................................................................................................................................................25
Inspection....................................................................................................................................................................................25
Reassembly.................................................................................................................................................................................25
Bypass Valve.....................................................................................................................................................................................25
Removal........................................................................................................................................................................................25
Inspection....................................................................................................................................................................................25
Reassembly.................................................................................................................................................................................25
Torque Chart Plug Size and Torque Chart........................................................................................................................................................27
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Contents
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Overview
This manual includes information on the installation, maintenance, and minor repair of LDU 20 pumps. It
includes a description of the unit and its individual components, troubleshooting information, and minor
repair procedures.
Performing minor repairs may require removal from the vehicle/machine. Thoroughly clean the unit
before beginning maintenance or repair activities. Since dirt and contamination are the greatest enemies
of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially important
when changing the system filter and when removing hoses or plumbing.
A worldwide network of Danfoss Authorized Service Centers is available for major repairs. Danfoss trains
and certifies Authorized Service Centers on a regular basis. You can locate your nearest Authorized
Service Center using the distributor locator at www.sauer-danfoss.com.
Warranty
Performing installation, maintenance, and minor repairs according to the procedures in this manual will
not affect your warranty. Major repairs requiring the removal of the units center section voids the
warranty unless completed by a Danfoss Global Service Partner.
General Instructions
Follow these general procedures.
Remove the unit
Prior to performing major repairs, remove the unit from the vehicle/machine. Chock the wheels on the
vehicle or lock the mechanism to inhibit movement. Be aware that hydraulic fluid may be under high
pressure and/or hot. Inspect the outside of the pump and fittings for damage. Cap hoses and plug ports
after removal to prevent contamination.
Keep it clean
Cleanliness is a primary means of assuring satisfactory pump life, on either new or repaired units. Clean
the outside of the pump thoroughly before disassembly. Take care to avoid contamination of the system
ports. Cleaning parts using a clean solvent wash and air drying is usually adequate.
As with any precision equipment, keep all parts free of foreign materials and chemicals. Protect all
exposed sealing surfaces and open cavities from damage and foreign material. If left unattended, cover
the pump with a protective layer of plastic.
Lubricate moving parts
During assembly, coat all moving parts with clean hydraulic fluid. This assures that these parts are
lubricated during start-up.
Replace all O-rings and gaskets
Danfoss recommends you replace all O-rings, seals, and gaskets during repair.Lightly lubricate all O-rings
with clean petroleum jelly prior to assembly. Grease must be soluable in hydraulic fluid.
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Introduction
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Secure the unit
For major repair, place the unit in a stable position with the shaft pointing downward. It is necessary to
secure the pump while removing and torquing components and fasteners.
Safety Precautions
Always consider safety precautions before beginning a service procedure. Protect yourself and others
from injury. Take the following general precautions whenever servicing a hydraulic system.
Unintended machine movement
W
Warning
Unintended movement of the machine or mechanism may cause injury to the technician or bystanders.
To protect against unintended movement, secure the machine or disable/disconnect the mechanism
while servicing.
Flammable cleaning solvents
W
Warning
Some cleaning solvents are flammable. To avoid possible fire, do not use cleaning solvents in an area
where a source of ignition may be present.
Fluid under pressure
W
Warning
Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious
injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing with
hydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, or
components. Never use your hand or any other body part to check for leaks in a pressurized line. Seek
medical attention immediately if you are cut by hydraulic fluid.
Personal safety
W
Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
Hazardous material
W
Warning
Hydraulic fluid contains hazardous material. Avoid prolonged contact with hydraulic fluid. Always
dispose of used hydraulic fluid according to environmental regulations.
Symbols Used in Danfoss Literature
WARNING may result in injury
CAUTION may result in damage to product or property
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Introduction
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Non-reusable part, use a new part
External hex head
Internal hex head
Lubricate with hydraulic fluid
Apply grease / petroleum jelly
Inspect for wear or damage
Clean area or part
Be careful not to scratch or damage
Note correct orientation
Torque specification
Press in – press fit
Measurement required
Pull out with tool – press fit
Flatness specification
Parallelism specification
Cover splines with installation cylinder
Mark orientation for reinstallation
The symbols above appear in the illustrations and text of this manual. They are intended to communicate
helpful information at the point where it is most useful to the reader. In most instances, the appearance
of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Introduction
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Basic Design
LDU20 is a U-style HST transmission, including a closed circuit variable displacement piston pump with
DDC (Direct displacement control) and a fixed motor. LDU20 is specially designed with optimized
performance, size, and cost, in order to fulfill the demand of the mobile applications marketplace. This
document provides the detailed specifications and features for LDU20.
LDU20 Cross-sectional view
Charge pressure relief valve
High pressure relief valve
Bypass
valve
Ball bearing
Ball bearing
Needle bearing
Output shaft
Working Center section
PTO shaft
Input shaft
Swash plate
Working
P400002
Key Features
•Easy to use design as Complete Hydrostatic Transmission package for Turf care machine & Compact
Utility Tractor of up to 22kw[30PS]
•Compact design
•U-style layout in One housing with Z-shaft configuration
•Available external charge
•Bypass valve for the pulling of the vehicle
•Same shaft center distance as BDU21 85mm…Between pump and motor shaft
•Same drive line design is available between BDU21 and LDU20
•Best in class Efficiency by Female Piston & Male slipper design…Can reach approximately 80% overall
efficiency
•Longer life kit, Higher Duty capability in most compact design in this class of HST
•Low operating force
•Serviced by a Worldwide Network of Danfoss
Typical Applications
•Compact utility tractor
•Turf care
•Small agricultural machinery
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
General Description
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System Diagram
Variable
displacement
pump
Cylinder block
assembly
Input
shaft
Charge pressure Case flow Suction flow
System pressure
Reservoir
Heat exchanger
HPRV valves
Filter
Charge relief
valve
Charge
pump
Heat exchanger
bypass
Fixed
displacement
motor
Output shaft
Cylinder block
assembly
P400003
Schematic Diagram
MA1
MB1
MA2
MB2
L1 L2
L3 S M3
P400004
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
General Description
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HPRV (High Pressure Relief Valve)
LDU20 is equipped with a combination high pressure relief and charge check valve. The high-pressure
relief function is a dissipative (with heat generation) pressure control valve for the purpose of limiting
excessive system pressures. The charge check function acts to replenish the low-pressure side of the
working loop with charge oil. Each side of the transmission loop has a dedicated HPRV valve that is non-
adjustable with a factory set pressure. When system pressure exceeds the factory setting of the valve, oil
is passed from the high pressure system loop, into the charge gallery, and into the low pressure system
loop via the charge check.
The pump order code allows for different pressure settings to be used at each system port. HPRV valve
with orifice is available to gain wider neutral dead-band. When HPRV valves with orifice are used, it is only
for High pressure ports when vehicle goes in reverse. The system pressure order code for pumps with
only HPRV is a reflection of the HPRV setting.
The system pressure order code for pumps configured with pressure limiter and HPRV is a reflection of
the pressure limiter setting.
HPRV settings
HPRV valve without orifice 5 l/min [1.3 US gal/min]
HPRV valve with orifice 17 l/min [4.5 US gal/min]
HPRV (High Pressure Relief Valve)
P400005
C
Caution
HPRV´s are factory set at a low flow condition. Any application or operating condition which leads to
elevated HPRV flow will cause a pressure rise with flow above a valve setting. Consult factory for
application review.
Charge Check Relief Valve with Orifice
As an option, LDU20 offers a charge check relief valve with an orifice in order to enlarge the neutral dead-
band.
In some applications, it is desirable to use charge check valve with orifice for expanding null dead band,
giving both the safety measure to prevent the vehicle movement in the neutral position of the control
shaft and easy adjustment of neutral position when connected to vehicle linkage. The orifice connects
the working loop, which is a main hydraulic circuit, to a charge circuit. It always allows some internal
leakage to ensure the expanding null dead band around neutral position of control shaft. However, it
decreases the volumetric efficiency, particularly at high system pressure in the working loop. It is
recommended to install the orifice in a specific working loop, which is pressurized when the vehicle
moves in reverse. A cross section and characteristics are shown above. The charge check valves with
orifice are available with 0.85mm orifice today. This option is allowable for only high pressure port when
vehicle goes in reverse.
Bypass Function
The LDU20 contains a dedicated bypass valve option. The bypass function is activated when the bypass
valve is mechanically backed out 3 full turns (maximum). The bypass function allows a machine or load to
be moved without rotating the pump shaft or prime mover.
Service Manual
LDU 20 Closed Circuit Axial Piston Transmission
Operation
10 | ©Danfoss | July 2017 11071687 | AX00000049en-US0202