A wide range of Steering Components....................................................................................................................................4
Survey of literature with technical data on Danfoss Steering Components...............................................................6
OSPU general information............................................................................................................................................................ 6
Steering with normal pump supply...........................................................................................................................................9
Displacement, amplification, flow and pressure: OSPU LS ............................................................................................12
A minimum standby pressure..............................................................................................................................................12
Valve functions in OSPU LS steering units............................................................................................................................14
Pilot pressure relief valve; (P - T, Qp) characteristic...........................................................................................................15
Check valve in P..............................................................................................................................................................................16
Check valve function in LS..........................................................................................................................................................16
Port thread versions for OSPU LS............................................................................................................................................. 17
Order specifications...................................................................................................................................................................... 20
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 3
Technical Information
OSPU Steering Unit
A wide range of Steering Components
A wide range of Steering Components
Danfoss is one of the largest producers in the world of steering components for hydrostatic steering
systems on off-road vehicles. Danfoss offers steering solutions both at component and system levels. Our
product range makes it possible to cover applications of all types - ranging from ordinary 2-wheel
steering (also known as Ackermann steering) to articulated steering, automatic steering (e.g. by sensor)
and remote controlled steering via satellite. We can offer more than 1,800 different steering units and 250
different priority valves categorized in types, variants and sizes.
For hydrostatic steering systems Danfoss offers:
•
Mini steering units with displacements from 32 to 100 cm3/rev [1.95 to 6.10 in3/rev], flow up to 20
l/min [5.28 US gal/min], steering pressure up to 140 bar [2030 psi].
•
Steering units with displacements from 40 to 1200 cm3/rev [2.44 to 73.2 in3/rev], flow up to 100 l/min
[26.4 US gaL/min, steering pressure up to 240 bar [3481 psi].
•
Priority valves for rated flows at 40, 80, 120, 160 and 320 l/min [10.6, 21.1, 31.7, 42.3 and 84.5 US gal/
min], pressure up to 350 bar [5076 psi].
•
Pilot operated flow-amplifiers with amplification factors of 4, 5, 8, 10 or 20 for rated oil flows of 240
and 400 l/min [63.4 and 105.7 US gal/min], steering pressure up to 210 bar [3045 psi].
•
Pilot operated steering valve with steering flow up to 100 l/min [26.4 US gal/min], steering pressure
up to 250 bar [3625 psi] and with integrated priority valve for pump flow up to 120 l/min [31.7 US gal/
min].
For electrohydraulic steering systems Danfoss offers:
•
Pilot operated steering valves (pilot operated by hydrostatic steering unit or by electrical signal) with
steering flows up to 100 l/min [26.4 US gal/min], steering pressure up to 250 bar [3625 psi].
•
Steering units with integrated electrical operated steering valve with steering flow up to 50 l/min
[13.2 US gal/min], steering pressure up to 210 bar [3045 psi].
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 5
Technical Information
OSPU Steering Unit
Technical literature survey
Survey of literature with technical data on Danfoss Steering Components
Detailed data on all Danfoss steering components and accessories can be found in our steering
component catalogues, which is divided in to the following individual sub catalogues:
General informationSteering components
Technical data on mini steering unitsOSPM
Technical data on open center, and closed center steering unitsOSPB, OSPC, and OSPD
Technical data on load sensing steering units, priority valves and flow
amplifiers
Technical data on hydraulic and electrohydraulic pilot operated steering
valves, electrical actuation modules and appropriate steering units.
Technical data on combined steering unit/electrohydraulic steering valves
and steering wheel sensors
Technical data on load sensing steering unit with amplificationOSPU
For technical information on individual variants, please contact the Danfoss Sales Organization.
OSPU general information
OSPU is a flow amplifying, load sensing steering unit, available with amplification factors 2, 3, or 4. OSPU
is a cost-attractive dual displacement steering unit alternative for heavier applications needing reduced
displacement for emergency (manual) steering, such as tractors, backhoe loaders, telehandlers, and
combines.
The OSPU total displacement ranges from 120-500 cc in normal steer mode (amplified). In emergency
steer mode the displacement ranges from 60-125 cc/rev. The standard OSPU has fully linear flow
characteristic (flow versus rpm).
OSPU is also available in a version with continuous progressive amplification factor. This feature will make
a simple “Fast Steer” steering system possible: it enables higher ratio steering flow at higher rpm
meaning less turns lock-lock at higher steering speed. This feature is especially attractive on backhoe
loaders and small wheel loaders.
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 7
A
5
A
4
A
3
A
2
A
1
A
u
A
d
A
1-5,d,u
P
T
LS
LR
P301 479
2
1
3
4
5
6
8
9
7
10
P301 480
T
LS
LR
P
2
1
3
4
5
6
7
8
10
9
Technical Information
OSPU Steering Unit
Function
Function, OSPU LS
Designation of OSPU elements
ItemDescription
1Shock valves
2Suction valves
3Torque compensator valve
4Emergency steering check valve
5Pilot pressure relief valve
6P-check valve
7Spool/sleeve set: including bleeds, A1-A5, Au and Ad
8Gear set
9LS copy valve
10Priority valve, dynamic type
OSPU Danfoss symbols
OSPU ISO-symbols
The OSPU is a Load Sensing Dynamic steering unit type with built in amplification function in the spool/
sleeve set (7).
The main circuit is identical to other OSP LS steering units like e.g. OSPC: Bleeds of spool/sleeve set (7):
A1-A5 and Ad plus gear set (8).
Additionally the OSPU includes an amplification circuit containing the Au bleed in spool/sleeve/set (7)
and a torque compensator valve (3).
Furthermore the OSPU contains a LS copy valve (9). This valve is needed to be able to use dynamic
priority valve.
Neutral position
The drain bleed Ad of spool/sleeve set (7) is open to tank. All other bleeds, A1-A5 and Au are closed.
When the pump runs, the dynamic flow from the LS line of the priority valve (10) will stream across the LS
copy valve (9) to tank.
When turning the steering wheel, the drain bleed Ad will be closed, and all other bleeds, A1-A5 and Au
will open in parallel. Opening area will depend on steering wheel speed. Pressure in LS line will rise
according to steering pressure demand: pressure will be transmitted across the LS copy valve (9) and the
priority valve (10) will supply the requested oil flow and pressure to P port of the steering unit.
The pump oil flow will be split between the parallel connected inlet bleeds: A1 and Au. The oil flow across
A1 is determined by the size of the gear set (8) and the steering wheel speed. The oil flow across Au is
determined by the opening area of Au. The amplification will be constantly independent on steering
speed under normal steering conditions: pump flow and standby pressure must be within demand for
the requested steering speed.
The function of the torque compensator valve (3) is to assure constant amplification: in case pressure
drop may occur across the gear set (8) e.g. due to dirt particles entering the steering unit, the torque
compensator valve (3) will generate the same pressure drop for the amplified oil.
When steering against end stroke, the steering pressure will be limited by the pilot pressure relief valve
(5): pressure in LS line will be limited and so the priority valve will lead the pump flow to EF port of the
priority valve and on to tank.
Emergency steering: Failing pump supply
When pressure in P-port does not match the steering pressure requested, the gear set (8) will act as a
hand pump, when torque is applied to the steering wheel. The displacement for emergency steering is
purely determined by the size of the gear set (8). The check valve function of the torque compensator
valve (3) will prevent back stream of oil across the Au bleed.
When pump flow becomes insufficient, the emergency steering check valve (4) will open and oil will be
led to the gear set (8) from return side of cylinder, additional flow will be sucked from tank as needed.
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 9
Technical Information
OSPU Steering Unit
Versions
OSPU LS
Load sensing dynamic
In load sensing steering systems both the steering system and the working hydraulics can be supplied
from just one pump. In addition LS steering systems make energy saving possible by the use of an LS
pump.
Load sensing steering units have a connection for load sensing (LS), so that a load pressure signal can be
directed via the steering unit to a Danfoss priority valve and/or an LS pump. The load sensing signal
controls the oil flow from the priority valve (and/or the LS pump) to the steering unit.
OSPU are all of load sensing dynamic type and require load sensing dynamic priority valves and/or load
sensing variable displacement pumps with “dynamic” control. Load sensing dynamic steering systems
have a constant oil flow in the LS connection direction steering unit also when the steering unit is in
neutral position.
Non-reaction
With non-reaction steering units there is no corresponding movement of the steering wheel when the
driver is not steering the vehicle.
Amplification, linear
The displacement is constant over the entire range of normal steering speed, 0-100 rpm.
Amplification, progressive
The displacement varies over the entire range of normal steering speed, 0-100 rpm.
Steering unitAmplificationMin. standby pressure*, P-LS bar [psi]
For max steering speed
80 rpm
OSPU 125/375 LS31113- - OSPU 125/500 LS4
*
Values valid for viscosity range 12-80 mm²/s [66-370 SUS] and temperature range of 30-60°C [86-140°F]
18- - -- - -
Missing values will be added when available.
Amplification characteristics
OSPU with linear amplification has constant displacement independent on steering speed inside normal
steering speed range, 0-100 rpm, e.g. OSPU 100/200 LS “Linear” has 200 cm³/rev.
In OSPU with progressive amplification the displacement varies over the entire range of normal steering
speed, 0-100 rpm. OSPU 100/200 LS “Progressive” has the following nominal displacements:
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 13
Metered out flow for OSPU 100 shown with amplification factors possible.
The steering unit can be used as a hand pump if oil supply to the steering unit fails.
Below graph can be used as a design guide to choose the needed size of gear set for the OSPU:
•
Determine steering pressure required for the emergency steering maneuver and draw a horizontal
line from this value for Pressure
•
Determine manual input torque allowed on steering wheel and draw a vertical line from this value for
Torque
•
The largest steering unit displacement suitable is the first angled line to the left of intersection. An
example is shown w. 25 bar [362 psi] pressure demand, and 38 Nm [336 lbf•in] allowed manual input
torque: OSPU 80/xxx, OSPU 70/xxx or OSPU 60/xxx are suitable to build up enough pressure for
emergency steering.
1100
1000
900
800
700
600
500
400
300
200
100
0
0100 200 300 400 500 600 700 800 900
Pressure,
[psi]
[lfb•in]
P301 483
0
10
20
30
40
50
60
70
80
020406080100
60
70
80
100
125
Bar
Torque,
Nm
Gear set size:
P
T
LS
LR
P301 481
2
1
3
4
5
6
7
Technical Information
OSPU Steering Unit
Technical data
OSPU LS emergency steer curves
Valve functions in OSPU LS steering units
Only physical testing on the vehicle in question can verify if the demands for emergency steer capability
will be fulfilled.
All OSPU have the following valves build in as standard:
•
Emergency steering check valve (4)
•
P-check valve (7)
•
Check valve function in LS:
LS copy valve (5)
•
Suction valves (2)
•
Torque compensator valve (3)
OSPU can have built in the following valves (option):
Pilot pressure relief valve; (P - T, Qp) characteristic
The pilot pressure relief valve protects the steering unit against excessive pressure. The pilot pressure
relief valve in the OSPU LS steering unit together with the priority valve limits the maximum steering
pressure P-T. The pilot pressure relief valve is set at an oil flow to the priority valve of 25 l/min [6.60 US
gal/min].
For OSPU Load Sensing dynamic steering units, the setting values are valid at a dynamic flow of 1.1 l/min
[0.29 US gal/min]
Setting tolerance:
</= 170 bar [2645 psi]: rated value +5 bar [72.5 psi].
> 170 bar [2645 psi]: rated value +10 bar [145 psi].
Danfoss | March 2016L1313806 | BC00000222en-US0202 | 15
The shock valves protect the steering unit and reduce external forces on the steering cylinder by limiting
the pressure difference from L to T and from R to T.
The shock valves are set at 3 l/min [0.792 US gal/min]
At higher flow pressure peaks may occur.
The shock valves are of the direct acting type, so they react very quickly.
Setting tolerance: rated value +20 bar [290 psi].
The suction valves allow oil suction to avoid cavitation in the steering cylinder. To provide correct
suction, a back pressure valve must be fitted in the tank line from the steering unit.
Generally Danfoss recommend a back pressure of 2 bar [29 psi], but on vehicles with strong selfstraightening tendencies and on articulated steered vehicles, we recommend 5-10 bar [72.5 - 145 psi]. For
further advice, please contact the Danfoss Sales Organisation.
A connection which incorporates a check valve must be established to allow oil flow to by-pass the back
pressure valve (and filter) from the tank to steering unit. See OSPU LS diagram examples.
The check valve in the P connection of the steering unit protects the driver against steering wheel jerks.
The check valve prevents oil from flowing backwards into the pump line when steering against a high
pressure on the cylinder side. The pressure drop across the check valve is indicated on the following
graph, which assumes the use of port adaptors with 11 mm [0.43 in] minimum bore.
The LS copy valve of OSPU protects the driver against steering wheel jerks. The LS copy valve prevents oil
from flowing backwards into the LS line to the priority valve when steering against a high pressure on the
cylinder side.
min.12[0.47]
min.Ø28[1.10]
B
30°
L
150-603.10-B
150-603.10-D
0.6[0.024]
Ø28.3[1.114]
Ø28.6[1.126]
N
min.15[0.59]
D
150-603.10-E
O
1[0.04]
min.11.5[0.453]
min.Ø22[0.87]
min.Ø26[1.02]
30°
E
150-603.10-F
0.6[0.024]
Ø28.6[1.126]
Ø28.3[1.114]
P
min.15[0.59]
F
Technical Information
OSPU Steering Unit
Technical data
Port thread versions for OSPU LS
B: G port w. spot face (LS)
L: DIN 3852-2 - G ¼
D: G ports w. spot face (P, T, L, R)
N: DIN 3852-2 - G ½
E: Metric port w. spot face and O-ring chamfer (LS)
O: ISO 6149-1 - M12 x 1.5
F: Metric ports w. spot face and O-ring chamfer (P, T, L, R)
P: ISO 6149-1 - M18 x 1.5
2800 East 13th Street
Ames, IA 50010, USA
Phone: +1 515 239 6000
Danfoss
Power Solutions Trading
(Shanghai) Co., Ltd.
Building #22, No. 1000 Jin Hai Rd
Jin Qiao, Pudong New District
Shanghai, China 201206
Phone: +86 21 3418 5200
Products we offer:
Comatrol
www.comatrol.com
Schwarzmüller-Inverter
www.schwarzmuellerinverter.com
Turolla
www.turollaocg.com
Hydro-Gear
www.hydro-gear.com
Daikin-Sauer-Danfoss
www.daikin-sauer-danfoss.com
Bent Axis Motors
•
Closed Circuit Axial Piston
•
Pumps and Motors
Displays
•
Electrohydraulic Power
•
Steering
Electrohydraulics
•
Hydraulic Power Steering
•
Integrated Systems
•
Joysticks and Control
•
Handles
Microcontrollers and
•
Software
Open Circuit Axial Piston
•
Pumps
Orbital Motors
•
PLUS+1® GUIDE
•
Proportional Valves
•
Sensors
•
Steering
•
Transit Mixer Drives
•
Danfoss Power Solutions is a global manufacturer and supplier of high-quality hydraulic and
electronic components. We specialize in providing state-of-the-art technology and solutions
that excel in the harsh operating conditions of the mobile off-highway market. Building on
our extensive applications expertise, we work closely with our customers to ensure
exceptional performance for a broad range of off-highway vehicles.
We help OEMs around the world speed up system development, reduce costs and bring
vehicles to market faster.
Danfoss – Your Strongest Partner in Mobile Hydraulics.
Go to www.powersolutions.danfoss.com for further product information.
Wherever off-highway vehicles are at work, so is Danfoss. We offer expert worldwide support
for our customers, ensuring the best possible solutions for outstanding performance. And
with an extensive network of Global Service Partners, we also provide comprehensive global
service for all of our components.
Please contact the Danfoss Power Solution representative nearest you.
Local address:
Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products
already on order provided that such alterations can be made without changes being necessary in specifications already agreed.
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