Technical Information Steering Unit LAGU /'/, WHITE together in motion

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Contents: Chapter 1 _______________________________________________________________________ 4 Steering Unit LAGU Technical Information _________________________________________________ 4 Features _____________________________________________________________________________________ 6 Ordering details _______________________________________________________________________________ 6 Function, section ______________________________________________________________________________ 8 Versions _____________________________________________________________________________________ 9 Functions in a steering...

• Ordering details • Function, section • Functions in a steering circuit • Technical data • Pressure fluid technical data • Calculating the steering moment • Defining the steering cylinder and steering pump • Dimensions LAGU/ LAGU LD / LAGU LDA • Ports LAGU/ LAGU LD / LAGU LDA

• The LAGU steering unit is used in hydraulic steering circuits on vehicles and mobile machines that have high axle loads and maximum travel speeds of 60 kph. • With the aid of a steering unit even heavy vehicles can be easily steered. The absence of a mechanical connection between the steering unit and steering axle allows the designer to realize solutions which would be impossible with conventional steering systems. • If the oil supply to the steering unit fails, vehicles can easily be steered manually with the help of the LAGU. The LAGU acts also as a hand pump but the driving torque from...

6 For thread dimensions see Dimensions LAGU/LAGULD /LAGULDA on page 18

Function, section Control spool (1) of the control valve is rotated via the steering column in relation to control sleeve (2). This opens cross-sections between the spool and the sleeve. The pressurized oil acts on the rotor set (3) and sets the latter into motion. The oil is then fed via the rotor set to the steering cylinder. The rotation of the rotor acts on the sleeve, which then follows the rotary movement of the spool. The size of the opened cross-section depends on the turning speed of the steering wheel and on the steering pressure, on Load-Sensing versions it depends exclusively on the...

Versions Standard version | Open Center with Non Reaction = OC / NR Mainly used in steering systems with fixed displacement hydraulic pumps (e.g. gear pumps). Figure 2: LAGU OC / NR schematic When no steering movement is performed, the connection between pump port (P) and tank port (T) is open (OC), and the pump flow is directed to the tank almost at zero pressure. Ports L 1 (left) and R1 (right) are blocked in the neutral position (NR). In this way, external forces acting via the steering cylinder are supported without the driver perceiving any resulting reaction forces on the steering wheel...

Low-noise version Steering units of the LAGU Open Center versions are generally delivered in the low-noise variant “N“. Load sensing version Steering units with load sensing provide a load signal that can be used to control a priority valve and/or a pump. They are designed as closed center steering systems whereby the connection pump (P) to tank (T) is locked while in a neutral position. If the steering and implement hydraulics are supplied by a common pump, then the use of a priority valve is necessary. The priority valve ensures that the steering unit gets a priority oil supply, whereby the...

11 Functions in a steering circuitPower-assisted mode - Servo operation Steering units of type LAGU consist of a manually operated rotary spool valve, one rotor set, which operates according to the gerotor principle, and the required valves for the steering circuit. The nominal size for the power-assisted mode results of the rotor set size. The size of the rotor set is to be selected so that with 3 to 5 turns of the steering wheel it becomes possible to steer from lock to lock. During normal operation of the steering unit, when a sufficient amount of oil gets supplied to the steering unit, the...

'5, WHITEInlet check valve The check valve of the P-port prevents the return flow of oil from the steer cylinder - due to external forces working onto the steer cylinder - into the hydraulic system. So it prevents kickback turning of the steering wheel. While manual steering it prevents sucking air from the P-port. I . Caution: The emergency operating mode is not intended for continuous operation! If a higher pressure is required for steering in emergency operation at 70 Nm, a steering unit with automatic displacement reduction - LAGZ - can be installed. During manual steering with 50 or 70 Nm...

'5, WHITE Steering unit Type 3 Related to the steering speed of 100 steering rotations/min. Before carrying out any engineering please refer to the extensive information regarding pressure fluid selection and application conditions in standards or manufacturer instructions. For pressure fluids that require FKM or other seals please contact your sales contact. We recommend that the operating viscosity (at operating temperature) for efficiency and service life, is selected within the optimum range of v opt = optimum operating viscosity range 16 to 46 mm2/s with reference to the temperature. For...

Pressure fluid filtration The finer the filtration the higher the cleanliness class of the pressure fluid is achieved and so the higher the service life of the entire hydraulic system. Note: To ensure the functionality of the steering pump a minimum pressure fluid cleanliness class of 19 / 16 / 13 to ISO 4406 is necessary (see Technical data on page 12). Caution: Operating the unit with contaminated hydraulic fluid may lead to the steering system failing. Figure 6: Selection diagram

Calculating the steering moment Table 3: Formula symbols Formula symbol Required cylinder area Cylinder piston area, differential cylinder Cylinder ring area, differential cylinder Tyre width Cylinder diameter Distance of swivel bearing to center of tire Steering force Steering axle force Cylinder stroke length No. of steering wheel turns Smallest, effective steering lever Steering moment Steering wheel rotational speed Steering pressure Pump flow Steering unit displacement Steering pump displacement Cylinder volume Figure 7: Steering geometry Steering moment ݑ = 0,05 װݐٰݐ ԃ