Steering unit. Table of contents. Features RE 11872/ Type LAGL. Frame sizes 500 to 1000 Component series 1X Maximum flow 80 l/min

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1 Steering unit RE 11872/05.06 /10 Type LAGL Frame sizes 500 to 1000 Component series 1X Maximum flow 80 l/min H7375 Table of contents Contents Page Features 1 Ordering code 2 Function, section 3 Device version: Open Center, symbols 4 Device version: Load-Sensing, symbols 5 Functions in the steering circuit 6 Technical data 6 Technical data of the hydraulic fluid, selection diagram 7 Determination of the steering moment 8 Dimensioning of steering cylinder and steering pump 9 Unit dimensions, connections 0 Features LAGL steering units are used in hydraulic steering circuits of vehicles and mobile machinery with great axle loads and travel speeds up to max. 50 km/h. With the help of a steering unit, even heavy vehicles can be easily steered. The absence of a mechanical connection between the steering unit and the steering axle allows the designer the implementation of solutions that would not be feasible with conventional steering systems. The steering unit includes all valves that are required in the hydraulic steering circuit for the protection of the steering unit and steering cylinders, which renders additional pipework unnecessary. The control valve is optimised for large frame sizes. When compared with type LAGC, pressure losses were reduced.

2 2/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Ordering code LAG L 1X M * Type of device Steering unit Design Large (for large frame sizes) Displacement (cm 3 /U) Frame size OC LD 500 = = = = 1000 Noise characteristics Standard 1) = Low 2) = N Component series Component series 10 to19 = 1X (10 to19 unchanged installation and connection dimensions) Load signal Without load signal in Open Center (OC) version Dynamic load signal = No code = LD M = For special specifications, please consult or sales organisation 4) Pipe connections P, T, L, R/LD 01 = Pipe threads (mounting bores to DIN ) 02 = Metric ISO threads (mounting bores to DIN ) Seal material NBR seals 3) Setting of pressure relief valve Pressure differential 140 = 140 bar 175 = 75 bar 210 = 210 bar 3) Setting of shock valve Pressure differential 200 = 200 bar 240 = 240 bar 260 = 260 bar = Standard product range = Extended product range 1) Specify for LD version 2) Indicate for Open Center (OC) version 3) The response pressure of the shock valves must be set 50 bar higher, but not more than 2.2 times higher, than the pressure relief valve of the hydraulic pump (see 38 StVZO (German road traffic licensing regulations)). Preferably 200 to 140; 240 to 175; 260 to 210 4) For thread dimensions, see unit dimensions on page 10 Order example: LAGL 800-1X/LD M01 Steering unit with integrated valves, size 800, dynamic load signal, shock valves 200 bar, pressure relief valve 140 bar, pipe connections P, T, L, R in G1/2; LD in G1/4 LAGL 800N1X/ M01 Steering unit with integrated valves, size 800, Open Center, low noise, shock valves 240 bar, pressure relief valve 175 bar, pipe connections P, T, L, R in G1/2

3 RE 11872/05.06 LAGL Hydraulics Bosch Rexroth AG 3/10 Function, section Control spool (1) of the control valve is rotated via the steering column in relation to control bush (2). This results in the opening of a cross-section between the spool and the bush. The hydraulic oil acts on rotor set (3) and sets it into motion. The oil is fed via the rotor set to the steering cylinder. The rotation of the rotor acts on the bush and causes it to follow 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; in the case of load-sensing versions, it depends exclusively on the turning speed. When the steering movement is stopped and the spool comes to a standstill, the oil flowing through the still open cross-section to the rotor causes the rotor and hence the bush to continue to rotate. The cross-section is then closed via the rotary movement - the rotor now also comes to a standstill; and together with it, the steering cylinder stops at the requested position. Centring spring (4) returns and holds the spool and bush in a neutral position to each other. The system pressure of the steering circuit is limited by pressure relief valve (5). In the case of load-sensing versions (see section), a pilot valve for the load signal is installed instead of the pressure relief valve. The two shock valves (6) protect ports L and R to the steering cylinder. When one of the shock valves responds, the discharging oil is fed by anti-cavitation valve (7) to the opposite side or missing leak-oil is re-aspired from the tank. (For the functional description of items 8 and 9, see also page 6) Control piston 2 Control bush 3 Rotor set 4 Centring spring 5 Pressure relief valve 6 Shock valve 7 Anti-cavitation valve 8 Suction valve 9 Check valve

4 4/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Device version: Open Center, symbols Low-noise version Open Center with Non Reaction = OC / NR Mainly used in steering systems with fixed displacement hydraulic pump. 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 R 1) (right) are closed in the neutral position. In this way, external forces are supported, which act via the steering cylinder, without the driver perceiving any reaction forces at the steering wheel (Non Reaction). Steering units of type LAGL Open Center are generally shipped in the low-noise version N. 1) In contrast to standard designations A and B, the working lines in steering systems are usually identified with L and R. Open Center version L R L R P T Simplified representation P T Detailed representation

5 RE 11872/05.06 LAGL Hydraulics Bosch Rexroth AG 5/10 Device version: Load Sensing, symbols Load-Sensing version Steering units with load-sensing feature provide a load signal, which can be used for controlling a priority valve and/or a pump. They are designed as Closed-Center steering units, with the connection of pump port (P) to tank port (T) being closed in the neutral position. If the steering system and the working hydraulics are supplied by a common pump, a priority valve must be used. This valve ensures the priority supply of the steering unit with oil, with the valve being controlled with the help of the load signal from the steering unit. When no steering movement is performed, the entire amount of oil from the pump is made available to the working hydraulics. The hydraulic pump can be a fixed or a variable displacement pump. Load-Sensing version L R L R LD LD P T Simplified representation P T Detailed representation Load signal, dynamic The oil flowing in the load signal line transmits the load signal, with the pilot oil flowing from the priority valve to the steering unit. A small pilot oil flow of approx. 1.0 l/min flows continuously also in the neutral position. Consequently, the steering unit has almost the same temperature as the oil. Temperature shocks can largely be ruled out. The LD version causes a faster reaction of the priority valve. The hard point when starting to steer - also under cold start conditions - is usually no longer perceivable.

6 6/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Functions in the steering circuit Power-assisted operation Steering units of type LAGL consist of a manually operated servo-valve of rotary spool design, a rotor set operating according to the gerotor principle, and the valves required for the steering circuit. The size of the rotor set determines the oil volume that flows to the steering cylinder per turn of the steering wheel. The size of the rotor set is to be selected so that it is possible to steer from one limit stop to the other with 3 to 5 turns of the steering wheel. Pressure relief valve The pressure relief valve is available with three standard settings: 140 bar, 175 bar, 210 bar Note! The pressure in the T-line adds to the set pressure. Shock and anti-cavitation valve These valves, which are installed in the LAGL on the cylinder side, are available with three standard settings: Suction valve 200 bar, 240 bar, 260 bar In the event of a hydraulic pump failure, this valve, which is installed between the P and the T-port, aspires hydraulic fluid from the tank. Check valve This valve, which is installed in the P-port, prevents: oil from flowing from the steering cylinder into the hydraulic system, if the cylinder pressure becomes higher than the system pressure due to travel obstructions. In this way, steering shocks acting on the steering wheel are largely suppressed. air from being aspired via the P-port during emergency operation. Technical data (for applications outside these parameters, please consult us!) General Nominal pressure p bar 175 Ambient temperature range ϑ C 20 to +80 Hydraulic fluid See page 7 Hydraulic fluid temperature range ϑ C 20 to +80 Viscosity range ν mm 2 /s 10 to 800 Max. permissible degree of contamination of the hydraulic fluid Cleanliness class to ISO 4406 (c) Steering moment - standard M Nm 5 Class 19/16/13; for this, we recommend a filter with a minimum retention rate of β to ISO Max. tightening torque for mounting screws M T Nm 30, see also RE steering column Hydraulic Frame sizes of LAGL Size Displacement cm Maximum flow 1) l/min Max. permissible operating pressure Port P bar Port T bar Port L, R bar ) Values for centring spring package, standard (2.5 to 4 Nm)

7 RE 11872/05.06 LAGL Hydraulics Bosch Rexroth AG 7/10 Technical data of the hydraulic fluid Hydraulic fluids Before starting your planning work, please read the detailed information about the selection of hydraulic fluids and the operating conditions provided in data sheets RE (mineral oil) and RE (environmentally friendly fluids). These data sheets refer to axial piston units, but the information is analogously also valid for steering units. In the case of hydraulic fluids that require FKM seals, please contact our sales organisation. Operating viscosity We recommend that the operating viscosity (at operating temperature) is selected within the range of ν opt = optimum operating viscosity range 16 to 46 mm 2 /s referred to temperature, which is optimal in terms of efficiency and service life. Limiting viscosity For limiting conditions, the following values are valid: ν min = 10 mm 2 /s at a max. permissible temperature of ϑ max = 80 C ν max = 800 mm 2 /s Hydraulic fluid temperature range (see selection diagram) ϑ min = 20 C ϑ max = 80 C Explanation with regard to the selection of the hydraulic fluid For the selection of the correct hydraulic fluid, the operating temperature and the ambient temperature must be known. The hydraulic fluid must be selected so that the operating viscosity is within the optimum range at operating temperature (see selection diagram). We recommend that the next higher viscosity class be selected. Example At an ambient temperature of X C the tank temperature stabilises at 60 C. Within the optimum viscosity range, this corresponds to viscosity classes VG 46 or VG 68; to be selected: VG 68. Filtration of the hydraulic fluid The finer the filtration, the better the cleanliness achieved for the hydraulic fluid, and the longer the service life of the entire hydraulic system. To ensure the operational reliability of the steering unit, the cleanliness class required for the hydraulic fluid must be at least 19/16/13 to ISO 4406 (c). Selection diagram 40º 20º Viscosity range VG 22 0 º 20º 40º 60º 80º 100º VG 32 VG 68 VG 46 VG º 25º 10º 0º 10º 30º 50º 70º 90º 115º Hydraulic fluid Temperature ϑ in C ϑ min = 40 C temperature range ϑ max = 115 C

8 l 8/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Determination of the steering moment Steering moment 1 b µ M = 0.05 F A [Nm] 1+ e b Steering force F = M I 10 3 [N] h b M e Table of formula symbols Formula symbol Designation Unit Formula symbol Designation Unit A Required cylinder area mm 2 l Smallest effective lever mm A 1 Cylinder piston area of single-rod cylinder mm 2 M Steering moment Nm A 2 Cylinder annulus area of single-rod cylinder mm 2 n Steering wheel turning speed min -1 b Tyre width mm n idle Motor idle speed min -1 d Piston rod diameter mm n Motor Motor operating speed min -1 D Cylinder diameter mm p Steering pressure bar e Distance of swivel bearing centre of tyre mm q vp Pump flow l/min F Steering force N V Displacement of steering unit cm 3 /rev F A Steering axle load N V P Displacement of steering pump cm 3 /rev h Cylinder stroke length mm V CYL Cylinder volume cm 3 i Number of steering wheel turns µ Friction coefficient

9 RE 11872/05.06 LAGL Hydraulics Bosch Rexroth AG 9/10 Dimensioning of steering cylinders and steering pump Steering cylinder Required cylinder area A = π 10 [mm 2 ] 4 Cylinder area (piston side) A 1 = π 4 D 2 [mm 2 ] Cylinder area (piston rod side) A 2 = π 4 (D 2 d 2 ) [mm 2 ] Steering pump The pump should be selected so that at idle speed of the motor, a steering speed of approx. 50 min 1 can still be achieved. The max. steering speed is approx. 100 to 150 min 1 depending on the steering wheel diameter. Pump flow q = V (n + 10) 10 3 l/min. The required displacement of the pump ( FS) must be determined for steering in the idling mode and at operating speed of the vehicle. Frame size of the pump in the idle mode When using a single-rod cylinder or a double-rod cylinder, A 2 must be greater than the required cylinder area. If two cross-connected single-rod cylinders are used, A 1 + A 2 must be greater than the required cylinder area. The size of the steering unit is calculated from the cylinder volume and the desired number of steering wheel turns. Cylinder volume Displacement of LAGL V CYL = A h 10 3 [cm 3 ] V = V CYL i [cm3 /U] The typical number of steering wheel turns from limit stop to limit stop is 3 to 5. q V P = VP 10 3 n idle Frame size of the pump at operating speed V P = q VP 10 3 n motor [cm 3 /rev] [cm 3 /rev] Further information! Suitable steering columns can be found in RE 11874, the associated priority valves for steering systems and load signal circuits in RE

10 10/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Unit dimensions LAGL.. /LAGL..LD.. (nominal dimensions in mm) 27,5 ±0,5 Ø44,4 Gear hub profile16/32 Diametrical pitch to ANS B ,3 2,8 60 Ø25,4 15 min. 61 ±0,5 L 38 ±1 T L M10; R L 1 P R L Bore, inch thread and metric thread for ports P, T, R, L, LD 90 Ød 4 d 1 Frame size L 1 L b a Ø82 ±0,3 59 M10; LD bore on version LAGL...LD Port Version d 1 Ød 4 1) b min. P, T, R, L 01 G 1/ max. 0.3 a 1 02 M22x max. 0.3 LD 01 G 1/ ± M12x ±0.5 1) Differing from DIN and DIN Bosch Rexroth AG Hydraulics Zum Eisengießer Lohr am Main, Germany Phone +49 (0) Fax +49 (0) documentation@boschrexroth.de Bosch Rexroth AG Hydraulics Parchim, Germany Ludwigsluster Chaussee 5 Phone +49 (0) Fax +49 (0) This document, as well as the data, specifications and other information set forth in it, are the exclusive property of Bosch Rexroth AG. It may not be reproduced or given to third parties without its consent. The data specified above only serve to describe the product. No statements concerning a certain condition or suitability for a certain application can be derived from our information. The information given does not release the user from the obligation of own judgment and verification. It must be remembered that our products are subject to a natural process of wear and aging.

11 RE 11872/05.06 LAGL Hydraulics Bosch Rexroth AG Bosch Rexroth AG Hydraulics Zum Eisengießer Lohr am Main, Germany Phone +49 (0) Fax +49 (0) documentation@boschrexroth.de Bosch Rexroth AG Hydraulics Parchim, Germany Ludwigsluster Chaussee 5 Phone +49 (0) Fax +49 (0) This document, as well as the data, specifications and other information set forth in it, are the exclusive property of Bosch Rexroth AG. It may not be reproduced or given to third parties without its consent. The data specified above only serve to describe the product. No statements concerning a certain condition or suitability for a certain application can be derived from our information. The information given does not release the user from the obligation of own judgment and verification. It must be remembered that our products are subject to a natural process of wear and aging.

12 12/10 Bosch Rexroth AG Hydraulics LAGL RE 11872/05.06 Notes Bosch Rexroth AG Hydraulics Zum Eisengießer Lohr am Main, Germany Phone +49 (0) Fax +49 (0) documentation@boschrexroth.de Bosch Rexroth AG Hydraulics Parchim, Germany Ludwigsluster Chaussee 5 Phone +49 (0) Fax +49 (0) This document, as well as the data, specifications and other information set forth in it, are the exclusive property of Bosch Rexroth AG. It may not be reproduced or given to third parties without its consent. The data specified above only serve to describe the product. No statements concerning a certain condition or suitability for a certain application can be derived from our information. The information given does not release the user from the obligation of own judgment and verification. It must be remembered that our products are subject to a natural process of wear and aging.