MODEL | 950.203 with REAR AXLE 749.109 |
with CODE AN9 (Hydraulically steered trailing axle) |
W46.80-1027-09
2 | Power steering pump | 5.3 | Steering circuit pressure sensor (PSX) (B95) | C2 | Connection (steering cylinder) | ||
3 | Steering oil reservoir | 5.4 | Pressure limiting valve (90+10 bar) | P1 | Connection (front axle steering system) | ||
4 | Flowcontrol | 5.5 | Pressure regulating valve (28 1 bar) | P2 | Connection (auxiliary steering system) | ||
4.1 | Displacement control valve | 5.7 | Common valve (Y78) | PP | Connection (power steering pump pressure side) | ||
4.2 | Control valve | 5.8 | Centering circuit pressure sensor (PSY) (B94) | PX | Connection (pressure side) | ||
4.3 | Monitoring valve (Y75) | 6 | Hydraulic pressure reservoir | T | Connection (steering cylinder return) | ||
4.4 | Oil filter | 7 | Steering cylinder | T2 | Connection (Flowcontrol return) | ||
4.5 | Wastegate | 7.1 | Main piston | TC | Connection (hydraulic control block return) | ||
4.6 | Throttle | 7.2 | Floating piston | TX | Connection (hydraulic control block return) | ||
5 | Hydraulic control block | I | Steering circuit | X1 | Connection (pressure side) | ||
5.1 | Control valve (Y76) | II | Centering circuit | X2 | Connection (pressure side) | ||
5.2 | Release valve (Y77) | C1 | Connection (steering cylinder) | Y | Connection (centering circuit) |
The centering circuit (II) is kept under pressure constantly by means of the hydraulic pressure reservoir (6), even with the engine switched off.
If the common valve (5.7) is deactivated, no hydraulic fluid can flow from the steering cylinder (7) to the hydraulic pressure reservoir (6). The hydraulic pressure reservoir (6) maintains the minimum pressure of 28 bar at the connections (Y) and, in doing so, keeps the steering cylinder (7) at the centering position (center position of the auxiliary steering EHZ).
During a steering maneuver, the common valve (5.7) is always open so that hydraulic fluid can flow from the steering cylinder (7) back to the hydraulic pressure reservoir (6). The centering circuit pressure sensor (PSY) (5.8) is attached to allow the centering system to be checked. If the pressure in the centering system drops below the fixed pressure of 23 bar, the pressure in the centering circuit (II) is adjusted.
The number and duration of charging cycles is limited. If they are exceeded or the pressure drops below 15 bar, the driver is made aware of the malfunction by means of the EHZ indicator lamp (H31).
The hydraulic fluid required to adjust the pressure in the centering circuit (II) is drawn from the steering circuit (I).
A restrictor is attached to the pressure regulating valve (5.5) in order to prevent the oil flow from becoming too strong in the centering circuit (II) during pressure adjustment. The restrictor also protects the steering circuit (I) of the auxiliary steering by preventing the hydraulic fluid from flowing out too rapidly if there is a sudden leak in the centering system.
During steering movements, oil pressures of 60 to 80 bar are produced in the centering circuit (II) as a result of the pressure compensation in the steering cylinder (7).
To ensure that the centering circuit (II) is not damaged at the hydraulic pressure reservoir (6), a pressure limiting valve (5.4) with a set pressure limitation of 90 to 100 bar is also installed.
Centering circuit pressure sensor, location/task | B94 | ||
Steering circuit pressure sensor, location/task | B95 | ||
Control valve, position/task | Y76 | ||
Release valve, position/task | Y77 | ||
Common valve, position/task | Y78 | ||
Steering cylinder, position/task/structure/function | |||
Hydraulic accumulator position/task/function | |||
Hydraulic control block position/task/design | |||
Pressure limiting valve position/task | |||
Pressure control valve, position/task |
Referenced documents
- gf4680w2021a Steering cylinder, position/task/structure/function
- gf4680w2103c Hydraulic accumulator position/task/function
- gf4680w2200c Hydraulic control block position/task/design
- gf4680w2202c Pressure limiting valve position/task
- gf4680w2214a Common valve, position/task
- gf4680w2216a Pressure control valve, position/task
- gf4680w2218a Control valve, position/task
- gf4680w2219a Release valve, position/task
- gf4680w2229a Steering circuit pressure sensor, location/task
- gf4680w2230a Centering circuit pressure sensor, location/task