Hydraulic wishbone bearing
A hydraulic axle-guide bearing (HALL) is a special type of Achslenkerlagers a bogie . The task of the wishbone bearing is to guide the wheel set and to enable the adjustment movement when cornering. In contrast to the conventional wishbone bearing, which only has static longitudinal rigidity, the HALL has a frequency-dependent rigidity.
In the bogie of a train, the setting angle of the axles is primarily determined by the longitudinal stiffness of the wishbone bearing. Radially adjusting wheel sets are a basic requirement for low-wear and low-noise cornering in all rail vehicles. Reducing the contact angle of the wheels on the rail reduces the forces between the wheel and rail and thus drastically minimizes wear on both components. To enable the wheels to be adjusted when cornering, the wishbone bearing must have the lowest possible longitudinal rigidity. On the other hand, the smooth straight-line stability, especially at higher speeds, requires a very high rigidity of the wishbone bearing.
The hydraulic wishbone bearing (HALL) makes it possible to combine the low longitudinal stiffness for cornering with high longitudinal stiffness for straight-ahead driving in a single component. The hydraulic active device integrated in the HALL leads to frequency-dependent changes in the longitudinal stiffness. As a result, the hydraulic wishbone bearing can be designed in such a way that a low level of rigidity is automatically available for low-frequency vibration excitations - i.e. when entering and exiting bends. The HALL enables the wheel sets to be adjusted to conform to curves.
The functional principle is based on the combination of rubber spring and hydraulic coupling link. The HALL consists of two fluid chambers connected by a hydraulic system. If the fluid exchange is hindered, the bearing stiffens and the longitudinal stiffness increases to a multiple of the static stiffness.
The first manufacturer and patent holder (Pat. No. EP 1 457 706 A1) is Freudenberg Schwab GmbH. In addition to the HALL (R) from FreudenbergSchwab, there is now also the functionally identical HydrALL (R) from GMT GmbH.