| 摘要 |
An auxiliary power steering unit is provided with a first power assistance system in the form of a working piston (12) inserted in a basic housing (A) of the steering gear, said piston being in engagement with a threaded spindle (3). The working piston (12) drives, via a gear system (14), a steering shaft (15) which carries a steering segment (16). The second power assistance system provided is an electric motor (37), which drives a shaft extension (23) via a reduction gear (34, 35) and an engageable clutch (25). The shaft extension (23) is linked in a non-rotatable manner with the threaded spindle (3). The second power assistance system is installed in a housing (B) flanged to the basic housing (A). In the event of failure of the hydraulic steering circuit (first power assistance system) the electric motor (37) and engageable clutch (25) of the second power assistance system are automatically switched on in order to reduce the steering force required.
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