Power steering motor having a noise dampening piston assembly

摘要

An apparatus ( 10 ) for turning steerable wheels of a vehicle comprises a housing ( 14 ) that defines a fluid chamber ( 24 ). A rack bar ( 26 ) extends longitudinally through the housing ( 14 ) and is connectable with the steerable wheels of the vehicle. The rack bar ( 26 ) is movable relative to the housing ( 14 ) for turning the steerable wheels. A piston assembly ( 34 ) is fixedly attached to the rack bar ( 26 ) and sealingly engages the housing ( 14 ). The piston assembly ( 34 ) divides the fluid chamber ( 24 ) into first and second chamber portions ( 40 and 42 ). A fluid source ( 80 ) directs fluid toward one of the first and second chamber portions ( 40 or 42 ) for creating a differential pressure between the first and second chamber portions ( 40 and 42 ). The piston assembly ( 34 ) and the rack bar ( 26 ) move relative to the housing ( 14 ) in response to the differential pressure. The piston assembly ( 34 ) includes structure ( 132 ) for dampening fluid pulsations emanating from the fluid source ( 80 ).