Floating ball-nut for an electric assist steering system.

摘要

The steering system includes a housing (60) surrounding a steering member (24) having rack teeth (55) thereon, a ball-nut drive assembly (200) circumscribing a thread portion (56) of the steering member for axially driving said steering member upon rotation of the ball-nut drive assembly, an electric assist motor (36) for driving said ball-nut assembly in response to a control signal and an electronic control unit for providing said control signal in response to a measured amount of driver input torque. The steering member is radially supported relative to the housing at two spaced apart locations (76, 78). The ball-nut drive assembly is axially spaced from the electric assist motor and connected thereto by a connection tube. Thrust bearings are located at each end of the ball-nut drive assembly and are operatively positioned between the ball-nut drive assembly and the housing. Each thrust bearing has an associated O-ring positioned between such thrust bearing and the housing. The thrust bearings and O-rings substantially restrain axial movement of the ball-nut drive assembly relative to the housing and enable radial movement of the ball-nut assembly relative to the housing.