Floating ball-nut for an electric assist steering system

摘要

An improved mounting arrangement for a ball nut drive assembly for a linear actuator is disclosed. The invention is described as embodied in an electric assist steering system. The steering system includes a housing surrounding at least a portion of a steering member having rack teeth thereon, a ball-nut drive assembly circumscribing a thread portion of the steering member for axially driving said steering member upon rotation of the ball-nut drive assembly, an electric assist motor for driving said ball-nut assembly into rotation 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. 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.