Steering Column Leadscrew Bearing Assembly With Consistent Preload
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Solution Overview
Problem
Current electrically powered rake and telescope leadscrew assembly designs are complex, requiring multiple components and torque operations for assembly, leading to variability in preload, increased noise due to runout, and non-uniform stiffness, with the nut performing multiple functions that can introduce bending and overload.
Innovation Solution
A simplified actuator leadscrew assembly using two pressed ball bearings and a housing, assembled through press operations without a nut, with a dynamically controlled press system for consistent preload and a retaining ring for crash load retention, providing uniform stiffness and decoupling functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a nut is used to control bearing preload through torque and back-off operations, then the preload can be adjusted, but the assembly process introduces variability and complexity
Solution Approach 1:
The patent removes the nut from the assembly entirely, extracting the problematic component that caused variability and complexity. Instead of using a nut with torque and back-off operations, the design uses a simplified bearing arrangement where the housing directly supports the bearings, eliminating the need for preload adjustment mechanisms and their associated assembly steps.
Solution Approach 2:
The bearing arrangement is designed to self-establish the required preload through its own structural configuration. The housing and bearing geometry are configured so that the bearings naturally maintain the correct preload without requiring external adjustment mechanisms, torque specifications, or back-off operations.
2Manufacturing precision
If torque and back-off operations are used to assemble the nut, then the bearing preload can be controlled, but the process is susceptible to variation
Solution Approach 1:
The patent eliminates the torque and back-off assembly process by removing the nut entirely. This extraction of the problematic assembly process eliminates the sources of variation inherent in torque specification and back-off operations, resulting in consistent preload without manufacturing variability.
Solution Approach 2:
The patent replaces the mechanical adjustment system (nut with threads and torque application) with a direct structural support system. The housing directly supports the bearings through pressed-fit connections, substituting a precision-adjustment mechanical system with a simpler, more consistent structural arrangement.
3Reliability
If the staking process is used to lock the nut position, then the preload is secured, but high loading is introduced into the lead screw causing bending
Solution Approach 1:
The patent removes the nut and staking process entirely, eliminating the source of high loading that caused leadscrew bending. The preload retention function is achieved through the inherent structural rigidity of the housing and bearing arrangement, which secures the bearings without requiring staking operations that apply damaging loads to the leadscrew.
Solution Approach 2:
The housing acts as an intermediary structure that provides both support and retention functions. Instead of directlystaking the nut to the leadscrew (which causes bending), the housing mediates the connection, providing a rigid structure that retains the bearings and secures the preload without transmitting harmful loads to the leadscrew.
4Stability of the object's composition
If the spring element is used to provide bearing preload, then the preload can be maintained, but the stiffness is not uniform in each direction
Solution Approach 1:
The patent removes the spring element from the design, eliminating the component that caused non-uniform stiffness. The bearing preload and stiffness are provided directly by the rigid housing and bearing arrangement, which maintains uniform stiffness in all directions without requiring elastic deformation of a spring.
Solution Approach 2:
The patent creates a homogeneous support structure where the housing uniformly supports the bearings in all directions. The rigid housing provides consistent stiffness and preload maintenance without the directional variability introduced by spring elements, achieving homogeneous mechanical properties throughout the assembly.
5Adaptability or versatility
If multiple components are used in the leadscrew assembly, then the functions can be fulfilled, but the component count increases and assembly complexity increases
Solution Approach 1:
The patent merges multiple functions into the housing component, which provides bearing support, alignment, and structural retention all in one piece. By combining these functions into the housing rather than using separate nuts, springs, and retention elements, the design reduces component count while maintaining all necessary functionalities.
Solution Approach 2:
The housing is designed as a multi-functional component that performs multiple roles: supporting the bearings, maintaining alignment, providing structural rigidity, and retaining the assembly. This universal component replaces what would otherwise require multiple specialized parts, reducing overall complexity while preserving all necessary functions.
Data Source
AI summary
An actuator leadscrew assembly is provided. The assembly includes a leadscrew shaft extending longitudinally. The assembly also includes a first bearing pressed over the leadscrew shaft. The assembly further includes a housing pressed over the leadscrew shaft and in abutment with the first bearing. The assembly yet further includes a second bearing pressed over the leadscrew shaft and in abutment with the housing. The assembly also includes a retaining ring disposed over the leadscrew shaft retaining the second bearing.