Coupled Steering Shaft Assembly for Misalignment Compensation
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Solution Overview
Problem
Conventional power steering assemblies face issues with misalignments that lead to increased wear on seals, reduced efficiency, and require special tooling for each platform, causing stress on input shafts and control valve components.
Innovation Solution
A steering shaft assembly with a mid-coupler and screw mechanism that allows for rotational and lateral movement to accommodate radial and angular misalignments, reducing stress and backlash, and featuring a modified Oldham coupling for two-axis adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power steering assemblies use a rigid torsion bar and recirculating ball screw shaft combined into a single unit, then torque transmission is achieved, but misalignments cause increased wear on seals and reduced operating life
Solution Approach 1:
The steering shaft assembly is divided into separate components: an input shaft, an output shaft, and a mid-coupler, allowing each component to be optimized independently and accommodate misalignments without transmitting stress to seals
Solution Approach 2:
A mid-coupler is introduced as an intermediary component between the output shaft and screw mechanism. This mid-coupler absorbs misalignments and prevents them from being transmitted to the seals, thereby reducing wear and extending operating life
2Adaptability or versatility
If conventional systems use platform-specific torsion bars and rotary valves with fixed lengths, then each platform's specific piston travel requirements are met, but special tooling is required for each platform
Solution Approach 1:
The steering shaft assembly uses a universal mid-coupler design with adjustable positioning features that can accommodate different piston travel lengths across multiple platforms. This standardized design eliminates the need for platform-specific components and special tooling, while still meeting each platform's specific requirements through adjustment rather than customization
3Manufacturing precision
If conventional input shafts have high radial stiffness to maintain precision, then positioning accuracy is improved, but misalignment or mounting errors cause excessive fatigue and malfunction over time
Solution Approach 1:
The input shaft is designed with controlled flexibility rather than rigid high radial stiffness. This allows the input shaft to dynamically accommodate misalignments and mounting errors through elastic deformation, preventing stress concentration and fatigue failure while maintaining sufficient positioning accuracy for normal operation
4Manufacturing precision
If conventional assemblies use tight tolerances between components to minimize backlash, then positioning precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The mid-coupler acts as a compensating intermediary that absorbs misalignments and backlash through its design features, such as floating connections or adjustable positioning. This allows the use of more relaxed tolerances in manufacturing while still achieving minimal backlash in the final assembly, reducing manufacturing complexity and cost
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces stress on input shaft and control valve components, improves reliability, and minimizes backlash and torsional stiffness, allowing for universal application across various vehicles without the need for special tooling.
Implementation Method 1
an elongated torsion bar joined to an input shaft and to an output shaft. The elongated torsion bar transfers torque applied to the input shaft (in response to rotation of a steering wheel) to the output shaft, causing the output shaft to rotate
Implementation Method 2
Rotation of the output shaft is typically converted by a recirculating ball screw into linear movement of a piston
Implementation Method 3
The mid-coupler is adapted to transfer power between the output shaft and a screw mechanism, optionally as a center disk of a modified Oldham coupling
Data Source
AI summary
An improved steering shaft assembly is provided. The steering shaft assembly further includes an output shaft that is rotatable with respect to the input shaft. The output shaft includes a rotary valve portion and a longitudinal portion. The steering shaft assembly further includes a torsion bar coupled to the input shaft and coupled to the output shaft distal from the input shaft. The steering shaft assembly further includes a mid-coupler extending around about the longitudinal portion of the output shaft and adapted to cooperate with the rotary valve portion of the output shaft. The steering shaft assembly further includes a screw mechanism extending about the longitudinal portion of the output shaft and adapted to cooperate with the mid-coupler. The screw mechanism is adapted to move laterally relative to the output shaft to maintain transfer of power from between output shaft and the screw mechanism despite misalignments therebetween.