Steering Column Actuator Travel Stop for Leadscrew Over-Travel
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Solution Overview
Problem
Existing vehicle steering systems face issues with over-travel prevention in adjustable steering columns, where the inertia of the actuator assembly can cause impact loading on the leadscrew threads, leading to component seating torque exceeding stall torque, and requiring costly additional components and error-proofing to prevent noise from loose parts.
Innovation Solution
An adjustment actuator assembly with a leadscrew having a threaded outer surface and a nut with a travel stop limiter, where the limiter is spring-biased into contact with the leadscrew's pocket to limit axial translation without axial loading, using a leg extending through the nut's opening and moving into the pocket to halt rotation, thus preventing over-travel without additional parts or assembly tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spacers and retainers are added to the leadscrew to limit travel, then over-travel prevention is improved, but component cost and assembly complexity increase
Solution Approach 1:
The travel stop limiter integrates multiple functions into a single component: it combines the travel stop function with the nut assembly, eliminating the need for separate spacers and retainers. The limiter is operatively coupled to the nut and biases into contact with the leadscrew, providing travel limitation while reducing part count and assembly complexity.
Solution Approach 2:
The travel stop limiter serves multiple purposes: it limits axial translation of the nut, prevents over-travel in both extending and retracting directions, and does so without requiring additional error-proofing or assembly verification. This multi-functional component replaces several traditional parts with a single versatile solution.
2Reliability
If spacers and retainers are added to the leadscrew to limit travel, then over-travel prevention is improved, but component cost increases
Solution Approach 1:
The travel stop limiter integrates multiple functions into a single component: it combines the travel stop function with the nut assembly, eliminating the need for separate spacers and retainers. The limiter is operatively coupled to the nut and biases into contact with the leadscrew, providing travel limitation while reducing part count and assembly complexity.
Solution Approach 2:
The travel stop limiter uses a spring-biased mechanism with a leg that contacts the leadscrew, providing a cost-effective solution compared to traditional spacers and retainers. The design eliminates the need for expensive additional components and assembly verification processes.
3Reliability
If mechanical travel limit is reached with traditional spacers, then axial translation is limited, but impact loading exceeds stall torque preventing unseating
Solution Approach 1:
The travel stop limiter uses a spring-biased leg that dynamically contacts the leadscrew, allowing the system to absorb impact forces without creating excessive seating torque. The spring mechanism provides compliance that prevents the inertia-induced impact from exceeding the actuator's stall torque, enabling the nut to unseat and reverse direction smoothly.
Solution Approach 2:
The spring-biased travel stop limiter provides cushioning before impact occurs. The spring mechanism absorbs and dampens the impact forces when the travel limit is reached, preventing the sudden shock that would otherwise cause the seating torque to exceed the stall torque and prevent unseating.
4Reliability
If traditional travel limit components are used, then over-travel is prevented, but loose fitting parts create noise requiring error proofing
Solution Approach 1:
The travel stop limiter integrates multiple functions into a single component: it combines the travel stop function with the nut assembly, eliminating the need for separate spacers and retainers. The limiter is operatively coupled to the nut and biases into contact with the leadscrew, providing travel limitation while reducing part count and assembly complexity.
Solution Approach 2:
The travel stop limiter is spring-biased into contact with the leadscrew, maintaining constant engagement without requiring additional error-proofing or assembly verification. The self-biasing mechanism ensures proper fitting and eliminates loose parts that would create noise, while the single-component design reduces assembly complexity.
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
This solution effectively prevents over-travel while avoiding axial loading, reducing component costs and assembly complexity, and eliminating noise issues by using a shear force to stop rotation, maintaining the breakaway torque equal to the unloaded thread assembly.
Implementation Method 1
travel stop limiter having a leg extending through an opening of the nut and spring biased into contact with the threaded outer surface of the leadscrew
Implementation Method 2
using a shear force to stop rotation
Data Source
AI summary
An adjustment actuator assembly for a vehicle steering system includes a leadscrew having a threaded outer surface and at least one pocket recessed radially inwardly from an outer diameter of the threaded outer surface. The adjustment actuator assembly also includes a nut having a threaded inner surface engaged with the threaded outer surface of the leadscrew, the nut axially moveable along the leadscrew during rotation of the leadscrew. The adjustment actuator assembly further includes a travel stop limiter operatively coupled to the nut, the travel stop limiter having a leg extending through an opening of the nut and spring biased into contact with the threaded outer surface of the leadscrew and moveable into the pocket of the leadscrew to limit axial translation of the nut.