Torsion Bar Assembly With Neutral-Position Shaft Alignment
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Solution Overview
Problem
Torsion bar assemblies in electric power assisted steering systems face challenges in measuring driver-applied torque while ensuring shaft flexibility to prevent damage from high torque loads, such as when a road wheel strikes an obstacle.
Innovation Solution
A torsion bar assembly with alignment features that self-center the input and output shafts to a neutral position during assembly, allowing for easy insertion of the torsion bar without rotational forces, and utilizing splines for secure engagement to prevent misalignment and ensure accurate torque measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the shaft is made torsionally flexible to achieve significant deflection for torque measurement, then the measurement range is improved, but the shaft becomes vulnerable to breaking or elastic deformation under high torque loads
Solution Approach 1:
The shaft is divided into multiple segments: a flexible torsion bar portion for torque measurement and rigid end portions with end stops for structural support. This segmentation allows the shaft to achieve both flexibility for measurement and rigidity for protection against damage.
Solution Approach 2:
End stops are provided at both ends of the torsion bar to limit the angular movement and prevent excessive deflection. This beforehand protection mechanism ensures that even under high torque loads, the shaft cannot deflect beyond safe limits, preventing breaking or permanent deformation.
2Ease of manufacture
If traditional assembly methods are used without alignment features, then the assembly process requires complex positioning procedures, but the invention introduces alignment features that simplify the assembly process
Solution Approach 1:
Alignment features are incorporated into the shaft design before assembly. These features automatically guide and position the shaft components in the correct angular relationship during assembly, eliminating the need for complex positioning procedures and specialized tooling.
Solution Approach 2:
The alignment features enable the shaft to self-align during assembly through its own geometric characteristics. The shaft automatically assumes the correct neutral position without requiring external alignment equipment or complex positioning procedures, making the assembly process intuitive and simple.
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
Simplifies the assembly process by ensuring correct angular alignment and preventing rotational misalignment during torsion bar insertion, allowing for reliable torque measurement across a wide range of angular deflections while maintaining structural integrity.
Implementation Method 1
The torsion bar is relatively flexible when subject to a torsional load, which causes an angular offset between to the input shaft and the output shaft to be generated that is a function of the torque applied
Data Source
AI summary
A torsion bar assembly comprises an input shaft, an output shaft, and a torsion bar that connects the input shaft to the output shaft. An end stop face on the input shaft that co-operates with a respective end stop face of the output shaft to limit an angular deflection of the torsion bar assembly in a first direction away from the neutral position and an end stop face on the input shaft that co-operates with a respective end stop face of the output shaft to limit an angular deflection of the torsion bar assembly in a second direction that opposes the first direction. A first alignment feature is provided at or close to the end of the input shaft nearest the output shaft and a second alignment feature is provided at or close to an end of the output shaft nearest to the input shaft, the first alignment feature facing the second alignment feature across a gap. The alignment features each define respective contact surfaces such that if the input shaft and the output shaft are pressed axially towards each other to close up the gap the contact faces co-operate to set relative angular positions of the input shaft and the output shaft to correspond to a neutral position.