Torque Transmission Unit Pin Alignment and Displacement Control
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Solution Overview
Problem
The existing torque transmission units in electric power steering devices face challenges in reliably regulating the axial displacement of the connecting pin, which connects the torque transmission shaft and the torsion bar, due to potential misalignment and visibility issues during assembly, leading to potential disconnection during repeated use.
Innovation Solution
A torque transmission unit design featuring a hollow torque transmission shaft with concentric outer and inner diameter through-holes, a yoke with a partially cut cylindrical base portion and flange portions, and a bolt system that secures the yoke to the shaft, ensuring the connecting pin is properly aligned and fixed, with a discontinuous portion width less than the pin diameter to prevent axial displacement and allow visual confirmation of pin installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the base portion of the yoke has a discontinuous portion to allow visual confirmation of pin installation, then the ease of operation during assembly is improved, but the reliability of preventing axial displacement of the connecting pin deteriorates due to potential misalignment
Solution Approach 1:
The base portion of the yoke is designed with a discontinuous portion (openings) at specific locations to allow visual confirmation of pin installation, while the rest of the base portion maintains its cylindrical shape to provide structural support and prevent axial displacement. This local modification approach allows the structure to simultaneously achieve transparency for inspection and integrity for constraint.
Solution Approach 2:
The base portion is segmented by introducing discontinuous portions that create separate viewing zones. These openings are strategically positioned to allow visual inspection of pin installation without compromising the overall structural integrity of the base portion for preventing axial displacement.
2Reliability
If the width of the discontinuous portion is made small to prevent pin misalignment, then the reliability of preventing axial displacement is improved, but the ease of operation for visual confirmation deteriorates
Solution Approach 1:
The discontinuous portions are designed with optimized dimensions where the width is sufficient to allow visual confirmation of pin installation but narrow enough to maintain structural integrity and prevent pin misalignment. The length of the discontinuous portions along the axial direction is extended to provide adequate viewing area while keeping the radial width constrained.
3Strength
If the connecting pin is press-fitted into through-holes to maintain torque transmission, then the strength of torque transmission is improved, but the device complexity increases due to precise alignment requirements
Solution Approach 1:
The outer diameter side through-holes and inner diameter side through-hole are pre-formed with precise positioning and alignment features before final assembly. The base portion of the yoke is pre-positioned on the torque transmission shaft, and the discontinuous portions are created at locations that naturally guide the connecting pin into correct alignment during installation, reducing the complexity of the assembly process.
Solution Approach 2:
The base portion of the yoke acts as an intermediary component that bridges the torque transmission shaft and the connecting pin. It provides a stable mounting platform with pre-positioned through-holes that facilitate accurate alignment, and the discontinuous portions serve as visual guides that mediate the alignment process during assembly.
Data Source
AI summary
A state where the connecting pin is laid across between at least one of the outer diameter side through-holes and the inner diameter side through-hole is maintained by an axial displacement of the connecting pin with respect to the outer diameter side through-hole and the inner diameter side through-hole being regulated based on an engagement between both edges of the connecting pin and a displacement-regulating portion which is a part of the yoke or the bolt.