Tension Roller Radial Spring Centring
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Solution Overview
Problem
Existing automatic tension roller devices for internal combustion engine distribution belts lack radial centring of the torsion spring, leading to premature wear due to radial displacement, especially in compact and cost-effective designs.
Innovation Solution
A tension roller device with a support shaft, securing plate, and eccentric hub, where the securing plate features a radial centring tongue and an offset opening to ensure radial centring of the spring, maintaining perpendicularity with the engine block and preventing incorrect positioning, while also providing a labyrinth seal to prevent pollutant intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spring support is added to ensure radial centring of the torsion spring, then the radial centring is improved, but the axial size and device complexity increase
Solution Approach 1:
The patent merges the spring support function directly into the securing plate by forming a tongue structure that integrates both the support and centring functions. This eliminates the need for a separate spring support component, reducing axial size while maintaining radial centring precision.
Solution Approach 2:
The securing plate is designed to perform multiple functions: it secures the torsion spring axially against the stop surface, provides radial centring through the integrated tongue structure, and eliminates the need for a separate spring support. This multi-functionality reduces device complexity and axial dimensions.
2Ease of manufacture
If the opening is formed axially opposite the stop surface to simplify structure, then manufacturing is easier, but perpendicularity between shaft axis and engine block face is compromised
Solution Approach 1:
The patent intentionally positions the opening asymmetrically relative to the stop surface, specifically offsetting it from the axial centerline. This asymmetric positioning prevents the opening from interfering with the perpendicularity between the shaft axis and the engine block mounting face, while still allowing easy formation of the opening.
Solution Approach 2:
The opening is positioned in a specific location on the securing plate that is optimized for both manufacturability and functional performance. By placing the opening away from the stop surface area, the local quality of the securing plate is maintained in the critical mounting region while allowing easy fabrication in the opening region.
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 ensures radial centring of the spring, preventing premature wear and maintaining axial compactness and cost-effectiveness, while ensuring proper perpendicular alignment and sealing to prevent contamination.
Implementation Method 1
a spring which is arranged axially between the eccentric hub and the securing plate
Implementation Method 2
The skirt and the guide portion can delimit sealing by means of a narrow passage of the labyrinth type, such as to limit the intrusion by pollutant particles between the eccentric hub and the securing plate
Data Source
AI summary
The tension roller device provides a support shaft, a securing plate that is fixed on the support shaft, an eccentric hub that is free to rotate relative to the shaft, and a spring that is arranged axially between the eccentric hub and the securing plate. The support shaft includes a stop surface, against which the securing plate is axially supported, and which is delimited radially on the outer side by a circular outer edge. At least one opening is formed in the securing plate, in order to delimit a tongue for radial centering of the spring. The opening is situated radially on the outer side relative to the circular outer edge of the stop surface of the support shaft.