Heavy-Duty Tyre Stiffener Positioning for Endurance
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Solution Overview
Problem
Heavy-duty tires face issues with endurance under excessive loads and inflation pressures, leading to damage, unwinding, and premature wear, particularly due to stress on the carcass reinforcement and stiffener elements.
Innovation Solution
A tire design with a radial carcass reinforcement featuring uncoated metal cables with saturated layers and a polymeric sheath, where the stiffener's radially outer end is closer to the carcass reinforcement's turnaround, reducing stress and improving the tire's resistance to deformation and unwinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radially outer end of the stiffener is positioned further from the bead to avoid stress concentration, then the risk of cracking in polymeric mixtures is reduced, but the carcass reinforcement becomes more susceptible to unwinding under excessive loads
Solution Approach 1:
The invention changes the radial positioning dimension of the stiffener's outer end, bringing it closer to the bead (within 5mm) rather than positioning it further away. This dimensional change simultaneously addresses both cracking resistance and unwinding prevention by optimizing the stiffener's proximity to the high-stress bead region while maintaining structural integrity
Solution Approach 2:
The invention modifies the positional parameter of the stiffener's radially outer end, specifying it should be located within 5mm of the bead. This parameter change optimizes the balance between stress distribution (preventing cracking) and mechanical support (preventing unwinding) under excessive loading conditions
2Reliability
If layers of reinforcing elements are arranged axially outside the turnaround to cover free ends, then protection against stress propagation is improved, but the stiffener becomes more vulnerable to breakage in compression zones
Solution Approach 1:
The invention applies local quality by positioning the stiffener's outer end at a specific location (within 5mm of the bead) where it can provide localized reinforcement exactly where needed. This creates different functional zones: the stiffener proximity provides compression zone protection, while the layered reinforcing elements provide stress propagation protection, with each element optimized for its specific location
3Reliability
If the carcass reinforcement is anchored further from the bead to reduce stress on the stiffener, then cracking risk is reduced, but the risk of unwinding increases
Solution Approach 1:
The invention implements preliminary action by pre-positioning the stiffener's outer end within 5mm of the bead before the tire undergoes excessive loading. This advance positioning ensures that the stiffener is optimally placed to prevent unwinding from the outset, while the layered reinforcing elements are already in position to prevent stress propagation and cracking
Data Source
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AI summary
The invention relates to a tyre with a radial carcass reinforcement consisting of at least one layer of reinforcing elements which is anchored in each of the beads by being wrapped around a bead wire, said wrapped-around portion of carcass reinforcement being reinforced with at least one layer of reinforcing elements or stiffener, the radially outer end of which is radially on the outside of the end of the wrapped-around portion. According to the invention, the reinforcing elements of at least one stiffener are unwrapped metal chords with saturated layers which on the test known as the permeability test return a flowrate less than 20 cm3/min and the distance between the radially outer end of the stiffener and the end of the wrapped-around portion of carcass reinforcement is less than 5 mm.