Pneumatic Radial Tire Sidewall Rigidity and Rolling Resistance
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Solution Overview
Problem
Conventional techniques for reducing rolling resistance in pneumatic radial tires often compromise stability and controllability due to decreased rigidity in sidewall portions, which cannot be reliably addressed by additional reinforcing layers or increased rubber thickness.
Innovation Solution
The tire design ensures a larger ground-contact area by adjusting the ground-contact lengths and curvatures on both sides of the tire, with a smaller radius of curvature on the outer side to enhance deformation and a more symmetrical footprint, combined with a turn-up portion of the carcass disposed at a significant height to maintain rigidity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the height of bead filler is reduced to decrease rolling resistance, then rolling resistance is reduced, but rigidity of sidewall portions deteriorates
Solution Approach 1:
The invention applies local quality by positioning the fold-back end of the carcass at a specific height (≤0.15 times the tire section height) and adding a short fiber reinforced layer only in the sidewall area between the belt end and the fold-back end. This localized reinforcement maintains sidewall rigidity where needed while allowing bead filler height to be reduced for lower rolling resistance.
Solution Approach 2:
The invention uses composite materials by incorporating a short fiber reinforced layer containing short fibers (such as glass fibers or organic fibers) mixed with rubber composition. This composite structure provides enhanced rigidity to the sidewall portions, compensating for the reduced bead filler height and maintaining overall tire stability.
2Strength
If additional reinforcing layers are added to sidewall portions to improve rigidity, then rigidity is improved, but device complexity increases
Solution Approach 1:
Instead of adding reinforcing layers throughout the entire tire structure, the invention applies reinforcement only in the specific sidewall area between the belt end and the fold-back end of the carcass. This targeted approach improves rigidity where needed without unnecessarily complicating the overall tire structure.
3Strength
If rubber thickness of sidewall portions is increased to improve rigidity, then rigidity is improved, but weight of tire increases
Solution Approach 1:
The invention uses short fiber reinforced layers as a lightweight alternative to increasing rubber thickness. The short fibers (glass fibers, organic fibers, etc.) provide high rigidity-to-weight ratio, enabling sidewall reinforcement without significantly increasing tire weight.
Solution Approach 2:
The reinforcement is applied only in the specific sidewall area where rigidity is needed, rather than increasing rubber thickness throughout the entire sidewall. This localized approach minimizes weight increase while achieving the desired rigidity improvement.
Data Source
AI summary
The present invention provides a pneumatic radial tire of the present invention is characterized in that: in a cross sectional view in the tire widthwise direction in the predetermined state thereof, provided that: i) Hout represents a distance in the tire radial direction between the maximum width position from the tire equatorial plane and a ground-contact end on the vehicle outer side of the tread and Hin represents a distance in the tire radial direction between the maximum width position from the tire equatorial plane and a ground-contact end on the vehicle inner side of the tread, Hout<Hin; ii) radius of curvature (Rout) of a tire side portion on the vehicle outer side, at the maximum width position thereof, is smaller than radius of curvature (Rin) of a tire side portion on the vehicle inner side, at the maximum width position thereof; and iii) a negative ratio of a ground-contact surface in a vehicle-outer side half portion of the tread is smaller than a negative ratio of a ground-contact surface in a vehicle-inner side half portion of the tread; and an outer end in the tire radial direction of a turn-up portion is disposed in each of the half portions of the tire at a height in the tire radial direction of at least 40% of the tire cross sectional height.