| 摘要 |
<p>A radial-ply pneumatic tire (200,400) has a carcass (220,420) that has a reverse curvature, that is, an outwardly concave shape, centered about the tire's equatorial plane (EP). A wedge (260,460) of elastomeric material is positioned above or below the belt structure (230,430) of the tire. If positioned above the belt structure, the wedge is used with a carcass cord angle in the range from 65 DEG to 80 DEG . This carcass structure also may be used when the wedge is positioned between the belt structure and carcass. The tire has an aspect ratio less than 75%, but an aspect ratio in the range from 40% to 65% is preferred. The wedge has a shape on its radially inner side that is similar to a low-amplitude cosine function. Particularly when the wedge is above the belt structure (providing both it and the belt structure with a reverse curvature), the belt cord angle is less than a "critical angle" of about 25 DEG . The invention, when practiced in its preferred form, provides a belted tire which has "natural shape" in its sidewall regions for whatever "radial" cord angle is selected for the carcass ply or plies. However, the tire also has "natural shape" in the portion of the radial carcass underlying the belt structure, but the "natural shape" is for a cord angle substantially equivalent to that or those low angles used in the belt structure. This low-angle "natural shape" for a bias-ply carcass is predicted by the equations of John F. Purdy in "Mathematics Underlying the Design of a Tire" to include a reverse curvature in the crown area of the bias-ply carcass.</p> |
