| 摘要 |
<p>A run-flat tyre comprises a carcass ply (6) extending between the bead portions (4) , and a sidewall reinforcing layer (10) disposed axially inside said carcass ply in each sidewall portion, wherein in a normally inflated unloaded state, a profile line from a tyre equator point (P) to a maximum tyre section width point (D) is curved substantially along an involute curve so as to have a radius of curvature decreasing continuously from the tyre equator point (P) towards the sidewall portion, the basic circle of the involute curve is an ellipse whose major axis extends in the tyre radial direction, the radial distance (h) between the tyre equator point (P) and the maximun tyre section width point (D) is more than 34 % but less than 50 % of the tyre section height (H). In a x-y co-ordinate system which is defined in a meridian section of the tyre such that: y-axis extends radially outwardly on the tyre equator; x-axis extends axially outwardly in the tyre axial direction; the x-y co-ordinates of said tyre equator point (P) is (0, B); B is a radius of curvature of the profile line at the tyre equator point (P), the elliptic function of the ellipse is <MATH> wherein 0 < a < b . <IMAGE></p> |
