PNEUMATIC TIRE

• US 20120042998A1
• Filed: 08/16/2011
• Published: 02/23/2012
• Est. Priority Date: 08/23/2010
• Status: Active Grant

• Current Assignee: Sumitomo Rubber Industries Limited
• Original Assignee: Sumitomo Rubber Industries Limited
• Inventors: UEDA, Kenji
• Granted Patent: US 8,910,682 B2
• Time in Patent Office: Days
• US Class Current: 152/209.18
• CPC Class Codes: B60C 11/0309 further characterised by the groove cross-section
• CPC Class Codes: B60C 11/1323 asymmetric

Abstract

A pneumatic tire having an enhanced cracking resistance at groove bottom, including at least one circumferential main groove 9 having such a sectional profile shape as including an axially inner wall portion 13, an inner arc portion 14 continuous with the inner wall portion 13, an axially outer wall portion 15 having a smaller length than the inner wall portion 13, an outer arc portion 16 continuous with outer wall portion 15, and a groove bottom portion 17 extending straight between the outer and inner arc portions while being inclined in a radially inward direction, in which the groove 9 has a maximum depth portion 18 on the tire equator side with respect to center position G1 of its width, and radius of curvature R1 of inner arc portion 14 and radius of curvature R2 of outer arc portion 16 satisfy the following relationships: R1≧0.6 mm and R2≧2×R1.

Claims

1. A pneumatic tire comprising a tread portion having at least one circumferential main groove extending in a circumferential direction of the tire at a location distant from a tire equator toward an axially outer side, said at least one circumferential main groove having a profile shape such that, in a meridian cross section including a rotation axis of the tire in a standard state that the tire is mounted on a standard rim and inflated to a normal inner pressure and no load is applied to the tire, the profile shape includes an inner wall portion extending radially inwardly from an axially inner edge on a tire equator side, an inner arc portion continuous with said inner wall portion and having a smaller radius of curvature than that of said inner wall portion, an outer wall portion extending radially inwardly from an axially outer edge on a tread edge side and having a smaller length than that of said inner wall portion, an outer arc portion continuous with said outer wall portion and having a smaller radius of curvature than that of said outer wall portion, and a groove bottom portion extending straight from said outer arc portion toward said inner arc portion while being inclined in a radially inward direction, whereby said main groove has a maximum depth portion on a tire equator side with respect to a center position of its width, and in which said inner arc portion and said outer arc portion satisfy the following relationships:

R1≧

0.6 mm

R2≧

2×

R1

in which R1 is the radius of curvature of the inner arc portion and R2 is the radius of curvature of the outer arc portion.

2. The pneumatic tire of claim 1, wherein the center position of the width of said at least one circumferential main groove is located at a position apart from the tire equator by a distance of 10 to 35% of a tread width TW which is an axial distance between both tread edges.

3. The pneumatic tire of claim 1, wherein said tread portion has a plurality of shoulder blocks arranged in the circumferential direction on the tread edge side of said at least one circumferential main groove, and the radius of curvature R2 of said outer arc portion of said at least one circumferential main groove is gradually decreased from a center portion of each shoulder block toward both end portions of each shoulder block in the circumferential direction.

4. The pneumatic tire of claim 1, wherein said at least one circumferential main groove extends at an angle of 45°

or less with respect to the circumferential direction of the tire.