Pneumatic tire

Abstract

An end of a block 18 formed on a tread surface of a tire is chamfered in such a manner that a curvature of a chamfer increases toward the end of the block. Accordingly, a ground contact pressure which usually increases locally at the end of the block 18 is equalized and handling stability of the tire improves. Particularly, since the curvature changes, the ground contact pressure can be controlled corresponding to an actual distribution of ground contact pressure. As a result, the ground contact pressure can be equalized still further and an improvement in handling stability of the tire is achieved.

1 . A pneumatic tire in which a plurality of blocks demarcated by circumferential grooves extending in a circumferential direction of the tire and grooves intersecting the circumferential grooves, are provided on a tread, 
 wherein at least a portion of a block edge is chamfered from the side of a block center to a groove wall surface of each of the blocks;    a heightwise cross sectional form of a chamfer portion perpendicular to the groove wall surface is formed by a combination of a plurality of chamfer forms;    an angle formed by a tangential line of the chamfer portion with respect to a horizontal extension line of the surface of the block center in a heightwise cross section perpendicular to the groove wall surface increases from the side of the block center to the side of the block end; and    the heightwise cross sectional form of the chamfer portion is provided such that a portion of the cross sectional form of the chamfer portion on the block central side is formed as a straight line portion and a portion of the cross sectional form of the chamfer portion on the block end side is formed by at least one curved line portion having a fixed curvature.    
   
   
       2 . (canceled)  
   
   
       3 . A pneumatic tire according to  claim 1 , wherein the cross sectional form of the chamfer portion is comprised of two curved line portions having different curvatures.  
   
   
       4 . A pneumatic tire according to  claim 1 , wherein when in the heightwise cross section perpendicular to the groove wall surface, a length of the chamfer portion measured along a horizontal extension line of the surface of the block central portion is represented by L 1  and a likewise measured length of the block is represented by LO, the ratio L 1 /LO is in the range from 0.02 to 0.3.  
   
   
       5 . A pneumatic tire according to  claim 1 , wherein a distance, measured along a radial direction of the tire, between the horizontal extension line of the surface of the block central portion and an intersection point of the chamfer portion and the groove wall surface is in the range from 0.10 to 2.50 mm.  
   
   
       6 . A pneumatic tire according to  claim 1 , wherein when a heightwise distance between a groove bottom of the block and the intersection point of the chamfer portion and the groove wall surface is represented by H 1  and the maximum height of the block is represented by H 0 , the ratio H 1 /H 0  is greater than or equal to 0.75 and less than 1.0.  
   
   
       7 . A pneumatic tire according to  claim 1 , wherein the cross sectional form of the chamfer portion changes at a peripheral edge of the block for each portion of the block.  
   
   
       8 - 22 . (canceled)