Pneumatic tire

Abstract

It is a subject to suitably decrease the rigidity of blocks, to generate suitable collapsing of the blocks, to sufficiently exhibit edge effects of sipes, and to improve braking performances and the like in the medium term of wear and thereafter; and for solving this subject, in a pneumatic tire formed with blocks on its tread and engraved with sipes 11 on the blocks, the sipes 11 are classified into a surface portion 12, an intermediate portion 13, and a bottom portion 14 in a depth direction from a tread surface 17 up to sipes bottom 18, wherein the surface portion 12 and the bottom portion 14 open in a wave-shaped form in which crest portions 21 and trough portions 22 of the wave-shaped form extend in directions vertical to the tread, while the intermediate portion 13 opens in a wave-shaped manner in which the crest portions 21 and trough portions 22 of the wave-shaped form extend in a zigzag-like manner.

1 . A pneumatic tire with blocks being formed on a tread and with sipes being formed on the blocks, 
 wherein the sipes are classified, in a depth direction from a tread surface up to a sipe bottom, into a surface portion, an intermediate portion and a bottom portion, wherein the surface portion and the bottom portion open in a wave-shaped form with crest portions and trough portions of the wave-shaped form extending in directions vertical to the tread, and wherein the intermediate portion opens in a wave-shaped form with crest portions and trough portions of the wave-shaped forms extending in a zigzag-like manner.    
   
   
       2 . The pneumatic tire as claimed in  claim 1 , wherein where a depth of the sipes is D, a depth D 1  from the tread surface to a boundary between the intermediate portion and the bottom portion is 40 to 90% of D, and a depth D 2  from the tread surface to a boundary between the surface portion and the intermediate portion is 10 to 40% of D.  
   
   
       3 . A pneumatic tire with blocks being formed on a tread and with sipes being formed on the blocks, 
 wherein the sipes are classified, in a depth direction from a tread surface up to a sipe bottom, into a surface portion and a bottom portion, wherein the surface portion is opened in a straight-linear form, the bottom portion is opened in a wave-shaped form, and the crest portions and trough portions of the wave-shaped forms extend in a zigzag-like manner.    
   
   
       4 . The pneumatic tire as set forth in  claim 3 , wherein where D is the depth of the sipe, D is 5 to 6 mm, and wherein where D 3  is the depth from the tread surface to the boundary of the surface portion and the bottom portion, D 3  is 10% to 50% of D.