Pneumatic tire

Abstract

A pneumatic tire comprises a tread portion, a pair of sidewall portions, a pair of bead portions, a bead core disposed in each bead portion, a carcass comprising a ply of carcass cords extending between the bead portions through the tread portion and sidewall portions and turned up around the bead core in each bead portion, and an inner liner made of air-impermeable rubber extending on the tire cavity side of the carcass from one of the bead portions to the other. The radially inner end of the inner liner is located radially inside the radially innermost end of the carcass. In a radial region between the radially innermost end of the carcass and the radially outermost end of the bead core, the thickness of the inner liner is not less than 0.15 time but not more than 4.0 times the cross section diameter of the carcass cord.

1 . A pneumatic tire comprising: 
 a tread portion,    a pair of sidewall portions,    a pair of bead portions,    a bead core disposed in each said bead portion,    a carcass comprising a ply of cords extending between the bead portions through the tread portion and sidewall portions and turned up around the bead core in each said bead portion and    an inner liner made of an air-impermeable rubber extending on the tire cavity side of the carcass from one of the bead portions to the other, wherein    the radially inner end of the inner liner is located radially inside the radially innermost end of the carcass, and    in a radial region defined between the radially innermost end of the carcass and the radially outermost end of the bead core, the thickness of the inner liner is not less than 0.15 time but not more than 4.0 times the cross section diameter of the carcass cord.    
   
   
       2 . The pneumatic tire according to  claim 1 , wherein 
 the bead portion is provided with a chafer made of a rubber having a 100% modulus (M100) of from 440 to 830 N/sq.cm disposed along the bottom surface and axially outer surface of the bead portion, and    a minimum rubber thickness of the chafer, which is defined as the shortest distance from the bottom surface of the bead portion to cords of an adjacent cord layer, is not less than 1.7 times but not more than 6.0 times the cross section diameter of the carcass cord.    
   
   
       3 . The pneumatic tire according to  claim 1  or  2 , wherein in the bead portion, an intersecting angle α between the bead bottom surface and the tire inner surface at a bead toe (t) is set to be not less than 38 degrees but not more than 90 degrees.  
   
   
       4 . The pneumatic tire according to  claim 1 , wherein 
 the radially inner end of the inner liner is located in a region defined between two radial lines, a radial line passing through the middle point in the axial direction between the axially innermost point and axially outermost point of the bead core, and a radial line passing through the axially innermost point of the bead core, and    a thickness of the inner liner is in a range of from 0.5 to 2.0 mm when measured along a straight line extending through the axially innermost point and axially outermost point of the bead core.    
   
   
       5 . The pneumatic tire according to  claim 4 , wherein 
 the bead portion is provided along the bottom surface, axially outer surface and axially inner surface thereof with a chafer made of a rubber having a 100% modulus (M100) of from 440 to 830 N/sq.cm, and    the radial distance between the radially outermost point of the bead core and the radially outer end of a portion of the chafer which portion extends upward along the axially inner surface of the bead portion, is not more than 5 mm.    
   
   
       6 . The pneumatic tire according to  claim 1 , wherein 
 the bead portion is provided at least on the axially inside of the bead core with an insulation, and    the insulation is disposed between the inner liner and a rubber layer including a layer of topping rubber for cords adjacent to the inner liner and made of a rubber having an excellent adhesive property with the rubber layer and inner liner.    
   
   
       7 . The pneumatic tire according to  claim 1 , wherein 
 in each said bead portion, the carcass ply is turned up around the bead core from the axially inside to the axially outside of the tire to form a pair of turnup portions and a main portion therebetween,    each said turnup portion is wound substantially once around the bead core to have a wound portion extending axially inwardly along the radially outer surface of the bead core,    a bead apex made of a hard rubber is disposed on the radially outside of the wound portion so as to secure the wound portion between the bead apex and bead core, and    the wound portion is bent before the carcass ply main portion and then terminated after extending along the axially outside of the carcass ply main portion for a small distance so that the bent part is secured between the carcass ply main portion and the bead apex.    
   
   
       8 . The pneumatic tire according to  claim 7 , wherein the bent part extends radially outwardly up to a point radially inwards of the radially outer end of a flange of a wheel rim on which the tire is mounted.  
   
   
       9 . The pneumatic tire according to  claim 1 , wherein 
 in each said bead portion, a bead apex made of a hard rubber is disposed on the radially outside of the bead core, and the carcass ply is turned up around the bead core from the axially inside to the axially outside of the tire to form a pair of turnup portions and a main portion therebetween,    each said turnup portion extends radially outwardly along the axially outer surface of the bead apex, and    each said bead portion is provided along the carcass with a reinforcing layer comprising a base portion beneath the bead core, an axially inner portion extending radially outwardly from the base portion along the carcass-ply main portion, and an axially outer portion extending radially outwardly from the base portion along the carcass-ply turnup portion.    
   
   
       10 . The pneumatic tire according to  claim 1 , wherein 
 in each said bead portion, a bead apex made of a hard rubber is disposed on the radially outside of the bead core, and the carcass ply is turned up around the bead core from the axially inside to the axially outside of the tire to form a pair of turnup portions and a main portion therebetween,    each said turnup portion extends radially outwardly along the axially outer surface of the bead apex beyond the radially outer end of the bead apex so that the turnup portion has a part extending parallel with and closely to the main portion.