Pneumatic radial tires

Abstract

A pneumatic radial tire capable of effectively controlling the occurrence of wandering phenomenon when being used in vehicles such as passenger car, small-size truck, truck, bus and the like is provided, in which a second tread zone contacting with a mountain side of a slant road surface is arranged so as to project toward a side of a first tread zone contacting with a flat road surface and camber thrust of the radial tire is increased by the second tread zone during the running on ruts and the like under loading.

1 . A pneumatic radial tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion toroidally extending between both sidewall portions, a radial carcass reinforcing these portions and a belt reinforcing the tread portion at the outer circumferential side of the radial carcass, in which the tread portion is comprised of a first tread zone contacting with a flat road surface and a second tread zone projecting toward the side of the first tread zone and contacting with a mountain side of a slant road surface, and the first tread zone is a maximum width region of a ground contact portion of the tire on a flat road surface under a normal loading in case of truck and bus tire and under a loading corresponding to 70% of a normal loading in case of tires having a size smaller than that of the truck and bus tire at an inflation state under a normal air pressure in accordance with a maximum loading capacity according to JATMA standard, and the second tread zone is a region extending outward from the first tread zone in widthwise direction of a ground contact portion on the flat road surface when a camber angle of 10° is applied to the tire under a normal loading in case of truck and bus tire and under a loading corresponding to 70% of a normal loading in case of tires having a size smaller than that of the truck and bus tire at an inflation state under a normal air pressure in accordance with a maximum loading capacity according to JATMA standard.  
     
     
         2 . A tire according to  claim 1 , wherein a reinforcing portion projecting outward from the second tread zone in the widthwise direction is arranged.  
     
     
         3 . A tire according to  claim 2 , wherein an outer profile line of the reinforcing portion at radial section of the tire is located inward from a phantom extending line of an outer profile line of the second tread zone in the radial direction of the tire.  
     
     
         4 . A tire according to  claim 2  or  3 , wherein the reinforcing portion is comprised of plural ribs arranged at given intervals in the circumferential direction of the tire.  
     
     
         5 . A tire according to anyone of claims  1 - 4 , wherein a tread width is within a range of 80-105% of a tire section width at an inflation state under a normal internal pressure.  
     
     
         6 . A tire according to anyone of claims  1 - 5 , wherein a maximum width of the belt is within a range of 60-100% of the tire section width at the inflation state under a normal internal pressure.  
     
     
         7 . A pneumatic radial tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion toroidally extending between both sidewall portions, a radial carcass reinforcing these portions and a belt reinforcing the tread portion at the outer circumferential side of the radial carcass, in which the tread portion comprised of a first tread zone contacting with a flat road surface and a second tread zone projecting toward the side of the first tread zone and contacting with a mountain side of a slant road surface, and a half-width (TW 1 ) of the first tread zone is a maximum ground contact width in a ground contact portion of the tire on the flat road surface from an equatorial plane of the tire under a normal loading in case of truck and bus tire and under a loading corresponding to 70% of a normal loading in case of tires having a size smaller than that of the truck and bus tire at an inflation state under a normal air pressure in accordance with the maximum loading capacity, and a width (TW 2 ) of the second tread zone satisfies the following condition: 
         TW   2   /TW   1 >4.0×10 −2   
       when this width is a ground contact width extending outward from the half-width (TW 1 ) of the first tread zone among the maximum ground contact width in the ground contact portion of the tire on the flat road surface from the equatorial plane of the tire when a camber angle of 10° is applied to the tire under a normal loading in case of truck and bus tire and under a loading corresponding to 70% of a normal loading in case of tires having a size smaller than that of the truck and bus tire at an inflation state under a normal air pressure in accordance with a maximum loading capacity, and a distance (b) from a side edge of the first tread zone to an outer profile line of the tire at a position corresponding to 0.95 times a height (H) of the carcass from the bead core at a state of inflating under an air pressure corresponding to 10% of a normal air pressure satisfies the following condition with respect to the width (TW 2 ) of the second tread zone: 
         b/TW   2 >1.2. 
     
     
         8 . A tire according to  claim 7 , wherein a total tire thickness of a middle part in the tire side portion locating within a range of 0.5-0.8 times the carcass height (H) from the bead core at the meridional section of the tire in a normal direction of the radial carcass is thinner than a total tire thickness of the other part in the tire side portion.  
     
     
         9 . A tire according to  claim 7  or  8 , wherein a maximum width position of the radial carcass is located within a range of 0.6-0.8 times the carcass height (H) from the bead core.  
     
     
         10 . A tire according to anyone of claims  7 - 9 , wherein the total tire thicknesses of the tire side portion in the normal direction of the radial tire at positions of 0.85 times and 0.4 times the carcass height (H) from the bead core at the meridional section of the tire are thicknesses exceeding 1.65 times the similar total tire thickness at the maximum width position of the carcass.  
     
     
         11 . A tire according to anyone of claims  7 - 10 , wherein a width of the tread at a state of inflating under an air pressure corresponding to 10% of the normal air pressure is within a range of 80-95% of the tire section width.  
     
     
         12 . A tire according to anyone of claims  7 - 11 , wherein a maximum width of the belt at a state of inflating under an air pressure corresponding to 10% of the normal air pressure is within a range of 60-90% of the tire section width.  
     
     
         13 . A pneumatic radial tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion toroidally extending between both sidewall portions, a radial carcass reinforcing these portions and a belt reinforcing the tread portion at the outer circumferential side of the radial carcass, in which a high-hardness rubber layer having a JIS A-hardness higher by 3 degree or more than rubber hardness of a tread rubber is arranged in a region at the meridional section of the tire including an outermost position of ground contact end at the meridional section of the tire under a normal loading in case of truck and bus tire and under a loading corresponding to 70% of a normal loading in case of tires having a size smaller than that of the truck and bus tire at an inflation state under a normal air pressure in accordance with the maximum loading capacity and a position measured from the bead core to ½ point of the carcass height from the bead core under an inflation of the above normal air pressure.  
     
     
         14 . A tire according to  claim 13 , wherein a surface of the high-hardness rubber layer at least facing an inner periphery side of the tire at the meridional section of the tire is rendered into a wavy form.  
     
     
         15 . A tire according to  claim 15 , wherein an average wavelength of the waved portion is not more than ⅓ of a total extension of the waved portion.  
     
     
         16 . A tire according to  claim 14  or  15 , wherein the total extension of the waved portion is longer by not less than 20% than a length of a line segment passing through a middle point of the wave.  
     
     
         17 . A tire according to anyone of claims  13 - 16 , wherein a thickness center of a maxi thickness in the high-hardness rubber layer as measured in a normal direction of the radial carcass at the meridional section of the tire under the inflation of the above normal air pressure is located outward toward the outer surface of the tire from a thickness center of a total tire thickness as measured on a normal line passing through the above maximum thickness position.  
     
     
         18 . A pneumatic radial tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion toroidally extending between both sidewall portions, a radial carcass reinforcing these portions and a belt reinforcing the tread portion at the outer circumferential side of the radial carcass, in which a thinned portion is formed in at least a part of the side portion locating within a range of 0.5-0.8 times the carcass height (H) from the bead core at a state of inflating under an air pressure corresponding to 10% of the normal air pressure in accordance with the maximum loading capacity so that a total tire thickness of this thinned portion as measured in the normal direction of the radial carcass at the meridional direction of the tire is not more than 75% of a similar total tire thickness of the other part in the tire side portion.  
     
     
         19 . A tire according to  claim 18 , wherein a position of the maximum width of the radial carcass is located within a range of 0.6-0.8 times the carcass height (H) from the bead core.  
     
     
         20 . A tire according to  claim 18  or  19 , wherein not less than 80% of a portion having a maximum curvature of the radial carcass at the meridional section of the tire is located within a range of 0.65-0.85 times the carcass height (H) from the bead core.  
     
     
         21 . A tire according to anyone of claims  18 - 20 , wherein the total tire thickness at the meridional section of the tire as measured in the normal direction of the radial carcass at a position corresponding to 0.85 times the carcass height (H) from the bead core is not less than 0.64 times the similar total tire thickness at a position of side edge of the belt.  
     
     
         22 . A tire according to anyone of claims  18 - 21 , wherein a thickened portion is formed in at least a part of the side portion locating within a range of 0.8-0.85 times the carcass height (H) from the bead core so that the total tire thickness of this thickened portion is not less than 1.5 times the similar total tire thickness at a position corresponding to 0.75 times the carcass height (H) from the bead core.